H11C-0634
Character of Submarine Groundwater Discharge (SGD) at the Coast of Mallorca Island
Preliminary results of geochemical tracers indicated that submarine groundwater discharge (SGD) is prevalent around the Mallorca coast, Spain; SGD would be an important source of trace metals and phosphorus to the coastal ocean. During September 2006, vented benthic chambers (a.k.a. seepage meters) were used at four diverse sites along the coast (Es Caragol, Porto Colom, Santa Pon\c{c}a and S\'{o}ller) to directly measure SGD in order to investigate the characteristics of SGD. Mallorca is an example of a (Miocene) carbonate platform. The site at S\'{o}ller on the northeast coast is located on a wide stretch of beach in an embayment surrounded by part of the high relief of the Tramuntana Range; the other three sites were in areas of relatively low relief. The average rate of groundwater seepage at the four sites ranged from 3 to 19 cm d-1, being highest at Es Caragol, a wide embayment on the southern coast of Mallorca. All sites were characterized by an irregular, spatial distribution of seepage which was dominated by low values, less than 15 cm d-1 in most locations, but punctuated by high values (up to 65 cm d-1) in discrete locations. This characteristic was best represented by the observations at S\'{o}ller, where one device documented a consistently higher SGD, averaging 52 cm d-1, while the rest of the study area had an average SGD of 6 cm d-1. Such an irregular distribution would be expected to characterize fractured rock or karstic aquifers. There was little or no tidal modulation of the SGD which suggested to us that the driving forces adjusted, for the most part, to the tidal elevations in open water. In addition, the water seeping across the sediment-water interface showed little or no dilution from the ambient, open-water salinity, in fact, in one case, the salinity of the SGD was greater than ambient sea water. SGD at these locations appeared to be dominated by the recirculation of sea water through the aquifer, driven by oceanic processes. This work was supported by the Balearic Island Government (Govern de les Illes Balears, Econom Hisen I Innov; N\'{u}m: 8171/2006: 6014/2007).
H11C-0635
Geochemical baseline survey based on streamwater chemistry of small mountainous watersheds in the Kanamaru area, Japan
It is generally known that all of the natural river water is supplied from groundwater under base flow condition. The variety of groundwater chemistry is caused by various factors such as the chemistry of aquifer and residence time, which are mainly controlled by the lithology and geological structure of the watershed. The quality of river water under base flow condition therefore reflects the lithology and geological structure of the watershed. There is an example which draws high resolution hydrogeochemical baseline map of large area in England based on the water quality of first and second order streams (average of catchment areas: 1.75km2). This mapping was conducted in dry summer season, which is essential to have successful result in this type of mapping. To conduct similar mapping in Japan, much attention has to be paid on hydrological condition to the measurement, because we do not have clear dry season in Japan. Main target of this study is to show hydrological condition on which successful mapping stands. We examined the relationships between the water quality and discharge of several small streams in the Kanamaru area, NE Japan, under various water level conditions. The water-quality parameters and concentrations of dissolved elements presented specific values under lower water level condition from base flow to low water discharge of about three times of base flow. Therefore, hydrological survey for the hydrogeochemical baseline mapping can be conducted under lower level condition when the discharge does not exceed three times of base flow in the watershed of Kaminosawa Stream. On the basis of these results, we investigated the water chemistry of 63 streams, their watershed are 0.5–2.0 km2 wide (average: 1.0 km2), under low water conditions, and tried to draw a hydrogeochemical baseline map around the Kanamaru area. We report the preliminary results of hydrogeochemical mapping around the Kanamaru area, and discuss its usefulness.
H11C-0636
Mathematical Model for Solute Transport in a Single Borehole Dipole Flow Tracer Test
The basic design of a single-borehole dipole-flow tracer test involves a well with an injection and an extraction chamber separated by some vertical distance and isolated from one another both using an inflatable packer. The test utilizes a small pump to create a vertical dipole-flow field. After the flow field is stabilized and the pumping rate and drawdowns in these chambers are recorded, a tracer mass is introduced instantaneously into injection chamber and the concentration breakthrough curve is monitored in the extraction chamber. The horizontal hydraulic conductivity, the vertical hydraulic conductivity and longitudinal dispersivity can be determined by using an appropriate mathematical model to analyze the breakthrough curves and drawdowns in these chambers. Existing mathematical models based on streamtube approach are only effective for interpreting tracer tests under advective-dominated condition. Furthermore, these solutions are appropriate for generation of breakthrough curve in the extraction chamber only because the transverse dispersion term is neglected. This study presents a novel mathematical model for describing solute transport in a single-borehole dipole-flow tracer test. In developing the mathematical model, a steady-state analytical solution for drawdown distribution is first obtained and the radial and vertical components of pore velocity are determined. Subsequently, the two-dimensional advection-dispersion equation in cylindrical coordinates for describing tracer transport in a dipole-flow field is derived based on the second order dispersion tensor theory. The Laplace transformed finite difference technique is applied to solve the two-dimensional advection-dispersion equation in cylindrical coordinates with variable- dependent coefficients. The developed model has an advantage over the existing models because it can be valid under a wide range of longitudianl dispersivity. The novel mathematical model is applied to simulate the concentration contour in the aquifer and the breakthrough curves in the chambers. Moreover, a curve-fitting method is proposed to determine the longitudinal dispersivity.
H11C-0637
pH Control for Effective Anaerobic Bioremediation of Chlorinated Solvents
SABRE (Source Area BioREmediation) is a 4-year collaborative project that aims to evaluate the performance of enhanced anaerobic bioremediation for the treatment of chlorinated solvent DNAPL source areas. The project focuses on a pilot scale demonstration at a trichloroethene (TCE) DNAPL field site, and includes complementary laboratory and modelling studies. Organic acids and hydrogen ions (HCl) typically build up in the treatment zone during anaerobic bioremediation. In aquifer systems with relatively low buffering capacity the generation of these products can cause significant groundwater acidification thereby inhibiting dehalogenating activity. Where the soil buffering capacity is exceeded, addition of buffer may be needed for the effective continuation of TCE degradation. As an aid to the design of remediation schemes, a geochemical model was designed to predict the amount of buffer required to maintain the source zone pH at a suitable level for dechlorinating bacteria (i.e. > 6.5). The model accounts for the amount of TCE to be degraded, site water chemistry, type of organic amendment and soil mineralogy. It assumes complete dechlorination of TCE, and further considers mineral dissolution and precipitation kinetics. The model is applicable to a wide range of sites. For illustration we present results pertinent to the SABRE field site. Model results indicate that, for the extensive dechlorination expected in proximity to the SABRE DNAPL source zone, significant buffer addition may be necessary. Additional simulations are performed to identify buffer requirements over a wider range of field conditions.
H11C-0638
River junction and reach vulnerability prediction in urban watershed: a methodology for identifying structural uncertainty
The mixing of water, solutes and sediments from two or more tributaries of urban watershed produces streamflow possessing unique biogeochemical, hydrological, morphological, and ecological signatures. To understand and predict these signatures, confluence locations within river networks are commonly used to divide a watershed into individual modeling units where hydrologic characteristics are spatially averaged and used to parameterize process models. In this context, model parameters from an individual unit directly influence the simulated hydrograph at its corresponding downstream junctions and reaches. However, the uncertainty of model predictions at and between junction locations due to parameter variability within individual modeling units is poorly understood. This research develops a methodology to map junction and reach locations that are sensitive to model parameter variability. The results can be used for risk assessment in sensitive applications such as the design of bridges, culverts and channels to convey flood flows. This paper presents (a) a methodology for identifying stream junctions and reaches that are potentially vulnerable to model uncertainty due to the structural arrangement of their drainage network, (2) two dimensionless indices: junction ratio and reach ratio to quantify drainage characteristics and the vulnerability of junction and reach to parameter uncertainty, (3) a case study of urban catchments in coastal southern California, using a rainfall-runoff model to explore the relationships between changes in peak discharge at junctions and along reaches with varying junction and/or reach ratios. Preliminary results show that 7 percent of junctions and 4 percent of reaches are vulnerable to model parameter uncertainty based on a threshold of 10 percent changes in peak discharge. http://spatialhydro.sdsu.edu
H11C-0639
Effect of impervious area estimation methods on simulated peak discharges
Knowing the percentage of a watershed covered with impervious area is critical for understanding its runoff characteristics and flooding potential. However, there are several available methods for estimating watershed imperviousness (IMP). The objective of this research is to understand the effect of the IMP estimation method on simulated flood frequency distribution. This research compares three common methods for estimating imperviousness: (1) directly measured from high-resolution aerial photographs, (2) derived from satellite imagery, and (3) estimated using lookup tables linking land use/land cover categories to IMP values. The HEC- HMS model is used to simulate rainfall-runoff and assess the effects of the estimated IMP on the flood frequency distribution for the Mission Creek Watershed in Santa Barbara, CA. The Mission Creek watershed drains 31 sq km and is approximately 55 percent developed. Basin-wide imperviousness ranges from 13 to 17 percent depending on the selected IMP estimation method. Results for each IMP estimation method are also presented for the sub-watershed (0.3 to 4.1 sq km) scales showing internal variations ranging from approximately +/- 15 percent IMP. The resulting impacts on the flood frequency distribution are highlighted using the 2- and 100-year flood discharges. Preliminary results show the effects of IMP variation are greatest for the 2-year flood and decrease with increasing return period. Simulation results are used to identify the range of IMP values where the estimation method is most influential on simulated flood discharges. A secondary finding is the identification of specific land use/land cover categories having the greatest variability in estimated IMP. http://spatialhydro.sdsu.edu
H11C-0640
Stability Analysis of a Large-scale Landslide Mass: a Case Study From Three Gorges Reservoir, China
The landslide mass investigated in this study has a volume of about 20.6¡Á106 m3 and is located 17km upstream from the Three Gorges Dam. The tremendous volume and the short distance from the dam threaten the overall dam's safety as well as the daily traffic within the reservoir. The main objectives of this study were to determine: 1) how the stability of the landslide mass will be altered with changing boundary conditions, especially considering the rising water levels in the reservoir, which will also fluctuate seasonally substantially; and 2) how strongly the mechanical properties of the slip zone and the extent of rainfall infiltration into the landslide mass influence the factor of safety (FoS). During the systematic site investigation, both disturbed and undisturbed samples were collected from both the slip zone and the landslide mass and an integrated set of in-situ and laboratory tests were performed. Considering the progressive multi-stage construction of the dam, the corresponding water levels (present 156m and final 175m) and the predefined operating scenarios in flood seasons (e.g. rapid lowering of water level from 175m down to 145m), totally 12 boundary conditions were recognized for FoS calculations by employing transfer coefficient method for two representative profiles. The results of the analysis suggest that the landslide mass is stable with FoS values around 1.5, except for 0.98 for the scenario in which the water level is rapidly lowered from 175m to 145 with a speed of about 0.67m to 1.0m/day. Sensitivity analysis of the influential factors indicates that an increase of 5kPa in cohesion or 2o in friction angle cause FoS to increase by 0.01 and 0.10 respectively. FoS decreases from 1.10 down to 0.98 if the rainfall infiltration percentage is increased from 20% to 50% for the historical maximum daily rainfall of 358mm.
H11C-0641
Helium Isotopic Characteristics Dissolved In Groundwater In The Area Of Heavy Soil Subsidence In The Saga Plain, Japan
There are many rice fields at the Shiroishi area in the Saga plain, Japan. The geological setting of the Saga plain is closely located along the Beppu-Shimabara graben that has potential volcanic activities from Beppu (the active geothermal area) to Mt. Unzen (the active volcano) via Mt. Aso (the active volcano). Since this area was originally manmade by reclamation of shallow sea in a few hundred years, the plain has a poor irrigation system owing to few rivers to supply enough water to rice fields. Rice needs much water in growing in the summer, but some times water is short. Much groundwater has to be pumped from the confined shallow aquifer below a thick marine clay layer, which is impermeable and covers with a few ten meters depth. Groundwater has been recharged only at the narrow margin area between mountains and the reclaimed flat land. Pumping much water has caused heavy soil subsidence owing to shrinking the aquifer matrix. The land surface subsided by more than 120 cm depth in a long term at the center of Shiroishi area. Since the regional groundwater simply flows from mountain area to the sea, groundwater accumulates the regional crustal He component, which has a higher ratio of 3He/4He than the atmospheric He 1.4E-6, with increasing flow path. The isotopic ratio of the regional He accumulated in groundwater is characterized by a significant amount of mixing of a mantle He component with the ratio of 1.1E-5 in the subduction area. The ratio has gradually increased with increasing the dissolved He content in the entire area of the plain except the Shiroishi area and finally reached maximum 5E-6. On the other hand, the lowest ratio reached finally 8.7E-7 with increasing dissolved He content in groundwater at the center of the Shiroishi area. This suggests that the He accumulating mechanism is different between Shiroishi area and other areas in the plain. In other words, groundwater at the central Shiroishi area has selectively accumulated more the radiogenic He component, which the ratio has very low 1E-8, rather than the regional He component. It is possible to explain this contradiction if groundwater is consisted of a significant amount of pore water that has been isolated from the regional flow and squeezed from the impermeable marine clay layer. Consequently, squeezing much pore water caused the heavy soil subsidence at the central Shiroishi area.
H11C-0642
Spatial Variation of Deep-seated Carbon Contribution in Groundwater, Central Japan
Carbon isotopic ratio in groundwater can be used for identifying a contribution of deep source carbon, e.g., magmatic or deep-seated crustal fluids. In the present study, we focused on giving an outline of the spatial variation of deep-seated crustal fluid contribution to groundwater in non-volcanic regions of Japan. We measured the stable carbon isotopic ratio of DIC, chemical compositions and stable isotope (δ18O and δD) in groundwater or hot-spring samples taken at Kanto, Tokai, and Kinki districts in central Japan. The contribution of deep-seated carbon in groundwater is computed using carbon isotopic mass balance. Spatial variation showed the high concentration of deep-seated carbon in the Arima area, the belt-like area along the Median Tectonic Line (MTL) excepting the Chubu area, the southwest region of the Kii Peninsula and the central region of Shizuoka Prefecture. Especially, the area along the MTL has quite a high concentration of deep- seated carbon. This suggests that the large tectonic line act as a path of deep-seated carbon from the depth grater than ~1500m, which is the deepest sampling depth of groundwater in the present study. Approximately half of such groundwater is indicated to be mixed with the Arima type thermal water or brine from the results of isotopic features and high Cl- concentration. It is considered that the carbon is supplied with them. The δ18O and δD relationship proves another half of groundwater showing high concentration of deep-seated carbon is originated from meteoric water. This type of groundwater is characterized by a relatively low concentration of Cl-. These suggest an existence of an external CO2 (deep-seated) from underlying crust. Our estimation of deep-seated carbon contribution has a large uncertainty, because of un-counting CO2 bubble, and estimation errors based on the isotopic fractionation at the bubbling of CO2 or methanation, and the assumption of δ13C values of endmember components. However, we can obtain the general trend of spatial variation of deep-seated carbon contribution using carbon isotopic ratios.
H11C-0643
Routing Water and Sediment in the Rillito River Using IALLUVIAL2: A Comparison Study.
Predicting flood flows in rivers that flow through populated areas is of great importance, and computer models are useful tools in such an endeavor. This paper outlines a comparison study that examined the water surface and bed elevations of the 100-year flood event in the Rillito River at Tucson, Arizona. The results from IALLUVIAL2 were compared with those from HEC-RAS and GSTARS, as well as stage data from the USGS. Results showed that IALLUVIAL2, which cannot compute bridge effects, predicted a flood similar to that of the more commonly used HEC-RAS model, which does take into account bridges. Both models underestimated the flooding by about 2 to 4 feet, but accurately predicted the recession of each flood flow. This study also compared different equations within the IALLUVIAL2 model to find the most appropriate sediment transport and roughness equations for this particular river and found that Laursen and Manning's gave the best results. The results indicated the need of an appropriate model for predicting flood flows in ephemeral streams for water resource managers, engineers and urban planners.
H11C-0644
Geologic Hazards Associated With a Proposed Dam on the Yarlung-Tsangpo River in SE Tibet
For a decade anecdotes and media reports have been circulating about a proposed dam on the Yarlung- Tsangpo River in SE Tibet. The proposed site is in the deep canyon of the Yarlung-Tsangpo where the river leaves the Tibetan Plateau across an immense knickpoint, falling ~2000 m along an irregular U-shaped reach ~100 km in length. The fundamental purpose of the dam is generation of ~40,000 MW of hydropower, to be used in diverting a portion of the impounded river to water-starved regions of northern China. Offsetting benefits that would accrue from improved water supply in the north, debate has centered on the water-flow and sediment-flux impacts that would be felt downstream in the Brahmaputra system in northeastern India and Bangladesh, as well as the impact of a dam and large lake on the pristine, ecologically and ethnographically diverse area around the Yarlung-Tsangpo canyon, an area of great significance to Tibetan Buddhists. We have been examining the geodynamic evolution of eastern Tibet, and have gathered considerable geophysical and geological data on the knickpoint region. The knickpoint traverses the Namche Barwa-Gyala Peri massif, one of the most geologically active regions on Earth. In this region, very rapid bedrock exhumation at rates of 7 mm/yr or more has exposed granites as young as 1 Ma, and these rates have been ongoing for at least the past 3 m.y. Detrital-dating evidence shows that these high rates continue at present and that erosion within the massif contributes fully 50% of the suspended-sediment load in the Yarlung-Tsangpo at the point where it enters the Brahmaputra (this would be about 100 Mt/yr derived from the massif). The steep slopes in the massif fail by pervasive landsliding and suggest a steady-state topography where the high erosion rates are balanced by equivalent rates of rock uplift accommodated by numerous active structures. At a more regional scale, GPS results show that steep three-dimensional velocity gradients exist across the region, in the easternmost Himalaya near Namche Barwa >50% of the Indian – Eurasian plate convergence is accommodated within the high-strain zone that reaches to the southern edge of the proposed reservoir. The 1950 Assam earthquake (M8.6) was one expression of the high local strain rates, and caused considerable damage within the canyon area. Seismic results from our portable deployment show that the area beneath the massif and the Yarlung-Tsangpo canyon is exceptionally active, with over 1000 events ranging in magnitude from 1.0 to 5.6 (mb) taking place over a 15-month period. The events occur almost entirely in the mid to shallow crust and show a range of first motions. Together these data suggest that any dam placed within the Yarlung-Tsangpo canyon would be at high risk, with the dam being prone to failure due to pronounced seismic hazards and focused deformation. As it fills water pressure behind the dam could help trigger shallow earthquakes and landslides, and the dam would be difficult to maintain given the high frequency of landsliding and extreme local bedrock exhumation rates that would lead to rapid siltation at the dam site. Further, this impoundment of the Yarlung-Tsangpo would greatly starve the sediment flux downstream in the Brahmaputra and ultimately Bay of Bengal systems.
H11C-0645
Nitrate Variability in Hydrological Flowpaths for a Mid-Appalachian Forested Catchment Following a Large-Scale Defoliation
Nitrogen (N) leakage from forested watersheds due to disturbance is a well-documented, but not well understood process that contributes to the degradation of receiving waters through eutrophication. Several studies have shown that large scale defoliation events in small forested watersheds in the Eastern U.S. cause immediate and dramatic increases in N flux to streams. Recovery times can differ dramatically depending upon location. Reasons for these differences are not well understood, however, because N transport and transformation processes are difficult to track over these long recovery timescales. This research focuses on a large-scale gypsy moth defoliation event that impacted Shenandoah National Park (SNP) in the late 1980s to early 1990s. Water chemistry and discharge have been monitored at a number of catchments within SNP over the timeframe since the defoliation. Recovery of these systems to pre-defoliation N levels has been observed to be unusually slow, lasting over a decade. Availability of high-frequency (i.e. hourly) stream chemistry and discharge data during storm events throughout the period of recovery allows us to investigate short- and long-term mechanisms for N "leaks" from forested watersheds. Through geochemical hydrograph separation techniques, we can determine how nitrate concentrations vary between event, soil, and groundwater during and in the years following a disturbance. Analyses focus on Paine Run, a 12.4 km2 catchment where over 50 storms have been characterized since the 1990-1992 defoliation. Standard geochemical hydrograph separation is performed using conservative tracers to determine the relative flow contributions from the three flow components for each measurement time step. Computed discharge components, along with measured steam nitrate concentrations (NO3 -) at each time-step, were used to solve for the relative concentration of NO3 - in each of the hydrologic zones for storms by solving the over-determined set of mixing model equations. This approach reveals how nitrogen moves through the catchment system and provides insight into the mechanisms that contribute to the observed long-term elevated nitrate levels.
H11C-0646
Using oceanic-atmospheric oscillations for long lead-time streamflow forecasting in the Upper Colorado River Basin
In the recent past, oceanic-atmospheric oscillations have been used successfully for long lead-time streamflow forecasting. Herein, we present a data-driven model, Support Vector Machine (SVM) for the long lead-time streamflow forecast incorporating oceanic-atmospheric oscillations. The SVM is based on Statistical Learning Theory that uses a hypothesis space of linear functions based on Kernel approach and can be used to predict a quantity forward in time based on training that uses past data. The principal strength of SVM lies in minimizing the empirical classification error and maximizing the geometric margin by solving inverse problems. The SVMs are considered superior to the Artificial Neural Networks (ANNs) due to the tendency of formulating a quadratic optimization problem which ensures a global optimum that is found missing in the traditional ANN approach. The SVM model was applied to four unimpaired gages in the Upper Colorado River Basin (UCRB). The streamflow data for the selected gages was used from 1906¡§C2004. Annual oceanic-atmospheric indexes comprising of Pacific Decadal Oscillation (PDO), North Atlantic Oscillation (NAO), Atlantic Multidecadal Oscillation (AMO), and El Nino-Southern Oscillations (ENSO) for a period of 1906¡§C2001 were used to generate streamflow volumes for three years ahead. The SVM model was trained with 86 years of data (1906¡§C1991) and tested for 10 years of data (1992-2001). The testing criteria used for the model effectiveness was based on correlation coefficient r, root means square error (RMSE) and nash sutcliffe efficiency coefficient e. Predictions during the testing phase showed a good agreement with measured streamflow volumes for the selected gages in UCRB. Rigorous sensitivity analysis was performed to evaluate the effect of individual oscillation. The results indicated a strong signal for NAO and ENSO indexes as compared to PDO and AMO indexes for the long lead-time streamflow forecast. The oceanic-atmospheric oscillations are helpful in providing long range streamflow predictions which can be potentially used for planning and management of water resources for the UCRB.
H11C-0647
Methodology of Historical Flood Evaluation from Korean Historical Documents during AD 1392 to 1910
Study on extreme flood events has critical limitation of shortage of historical data because modern systematic data don't implement long time series. The historical documentary records hence can be one of the important sources to contribute additional information on extreme flood events which had occurred before the instrumental observations began. For the proper data mining, documentary records satisfying following four conditions are preferred. 1. Long enough time series, 2. Official archives covering over all Korean peninsular, 3. Abundant enough record number, and 4. Detailed damage description. The Annals of Choson Dynasty includes about 500 years and 511 number of flood records during Choson Dynasty in ancient Korea. According to the annals, there were highly dense flood damage records in the middle of 17th century and the largest human damage and residence damage occurred in 1739 and 1856 respectively. Another source is Jeungbo-Munheonbigo. Jeungbo-Munheonbigo is a taxonomic document categorized by the themes such as cultures, social systems, and climates as well as contains 79 number of flood damage records. An effective way to analyze those historical floods without water level data is to classify and categorize the flood damage records because all records are written in descriptive way. Consequently, 556 records are categorized into 10 items by flood damage types and each categorized record is classified into three grades by numerical level that is how much the record is expressed in numerical way. These grouping results are applied to decide reasonable period range to get detailed information from entire inspection period. In addition, Historical Flood Evaluation Index (HFEI) thereby can be derived from the processes in quantitative and statistical ways to evaluate the magnitude of each ancient flood. In this research, flood damage evaluation is mainly focused on the damage of human beings and residences. Also degree ranges based on cumulative probability are induced with two damage inventory. HFEI by conditional weighted factors is applied to every flood record and to analysis for flood distribution in annual series.
H11C-0648
Isotopic approach to understanding the groundwater flow system within an andesitic stratovolcano in a temperate humid region: case study of Ontake volcano, central Japan
We used isotope tracer methods to clarify the groundwater flow system within Mt. Ontake: a stratovolcano consisted of andesite lava and pyroclastic rock, located within a temperate humid region. Precipitation was collected monthly at 11 sites on the south, east, north, and west slopes of the volcano for a period of 26 months. The weighted mean delta-value in precipitation show a clear decrease with increasing elevation (altitude effect) on all slopes and is relatively low on the leeward slope (rain-shadowing effect). The springs collected over the entire area of the volcano show δ values that are controlled by the altitude effect and the rain-shadowing effect on precipitation. The average recharge elevation of the individual springs was calculated from their δ18O values and the equation of the altitude effect of groundwater for corresponding slope. The average recharge elevation and tritium concentration in springs indicate that the large-scale groundwater flow systems (vertical drop: ca. 800m) with a relatively long residence time are maintained along the lava flow in the younger volcano north zone, whereas a relatively small-scale groundwater flow systems (vertical drop: ca. 400m) distribute across a wide range of elevation in the younger volcano south zone. In older volcano zone at the foot of the volcano body, it is inferred that local groundwater flow systems (vertical drop: less than 200m) dominate and that these flow systems are not connected to those in the younger volcano zone. Consequently, the scale of the groundwater flow system decreases with increasing age of the volcano body. This contraction of the flow system with time might reflect the progressive erosion of the volcano body, especially within the younger volcano zone.
H11C-0649
Recourse to Dry Land Farming as a Possible Way to Arrest the Degradation of Groundwater, Soil and Land in Haryana, India
The Green Revolution enabled the small state of Haryna to become the wheat granary of India – though occupying 1.3% of geographical area of India, it accounts for 13% of wheat, and 3% of quality rice production in India. Haryana paid a heavy price for the impressive agricultural development - one-third of the irrigated land is salinity affected, water level declined by 3-12 m, and excessive nitrate levels in the groundwater (114-1800 mg/l) have rendered the groundwater non-potable in many areas. Groundwater in the arid western Haryana has become mostly saline ( TDS > 4000 mg/l). Improper canal irrigation has raised the water table by 3.0 -9.0 m in some areas, causing water logging over 2346 km2 of land. One possible way to arrest the degradation of groundwater and soil, is to switch to dryland farming. This would involve change in the irrigation method as well as proper selection and rotation of food crops like barley, sorghum, maize, different types of beans (pulses) and oil seeds like mustard, groundnut, etc and restricted use of chemical fertilizers and pesticides. Dryland farming could go hand in hand with the plantation of fruit trees, grasses and medicinal plants suitable to this agro- climatic zone, and animal husbandry. The same considerations hold good to eastern Rajasthan as well.
H11C-0650
The seasonal variation for the discharge and water quality of a stream in volcanic island, Korea
Assessment of the groundwater resources in a volcanic island is so difficult, because permeable and impermeable layers were formed from lava flows in different times and various lithologies. Jeju island is the largest volcanic island in Korea, and is composed of plateau and shield forming basaltic to trachytic lava flows, numerous tuff rings/cones, scoria cones during its long volcanic history (about 1.8 Ma). Most of streams in Jeju island are dry in normal times. Owing to high permeable geologic features such as clinkers, stream run-off occurs when precipitation is over 40 mm/day. To understand runoff phenomena in Jeju island, some streams are monitored automatically about stream stage, and water quality. Oedocheon (cheon means stream) is monitored during the normal and runoff period. Oedocheon is a permanent stream in Jeju island, and its water quantity and quality is originated by a spring water from lava flow boundaries. The surface limit and watershed parameters for the Oedocheon watershed were created and calculated by WMS software. Stream stages respond very quick during the runoff time, but the duration of the runoff is so short about a few hours. Parameters such as landuse, soil condition, preconditioned rainfall, and vegetables influence runoff phenomena. Periodic stream discharge measurements and chemical analyses of the water were preformed in order to analyze the seasonal variation of the stream water quantity and quality in normal times. Considering water intake quantities, ordinary stream discharge is 2,569~50,415 m3/day, average 21,215m3/day. Water qualities are dependent on each measurement season. Electrical conductivity is 101.7-202.0 ¥ìS/cm, pH is 7.38-8.38, and water temperature is 10.8-23.3¡É. Major ion concentrations also varies seasonally. Mg is 2.39-7.45 mg/l, Ca is 4.11-11.54 mg/l, Na is 4.80-13.24 mg/l, K is 1.64-3.47 mg/l, SO4 is 2.78-8.25 mg/l, HCO3 is 17.78-36.61 mg/l, and Cl is 6.43-22.77 mg/l. The stream discharge and water quality are so correlated with rainfall. The analyses of the responses to the rainfall in each season can be used to estimate the size of the underground groundwater watershed.
H11C-0651
Isotopic Exchange Rate Constant between Snow and Liquid Water
Isotopic exchange rate between liquid water and ice is crucial in determining the isotopic evolution of a snowpack and its melt. The rate constant for oxygen isotopic exchange has been reported by Taylor et al. [2002] using three column melting experiments with different heights and melt rates. In this work, we obtained the hydrogen isotopic exchange rate constant using samples from two out of three experiments in Taylor et al [2002]. The 1-D model developed by Feng et al. [2002] was fit to the isotopic results by adjusting the value of two parameters: the isotopic exchange rate constant ( kr) and the fraction of ice participating in the exchange (f). To assess whether oxygen and hydrogen isotopic exchange rate are the same, we rigorously examined uncertainties of fitting parameters for both the oxygen and hydrogen data. The optimized yielded from oxygen isotopic simulations are 0.19 hr–1 for column A, 0.15 hr–1 for column B, and 0.07 hr–1 for column C. The optimized kr yielded from hydrogen isotopic simulations are 0.20 hr–1 for column A and 0.08 hr–1 for column C. Although it might seem that the hydrogen exchange rate constant is slightly higher for each given column experiment, the confidence regions for the adjustable parameters show that the differences are not significant. The model results suggest that f, the fraction of ice involved in the isotopic exchange increases with increasing wetness of snow. This makes sense because the isotopic exchange rate increases with 1) increasing surface area of contact between liquid and ice and 2) the rate of dissolution and recrystallization; both being related to the wetness of snow. The best fit kr increases with the mean pore water velocity of the snow column. It is not clear what results in the dependency of kr on pore water velocity. One possibility is that at low flow water may be channelized, so it bypasses some of the immobile water that exchanges with the ice and not all the exchanged isotopes are reflected in the discharge. However, the model does not consider preferential flow, and this effect would thus cause a lower value of the best fit exchange rate constant.
H11C-0652
Comparing Least Squares and Robust Methods in Linear Regression Analysis of the Discharge of the Flathead River, Northwestern Montana.
The Flathead River in Northwestern Montana drains the relatively pristine, high-mountain watersheds of Glacier- Waterton national parks and large wilderness areas making it an excellent test-bed for hydrologic response to climate change. Flows in the North Fork and Middle Fork of the Flathead River are relatively unmodified by humans, whereas the South Fork has a large hydroelectric reservoir (Hungry Horse) in the lower end of the basin. USGS stream gage data for the North, Middle and South forks from 1940 to 2006 were analyzed for significant trends in the timing of quantiles of flow to examine climate forcing vs. direct modification of flow from the dam. The trends in timing were analyzed for climate change influences using the PRISM model output for 1940 to 2006 for the respective basin. The analysis of trends in timing employed two linear regression methods, typical least squares estimation and robust estimation using weighted least squares. Least squares estimation is the standard method employed when performing regression analysis. The power of this method is sensitive to the violation of the assumptions of normally distributed errors with constant variance (homoscedasticity). Considering that violations of these assumptions are common in hydrologic data, robust estimation was used to preserve the desired statistical power because it is not significantly affected by non-normality or heteroscedasticity. Least squares estimated trends that were found to be significant, using a 10% significance level, were typically not significant using a robust estimation method. This could have implications for interpreting the meaning of significant trends found using the least squares estimator. Utilizing robust estimation methods for analyzing hydrologic data may allow investigators to more accurately summarize any trends.
H11C-0653
Development of Floating Wave Barriers for Cost Effective Protection of Irrigation and Catfish Pond Levees
Earth levees for catfish ponds and irrigation water storage experience significant embankment erosion due to wind generated waves. Large seasonal fluctuations in water level make vegetative bank protection impractical, and other stabilization methods such as the use of old tires or riprap are not acceptable due to ecological and economic concerns. The goal of the present work is to define configurations and construction techniques for inexpensive floating breakwaters made of polyethylene irrigation tubing. Based on wave characteristics measured in an irrigation pond near Lonoke, Arkansas, a laboratory scale wave generating flume was designed, constructed, and used to test multiple wave barrier configurations for regular waves in deep and transitional water depths. Wave transmission characteristics were investigated for the following breakwater arrangements: (1) fully restrained, (2) vertically restrained with a single mooring line, (3) horizontally restrained with a rigid arm hinged at one end, and (4) horizontally restrained with piles at both sides of the breakwater. The test results show that cylindrical pipes can be used effectively as floating breakwaters and that wave transmission characteristics strongly depend on the draft of the breakwater and the mooring configuration. The use of multiple small cylinders instead of a single large one can reduce cost while maintaining the same level of wave attenuation. The wave characteristics measured in the field and the results of laboratory testing resulted in a final design that is to be tested at the prototype scale in an irrigation pond.
H11C-0654
The Effect of Land-Surface Subsidence Processes on the Remaining Peat in the Sacramento-San Joaquin Delta, California, USA
The Sacramento-San Joaquin Delta (henceforth, the Delta) was once a 1,400 km2 tidal wetland that was drained and reclaimed for agricultural production beginning in the mid-nineteenth century. Drainage of the organic, peat soils has resulted in land-surface subsidence in the region to as much as 8 m below sea level. Although the factors causing land-surface subsidence are well known (principally oxidation of organic matter), little is known about the physical and chemical condition of the remaining peat. As part of a project called Rates and Evolution of Peat Accretion through Time in the Delta, the physical and chemical condition of the remaining peat layer was studied on four farmed islands and four relatively undisturbed marsh islands. Peat cores were collected from all sites using a modified Livingstone corer. Core samples were analyzed for bulk density, percent organic matter and carbon, and for radiocarbon. On the marsh islands, the thickness of the relatively undisturbed peat layer ranged from 4.2 to 8.2 m, and on the farmed islands, it ranged from 1.2 to 1.5 m. On the farmed islands, the unoxidized and intact peat layer lies underneath a 0.4- to 0.9-m-thick layer of compacted and oxidized peat. Radiocarbon ages obtained from Scirpus seeds within the basal peat of the farmed islands indicate that peat formation began 6,035-6,785 cal yr BP. Although peat is still forming on marsh islands today, the youngest intact peat at the farmed island sites formed 4,415-4,985 cal yr BP. The mean bulk density of marsh island peat (0.17 g/cm3) is less than the intact and unoxidized peat layer on the farmed islands (0.21 g/cm3; Student's t-test, p < 0.0001), and much less than the compacted and oxidized zone at the surface of the farmed islands (0.65 g/cm3; Student's t-test, p < 0.0001). In the peat samples, there is an inverse relationship between bulk density and organic matter. The higher bulk densities and lower carbon content of the upper compacted and oxidized peat layer on farmed islands are a result of surface drainage for agricultural practices. Although the remaining intact peat below this zone does not appear to be oxidized, it has been altered through physical compaction.
H11C-0655
Markov processes for Advection-Diffusion Transport in Non-Smooth Media: Skew Brownian Motion and the Generalized Taylor-Aris Formula.
Markov processes are used to study advective-diffusive transport of passive solutes in media with non-smooth diffusion tensor D and drift coefficient U. The classical Taylor-Aris formula for the effective dispersion in a cylinder is generalized to the case where U is bounded and D is bounded positive definite; both functions depending only on the transversal spatial coordinate. In the particular case of a two-dimensional arrangement of layers of constant D parallel to the direction of flow, we identify the Markov process modeling the motion of individual particles: in the transversal direction the motion is a generalization of skew Brownian motion; longitudinally the motion is an Itô process with paths depending on the transversal process. At an interface between layers where D takes two different values, the diffusing particles are more likely to go into the medium with the higher value of D. This feature is analytically characterized by the sample path properties of skew Brownian motion. The results are applied to give theoretical foundation to classical particle tracking methods for mass transfer in porous media.
H11C-0656
Eliminating kinetic effects on the pore size distribution as determined from water-retention curves
The procedure described requires some knowledge of a critical moisture content for percolation as described by the Moldrup et al. (2001) experimental results for a moisture content at which solute diffusion vanishes. This can be obtained experimentally by using N2 BET measurements or theoretically from the particle size distribution. Alternatively one can estimate the critical moisture content as the residual moisture content on a water retention curve. We use critical path analysis to find the saturation S dependence of the hydraulic conductivity from the pore size distribution inferred from a water-retention curve. As S is reduced towards the critical value we test our calculated K with K obtained by universal percolation scaling. When the latter formulation predicts the more rapid drop of K with decreasing moisture content, we assume that equilibration effects (as described in a previous publication) interfere with the interpretation that the water retention curve reflects only medium properties and renormalize the water retention by kinetic effects. We then use the inverse of this renormalization to extract a "true" pore size distribution.
H11C-0657
Landuse affects on Bankfull Discharge in Agricultural and Urban Regions in South Western Wisconsin
Many stream restoration projects are based on the Rosgen's classification system, which uses bankfull discharge to categorize streams. When regional curves or survey data are not available, bankfull discharge is determined by maximum annual flood recurrence intervals. The latter method is problematic as it requires gauging station data and assumes the bankfull discharge to be equal to the 1.5 year flood. The 1.5-year figure is based on an average from a large data set of multiple regions throughout the country, where regional trends may determine that discharges between 1.3-1.7 years may be more accurate. In Wisconsin there are major regional differences in stream networks and morphology, but no regional curves are available for these region. In addition, Wisconsin is one of the nation leaders in dam removal, which often requires restoration efforts afterwards. The objective of our research is to determine bankfull discharge using field techniques and compare them to the gauging station flow data for two regions in Wisconsin. One region is heavily agriculture, and the other is highly urbanized, and Lowlands. Our hypothesis is that regions have different agreement with bankfull discharge recurrence values and survey data, but similar drainage patterns. This research will enable restoration efforts to precede with higher success rates and indicate the significance of regional curve development.
H11C-0658
Modeling of Thin-Film Flows: Some Hydrologic Applications.
A potential mechanism to describe a very fast transport through an unsaturated porous media is a development of thin-film flows in air-filled fractures. Such films can transport fluid and contaminants over significant distances in a very short time, especially comparing to a conventional plug flow model. We obtain certain analytical solutions for a distribution of a contaminant in an idealized thin film. Also, we generalized an earlier developed hydrological model that represents a thin-film as a chaotic flow with one type of solitory waves developing on a surface.
H11C-0659
Spatial and Temporal Variability in Flood Conveyancing in a Semi-Arid Australian Catchment: Implications for Floodplain Deposition.
This study investigates the effect of spatial and temporal variability in flood generation and conveyance at a constricted tributary junction within a semi-arid catchment in north-eastern Queensland Australia. Flood discharge and rainfall records indicate that floods with a 5y recurrence interval occurred regularly in the period from 1972 to 1984. The floodplain inundation and flow velocities of several of these events are modelled using a one-dimensional flow routing model, HEC-RAS. For flood events dominated by one of the main tributaries, the Medway Creek catchment alone, floodplain inundation in the constriction occurred during a 1.5y equivalent event. In contrast, a 5y flood discharge is required to inundate the floodplain prior to the zone of valley narrowing. This is due to the abundance of secondary channels which increase the total channel capacity. 137Cs measurements of floodplain sediments indicated deposition rates of ~0.5 cm a year on average since peak fallout (~1964). 137Cs measurements also show that floodplain erosion (¡Ý 6 cm since fallout) has occurred within the zone of valley narrowing. It appears that the affect of flow concentration through this feature in the past has been local channel scouring thereby increasing channel capacity. Differences in elevation between the two major tributaries appears critical to the currently enhanced rate of floodplain deposition within the constriction reach, because it is more frequently inundated by slow-moving back-water flows from the Nogoa River.
H11C-0660
Characterizing the Response of an Unconfined Aquifer to Pumping with Borehole Ground Penetrating Radar
Paired measurements of water table elevation and water content profiles were collected within the combined zone of influence of three pumped wells during pumping and recovery. Water content profiles were measured using zero offset borehole ground penetrating radar (BGPR). This electromagnetic method gives high-resolution (25 cm) rapid (<10 seconds per depth) measurements. But, each water content measurement represents an average over a 1 m depth interval. To analyze the hydrologic response, a one dimensional water flow model was coupled with a BPGR instrument response model. The flow model predicted the water content profile with time, using the water table elevation as a time-varying lower boundary condition and a zero flux ground surface boundary condition. The hydrologic and petrophysical parameters in the flow and instrument model were simultaneously optimized with the Shuffled Complex Evolution Metropolis stochastic optimization algorithm using the difference between predicted and measured BGPR travel times. Results demonstrate that the hydrologic and petrophysical parameters are well constrained by calibration against measured BPGR travel times. Moreover, we sequentially estimated the hydraulic properties that apply during pumping and recovery, providing a field demonstration of hysteresis. The results also quantify both the timing and location of delayed drainage during pumping and recovery in an unconfined aquifer.
H11C-0661
Identification of groundwater contamination sources of nitrate and sulfate in shallow alluvial aquifers using a dual-isotope approach in an agricultural area
The elevated level of nitrate in groundwater is a serious problem in Korean agricultural areas. Yupori, a small agricultural area in Chuncheon (Korea), shows a rising level of NO3-N and displays multiple NO3-N sources from non-point and point sources in shallow aquifer groundwater. Numerous vegetable fields are located in the western part of the study area and fruit orchards dominate the landscape with only few vegetable fields in the eastern part of the study area. The source identification of groundwater contamination from overburden agricultural area was undertaken by analyzing hydrochemical data and stable isotopic compositions of dissolved nitrate and sulfate (¥ä15N-NO3-, ¥ä18O-NO3-, ¥ä34S-SO42-, and ¥ä18O-SO42-). The measurements of ¥ä15N- NO3- are in the range of 7.1 to 14.4¢¶ and the values of ¥ä18O-NO3- are in the range of -1.8 to 6.5¢¶. High ¥ä15N-NO3- values shown at low concentrations of nitrate in the eastern Yupori are characteristics of manure- derived nitrate and organic soil. The values of ¥ä34S-SO4-2 ranged from 2.9 to 9.9¢¶ and ¥ä18O-SO42- ranged from 2.5 to 4.7¢¶. At high concentrations of SO42- in the western Yupori, the value of ¥ä34S-SO42- are low around 3-4¢¶. The value of ¥ä34S-SO42- increased with decreasing SO42- concentration in the eastern Yupori. Groundwater quality and stable isotopic compositions of dissolved nitrate and sulfate seem to be significantly affected by agricultural land use pattern of the study site.
H11C-0662
Evaluation of Distributed Model Structures in Catchment Scale Modeling to Capture Heterogeneous Landscape Characteristics
The ability of a model to capture dominant ecological and hydrological processes is a prerequisite for the use of the model in studying impacts of landuse change on the water balance and nutrient fluxes from a watershed. However, in many cases, available model structures do not adequately represent processes of interest. In these cases, a pragmatic response is to revise the structure to better represent key processes. In this paper we outline a model application strategy designed to inject additional realism into a commonly applied model structure. Here we focus on the SWAT model in an application to the mesoscale (514 km 2) Wetter catchment, in central Germany. The catchment is characterized by a heterogeneous landscape structure and characteristics. The southwestern part is formed by a low mountain range with shallow soils over bedrock and steep slopes. Here lateral subsurface stormflow appears to be the dominant runoff generation process. The central and north- eastern regions of the basin are characterized by deep loess born soils and shallow slopes. We hypothesize that the much larger storage potential of the soils promotes vertical infiltration and storage, and that lateral runoff is much less significant. We utilize a variety of SWAT versions to evaluate the potential effects of this hypothesis on the capacity of the model to capture the measured runoff response. Our results indicate that the original SWAT- structure as well as the SWAT-G structure (which was applied to other low mountain catchments in Germany) are not able to acceptably represent the hydrograph. However, a hybrid of the two structures, specifically designed to reflect differences between the mountainous regions and the more gentle topography does result in a satisfactory representation of the hydrograph. The inclusion of elements from of both model structures (original SWAT and SWAT-G) seems to be the best way to reflect our hydrological process understanding, producing results which capture both the runoff response and the spatial variation in the mechanisms responsible for it.
H11C-0663
Estimation Of Groundwater Residence Times By A Multi-tracer Approach In A High Alpine Catchment Area, Switzerland
The groundwater flow paths and residence times are investigated to establish a model for a high alpine catchment area in the Swiss Alps. The study area is located in the periglacial zone with mean surface temperatures around 0° C. All springs in the study area have been mapped cartographically and several natural springs were examined in detail on physiochemical parameters. However, the major element composition alone could not give satisfying information to understand the hydrogeological setting in the catchement area. Therefore, a multi-tracer approach using chlorofluorocarbons (CFCs), sulfur hexafluoride (SF6) and tritium/helium (3H/3He) is taken to obtain further details on groundwater behaviour. CFCs (CFC-11, CFC-12 and CFC-113) concentrations showed a similar residence time for all but two sampled springs when we applied a piston-flow model to calculate residence times. Consistent results were obtained from CFC-12/CFC-113 ratios, supporting the applicability of a simple piston-flow model for the study area. Two springs contained much smaller CFCs concentrations compared to the other ten measured springs, indicating the existence of groundwater with longer residence times. These springs also showed high sulphate and calcium concentrations. Together with 3H/3He and SF6, the CFC based residence time can be calibrated. This multi-tracer approach allows a better understanding of groundwater behaviour and infiltration processes in a high alpine area.
H11C-0664
Estimation method of slip surface by ground surface displacement
After a landslide has occurred, it is important to take emergency countermeasures as soon as possible to prevent the damage from worsening. To do this, it is necessary to quickly identify the characteristics and size of movement of the landslide. However, conventional methods such as investigating the slip surface by taking core samples and monitoring the movement of land mass using vertical boring holes is time-consuming and involves risk, as the work must be carried out directly on the unstable landslide. This paper introduces a method of estimating the depth of the landslide slip surface using by ground surface displacement. The method involves dividing the landslide block and deriving a formula that approximates the line of the slip surface. Inputs for this method include the lengthwise section of the ground surface, displacement of ground surface, points of the scarp and tip of the landslide. We applied this method to several landslides and proved that the slip surface estimated by this method closely matched the actual surface determined by conventional methods, provided that measuring points were properly arranged. The results suggest that this method can estimate the slip surface of landslides. In future, it is necessary to improve systems of monitoring active landslide masses and methods of estimating their size in a quick, easy, and reliable manner to be practically applicable to disaster areas.
H11C-0665
Baseflow Recession Model Dependence on Drainage Basin Spatial Characteristics
The Natural Resource Analysis Center (NRAC) at West Virginia University (WVU) has developed an ArcGIS 9.x extension application called the Watershed Characterization and Modeling System (WCMS). WCMS is a GIS- based watershed analysis tool currently used by permit writers in the West Virginia Department of Environmental Protection (WVDEP) Divisions of Water Resources and Mining and Reclamation. WCMS utilizes drainage basin subdivisions consistent with the 1:24,000 NHD (National Hydrography Dataset) stream segments. The recent addition of the U.S. Environmental Protection Agency surface water model HSPF (Hydrological Simulation Program – FORTRAN ) to WCMS provides surface water quality modeling capabilities. Calibration of HSPF to representative drainage basins uncovered inadequacies in the groundwater outflow modeling component that produces recessionary streamflow. As is the case with many popular watershed models, HSPF includes its groundwater storage and outflow components within each subbasin water budget through the use of a relatively simple storage-outflow function. An examination of the groundwater flow behavior typical in mountainous West Virginia drainage basins shows that stream segment groundwater outflows have their source both within the immediate subbasin and from adjacent and upstream subbasins. Therefore, each subbasin water budget must include groundwater inputs from other subbasins to which it is hydraulically linked. To gain insight into these linkages, and to identify spatially dependent parameters important in modeling subbasin recessionary outflows, numerical experiments have been conducted on a representative drainage basin using the USGS MODFLOW groundwater model. The results support the conclusion that subbasin stream segment outflows partially originate from groundwater within adjacent and upstream subbasins, and that spatially dependent measures such as flow path distances and groundwater storage distributions within this hydraulically connected region are just as relevant as the local subbasin groundwater parameters in determining baseflow recession characteristics.
H11C-0666
Model selection criteria for flood frequency analysis
One of the main goals of flood frequency analysis is to estimate the design flood, namely, the discharge value corresponding to an assigned return period. Usually this problem is solved by fitting a suitable probability distribution to the observed peak flow data. However, the choice of the probabilistic model is often a relevant issue. This study aims at identifying an objective criterion for the selection of the most appropriate extreme value probability distribution. A relevant contribution to the subject of model identification is in the work by Akaike (1973), who proposes the use of the principle of maximum entropy for model selection. Later, Schwartz (1978) developed a similar idea in a Bayesian context, therefore formulating the Bayesian Information Criterion. Applications of model selection techniques within flood frequency analysis are rare. The objective of this study is to verify whether the model selection techniques proposed by Akaike and Schwartz work correctly when they are applied for identifying the probability distribution of extreme events. A comparison of these and others model selection techniques is carried out trough an extensive numerical analysis in order to check the performances of the considered methods when dealing with small sample sizes and highly asymmetric distributions.
H11C-0667
Fingerprinting Persistent Turbidity in Sheep Creek Reservoir, Owhyee, Nevada
Sheep Creek Reservoir near Owyhee, NV is historically a quality rainbow trout fishery. Persistent high-turbidity has been an issue since a major storm event in 2005 resulted in surface water runoff into the Reservoir. The high turbidity is adversely impacting the quality of the fishery. Initial turbidity measurements in 2005 were upwards of 80NTU and these numbers have only decreased to 30NTU over the past two summers. Field parameters indicate the turbidity is associated with high total suspended solids (TSS) and not algae. Five water samples collected from around the reservoir during June, 2007 indicated uniform TSS values in the range of 5 to 12mg/L and oriented powder x-ray diffraction(XRD) and transmission electron microscopy(TEM) analyses of suspended sediment shows very uniform suspended particulate mineralogy including smectite, mixed layer illite/smectite (I/S), discrete illite, lesser amounts of kaolin, sub-micron quartz and feldspar. Diatoms represent a ubiquitous but minor component of the suspended solids. Six soil samples collected from possible source areas around the reservoir were analyzed using both XRD and TEM to see if a source area for the suspended solids could be unambiguously identified. Soils on the east side of the reservoir contain smectite and mixed layer I/S but very little of the other clays. The less than 2 micron size fraction from soils collected from a playa on the topographic bench immediately to the west of the reservoir show a mineralogic finger-print essentially identical to the current suspended sediment. The suspended sediment probably originates on the bench to the west of the reservoir and cascades into the reservoir over the topographic break during extreme storm events. The topographic relief, short travel distance and lack of a suitable vegetated buffer zone to the west are all consistent with a primary persistent suspended sediment source from the west. Identification of the sediment source allows for design of a cost effective remediation plan that includes minimizing future loading of the reservoir with soils capable of producing extended turbidity.
H11C-0668
Assessment of Filter Materials for Removal of Contaminants From Agricultural Drainage Waters
Fertilizer nutrients and pesticides applied on farm fields, especially in the Midwest U.S., are commonly intercepted by buried agricultural drainage pipes and then discharged into local streams and lakes, oftentimes resulting in an adverse environmental impact on these surface water bodies. Low cost filter materials have the potential to remove nutrient and pesticide contaminants from agricultural drainage waters before these waters are released from the farm site. Batch tests were conducted to find filter materials potentially capable of removing nutrient (nitrate and phosphate) and pesticide (atrazine) contaminants from subsurface drainage waters. For each batch test, stock solution (40 g) and filter material (5 g) were combined in 50 mL Teflon centrifuge tubes and mixed with a rotator for 24 hours. The stock solution contained 50 mg/L nitrate-N, 0.25 mg/L phosphate-P, 0.4 mg/L atrazine, 570 mg/L calcium sulfate, and 140 mg/L potassium chloride. Calcium sulfate and potassium chloride were added so that the stock solution would contain anions and cations normally found in agricultural drainage waters. There were six replicate batch tests for each filter material. At the completion of each test, solution was removed from the centrifuge tube and analyzed for nitrate-N, phosphate-P, and atrazine. A total of 38 filter materials were tested, which were divided into five classes; high carbon content substances, high iron content substances, high aluminum content substances, surfactant modified clay/zeolite, and coal combustion products. Batch test results generally indicate, that with regard to the five classes of filter materials; high carbon content substances adsorbed atrazine very effectively; high iron content substances worked especially well removing almost all of the phosphate present; high aluminum content substances lowered phosphate levels; surfactant modified clay/zeolite substantially reduced both nitrate and atrazine; and coal combustion products significantly decreased phosphate amounts. For the 38 specific filter materials evaluated, based on a 60 percent contaminant reduction level, 12 materials removed nitrate, 26 materials removed phosphate, and 21 materials removed atrazine. Furthermore, 2 materials removed zero contaminants, 16 materials removed one contaminant, 17 materials removed two contaminants, and 3 of the materials removed all three contaminants. The most effective filter materials proved to be a steam activated carbon, a zero valent iron and sulfer modified iron mixture, and a surfactant modified clay. The findings of this study indicate that there are a variety of filter materials, either separately or in combination, which have the potential to treat agricultural drainage waters.
H11C-0669
Flow resistance in step-pool channels
Step-pools are characteristic bedforms that are common in steep mountain streams with gradients between 3% and 30%. The step-pool pattern plays a fundamental role in mountain stream hydraulics, developing the major portion of flow resistance. This flow resistance is essentially due to a loss of kinetic energy, dissipated by roller eddies that occur when water flows over a step rise and plunges into the pool below, creating a tumbling flow. An extensive laboratory experimental activity over a schematic arrangement of macro-roughness, represented by a regularly spaced stripe pattern, recently presented (Canovaro and Solari, 2007) has shown that when the macro-roughness is positioned according to an ‘optimal' spacing value flow resistance is maximum. A statistical analysis of a large amount of geometrical data about step-pool sequences observed in the field and reproduced in the laboratory suggests that this ‘optimal' spacing is close to what is frequently encountered in natural streams. Following such results both field measurements, concerning step-pool geometry and flow discharge, and numerical simulations have been started. The aim of this investigation is to validate the hypothesis that step-pool streams evolve towards a morphology that develops maximum flow resistance. Canovaro, F. & Solari, L. (2007) "Dissipative analogies between a schematic macro-roughness arrangement and step-pool morphology". Earth Surface Processes and Landforms. (Accepted)
H11C-0670
Global Sea Level Variation Due to Water Impoundment in Artificial Reservoirs
The causes for the modern global sea level (GSL) rise are investigated and debated in the era of global warming. A negative contribution, namely that due to water impoundment in artificial reservoirs, has long been suspected to be a significant budget item. This water impoundment constitute by far the largest anthropogenic hydrological change in terms of the water volume involved, but ironically only very incomplete information exists in compiled form, hence exactly how much of this water is stored behind dams on land has been shrouded in uncertainty. This has become a critical missing piece in the effort to understand and close the budget ¡§puzzle¡¨ of the observed GSL rise. Here we report an in-depth compilation of artificial reservoirs and their accumulation scenario; we assert that to date there is about 10,000 km3 of water impounded on land. This is equivalent to the total atmospheric moisture, or 10 times the world's biological water. In terms of GSL, it corresponds to a drop of about 3 cm. This happened in the last half century, giving a mean GSL drop rate of about 0.5 mm/year, comparable in magnitude to the significant natural contributions such as melting of land ice.
H11C-0671
Examining Sources of Water in Springs, Wetlands, and Oases in Coachella Valley
The All American and Coachella Canals were constructed in the 1930's to supply irrigation to the Imperial and Coachella Valleys. The diverted Colorado River water is the only source of water in the valleys, and an extensive series of wetlands have been created by leakage from the unlined portions of these canals. Although the wetlands were natural features prior to canal construction, their extent was limited due to minimal recharge. As of December of 2006 these canals have been completely lined which is predicted to decrease the flow to the wetlands and may affect the flora and fauna they have come to support. Samples were collected prior to the lining of the canal from June to October 2006 from several springs and well locations downgradient from Coachella canal to assess their geochemical and isotopic signatures for comparison to canal and native groundwater sources. Analysis of stable isotopes identified three distinct groups of water: one group consisting of nearly pure Canal water with delta 18O ranging from -11.3 to -11.7 per mille and delta 2H ranging from -84 to - 95 per mille, a second group consisting of nearly pure native groundwater with delta 18O ranging from -7.3 to -8.7 per mille and delta 2H ranging from -59.5 to -71 per mille, and a third group consisting of various mixtures of Canal and native groundwater with delta 18O ranging from -8.7 to -11.1 per mille and delta 2H ranging from -80 to -91 per mille. Minimal isotopic change has occurred in a sampling campaign conducted June, 2007. Continued monitoring of the isotopic and hydrochemical signature of the waters will reveal how quickly they might evolve toward that of native groundwater as a direct result of decreased recharge from the now lined Coachella Canal.
H11C-0672
Improving lakebed sediment quality in an urban estuary, Presque Isle Bay, Lake Erie, USA
Presque Isle Bay, Lake Erie, is a microtidal freshwater estuary on the North American Great Lakes. It is one of 40 remaining environmental Areas of Concern (AoCs) on the Great Lakes that have one or more water, habitat, or sediment quality impairments as defined by the International Joint Commission. In-situ natural capping using sediment from to-be-remediated watersheds and other sources is being considered as the most feasible means of remediating contaminated sediments in the estuary. A multi-decade sediment budget shows that, when localized anthropogenic effects are accounted for, the estuary net-accumulated sediment over time from three major sources: the Lake Erie littoral system (20%), streams (25%), and bank erosion and bluff recession (41%). The non-stream sources supply environmentally clean sediment from ancient coastal deposits along the shoreline, and from the modern littoral system. However, organic and metallic contaminants are supplied by streams and run-off and remain a remediation challenge. From a geological perspective, natural capping of contaminated sediment over the next several decades is a viable solution for the majority of the bay. The mechanism may not work effectively in all areas because approximately 25% of the bay floor is moderately net- erosional or accumulates sediments very slowly.
H11C-0673
Development of a Hydrologic Model to Assess the Feasibility of Water Leasing in the Middle Rio Grande Basin
The demand for water in the southwestern United States has increased in tandem with a rapid growth of population over the past 50 years. With ever increasing demands being placed on available water supplies, improving water management becomes crucial to the sustainability of the region's water resources. The National Science Foundation (NSF) Science and Technology Center (STC) for the Sustainability of semi-Arid Hydrology and Riparian Areas (SAHRA) is interested in the feasibility of water leasing as a method for more efficiently distributing water among competing users. Economists working on the project will run water leasing simulations in an auction-type environment to understand the pros and cons of water leasing in a free market system. To include hydrologic processes in the water leasing simulations, an MMS-PRMS hydrologic model was developed for a portion of the Middle Rio Grande Basin (MRGB) near Albuquerque, New Mexico. This portion of the MRGB contains a detailed network of diversions, canals, and drains that transport water through the system. In order to capture the complexity of the system, the model was developed using the highest resolution information available. In the model, each Hydrologic Response Unit (HRU) is represented as a trader. To achieve the 15 trader limit desired by economists, the model structure was simplified using two basic constraints; 1) HRUs having a common source and point of return to the river were lumped; and 2) HRUs with less than 20% agricultural land use were omitted from the auction simulations. A new Evapotranspiration (ET) module was implemented in the model to better estimate ET associated with different crops. Modules were also developed so that the end user has the flexibility to manipulate water deliveries based on crop type and land use. The MMS- PRMS model for the MRGB should help economists determine if the incentive to profit by selling or buying water can make more efficient use of the available water supply.
H11C-0674
Infiltration History and Spatial Variability Derived from Chloride Mass Balance
Chloride mass balance was applied to drill cuttings collected from the unsaturated zone surrounding the Yucca Mountain Project. Samples correspond to four Nye County Early Warning Drilling Program boreholes where air was used as the drilling fluid to preserve sample integrity. Infiltration dates before present and pore velocities were calculated using a range of annual chloride deposition rates obtained from the literature. The lower chloride loading corresponds to contemporary values, and the upper loading corresponds to an attempt to correct for either past greater chloride deposition or a past higher precipitation with chloride concentration remaining constant. In each borehole, pore velocities present two distinct slopes corresponding to different infiltration regimes. The first one, near the surface, presents the slowest infiltration rate. The second pore velocity corresponds to a past wetter period (late Pleistocene to early Holocene) with much faster pore velocities. Results indicate that pore velocities among the boreholes differ at most by a factor of approximately 3.5. Boreholes located in areas of little or gradual slope present faster infiltration rates than those in areas of greater slope. Borehole NC-EWDP-22S, near Fortymile Wash east of Yucca Mountain, exhibits the most rapid pore velocities where as boreholes further from the wash demonstrate lower velocities. These results denote the effects climate change, and runoff and run-on at the surface have over infiltration rates in arid regions.
H11C-0675
Evaluating Channel Head Conditions for Environmental Impact Assessment in Northwestern Sonoma County, California
Erosion and sedimentation have been identified as processes significantly affecting water quality in northern California Coast Range watersheds. These watersheds, including the Gualala River watershed in northwestern Sonoma County, have been designated as having water quality impaired by sediment under provisions of the Clean Water Act Section 303(d). A study was performed to estimate potential increases in erosion rates resulting from proposed vineyard development of ridge top forestland in the Gualala River watershed. The study area has an extensive history of logging, with substantial ground disturbance from tractors. The study area is characterized by flat ridge tops with steeply incised drainages shaped by debris slides, rock slides and earth flows. Jurassic age sedimentary and meta-sedimentary rocks of the coastal and central belt Franciscan formation comprise the underlying bedrock. Channel head development and advancement has long been understood to play a key role in sediment delivery and is possibly the most sensitive to changes in the external factors such as changes in climate or land use (Dietrich and Dunne 1993). Quantifying the amount of sediment contributed by potential channel head incision and/or initiation is an objective of environmental analysis for the project. Field surveys were performed during the field seasons of 2005 and 2006 to acquire measurements of channel head locations and slope, channel dimensions and substrate associated with the proposed development sites. Analysis of this field data, including the use of ArcGIS, allowed us to examine the local relationships between variables that influence channel initiation. Variables considered include drainage area, slope, soil type, geology and vegetation. An initial analysis of a selection of area-slope data failed to produce an inverse area-slope relationship as has been found in previous studies by Montgomery and Dietrich (1988). A more complete evaluation of the entire data set is presented here.
H11C-0676
Water Well Record Studies of Geologic History in Indiana Including Examples of Geomorphology of Buried River Valleys, Geomorphic Expression of Earthquake Faults, and Deep Groundwater Flow Paths.
The Indiana Department of Natural Resources water well record data base is used to produce maps exploring aspects of the geologic history of the state with a emphasis on East Central Indiana. This study includes the geomorphology of buried preglacial valleys, the geomorphic expression of possible fairly recent fault lines in East Central Indiana, and suggestion for the deep groundwater circulation paths. An excellent region to study geology and groundwater configuration the Midwest is East Central Indiana as there is are almost equal numbers of glacial and bedrock wells ranging over 300 feet depth. There is over 600 feet of relief on the bedrock surface with deep glacial drift in two distinctly different buried valleys, and two distinctly different till plains. The focus of this work uses over 33000 UTM located water well records from a 17250 km2, 13 county area. Over several years we have studied details of bedrock topography, bedrock and glacial geology and groundwater productivity, horizontal and vertical flow using static water level information, buried preglacial cavern systems, and applications to groundwater modeling. In the southern more maturely developed Anderson River valley there are larger numbers of deep glacial wells in many tributaries while in the north deep wells are restricted to just the deep course of the Teays River valley with less glacial productivity in the shorter less mature tributaries. To the north there many indications of a paleokarst history with sinkhole entrances on the plateaus above the Teays and outlet into the Teays tributaries. Details of the buried bedrock surface show a linear N28E trend parallel to several bedrock faults and also to recent stream valleys. Other studies by the author have shown the dominant Paleozoic bedrock fracture directions in this area to be N78E and N12W. Therefore the N28E trend is distinctly different and can be related to trends seen in active earthquake areas in northwest Ohio and southwest Indiana. The possibility of late Cenozoic seismicity related to other activity in the Midwest will be summarized. Maps comparing static water levels in shallow versus deep wells show areas of vertical downward or upward gradient which indicate three dimensional flow directions. The major deep groundwater recharge from the till plains moves to areas of upward gradient in the Wabash and Whitewater River valleys rather than other vallies on the till plains. The interpreted paths allow for discussion of ground water travel times.
H11C-0677
Statistical and Spatial Analysis of Borderland Ground Water Geochemistry
The border region is growing rapidly and experiencing a sharp decline both in water quality and availability putting a strain on the quickly diminishing resource. Since water is used primarily for agricultural, domestic, commercial, livestock, mining and power generation, its rapid depletion is of major concern in the region. Tools such as Principal Component Analysis (PCA), Correspondence Analysis and Cluster Analysis have the potential to present new insight into this problem. The Borderland groundwater is analyzed here using some of these Multivariate Analysis methods. PCA is applied to geo-chemical data from the region and a Cluster Analysis is applied to the results in order to group wells with similar characteristics. The derived Principal Axis and well groups are presented as biplots and overlaid on a digital elevation map of the region providing a visualization of potential interactions and flow path between surface water and ground water. Simulation by this modeling technique give a valuable insight to the water chemistry and the potential pollution threats to the already water diminishing resources.
H11C-0678
Numerical Modeling of Dam Break/Removal Hydraulics and Morphology
Dam break hydraulic is drawing increasing attention due to the potential occurrence of extreme hydrological events as result of climate change and its catastrophic nature (Cao et al, 2004). On the other hand, many dams have been removed and more are under consideration of removal (Cui et al., 2006). Both dam break and dam removal have the same essential properties such as rapid varying flows and discontinuities, releases of sediment from reservoir to downstream etc. A numerical model that couples the water flow and sediment transport processes is developed to simulate the hydraulics and the induced sediment transport and morphological evolution following dam break/removal. The systems of equations are reformulated in conservation form to correctly capture the solutions. Four numerical schemes including slope-limiting second- order upwind methods (Roe's and HLLC) and center method (Kurganov-Tadmor), and composite method (LWLF4) are tested under different hydrological events. A third-order total variation diminishing Rugne-Kutta method is used for the time integration. The numerical simulations give insight into the processes and consequences of releases of reservoir flow and sediment which is important for economics, safety, and environmental ecology. Computed results are compared with experimental or published numerical solutions to examine the limitations of the numerical schemes.
H11C-0679
Evaluation of Ensemble Meteorological Forcing in a Distributed Hydrological Model: Decomposing the Nonlinear Basin Response
In this study, we perform a sensitivity study of a distributed hydrological model using ensemble meteorological forcing, which can contribute to the development of a fully- coupled hydrometeorological prediction system. To do so, we couple the Advanced Research Weather Research Forecasting (WRF) model to the TIN-based Real-time Integrated Basin Simulator (tRIBS) hydrological model in an off-line mode. Our particular case study focuses on a warm-season mesoscale convective storm event occurring in the Four Corners region of the Southwest US during the late monsoon season of September 2003. We are primarily interested in assessing the non-linearity in the simulated hydrological response for a set of different rainfall products during a large, semiarid flood event in Upper Rio Puerco, New Mexico. We test three different rainfall products: (1) a simple multiplicative method to rescale observed NEXRAD fields; (2) a simple rescaling of the simulated WRF precipitation fields; (3) and an ensemble of WRF simulations generated using different initial soil moisture condition. For each case, we determine the degree of nonlinearity observed in the simulated streamflow as a measure of the hydrologic sensitivity to precipitation forcing. For the WRF ensemble runs, we assign a range of soil moisture perturbations uniformly across the model domain. The results from the various experiments are statistically analyzed in order to isolate the hydrologic impacts of changes in precipitation character (intensity, distribution and frequency) and initial soil moisture. Our results quantify the amount of nonlinearity that is due to the imposed changes in precipitation or soil moisture character. For many of our results, the hydrologic system amplifies small spatial and temporal errors in rainfall input introduced either through the ensemble method or via the sensitivity analysis. This study provide insights to the generation of ensemble WRF rainfall forcing and its subsequent impact on warm season flood forecasting in the North American Monsoon region.
H11C-0680
A Portable Membrane-based Gas Sampler for Gases Dissolved in Groundwater
The complications that arise while collecting, transporting and storing groundwater for trace gas analysis have prompted a new approach, which uses membrane technology to obtain a gas sample from the water stream, in the field. This portable groundwater sampler uses a microporous hydrophobic membrane to collect a finite volume of gas, which is in solubility equilibrium with a time-invariant stream of water. Samples of the gas volume can be analyzed to determine original water concentrations for virtually any dissolved gas. The sampler does not require the use of compressed inert gas and its power consumption is minimal. During the development stages, N2, Ar, O2, CO2 and SF6 were sampled and measured using gas chromatography to evaluate the equilibrium condition and confirm the equilibration time, which was initially gauged using a pressure transducer. Equilibration studies were conducted in the laboratory and at Black Rock Forest, a field site near the Lamont Campus of Columbia University. The time required to achieve solubility equilibrium depends on the dissolved gas content and the water flow rate; 100 cc of gas can be collected, from water in equilibrium with the atmosphere, at low flow (ca. 2 L min-1) in less than 1 hour. The initial results demonstrate that gauge pressure is a good proxy for solubility equilibrium, and that diffusion can fractionate the gas ratios during rapid mass transfer as indicated by rapid pressure changes.
H11C-0681
Corps Water Management System (CWMS) Decision Support Modeling and Integration Use in the June 2007 Texas Floods
The U.S. Army Corps of Engineers Corps Water Management System (CWMS) is a comprehensive data acquisition and hydrologic modeling system for short-term decision support of water control operations in real time. It encompasses data collection, validation and transformation, data storage, visualization, real time model simulation for decision-making support, and data dissemination. CWMS uses an Oracle database and Sun Solaris workstations for data processes, storage and the execution of models, with a client application (the Control and Visualization Interface, or CAVI) that can run on a Windows PC. CWMS was used by the Lower Colorado River Authority (LCRA) to make hydrologic forecasts of flows on the Lower Colorado River and operate reservoirs during the June 2007 event in Texas. The LCRA receives real-time observed gridded spatial rainfall data from OneRain, Inc. that which is a result of adjusting NexRad rainfall data with precipitation gages. This data is used, along with future precipitation estimates, for hydrologic forecasting by the rainfall-runoff modeling program HEC-HMS. Forecasted flows from HEC-HMS and combined with observed flows and reservoir information to simulate LCRA's reservoir operations and help engineers make release decisions based on the results. The river hydraulics program, HEC-RAS, computes river stages and water surface profiles for the computed flow. An inundation boundary and depth map of water in the flood plain can be calculated from the HEC-RAS results using ArcInfo. By varying future precipitation and releases, engineers can evaluate different "What if?" scenarios. What was described as an "extraordinary cluster of thunderstorms" that stalled over Burnet and Llano counties in Texas on June 27, 2007, dropped 17 to 19 inches of rainfall over a 6-hour period. The storm was classified over a 500-year event and the resulting flow over some of the smaller tributaries as a 100-year or better. CWMS was used by LCRA for flood forecasting and reservoir operations. The models accurately forecasting the flows and allowed engineers to determine that only four floodgates needed to be opened for Mansfield dam, in the Chain of Highland lakes. CWMS also forecasted the peak of the flood well before it happened. Smaller rain storms continued for a period of weeks and CWMS was used throughout the event calculating lake levels, closing of gates along with a hydro-generation schedule. http://www.hec.usace.army.mil
H11C-0682
Long-Term Springflow Reconstructions Based On Instrumental And Tree Ring Climate Records In The Missouri Ozarks
To manage fresh water sustainably it is important to understand the variability of streamflow over time. Instrumental and gauged records are usually less than 50 years long and are unlikely to capture the full range of variability. Tree-ring reconstructions of streamflow are known to provide a valuable indices for past hydroclimatic trends. However, little is known of peak and low-flow attenuation of flow in karst systems, and less is known about the use of tree rings to reconstruct long-term changes in karst features such as springs. Conceptually, since underground spring (karst) systems may attenuate annual peak, high, and low flows normally shown in surface flow, springs may serve as a better proxy for flow and response time (i.e. lag time) between hydroclimatic conditions and annual tree growth. Additionally, the flows of large springs are directly affected by climate on longer time scales. This work developed spring flow reconstructions using five long-lived tree species including white oak, post oak, shortleaf pine, eastern redcedar and bur oak. Tree ring chronologies were compared to long term annual water yield records from the Current River and Big Spring near Van Buren, Missouri for the time period of 1922 through 2002 based on annual average daily flow in cubic meters per second. Average annual flow during this time period was over 56 and 12 cubic meters per second for the Current River and Big Spring respectively. Annual peak and low flow periods were substantially attenuated in the Big Spring system by approximately 20 % relative to the surface flow system of the Current River. Analysis of Variance indicated a close relationship between river flow and spring flow (R2 = 0.86). Coefficients of determination for tree ring correlations to stream flow were < 0.50 for all preliminary analyses. Continued analyses including smaller stream and spring data sets will be compared to annual tree ring increment. Different classes of springs based on their elevation, stratigraphy, flow rates, and other karst features will be modeled with both instrumental and tree ring climate data. The long-term (> 5 years) climatic response and modeling of spring flows will result in the improved ability to differentiate between climate affects and land use changes in karst systems thereby better equipping land-use managers to make sound decisions facing future population, land use, and climate change scenarios.
H11C-0684
Sources of Nitrate to Tucson, Arizona Groundwaters.
The quality of groundwater is of major concern in the Southwest where water resources are scarce and we highly depend on groundwater for domestic use. Due to adverse health effects, waters with high nitrate concentrations (>45 mg/L) have been banned for domestic use by the Environmental Protection Agency. Furthermore, nitrate contamination is the leading cause for removing wells from drinking water consumption in Arizona and the United States. Therefore, it is important to consider the different sources and possible processes affecting nitrate concentration. Many studies have shown that anthropogenic sources such as agricultural fertilizers and waste water have been the dominant sources of nitrate contamination. Others have attempted to quantify the natural contributions. In this study, we focus on groundwater beneath the Tucson, Arizona basin where agricultural practices are not significant and waste water is allowed to infiltrate and recharge ground waters. We assume our groundwater to be a mixture of infiltrated rainwater, waste water and Central Arizona Project (CAP) water. We analyzed ground water samples collected along a several transects: 1) along an established flow path and 2) along two cross-sections downstream from a waste water treatment plant. In addition, surface water samples were collected from ephemeral washes during rain events, from a waste water dominated stream and from the CAP. Preliminary nitrate data show some fluxes along the first transects with an overall increase downstream (from 10 to 18 mg/L with a peak of 43.8 mg/L. In the two cross-sections downstream from the waste water, the nitrate concentrations doubled down gradient (from an average of 38 to 79 mg/L). In both transects, concentrations were highest in the middle (61 and 237 mg/L) and decreased sideways. These perplexing trends either decreasing or increasing along the flow paths cannot be explained based on geochemical concentrations alone. We are awaiting key isotopic data (d15N and d18O of nitrate). Thanks to the distinct isotopic signatures of our source waters, this data will allow us to tease apart the nitrate sources between anthropogenic and natural processes.
H11C-0685
Uranium Geochemistry in Hypersaline Soda Lakes in Eastern Mongolia
Extremely high concentrations of uranium were discovered in water samples from hypersaline soda lakes in eastern Mongolia. The origin and fate of uranium in these lakes was examined using geochemical analyses and modeling, using samples collected from five lakes, six wells and one stream. Samples were analyzed for strontium and uranium isotopes, cations and trace metals, anions, alkalinity, and unstable field parameters. The lakes are small, shallow (<1Km2, <1m) and terminal; their size fluctuates seasonally and they periodically completely desiccate. The region is characterized by rolling semi arid grassland steppe covered by a thick loess deposit of unknown thickness that is underlain by Neogene rhyolite. A typical groundwater in the field area is alkaline (pH = 7.9, 10.7 meq alk/L), 4.4 ° C, with an average T.D.S. of 1500 and low calcium concentration (20 ppm). A strong linear correlation was found between groundwater and lake water chlorine to bromine ratios implying groundwater discharges to lake water and is subsequently evaporated. Evaporation is intense with lake waters having average chlorine concentrations 300 times that of well waters. Uranium in well samples is higher than typical for shallow groundwaters (7-101ppb) suggesting discharging groundwater as a probable source of uranium in lake water. Concentrations of uranium in lake water ranges from 57-14,900ppb making these lakes possibly the highest naturally occurring uranium concentration reported. Lake water alkalinity is strongly correlated to uranium abundance suggesting uranium is complexed with carbonate as the aqueous species UO2CO3. Consequently, the extremely high alkalinity of the most alkaline lake (pH = 9.8, 1288.8 meq alk/L) also has the highest uranium concentrations. Stable strontium isotopes were used to assess the degree of water rock interactions and the presence of 90Sr was checked for to test the possibility of input of nuclear fallout. 90Sr was not detected in lake water samples suggesting the high uranium is of natural origins. A large difference in the 87Sr/86Sr ratio was found between groundwater and lake water samples. Groundwater samples displayed large variation in the 87Sr/86Sr ratio (0.70612-0.709776) whereas lake water samples averaged a high radiogenic ratio (0.709432). The large variation in the strontium isotopes in groundwater samples suggests varying degrees of water rock interactions, however the least radiogenic samples likely are derived from interaction with the young rhyolite. The strontium isotopes of the lake water samples are likely most affected by windblown sediment of continental sources.
H11C-0686
Numerical Simulation of Water Distribution in Plenum Within the Inclined Plate Settler
Inclined plate settlers are generally considered as a substitute for conventional sedimentation or clarifiers used in municipal water and wastewater treatment plants. The inclined plate settlers are generally considered for water and wastewater treatment when an upgrade is needed or when there exists a high overflow rate and less available land area. The principal feature of inclined plate settlers compared with conventional sedimentation is increasing the particle settling velocities with self cleaning capabilities and reducing the overall settling tank surface area. Inclined plates are usually arranged at an angle where the settled solid particles will slide by gravity and be deposited in the solid collection zone. The plates are found to perform best when they are arranged at 55 degree angle. One major problem associated with inclined plates is equal distribution of water flow in plenum. To address this problem, we used a typical inclined plate sedimentation tank design and performed three-dimensional numerical flow simulations by focusing on the plenum area by utilizing computational-fluid-dynamics (CFD) programming. Through these simulations we will show that an unequal water distribution in plenum will highly affect the particle settling efficiency in the inclined plate settler system. Additional simulations will be performed under varying flow patterns until an equal water distribution in plenum is accomplished and hence an optimum tank design will be identified.
H11C-0687
Slope instability risk at North part from State of Colima, Mexico analysing the hydrology, topography and erosion of deposits
Slope instability is presented each year in Colima State during rain season ( May to November). Here we show description and analysis of the principal factors that originate risk to the population that live especially in the North part of the Colima state due to these geological phenomena. The hydrology of the region will be presented to calculate the hydrological balance. Analysis of the topography and erosion of the state will be described here to present a zonification of the areas where the instability risk will be dangerous to the population of the state. Colima state is located in the central western part of Mexico limited by the Pacific Ocean on South and it is surrounded by the Jalisco and Michoacan States. It is located between the Trans Mexican Volcanic Belt and the Sierra Madre del Sur Provinces. The Colima Volcano is located in the northern part of the state. Physiographical the state is characterized to have 50.5 % Mountain range, 23.4 % Plain, 14.6 % Valley, 9.3 % Hill and 2.4 % Plateau. More than 600,000 inhabitants are living in an area of about 5,542.74 km2. The weather is influenced principally by the mountain range relief which is covered at North and West of the state where the high precipitation occurred, high elevation and cold temperature is found there. These factors contribute to accelerate the instability of materials deposits in the North part of Colima as here presented.
H11C-0688
Characteristics of Sediment Load Dynamics: A Nonlinear Pattern Recognition Approach
Adequate knowledge of the dynamic characteristics of sediment load in rivers (and channels) is important for studies of river morphology, reservoir sedimentation, soil and water conservation planning, water quality modeling, and design of erosion control structures. Although numerous variables contribute to the occurrence and movement of sediment load (e.g. water flow, land use, sediment concentration, particle size and shape), their levels of influence are often significantly different. Reliable determination of the dominant variables is, therefore, necessary for modeling and prediction purposes, especially from the viewpoints of model complexity and data collection. To this end, an attempt is made in the present study to investigate the utility of a nonlinear dynamic pattern recognition approach, which provides reliable information on the ‘extent of complexity' of the underlying dynamics. Such an approach involves two steps: (1) representation of the multi-variable dynamic system through reconstruction of the available single- or multi-variable data series; and (2) determination of the complexity of the system (defined especially in the context of variability of relevant data) using a neighbor searching procedure. In order to study the general utility and effectiveness of this approach for river systems, sediment load and other river-related data from a large number of sediment gaging stations around the United States (representing different geographic regions, climatic conditions, river sizes and complexities, and land uses) are analyzed.