H22A-01
Hydrological Parameter Estimation for Ungauged Basin Based on Satellite Altimeter Data and Discharge Modeling. A Simulation for the Caqueta River (Amazonian Basin, Colombia)
The main objective of this paper is to review the usefulness of altimetric data in ungauged or very poorly monitored basin. It is shown that altimetric measurements can be combined with a single in-situ gauge to derive a reliable stage-discharge relationship upstream from the gauge. The Caqueta River in the Colombian Amazon Basin was selected to simulate a poorly monitored basin. Thus it was possible to derive the stage-discharge relationship for 13 "virtual gauge stations" defined at river crossing with radar altimetric ground tracks. Stage measurements are derived from altimetric data following the methodology developed by Leon et al. (2006) . Discharge is modeled using PROGUM - a flow routing model based on the Muskingum Cunge (M-C) approach considering a diffusion-cum-dynamic wave propagation (Leon et al., submitted) using a single gauge located downstream from the basin under study. Rating curve parameters at virtual stations are estimated by fitting with a power law the temporal series of water surface altitude derived from satellite measurements and the modelled discharges. The methodology allows the ellipsoidal height of effective zero flow to be estimated. This parameter is a good proxy of the mean water depth from which the bottom slope of the reaches can be computed. Validation has been conducted by comparing the results with stages and discharges measured at five other gauges available on the Caqueta basin. Outflow errors range from 10% to 20% between the upper basin and the lower basin, respectively. Mean absolute differences less than 1.10 m between estimated equivalent water depth and measured water depth indicates the reliability of the proposed method. Finally, a 1,2 x 10-4 m.m-1 mean bottom slope has been obtained for the 730 km long reach of the Caqueta main stream considered.
H22A-02
Observations On Some Upper Amazonian Wetlands of Southeastern Peru
Upper Amazonian wetlands represent little studied, poorly understood, and grossly under protected systems. Scientific investigation of Amazonian wetlands is in its infancy; nor is there much known about their ecological services. Regionally, wetlands form a ubiquitous and significant component of floodplain habitat fed by perennial springs as well as overland runoff. Locally, wetland vegetation forms bewilderingly complex vegetation mosaics that seem to be governed by local topography and hydrology. Drawing upon intensive field campaigns and remotely sensed imagery, we summarize the results and experiences gathered in wetlands of southeastern Peru.
H22A-03
Obtaining drainage directions in flooded areas: a new burning approach
Drainage direction extraction from a Digital Elevation Model (DEM) is becoming a current practice in hydrological studies. Nevertheless, these models are not free of errors and problems may appear along the process. A particular case of error occurs in flat areas caused by inundated areas. In these areas, it is difficult or impossible to identify the exact drainage direction without another source of information. In these cases, it is recommended the execution of corrections in the DEM by using methods such as stream burning (SB). But as it is demonstrated in this paper, there are situations where the use of SB methods is not enough to achieve good drainage directions maps and basin delineations. This paper aims to present a method to obtain drainage directions and consequently more accurate watershed information in flooded areas close to rivers. In this new method the procedures are similar to the ones adopted in the standard SB method. The difference between them is the combination of a classified radar image to the vectors of rivers. In this cense, the DEM is burned twice: in the main rivers with the vectors and in the inundated areas with the classified image. A potential equation is used to vary the deepness burned in each pixel representing the inundated area in the classified image according to the distance of the vectors. In the example, it is used a classified composition map of two JERS-1 images. Different combinations of classes were evaluated and the outputs were compared to previous studies of the same area and validated with the interpretation of the original JERS-1 images. The results demonstrated that the new method offers a better accuracy in obtaining drainage directions and watershed information than the traditional SB methods when dealing with this sort of situation.
H22A-04
Use of Precipitation - Runoff Models to Generate Hydrologic Scenarios in a High-altitude Andean Basin of the Ecuadorian Amazon Region. Case study of the Quijos River Basin.
Little is known of the hydrology and meteorology of the expansive Andean Amazon region in South America, which extends for approximately 600.000 Km2 and represents around the 10% of the total Amazon region. Climatic processes that occur in the Andean part of the Amazon influence the middle and lower parts of the Amazon Region. Consequently, there is a need to understand the hydro-climatic characteristics in the high lands of the Andean Amazon. Understanding hydrologic processes in the Andean Amazon is challenged by the lack of hydro meteorological data at all levels. Especially challenging is the absence of data at the appropriate scale for adequate calibration and verification of mathematical models, mainly for understanding precipitation - runoff of high altitude watersheds located on the western most part of the Amazon. The study area is located on the upper part of the Napo River named the Quijos river basin after the junction of the Oyacachi River with a surface area of about 2.500,00 Km2. It is composed mainly of high altitude lands named Paramo, Andean grass lands, primary cloudy forest known for their high water retention and regulatory capacity. The models used in the Quijos river basin in the upper part of the Amazon region of Ecuador are precipitation-runoff models widely used around the world. The Simulator for Water Resources in Rural Basins - Water Quality (SWRRBWQ ) (Arnold et. al. 1990, Williams et. al. 1985), works on a daily time steps basis with daily values of meteorological data both observed in the field or generated by the model, and by sub diving the main basin into a suitable number of sub basins with a meteorological station in it The second model used is the Hydrologic Modeling System from the Hydrologic Engineering Center which is a precipitation - runoff model run at a daily basis as well. Input data sets are basic climate data as precipitation, evapotranspiration, temperature, relative humidity basin wide at daily basis; land cover, soil type, soil characteristics, hydrographic characteristics, as well as registered discharge information in several control points of the basin, that were used for calibration purposes. Several runs of the models were done in order to assess parameter sensibility of the models using appropriate parameter for each case. Calibration for the two models were done for a period where enough information exists even though the time record for verification purposes is well ahead of time so it is assumed that basin wide conditions have not change in time. Three hydrologic scenarios for future discharge prediction based on conservation policies, urbanization, deforestation, or land use change on the area were generated by using HEC-HMS model for the January 1984 - December 1987 period because of its better performance in comparison to the SWRRBWQ model. Scenarios one and two showed almost no difference with the original discharge but scenario three showed an increase in water discharge with time. Results show that in high altitude basins the HEC-HMS performs better than SWRRBWQ model in determining mainly peak discharges but differed in reproducing the total volume of run-off, keeping a good agreement to reproduce seasonality patterns of water discharge. Better information of basin wide characteristics like soil antecedent moisture conditions, land cover, and surface albedo during the calibration period is needed in order to improve model results mainly in volume discharge.
H22A-05 INVITED
Review of the Isotope Aided Studies on the Water Balance of the Amazon Basin
Early surveys of the isotope composition of precipitation throughout the Amazonian region, conducted by the GNIP program, revealed the absence of the expected Rayleigh depletion of the heavy isotopomers from the coast inland which would have resulted from the rainout along the trajectory. This was interpreted to be due to the re- introduction of the moisture into the atmosphere by transpiration and thus suggested that the isotope survey could verify the hydrological models, and further monitor any change in the water balance resulting from changes in the ecological structure, in particular deforestation. This required a closer look at the eco-hydrological processes at the lithosphere/ecosphere/atmosphere interface as they affect the isotopic composition of runoff and the evapo-transpiration flux. An observed increase of the d-excess parameter of precipitation from Belem to Manaus and Izobamba further indicated that evaporation from open-surface water also contributed to the moisture recycling in the basin ; the site of this effect, whether from canopy interception or flooded wetlands remains under investigation. The amount of the atmospheric moisture is a direct reflection of the water balance in the atmosphere; the resultant precipitation depends, in addition, on the dynamic structure of the atmospheric boundary layer which is also affected by ecological changes on the surface which affects among others the albedo, surface roughness and convectivity. Due to the limited amount of data on the isotope composition of the atmospheric vapour, one was limited so far in the quantitative interpretation of the isotopic data in terms of the effect of changes in the ecological structure on the water balance and precipitation pattern in Amazonia. The review will outline the new possibilities opening up from the recent advances in direct measurement of the isotopic composition of vapour and the MIBA data set. Suggestions for a continuing monitoring program will then be outlined.