H51C-01
The National Airborne Field Experiment 2006 (NAFE'06) Dataset
Remote sensing technology has a huge potential for improving hydrologic prediction through soil moisture measurement. This is particularly so given that the first dedicated soil moisture satellite, the Soil Moisture and Ocean Salinity (SMOS) mission, is to be launched in late 2007. However, targeted field experiments must be undertaken and the data analysed prior to launch so that immediate use can be made of this data when it becomes available. Consequently, the National Airborne Field Experiment was conducted in the Murrumbidge catchment, located in south-eastern Australia, during November 2006 (NAFE'06). The intent of this experiment was to provide simulated SMOS observations supported by ground measurement of soil moisture and other relevant ground data for i) development of the SMOS retrieval algorithms, ii) developing approaches for downscaling the low resolution data from SMOS to 1km resolution, and iii) testing its assimilation into land surface models for root zone soil moisture retrieval. This paper describes the NAFE'06 data set. The SMOS-type data were collected using a Polarimetric L-band Multi-beam Radiometer (PLMR), together with supporting instruments (thermal imager, tri-spectral scanner, lidar and digital photograph). Flights included 1km resolution passive microwave data across the main 40km x 55km Yanco study area every 2-3 days, for simulation of a SMOS pixel, verification of downscaling techniques and assimilation, and a transect across the area twice a week to provide both 500m multi-angular passive microwave data for SMOS algorithm development and 50m resolution passive microwave data for algorithm verification. This was done alternatively at 6am and 6pm, so that both SMOS overpass times could be tested. A medium resolution flight (250m for PLMR) was also performed once per week across an irrigated portion of the Yanco study area to study the effect of standing water on microwave emission. The NDVI, lidar and aerial photo supporting observations were collected once along the Yanco transect and medium resolution areas during cloud-free conditions. The data described in this paper will soon be available on the World Wide Web at www.nafe.unimelb.edu.au.
H51C-02
Large Scale Evaluation of AMSR-E Soil Moisture Products Based on Ground Soil Moisture Network Measurements
This paper presents an evaluation of AMSR-E (Advanced Microwave Scanning Radiometer for EOS) soil moisture products, based on a comparison with three ground soil moisture networks. The selected ground sites are representative of various climatic, hydrologic and environmental conditions in temperate and semi-arid areas. They are located in the south-west of France, south-east of Australia and the Gourma region of the Sahel. These sites were respectively implemented in the framework of the projects SMOSREX (Surface Monitoring Of Soil Reservoir Experiment), SASMAS/GoREx (Scaling and Assimilation of Soil Moisture and Streamflow in the Goulburn River Experimental catchment) and AMMA (African Monsoon Multidisciplinary Analysis). In all cases, the arrangement of the soil moisture measuring sites was specifically designed to address the validation of remotely sensed soil moisture in the context of the preparation of the SMOS (Soil Moisture and Ocean Salinity) project. For the purpose of this study, 25km AMSR-E products were used, including brightness temperatures at 6.9 and 10.7 GHz, and derived soil moisture. The study is focused on the year 2005. It is based on ground soil moisture network measurements from 4 stations for SMOSREX extended to the SUDOUEST project of CESBIO, 12 stations for GoRex, and 4 stations for AMMA. Temporal and spatial features of soil moisture variability and stability is a critical issue to be addressed for remotely sensed soil moisture validation. While ground measurements provide information on soil moisture dynamics at local scale and high temporal resolution (hourly), satellite measurements are sparser in time (up to several days), but cover a larger region (25km x 25km for AMSR-E). First, a statistical analysis, including mean relative difference and Spearman rank, is conducted for the three soil moisture networks. This method is mainly based on the approach proposed by Cosh et al. (2004) for the purpose of the use of ground networks for satellite remote sensing validation. It allows to capture soil moisture variability features and to identify for each site the most representative station. Second, a comparison of AMSR-E derived and in-situ soil moisture measurements was conducted. Volumetric soil moisture obtained from ground and satellite measurements are compared for both absolute and normalized values. For the three sites, results suggest that although AMSR-E soil moisture products are not able to capture the same range of soil moisture values as in-situ measurements, they provide reliable information on surface soil moisture temporal variability over the three sites. It is shown, however, that the use of radiometric products such as polarization ratio provide better agreement with ground stations, than the derived soil moisture products.
H51C-03
How well does AMSR-E capture soil moisture over Australia?
Studies in several regions have indicated that data from the Advanced Microwave Scanning Radiometer - Earth Observing System (AMSR-E) onboard Aqua, can provide useful information regarding surface soil moisture content. Such information could be useful in a range of applications, including atmospheric modelling. Consequently, this paper presents an assessment of AMSR-E derived surface soil moisture over Australia, using the C-band (6.92 GHz) soil moisture product developed at the Free University of Amsterdam. The AMSR-E soil moisture is assessed by comparing time-series of individual pixels with in-situ data from soil moisture networks in the Goulburn River and Murrumbidgee River basins in south-east Australia, over 2005. The broad spatial behaviour of the AMSR-E soil moisture is also assessed through comparison to observed precipitation over Australia. Australia is well suited to testing AMSR-E soil moisture products, since frozen cover and vegetation are sparse across the country. Furthermore, radio frequency interference is not a significant problem over Australia, as it is in Europe and north America.
H51C-04
Two-Source Energy Balance Model Evaluation for Mapping Evapotranspiration on the Semi- arid Southern High Plains
Evapotranspiration (ET) is an essential component of the water balance and a major consumptive use of irrigation water and precipitation on cropland. In this study, we applied the Two-Source Energy Balance (T-SEB) model to estimate hourly ET from Landsat Thematic Mapper (TM) data for the semi-arid Southern High Plains of the United States where more than 90 percent of the groundwater withdrawals are used for irrigation. For this purpose, a Landsat TM image covering a major portion of the Southern High Plains (parts of Texas Panhandle and northeastern New Mexico) was acquired for 23 July 2006 for the overpass at 11:26 AM CST. Atmospheric correction on the TM imagery was done using MODTRAN, an atmospheric radiative transfer model. Comprehensive ground-truth data were collected to develop a detailed land use map showing major crops grown in the region. Performance of the T SEB model was evaluated by comparing mapped ET data with measured hourly ET data on five weighing lysimeters at Bushland, TX [35 Deg. 11' N, 102 Deg. 06' W; 1,170 m elevation MSL] managed by the Conservation and Production Research Laboratory, USDA-ARS. Lysimeter-measured ET rates varied from 0.24 to 0.71 mm/h. Comparison of estimated hourly mapped ET values with lysimetric measurements had an accuracy within 6% of the measured ET (r2=0.99), with a root mean squared error of 0.03 mm/h. These results support the use of the T-SEB model for the semi-arid Southern High Plains; however, more evaluation is needed for different agroclimatological conditions in the region.
H51C-05
Remote Sensing Solutions for Continuous Rainfall Runoff Modeling
Efforts to understand and to quantify the interplay between precipitation, runoff, and recharge are often hampered by the absence or paucity of appropriate monitoring systems. We developed methodologies for rainfall-runoff and groundwater recharge computations that heavily rely on observations extracted from a wide-range of global remote sensing data sets (TRMM, SSM/I, Landsat TM, AVHRR, MODIS, AMSR, and SRTM) using the arid Eastern Desert (ED) of Egypt as our test site for the time period of 2002-2005. We conducted a two-fold exercise: First, precipitation events were identified from TRMM data and verified using difference images extracted from Normalized Difference Vegetation Index (from AVHRR), and soil moisture images (from AMSR) acquired before and after the selected precipitation events. Second, a calibrated catchment-based continuously distributed (over 3 years) hydrologic model (Soil Water and Assessment Tool model; SWAT) was adopted to provide a continuous simulation of the overland flow, channel flow, transmission losses, evaporation on bare soils and evapo- transpiration (ET), surface runoff, and groundwater recharge. Due to the lack of observed stream flow measurements in the Eastern Desert, we calibrated (RMSE: 0.84) our model against observed runoff values (1998-2003) for the Wadi (Nahal) Paran Watershed (3350km2) in the neighboring Sinai Peninsula and Israel. Given the similarities in climatic, geologic, and hydrogeologic settings between the watersheds in Sinai and the ED, the calibrated model was then used to quantify surface runoff and recharge to several of the larger watersheds (Qena: 15738 km2; Asyuti: 6072 km2; Tarfa 4931 km2; and Hammamat: 7745 km2) in the ED. Three-hourly precipitation data were extracted from global TRMM data sets over the watersheds in the Egypt and Sinai using our recently developed Remote Sensing Data Extraction Model (RESDEM). Model results (simulation period: 1998-2000) for rainfall events (5-7) in the study area indicate an average annual rainfall for Qena, Asyuti, Tarfa, and Hammamat watersheds of 14 x 106 m3, 6 x 106 m3, 5.9 x 106 m3, 5.4 x 106 m3, respectively. Only 1-3 percent of the precipitation reached the watershed outlets and recorded average annual surface runoff of 9 x 105 m3, 3.6 x 105 m3, 3.1 x 106 m3, and 2.3 x 105 m3, respectively. Groundwater recharge rates through transmission losses were estimated for the alluvial aquifers within these major watersheds as 6.0 x 106 m3, 5.7 x 106 m3, 2.8 x 106 m3, 2.0 x 106 m3, respectively. Applications utilizing temporal global remote sensing data for conducting continuous rainfall/runoff models on global and regional scales for the past two decades are now within reach.
H51C-06
An Integrated Approach (Remote Sensing, GIS, Geochemistry, Field, Geophysics) for Assessment of Groundwater Potential in Large Transcurrent Fault Systems
We assessed the ground water potential for major transcurrent fault systems in basement complex terraines using as our test case, the extension of the Najd transcurrent Shear System (NSS) of the Eastern Desert of Egypt, the largest (length: 1600 km; width: 200 km) recognized pre-Mesozoic (550-630 Ma) transcurrent fault system. Spatial analysis (in a GIS environment) of remote sensing data together with relevant geologic (e.g., geologic maps), hydrologic (e.g., depth to water table), and geochemical (e.g., anions, cations) and isotopic (O, H, and tritium) data sets revealed a causal association between the locations of productive wells and distribution of NSS structural elements (faults, shear zones, mélange, dykes) within highly fractured domains. Specifically at: (1) intersection of Najd shear zones and fault systems, (2) intersections of two or more fault systems, (3) intersections of Najd-related dykes with main valleys, and (4) within tectonic mélange. For each reservoir type, reservoir-specific field and satellite-based characteristics were identified and used in conjunction with complementary data to target reservoirs of similar settings. Postulated well locations were then successfully tested using VLF technologies. Utilizied remote sensing data include: (1) Landsat TM bands, TM band ratio, and SIR-C for identification of lithologies and mapping structures; (2) TRMM and SSMI for precipitation, (3) SRTM for delineation of watersheds and stream networks, and (4) NDVI (from Landsat TM) and soil moisture (from AMSR) as proxies to locations of shallow groundwater. Results highlight the importance of major transcurrent fault systems for trapping and storing groundwater and serve as a replicable model for regional assessment of groundwater potentials in arid lands elsewhere.
H51C-07
A Multi-Faceted Approach for the Assessment of the Evolution (1964-2000) of the Tigris- Euphrates Watershed
Rising demands on fresh water supplies are leading to water management practices that are altering natural flow systems world-wide. The most devastated of these natural systems is the Tigris-Euphrates watershed that over the past three decades have witnessed the construction of over 60 engineering projects that eliminated seasonal flooding, reduced natural flow (e.g., approx. 20 percent, between 1964-1980) and reduced marshes downstream. We constructed a continuous (1964 to 2000) catchment-based rainfall runoff model for the entire watershed (area: approx. 1,000,000 km2) using the SWAT model to understand the natural flow system, and investigate the impacts of reduced overall flow and the related LCLUC downstream in the marshes. Precipitation was derived from daily and monthly rain gauge data (56 stations) from 1964-1990 and from SSMI data (1990-2000). Soil types were derived from a global soil map (Natural Resources Conservation Service). Spatial extent of drainage basins, reservoir volume, and marshland volume were derived DTED and SRTM data, evaporation on bare soils and ET on vegetated canopy was calculated using the Penman-Monteith method. A modified Soil Conservation Service (SCS) curve number method was adopted to estimate direct runoff using rainfall excess and Channel routing was conducted using the variable storage method. The model was calibrated against stream flow data in Iraq, Turkey, Iran, and Syria (8, 4, 2, 1, gauges, respectively). Our model results show a substantial decrease in the Euphrates river flow and diminished seasonal flooding following the construction (1975) of the Keban in Turkey (Storing capacity: 31 bcm) and the Tabaqa in Syria dams (storing capacity: 11.7 bcm). Average flow (computed at the Syria-Iraq border) was reduced from 32.6 bcm/yr (1964 to 1974) to 23.15 bcm/yr (1975 to 1985). Prior to damming, the monthly flow peaked in May (average flow: 2130 cms) and bottomed in October (average flow: 117 cms). Seasonal variations resulted primarily from melting of snow in the highlands of Turkey, where melting (March-June) contributed approximately 55 percent of the annual flow. Following the construction of the dams, average peak flow was reduced 1037 cms and base flow increased to 582 cms. In contrast, the input of the Tigris River at the Iraqi border has experienced only minor variations from1964 to1990 and the flow pattern remained quite variable (maximum flow in 1972: 28 bcm; minimum flow in 1973: 15 bcm). Much like the Euphrates, the Tigris receives most (approx. 65 percent) of its annual flow at the Iraqi border from snow melt in Turkey. Currently, the calibrated model is being used to evaluate the effects of the projected decease in flow, resulting from the construction of the Ataturk dam in Turkey (storage capacity: 48.7 bcm).