Project Number: 3070-11130-005-06-S
Project Type: Non-Assistance Cooperative Agreement
Start Date: Sep 1, 2010
End Date: Aug 30, 2015
This is to provide partial funding to support the effort of evaluating the soil erosion components of the SWAT, finger-printing sediment sources and spatial distributions, and collecting and dating reservoir sediment using nuclear isotopes.
In SWAT, a basin is divided into sub-basins, and sub-basins are further divided into Hydrological Response Units (HRU). The soil erosion is calculated using MUSLE separately and independently for each HRU without linkage between HRUs, which is oversimplified and sometimes unrealistic in terms of water and sediment routing. The hydrological and soil erosion components will be restructured to allow linkage between HRUs (i.e., allow water and sediment to discharge to another HRU). Radionuclide 137Cs and other geochemical tracers will be used in selected watersheds for model evaluation. The modified model will also be evaluated using reservoir sediment data, along with historical land use and climate of selected watersheds. Multiple sediment cores will be taken from selected reservoirs, and basic physical (e.g., particle size distribution) and chemical properties (e.g., mineral oxides) of sediment will be measured by depth. Nuclear isotopes including 137Cs, 210Pb, 226Ra, and 232Th will be measured using a gamma spectrometer. The measured isotope ratios will be used to estimate how much soil loss is from overlands and how much is from gullies. These sediment source data, rarely measured in field, will be used to evaluate the modified SWAT. The validated model will be used to evaluate the effects of land use changes and climate variability on water resource and soil erosion in the selected watersheds.