1a. Objectives (from AD-416):
To quantify interactive effects of variable climate, dynamic land use, and land management, particularly conservation practices, on surface and subsurface water quality at the watershed scale. Specific objectives are: 1) Develop and implement a multi-site data system to organize, document, manipulate, and compile water, soil, management, and socio-economic data for assessment of conservation practices from ARS Benchmark watersheds; 2) Quantify water quality, water quantity, and soil quality effects of conservation practices across field to watershed scales within the Upper Washita River Watershed; and 3) Quantify accuracy and uncertainty in model output across field to watershed scales and incorporate this information into assessment tools. The anticipated result of the research are new methods to quantify environmental effects of conservation practices implemented on the landscape and tools to support future strategic placement of conservation practices on the landscape.
1b. Approach (from AD-416):
Multi-temporal land use data sets (both current and retrospective) will be developed for incorporation into watershed-scale hydrologic models to determine the effects of changing land use and management on model predictions. Geomorphic assessments and sediment source tracking will be conducted to determine potential sources and contributions of sediments from overland processes and stream banks. The historical and existing hydrologic, geomorphic, geologic, soil, climate, and land use and management conditions that govern the movement of water, sediment, and nutrients through selected sub-basins within the Upper Washita River watershed will be quantified. Hydrologic modeling studies will be conducted at multiple scales to monitor water quantity and quality responses to conservation practice implementation. The soil management assessment framework (SMAF), developed for mid-western soils and cropping conditions, will be used to evaluate the effects of management practices on soil parameters, and evaluate the hydrologic sensitivity to the soil parameters.
3. Progress Report:
Over the course of the last five years of study, we have demonstrated that stream banks contribute as much as one-half of sediments that are suspended in stream waters. This result indicates that more concentrated effort at installing conservation practices along streams is needed to reduce suspended sediments. We also showed that a denser network of rainfall measurements is needed to properly model some watershed processes, and that the National Weather Service's NEXRAD rainfall data may be adequate for such purposes. In a related study we demonstrated that more spatially dense information in NRCS's SSURGO datasets does not necessarily lead to better hydrologic simulations than when the less spatially dense STATSGO data set is used. The STATSGO-based simulations take less time and computer resources and thereby provide adequate and timely modeling results. Our Unit contributed to development and population of the ARS' STEWARDS (Sustaining the Earth's Watersheds Agricultural Research Data System) which is designed to deliver, organize, and document soil, water, climate, land-management, and socio-economic data to the public that was/is collected through the USDA's Conservation Effects Assessment Program (CEAP). We demonstrated that high spatial resolution satellite data can be used to measure above-ground mass of redcedar to support rangeland conservation efforts and to support commercial and Federal biofuel initiatives. We, along with a team of ARS scientists, demonstrated that a subset of measurements of soil water content can be used to validate the soil moisture products derived from the recently deployed Advanced Microwave Scanning Radiometer (AMSR). Standardized model calibration and validation guidelines were developed and published to establish a common system for judging model performance and comparing various models for the 14 ARS benchmark and 35 NRCS special emphasis watersheds of the CEAP- Watershed Assessment Study (CEAP-WAS).
1. Studying Eastern redcedar. The impact of encroaching Eastern redcedar into grasslands on components of the hydrological balance is being investigated through measurement of canopy interception of rainfall and transpiration. Four redcedars have been instrumented to compute rainfall interception by redcedar canopy, and four redcedars have been instrumented to measure daily transpiration rates. A modeling study was recently completed showing the beneficial impacts of riparian conservation practices on reducing stream bank contributions of suspended sediment in streams. We also investigated potential improvements in large-scale hydrologic modeling by assimilating soil moisture measurements into the SWAT model. Results were mixed, but the study indicated a weakness in SWAT that did not allow full analysis of potential benefits of soil moisture assimilation.
Brown, M.A., Starks, P.J., Gao, F.Q., Wang, X.Z., Wu, J.P. 2012. Bermudagrass intake and efficiency of utilization in Katahdin, Suffolk, and reciprocal-cross lambs. Professional Animal Scientist. 28:358-363.