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
Scientists from the Grazinglands Research Laboratory (GRL) completed collection of multi-decade aerial photographs to support a study on the integrative effects of land use and climate on reservoir sedimentation in the Ft. Cobb Reservoir Experimental Watershed (FCREW) and Little Washita River Experimental Watershed (LWREW). The aerial photographs are being assembled in a GIS to depict land cover conditions by decade for the 1940s, 1950s, and 1960s. The USGS was contracted to continue water quality sampling for six high-flow runoff events. For the sixth straight year, water samples were collected on a bi-weekly basis from 15 locations in the FCREW. The multi-year, bi-weekly water quality data set is being analyzed, and manuscripts are being prepared to report results. Scientists from the GRL and from the ARS laboratory in Watkinsville, GA, will present study findings at the annual Soil and Water Conservation Society Meeting in Washington, DC, in July.
1. Satellite data can be used to measure redcedar mass. There is a need to quantify the amount of Eastern redcedar above-ground mass over large land areas to support rangeland conservation efforts and to support commercial and Federal biofuel initiatives. However, large-area measurements of aboveground mass are only feasible using remote sensing methods. It was demonstrated that QuickBird high spatial resolution satellite imagery can be used to measure aboveground mass. From the study, an allometric equation relating vertically projected canopy surface area to aboveground dry mass was produced and successfully tested on an independent study site. The equation was then used to estimate aboveground mass for 17 counties in Oklahoma. The allometric equation is being used by personnel from the Bureau of Indian Affairs to estimate redcedar mass on selected land allotments and will be useful to other agencies and businesses trying to assess redcedar mass for commercial use.
2. Stream morphology successfully integrated into SWAT. Lack of data for hydrologic models, such as the Soil and Water Assessment Tool (SWAT), for model parameterization and evaluation remains a weakness to modeling globally. A study was conducted using low-cost geomorphic data, obtained through aerial reconnaissance, to parameterize SWAT stream channel variables. The study was conducted in southwestern Oklahoma within the Cobb Creek sub-watershed. Model simulations of reservoir sedimentation were compared to long-term average annual reservoir sedimentation rates measured using a sonic surveying system. In the modeling study, establishment of vegetative buffers along unstable stream reaches identified by the Rapid Geomorphic Assessment (RGA) reduced suspended sediment concentration at the sub-watershed outlet by 67%, which is within the same order of magnitude as the findings of previous field studies. Study results indicate promise for using the RGA and Acoustic Profiling Sytem (APS) methods to obtain data to improve water quality simulations in ungauged watersheds.Starks, P.J., Venuto, B.C., Eckroat, J.A. 2011. Estimating eastern redcedar (Juniperus virginiana L.) biomass using satellite imagery. Rangeland Ecology and Management. 64(2):178-186.