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), in cooperation with scientists from Oklahoma State University, conducted and completed a satellite-based land use study in the Ft. Cobb Reservoir Experimental Watershed (FCREW) reflecting conditions for the year 2005. The 2005 land use study has been written up and will be included as a chapter in a special USGS report on water quality studies conducted in the FCREW. Data from the 2005 land use study were used to investigate land use changes in the watershed from the late 1990s to 2005, resulting in a Master's Thesis. A retrospective land use study has been initiated covering the period 1973-2005. Soil cores were collected at 40 sites in the FCREW from fields representing differences in soil types, land use, and land management. The soil cores have been sectioned and analyzed for bulk density and soil texture. Chemical analysis of the soil cores has been initiated. Data from the soil cores will be used in modeling studies investigating the impact of land management on movement of agrochemicals through the soil column. Soils data, along with corresponding land management data, were shared with ARS colleagues in Lubbock, TX, for the purpose of investigating wind erosion potential of soils in the FCREW. A fourth year of six low-flow and six high-flow runoff events are sampled and analyzed for selected water quality variables. The data will be used to develop equations relating water quality to streamflow. Preliminary results were presented at scientific meetings and will be included as a chapter in a special USGS report on water quality studies conducted in the FCREW. Water samples were collected on a bi-weekly basis from 15 locations in the FCREW, which are used to help identify potential problem areas within the FCREW and to investigate seasonal variations in selected water quality variables. A two-year portion of the data set was analyzed and presented at scientific meetings. A scientist from the GRL implemented and tested tile drainage equations in SWAT. Prior to this implementation, SWAT had limited capability to evaluate conservation practices associated with fields having tile drains. This same scientist also added to and tested water table depth routines in SWAT. Downhole geophysical logs obtained from federal, state, and local sources were evaluated, sorted, and incorporated into database of sedimentologic characteristics of aquifer. Drain gauges were installed at two experimental locations in the Little Washita River watershed. Preliminary results were reported at a professional meeting in Chile. Ground water levels recording devises and data loggers were installed on selected ground water wells in research watersheds to monitor water levels changes related to agricultural land use. (NP211, Problem Area 1)
1. A framework for conservation impact assessment in the Fort Cobb Reservoir watershed: Research was established on quantifying the effects of conservation practices on water quality in subwatersheds of the Washita River, Oklahoma, as part of USDA's Conservation Effects Assessment Project (CEAP). Analysis of the 1940-2005 climate, runoff, and sediment records from the Fort Cobb Reservoir watershed showed that precipitation increased 33%, corresponding runoff increased 101%, and sediment yield increased 183% when comparing multi-year wet periods to multi-year dry periods. Depth to groundwater exhibited seasonal and inter-annual variation, which would result in variable transport of nitrogen or other pollutants to stream base flow. A geomorphic assessment indicated that unstable stream channels dominate the stream networks. Analysis of one storm event indicated that 50% of suspended sediment was from upland soils and 50% from stream bank soils. Phosphorus concentration in streams was correlated to multiple watershed attributes, including contributing area, slope, stream density, and channel stability. The results provide insight into sediment and nutrient sources and transport pathways in this watershed that must be understood to properly quantify conservation effects. Anticipated outcomes are improved understanding of environmental effects of conservation, new approaches to mitigation of water quality problems, and tools to support strategic placement of conservation practices on the landscape to achieve environmental goals. (NP211, Problem Area 1).
2. Data management enhances watershed research capacity: Interdisciplinary research across natural and social sciences to address challenges in water resource management requires comprehensive and long-term data. As part of USDA's Conservation Effects Assessment Project (CEAP), STEWARDS (Sustaining the Earth's Watersheds, Agricultural Research Data System) was developed to compile, document, and provide access to data from ARS research watersheds. These data represent one of the largest research watershed data collections in the world, with many of the watersheds offering decades of data required to address issues of climate variability and global change. This data system represents a move forward for hydrologic and environmental research by providing access to a multitude of data needed to support complex analyses. Anticipated impacts include increased productivity and collaborative opportunities for individual scientists, watershed teams, and the ARS water resources program and better accountability at the agency level for investment in long-term watershed research. (NP211, Problem Area 1).
3. Seasonal variation of nutrient loading: Beginning in December 2004, bi-weekly water samples were collected from a network of stream sampling sites across four subwatersheds within the Fort Cobb Reservoir Experimental Watershed, Oklahoma. The water samples were collected to help identify potential problem sites within this CEAP watershed, and to quantify seasonal variations in selected nutrients affecting water quality. Results to date indicate that seasonal variation of nutrient loadings in the subwatersheds are significant, with an increase in phosphorus loadings related to late spring rains, while an increase in nitrogen loading occurs in the winter season. Findings from this study are expected to provide insight in selecting, implementing, and evaluating conservation practices expected to reduce movement of nutrients into surface water bodies. (NP211, Problem Area 1).
5. Significant Activities that Support Special Target Populations
A scientist from the Grazinglands Research Laboratory in El Reno, Oklahoma participated as ex officio member at annual meeting of Southern Plains Natural Resources Coalition (small enterprise farmers). A scientist from the Grazinglands Research Laboratory in El Reno, Oklahoma participated as ex officio member at meetings of Oklahoma Grazing Lands Conservation Association (small enterprise farmers) A scientist from the Grazinglands Research Laboratory participated as representative in a Regional Input Meeting regarding update of the Region 5 Oklahoma Comprehensive Water Plan (small farmers).
Moriasi, D.N., Fouss, J.L., Hall, S.G., Kornecki, T.S. 2008. Application of DRAINMOD-Ks-STMAX to predict deep chiseling effects on a drained southern alluvial soil. Applied Engineering in Agriculture. 24(3):1-10.