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United States Department of Agriculture

Agricultural Research Service

Research Project: HYDROLOGIC AND ENVIRONMENTAL IMPACTS OF CONSERVATION PRACTICES IN OKLAHOMA AGRICULTURAL WATERSHEDS Title: Sediment measurement and transport modeling: impact of riparian and filter strip buffers

Authors
item Moriasi, Daniel
item Steiner, Jean
item Arnold, Jeffrey

Submitted to: Journal of Environmental Quality
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: June 24, 2010
Publication Date: May 4, 2011
Citation: Moriasi, D.N., Steiner, J.L., Arnold, J.G. 2011. Sediment measurement and transport modeling: Impact of riparian and filter strip buffers. Journal of Environmental Quality. 40:807-814.

Interpretive Summary: Watershed models such as the Soil and Water Assessment Tool (SWAT) are widely used to simulate watershed hydrologic processes and the effect of conservation practices such as those used by private landowners participating in selected USDA conservation programs. Lack of data for parameterization and evaluation remains a weakness to modeling globally. Research was conducted in southwestern Oklahoma within the Cobb Creek sub-watershed to develop more cost-effective methods to collect parameterization and validation data for modeling in watersheds with sparse data. The specific objectives were to use: 1) rapid geomorphic assessment (RGA) data to parameterize SWAT stream channel variables, 2) long-term average annual reservoir sedimentation rates obtained from a bathymetric survey at the Crowder Lake using the acoustic profiling system (APS) to validate sediment delivery rates simulated by the calibrated SWAT model, and 3 use the validated SWAT model to simulate impacts of riparian forest and Bermuda grass filter strip buffers on sediment yield (from overland erosion only) and concentration (includes contributions from overland and channel erosion for the contributing sub-basins). Additionally, the calibrated and validated SWAT model was used to simulate impacts of riparian forest buffer and Bermuda grass filter strip buffer on sediment yield and concentration in the sub-watershed. The average annual sediment delivery rate to Crowder Lake simulated by the calibrated SWAT model was 1.9 mt ha-1 yr-1, which is in the same order of magnitude as the long-term average annual reservoir sedimentation rates obtained using the APS between 1.2 and 2.6 mt ha-1 yr-1 depending on sediment bulk densities between 450 and 950 kg m-3. Application of buffer strip across cropped fields resulted in a 72% reduction of sediment delivery to the stream, while the riparian buffer and the combined riparian buffer and buffer strip reduced the suspended sediment concentration at the sub-watershed outlet by 67% and 70%, respectively. Effective riparian practices have potential to increase reservoir life. These results indicate that the RGA and APS techniques are potential cost-effective methods to obtain data to parameterize and evaluate watershed models in ungauged watersheds globally. In addition, the RGA data alongside a calibrated and validated SWAT model is a potential method that can be used to evaluate the impact of the riparian forest buffer on water quantity and quality.

Technical Abstract: Well calibrated models are cost-effective tools used to quantify environmental benefits of conservation practices, but lack of data for calibration remains a weakness to modeling. Research was conducted in southwestern Oklahoma within the Cobb Creek sub-watershed to develop more cost effective methods to collect parameterization and validation data for modeling in watersheds with sparse data. Specifically, applying simple geomorphic observations to parameterize the Soil and Water Assessment Tool (SWAT) model stream channel variables, and using long-term average annual reservoir sedimentation rate measured at the Crowder Lake using the acoustic profiling system (APS) to validate sediment delivery rate simulated by SWAT. Additionally, validated SWAT model was used to simulate impacts of riparian buffer and Bermuda grass filter strip buffer on sediment yield and concentration in the stream outlet. SWAT was calibrated for streamflow and sediment, and the APS bathymetric survey was used to independently validate average annual sediment. Based on the sediment bulk densities ranging from 450 to 950 kg m-3, the average annual reservoir sedimentation rate ranged from 1.2 to 2.6 mt ha-1 yr-1 compared to simulated sediment rate of 1.9 mt ha-1 yr-1. Application of buffer strips across cropped fields resulted in a 72% reduction of sediment delivery to the stream, while the riparian buffer and the combined riparian buffer and buffer strip reduced the suspended sediment concentration at the sub-watershed outlet by 67% and 70%, respectively. Effective riparian practices have potential to increase reservoir life. These results indicate promise for rapid, cost effective methods to improve hydrologic modeling to support assessments of management and policy alternatives.

Last Modified: 12/19/2014
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