INTEGRATED ASSESSMENT AND ANALYSIS OF PHYSICAL LANDSCAPE PROCESSES THAT IMPACT THE QUALITY AND MANAGEMENT OF AGRICULTURAL WATERSHEDS
Watershed Physical Processes Research Unit
Project Number: 6408-13000-018-00
Start Date: Jun 11, 2007
End Date: Mar 12, 2012
Assisting agricultural landowners to produce food and fiber in an economically and environmentally sustainable manner requires an integrated approach to land management practices, and protection of streams and impounded waters. This project contributes to those goals by developing and testing practices based on a scientific understanding of hydrologic, erosion, and sedimentation processes. This project also contributes to the Conservation Effects Assessment Project (CEAP) with the goal of quantifying effects of conservation management in selected CEAP watersheds, two of them managed within this project. To meet these challenges, the focus of all the proposed research activities has been chosen to evaluate innovative practices and to fill knowledge gaps in watershed models currently in use. This is realized by: (1) developing databases of weather, soil, land use, soil conservation practices, runoff, sediment yield, and nutrient data for assessing the impacts of conservation practices on the Goodwin Creek and Topashaw Creek CEAP watersheds; (2) evaluating relative magnitudes of sources and fates of sediment in CEAP-benchmark and other watersheds, and develop methodologies to establish criteria for identifying agricultural watersheds impaired by clean-sediment loadings; (3) quantifying and validating the uncertainties of model predictions at field, farm, and watershed scales for Yazoo River Basin CEAP sub-watersheds; (4) conducting field and laboratory studies to quantify the surface and subsurface flow processes governing the initiation, development and migration of ephemeral gullies and the effect of conservation management practices on infiltration, erosion, and transport; (5) conducting field and laboratory studies to improve the understanding of stream channel processes including channel evolution, sediment transport, protection of erodible embankments, edge-of-field gullies, and sediment deposition in impounded waters for CEAP and other watersheds; and (6) improving models to identify sources of sediment, determine their fate and transport within watersheds with complex channel drainage networks, and evaluate watershed water quality impacts in terms of implementation of land conservation and stream rehabilitation practices.
An extensive body of literature exists that describes plot or field-scale conservation practices aimed at reducing soil erosion or enhancing water conservation. However, results from plot- and field-scale studies are limited in that they cannot capture the complexities and interactions of conservation practices at the whole-farm level or at the watershed scale. Soil erosion and sediment movement processes involve the interactions of land management practices with climate, weather, soil, and landscape properties. Concentrated runoff and subsurface flow results in rill and gully erosion thus increasing soil losses and downstream sediment loads leading to increased costs of crop production, ecological degradation, and impairment of water supplies. This research focuses on developing tools and techniques to quantify the impact of implementing conservation practices within a watershed in the most efficient manner to achieve sustainable and targeted reductions of sediment loadings to the nation’s stream waters to help establish total maximum daily load requirements. New methods to measure and characterize changes in runoff, gully and stream channel erosion, and sediment deposition rates utilizing hydrological, geomorphic, and hydraulic engineering principles, and remote-sensing techniques will be tested in CEAP watersheds within the Yazoo River Basin, and in other watersheds when appropriate. Improved computer models and assessment tools will be provided to evaluate the impact of land conservation and stream rehabilitation practices in the most efficient manner to assist watershed managers achieve sustainable crop production systems and targeted reductions of sediment loadings.