Location: National Soil Erosion Research2013 Annual Report
1a. Objectives (from AD-416):
Objective 1. Advance the knowledge and improve mathematical representation of physical and biogeochemical processes affecting sediment, nutrient, and pesticide losses in runoff. Subobjective 1.1. Quantify surface and subsurface hydrologic effects on runoff chemical transport and ephemeral gully erosion. Subobjective 1.2. To identify practices that will optimize the benefits of no-tillage, while minimizing the risk of P losses via runoff, without sacrificing crop productivity. Subobjective 1.3. Identify practices to optimize drainage while maximizing nutrient removal efficiency. Objective 2. Protect off-site water quality by developing methods to reduce pollutant losses from agricultural fields and watersheds. Subobjective 2.1. Develop a BMP (Best Management Practice) to reduce nutrient and pesticide delivery from landscapes to drainage systems and water bodies and reduce greenhouse gas emissions. Subobjective 2.2. Test the impact of established and new conservation practices at the field and watershed scale. Subobjective 2.3. Determination of optimal BMPs for control of runoff, sediment, and chemical losses from agricultural fields and watersheds, under existing and future climates. Objective 3. Improve soil erosion and water quality models for better assessment and management of cropland, forestland, and other managed lands. Subobjective 3.1. Improve our ability to predict soil erosion and water quality. Subobjective 3.2. Develop techniques that enhance field-to-watershed model parameterization for improved hydrologic model predictions. Subobjective 3.3. Develop methods to optimize chemical monitoring parameters to minimize costs and uncertainties associated with characterizing selected endocrine disrupting chemicals in artificially drained landscapes.
1b. Approach (from AD-416):
Laboratory studies will be used to gain process-level understanding on the effects of topographic driven surface water convergence and soil hydraulic gradient driven subsurface flow on sediment and chemical loadings. Landscape attributes affecting convergence of surface and subsurface flows will be used to validate the lab findings on conditions for channel initiation and chemical transport. To identify practices that optimize the benefits of no-till while minimizing risk of P losses, laboratory experiments will be used to test a large array of fertilizers and production practices. Plot scale experiments will be used to evaluate practices over a 5 to 10 yr period as they relate to soil and water quality. To identify practices that optimize drainage while maximizing nutrient removal, lab and streamside fluvaria will be utilized. Treatments of various materials including gravel and woodchips below stream sediment will be tested, as will use of various heights of sediment dams, to reduce nutrient losses in stream water. Controlled drainage on tile drained fields to optimize soil moisture status to reduce excess loss of nutrients, in combination with a soil amendment of flue gas desulfurization (FGD) gypsum will be evaluated. This project will continue to monitor runoff and water quality in subwatersheds of the St. Joseph River (SJR) in northeastern Indiana, and also conduct ecological studies through an SCA with Indiana-Purdue University Ft. Wayne and a cooperative project with ARS-Columbus. Detailed flow and pollutant data in the SJR subwatersheds are available from 2003-present, allowing for both uncalibrated, calibration, and validation studies with a number of watershed hydrology, sediment, and water quality models. The models can also be applied in a forecasting mode, to examine impacts of widespread or targeted placement and implementation of various land management practices (e.g. conservation tillage, different crop rotations, buffer strips, etc.) on predicted runoff and pollutant losses. Use of information from Global Environment Models will be downscaled to develop modified climate inputs to the Water Erosion Prediction Project (WEPP) model. In-house and cooperative erosion model development, testing, and validation efforts will be conducted. Work will include maintenance of WEPP, including model scientific code, user interfaces, model databases, and user support. Cooperative efforts on development of a combined wind and water erosion model will be continued. A new WEPP-Water Quality model will be developed which will also allow examination of the impacts of projected future climate change on runoff, sediment, and chemical losses and how management practices to reduce these losses may change. Geostatistical scaling techniques will be applied and evaluated to allow linkage of various soil parameters (i.e., hydraulic conductivity, porosity) across scales ranging from a few hectares to subbasins of 10,000+ ha. Loading of endocrine disruptors and selected metabolites to the SJR will be examined for significant relationships between analytes. Through statistical correlation analysis, potential surrogate analytes will be identified.
3. Progress Report:
Lab studies on surface depression and mound effects on runoff and sediment loss and subsurface hydrologic effects on Bromide transport in runoff have been completed. A model for chemical transport is being developed using runoff response as the surrogate for dissolved phase transport and sediment response for adsorbed chemicals. Field data collection on gully development is delayed until fall 2013 due to land ownership change making it difficult to access Kansas field sites and shifting focus to lab verification of sediment deposition under different surface and subsurface hydrologic attributes. For the development of a new best management practice, gypsum at the rate of 2 t/ha was applied to the proper research plots before planting corn in spring 2013. Four lysimeters/plot were installed to obtain water samples from the soils to analyze for available nutrients, and flow rates are being monitored using data loggers. In late June 2013 the water level control gates were installed in the control drainage structures to keep the water table at a maximum 2 feet below the soil surface. In the St. Joseph River Watershed, data collection on climate, soil moisture, nutrient and pesticides continues. Field and watershed scale multiple data sets have been obtained and verified for the 2013 summer pre-launch Soil Moisture Active Passive (SMAP) mission. Measured field to watershed scale soil moisture data has been processed for 2011 and 2012. Remotely sensed Landsat Thematic Mapper (TM) data has been obtained for the Cedar Creek watershed. Field scale hydrologic modeling has been successfully completed for assimilating Landsat TM data into the Agricultural Policy/Environmental Extender (APEX) model in a surrogate watershed. A new Water Erosion Prediction Project (WEPP) model version was released that contains updated channel routing options to better simulated larger streams, ability to estimate baseflow, and corrected tile drainage routines. The Natural Resources Conservation Service (NRCS) has communicated their intent to begin implementation of WEPP in its conservation toolbox. Soil and Water Assessment Tool (SWAT) model developers have requested WEPP model and interface code and developer assistance, with the desire to incorporate the WEPP erosion code into SWAT. Additionally, cooperative project between WEPP and SWAT will develop a global web-based GIS interface for application of both models to watersheds anywhere in the world. APEX model developers have also expressed desire to incorporate WEPP erosion capability within their model. New work on soil erodibility began in late 2012 at the request of NRCS. State soil scientists in South Dakota (SD) and Vermont (VT) requested help with determining Universal Soil Loss Equation (USLE) “K” erodibility factors for high clay soils. Soils from SD and VT were provided and lab experiments to measure interrill and rill erodibility parameters for WEPP conducted. WEPP simulations were made for locations in the two states, and predicted long-term average annual soil loss values used to back-calculate a “K” erodibility factor, using the climate and USLE “R” rainfall/runoff erosivity factor for the sites.
Flanagan, D.C., Frankenberger, J.R., Ascough II, J.C. 2012. WEPP: Model use, calibration and validation. Transactions of the American Society of Agricultural and Biological Engineers. 55(4):1463-1477.