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ARS Home » Midwest Area » Ames, Iowa » National Laboratory for Agriculture and The Environment » Agroecosystems Management Research » Research » Research Project #437738

Research Project: Evaluation of Saturated Buffers as a Conservation Drainage Practice for Treating Agricultural Subsurface Drainage

Location: Agroecosystems Management Research

Project Number: 5030-13000-011-074-N
Project Type: Non-Funded Cooperative Agreement

Start Date: Mar 16, 2020
End Date: Jun 30, 2020

1. Develop a model of groundwater flow and nutrient transport through saturated buffers (SBs); 2. Devise and test an approach for estimating the horizontal hydraulic conductivity (Kx); and 3. Identify and characterize the key processes that allow SBs to reduce export of nitrogen and phosphorus.

The model for the research will use MODFLOW for the groundwater flow, MT3D-USGS software for nutrient transport, software for drain tile, and the USGS RIP-ET software for evapotranspiration from plants in the SB. All of these software are available in the public domain. The model developed in Objective 1 will identify water flows and provide detail that complements previous water budgets for SB. This will be used to address Objective 2 and develop an approach to estimate the Kx. In addition to the MODFLOW simulations, the groundwater flow will be computed with a one-dimensional or two­ dimensional analytical model, and the value of Kx obtained from this model will be compared to that from MODFLOW to assess whether a simpler approach to the flow analysis can be applied. The developed model will be tested against field measurements at several existing SB installations in Iowa. The sites will be chosen from the six existing locations previously used by ARS and the cooperator. Slug tests will be conducted at each of the wells to determine the Kx and compare with the values obtained from the approach using MODFLOW. To address Objective 3, we will use the model from Objective 1 to assess the pathways for removing nitrogen and phosphorus. We will evaluate the nutrient transport part of the model by: (a) conducting tracer studies with bromide and comparing to model predictions; and (b) comparing the overall budgets of nitrogen from the model and measurements at the field sites. Using the model to quantify these pathways will provide guidance for designing more effective SBs.