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ARS Home » Midwest Area » Ames, Iowa » National Laboratory for Agriculture and The Environment » Agroecosystems Management Research » Research » Research Project #437529

Research Project: Watershed-scale Phosphorus Inputs from Streambanks

Location: Agroecosystems Management Research

Project Number: 5030-12210-003-74-N
Project Type: Non-Funded Cooperative Agreement

Start Date: Oct 1, 2019
End Date: Jun 30, 2021

Objective:
This research will extend previous work in the Onion Creek watershed and within the Loess Hills and Rolling Loess Prairies ecoregion of western Iowa. Continuing research will serve to better quantify poorly-constrained components of the sediment and P budgets, including storage in stream beds and floodplains. Our first objective is to continue and extend ongoing work in the Onion Creek watershed that began in 2011. Periodic eroding-length assessments and erosion pin measurements will continue along with continued manual and automated water sampling near the watershed outlet. The second objective is to extend the application of the Aerial Imagery Migration Model (AIMM) beyond the initial test watersheds to the entire state of Iowa. The third objective is to use AIMM and manual bank delineation to evaluate the effectiveness of bank stabilization and flow-training structures in reducing streambank contributions of P at a multi-reach scale.

Approach:
The research will include field measurements of bank erosion, sediment sampling, laboratory processing, and analysis of geospatial data. Onion Creek work will be extended using the water-quality monitoring station near the mouth of the creek, installed in fall 2015 as part of INRC-funded work. Measurements will also take place in the Nishnabotna River watershed in southwest Iowa. Soil samples will be taken from each major unit represented in eroding streambanks, and will be analyzed for P concentration and bulk density. Erosion rates will be estimated from aerial-photo analysis and converted to P source estimates using LiDAR-derived channel geometry and laboratory measurements of sediment P concentrations. We will compare AIMM estimates of erosion and deposition to those obtained by the Iowa DNR using manual bank delineations in a subset of watersheds around the state. This comparison will allow us to test the sensitivity of AIMM to variables that differ among landform regions in Iowa, such as the extent of canopy cover and the abundance of mid-channel bars. AIMM will then be used in combination with soil P-concentrations estimated from GIS layers developed by partners in the Iowa DNR to estimate P contributions from streambanks for each HUC-10 watershed in the state. Research will improve understanding of spatial and temporal P dynamics in a well-constrained, small watershed, while also taking advantage of widely-available data sources and easily-implemented field measurements to estimate streambank-sourced P in larger watersheds. The latter approach could enable much broader assessment of the importance of streambank erosion to P export from croplands across all of Iowa.