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United States Department of Agriculture

Agricultural Research Service


Location: Agroecosystems Management Research

2007 Annual Report

1a. Objectives (from AD-416)
This project describes Watershed Assessment Studies (WAS) to be conducted in two Iowa watersheds that are benchmark watersheds of ARS’s Conservation Effects Assessment Project (CEAP). This project consists of three objectives that are to: 1) Develop and implement a data system to organize, document, manipulate, and compile water, soil, management, and socio-economic data for assessment of conservation practices at field, farm, and watershed scales for the South Fork of the Iowa River and Walnut Creek, Story County watersheds. 2) Measure and quantify water quality, water quantity, and soil quality effects of conservation practices at the field, farm, and watershed scale for the South Fork of the Iowa River and Walnut Creek (Story County) watersheds. Two sub-objectives are: a) Quantify extent and placement of conservation practices in the South Fork watershed and impacts of those practices on water and soil quality. b) Relate contaminant sources to transport paths and processes for pathogens, antibiotics and nutrients using hydrologic and land use data with isotope- and DNA-based methods. 3)Assess and evaluate watershed and river basin responses to current and improved management practices for water quality by comparing observed to model-predicted results for the South Fork of the Iowa River and Walnut Creek (Story County) watersheds.

1b. Approach (from AD-416)
The work will take place in the Iowa River’s South Fork watershed (78,000 ha), and in Walnut Creek watershed, Story County (5,200 ha). Both watersheds are within the area of most recent glaciation in Iowa (about 10,000 years B.P.), known as the Des Moines lobe. Walnut Creek has a water quality database dating to 1991, and a history of watershed modeling and nutrient-management research. The South Fork watershed also has challenges associated with intensive livestock production. Its water quality database dates back to 2001, and information on conservation practices have been gathered and targeting methods explored. This research will leverage these assets towards attaining CEAP goals through database development, watershed assessments and modeling studies. Watershed assessment studies for the South Fork will include combined geographic analyses of soil survey, topographic, crop cover, and conservation-practices inventory data to improve our ability to assess the targeting of conservation practices towards sensitive lands. Combined hydrologic and water quality data will be used to evaluate effects of practices on runoff water quality and better understand how different pathways of water movement impact water quality as measured at the watershed scale. Source tracking methods for fecal-contaminant indicator bacteria will be developed and tested. Finally watershed models will be evaluated to improve our ability to predict the impact of changes in conservation systems that are reasonable future scenarios. Thereby, the project will develop information that can increase the effectiveness of USDA’s conservation programs in tile-drained watersheds.

3. Progress Report
Major activities on this project included: 1. Significant progress on the development of a multi-location CEAP database that will be housed at National Soil Tilth Laboratory. Development of the database, named STEWARDS, includes establishment of a methods catalog for metadata documentation and geographic linkages. Progress has been excellent with several other CEAP watersheds beginning to contribute data, which puts the objective substantially ahead of schedule. 2. Continuation of ongoing water quality monitoring (for nutrients and E. coli) and stream gauging in the South Fork watershed. In November, we obtained three hours of video, taken from a helicopter, which covers 88 miles of streambank conditions in the South Fork watershed. Analysis of the video is ongoing, in collaboration with scientists at the National Sedimentation Laboratory (USDA-ARS), and aimed at a geomorphic assessment of the riparian corridor. Results should help characterize stream channel processes and identify priority areas for restoration efforts. Technical staff members have met the associated challenges exceedingly well. 3. Research reporting on five years of CEAP research in Iowa, which was combined with reporting from other ARS CEAP watersheds (see accomplishments). The accomplishments listed on this report resulted from work completed on a project of the same title, as project number 3625-13000-008-00D, which was terminated April 2006.

4. Accomplishments
Integrated water quality assessment for CEAP watershed. Interactions between hydrology and water quality help determine the effectiveness of conservation practices in agricultural watersheds. In the Iowa River's South Fork watershed, from 2002-2005, nitrate losses averaged >20 kg N/ha.yr, phosphorus (P) concentrations frequently exceeded ecological thresholds, and E. coli counts frequently exceeded recommended values for contact recreation during summer. Comparison of nitrate concentrations obtained by two sampling methods provides performance benchmarks for watershed-model validation. Patterns of E. coli indicated multiple sources are important; seasonal temperature effects and stream discharge accounted for half the variation in E. coli. Distinct seasonal patterns among the three contaminants highlights the complexity of integrated water quality assessments. Results are of interest to watershed modelers, conservation practitioners, and policy makers involved in CEAP or other watershed assessment studies. The research supports Problem Area 1 (Effectiveness of Conservation Practices) of NP211 (Water Availability and Watershed Management). Sulfamethazine Degradation in Aquatic Environments. Antibiotics have been observed in surface waters apparently resulting from land applications of animal manures. This research was conducted to evaluate the sorption (binding) and degradation of sulfamethazine to soils and in water/sediment aquatic systems. Sulfamethazine degrades rapidly in soil and in pond water, but more slowly in anaerobic soils or sediments. Sulfamethazine is weakly bound to soil, especially in soils with high pH and low organic matter. These results suggest that sulfamethazine will leach in soil, but is not likely to be persistent. This research identifies the major factors controlling the environmental fate of this veterinary antibiotic. This information contributes to analyzing the risk of animal manure application and practices for minimizing transport of antibiotics to stream waters. The research supports Problem Area 1 (Effectiveness of Conservation Practices) of NP211 (Water Availability and Watershed Management).

4. Accomplishments

5. Significant Activities that Support Special Target Populations

Last Modified: 2/23/2016
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