Submitted to: Soil and Water Conservation Society Proceedings
Publication Type: Popular Publication
Publication Acceptance Date: July 28, 2004
Publication Date: July 28, 2004
Citation: Tomer, M.D., Burkart, M.R., James, D.E., Cole, K.J., Greenan, C.M., Green, C.H. 2004. The Iowa River's South Fork watershed: terrain, land use, and water quality. Soil and Water Conservation Society Proceedings. p. 15.
The Iowa River's South Fork drains a 78,000 ha in north-central Iowa, an area dominated by recent glacial deposits. Streams have not fully dissected the young terrain, and internally drained 'potholes' are common. Hydric soils occupy 54% of the watershed. Artificial drainage was installed to allow agricultural production beginning about 100 years ago. The Clarion-Nicollet-Webster soil association is dominant. The area is 85% in corn and soybean rotations. There are about 100 confined livestock operations in the watershed, most producing swine. We estimate that manure from these operations could be applied to 27% of the watershed, at 200 kg N/ha for corn. Research objectives are to: 1) determine spatial and temporal patterns of pollutants; 2) provide data for model validation; and 3) evaluate conservation practices. Stream discharge, nutrient and sediment concentrations, and pathogen indicators (E. coli) are being monitored, with four stream sites permanently gauged, and manual sampling at nine additional stream sites and six tile outlets. Monitoring has shown significant amounts of all these pollutants in streams. Analyses are underway to identify where conservation practices can best improve water quality. Terrain-analysis methods have identified suitable locations for wetlands and riparian buffers. Soil & Water Assessment Tool (SWAT) modeling is being initiated to evaluate possible conservation scenarios.