Submitted to: ASA-CSSA-SSSA Annual Meeting Abstracts
Publication Type: Abstract Only
Publication Acceptance Date: November 6, 2003
Publication Date: November 6, 2003
Citation: TOMER, M.D., MOORMAN, T.B., GREENAN, C.M. WATER QUALITY IN A LARGE AGRICULTURAL WATERSHED IN IOWA. ASA-CSSA-SSSA ANNUAL MEETING ABSTRACTS. 2003. CD-ROM. MADISON, WI. Technical Abstract: The Iowa River's South Fork drains a 78,000 ha watershed in Iowa. About 85% of the area is under corn and soybean rotations. There are about 50 confined swine-feeding operations, with most located in Tipton Creek (20,000 ha). Artificial drainage is extensive, as hydric soils occupy 54% of the area. Since 2001, water monitoring has been conducted at four permanent stations plus nine manually sampled sites. Stream discharge, nutrient and sediment concentrations, and pathogen indicators (E. coli) are being monitored. Objectives are to determine spatial and temporal patterns of pollutants, and provide a database to support model validation and evaluation of conservation practices. Here we summarize early results. NO3-N concentrations often exceed 20 mg L-1, particularly in late spring and early summer. Phosphorus and sediment concentrations increase during runoff events. Contaminant hydrographs on indicate NO3-N delivery lags behind sediment and P. Spatially, NO3-N concentrations decrease downstream, particularly during low flow, whereas P and sediment often increase downstream. E. coli populations exceeding the recreational-contact standard of 200 cells/100 ml occurred with 50% frequency during a 12-month period. Increased populations were observed downstream, and during spring and summer. Precipitation patterns, and pollutant processes, sources, and pathways affect results.