EFFECTS OF AGRICULTURAL LAND RETIREMENT IN THE MINNESOTA RIVER BASIN(2008 AWRA Summer Specialty Conference)

The effects of agricultural land retirement on nutrient concentrations and biological conditions of three streams in the Minnesota River Basin were assessed using data collected during 2005-2007. The Chetomba Creek, West Fork Beaver Creek, and South Branch Rush River subbasins, which range in size from 52,500 to 96,031 acres, have similar geologic and hydrologic settings, but differ with respect to the amount, type, and location of retired land. Preliminary results show that nitrite plus nitrate concentrations were highest (mean=13.4 milligrams per liter [mg/L]) in South Branch Rush River, the subbasin with little to no land retirement, and lower in Chetomba Creek (mean=10.9 mg/L) and West Fork Beaver Creek (mean=7.8 mg/L), subbasins with more riparian or upland land retirement. Fish data indicate better resource quality for the West Fork Beaver Creek than other streams likely due to a combination of factors including habitat quality, food resources, and dissolved oxygen characteristics. Index of biotic integrity (IBI) scores increased as local land retirement percentages (50- and 100-ft buffers) increased. Data and analysis from this study can be used to evaluate the success of agricultural best management practices (BMPs) and land retirement programs for improving stream quality. KEY TERMS: Minnesota River Basin, agricultural land retirement, CRP, nutrients, physical habitat, IBI scores.