APPLICATION OF AGRICULTURAL DRAINAGE AND PESTICIDE TRANSPORT (ADAPT) MODEL TO THE UPPER SOUTH AMANA SUB-CATCHMENT OF THE CLEAR CREEK WATERSHED, IA

Clear Creek, a tributary of the Iowa River, IA, is located within Iowa and Johnson counties and has been a targeted watershed by the State's Geological Survey, IDNR, NRCS and other non-profit organizations (e.g. Clear Watershed Board). The Clear Creek Watershed is primarily agricultural, with 60% of land cover being row crops and about 20% in pasture/hay. The remaining 20% represents other landuses (roads, floodplains) and lands placed under the NRCS CRP program. Since 1940s, different anthropogenic activities (e.g., intense farming), and natural events (e.g., floods) within the watershed increased the erodibility of uplands and have contributed significantly to the increased influx of fine sediments and associated pollutants into the Creek. In order to be able to take the necessary steps for BMPs, it is important to estimate the source of eroded soil and also improve our understanding of the erosion triggering mechanisms within the watershed. This paper reports the results of the application of Agricultural Drainage and Pesticide Transport (ADAPT) model to the Upper South Amana Sub-catchment of the Clear Creek Watershed, IA. The ADAPT model gives estimates of nutrients and pesticides in drainage effluent in addition to the normal GLEAMS output. The ADAPT model accounts for four mechanisms: hydrology, erosion, nutrient, and pesticide. It can handle tile drainage, erosion, crop growth, nutrient cycling, and frozen soil conditions. This is applicable to Iowa where farms have been implanted with dense tile drainage networks. Another advantage of ADAPT is that it can differentiate between Total Phosphorus and its dissolved phase. The results will be used to identify agricultural areas that may be prone to contribute to nutrient loading to nearby streams and rivers.