Application of SWAT and APEX models for Upper Maquoketa River Watershed in Northeast Iowa

Abstract

The watershed-scale SWAT (Soil and Water Assessment Tool) and field-scale APEX(Agricultural Policy/Environmental eXtender) models were used to estimate flow and nitrate N (NO3-N) loads within theUpper Maquoketa River Watershed (UMRW). The UMRW is highly impacted by swine, cattle, and dairy operations. AGIS interface was used to generate much of the required data for the models. Simulation of manure applications at thefield-scale was performed using APEX. The predicted flow and NO3-N loading from the manure application fields werethen input into SWAT as direct point sources. The predicted flow and NO3-N loading obtained from SWAT werecompared with measured flow and NO3-N data from four monitoring sites within the UMRW. Considering the size andvariation of land use, land cover, geology, and soils within the UMRW, the predicted flow and NO3-N loading by SWATfell reasonably well within the range of measured values.