The Delaware watershed, an area of land in northeast Kansas of over 1110 square miles, has degraded water quality due to intensive cultivation of crops and subsequent nutrient enrichment and erosion. The current conditions may be further aggravated by agricultural intensification due to increased biofuel demand in the Midwest Corn Belt region. This could further impair the suitability of water for aquatic life and human use. This watershed is designated as a special aquatic life use as it provides unique support for wildlife, aquatic species and other biota. In this study, we simulate different environmental flow releases into Perry Lake, a federal reservoir on the southern end of the watershed, to estimate water quality and quantity metrics using a distributed parameter watershed model (Soil and Water Assessment Tool, SWAT) for future crop coverage scenarios.
Initial modeling results indicate that substituting corn acreage for current agricultural, pasture and grassland usage results in lower environmental flows, higher sediment loadings and degraded water quality. Intensification of winter wheat cropland scenario to either corn or grain sorghum produced the least impact on overall water quality. Corn-soy rotation in corn and winter wheat crop lands ameliorated these impacts by increasing sustainable environmental flow and reducing nitrate export. These results indicate that careful selection of crop practices could improve lake water quality in the Delaware watershed.