Articles | Volume 20, issue 8
Research article
15 Aug 2016
Research article |  | 15 Aug 2016

Assessment of impacts of agricultural and climate change scenarios on watershed water quantity and quality, and crop production

Awoke D. Teshager, Philip W. Gassman, Justin T. Schoof, and Silvia Secchi

Abstract. Modeling impacts of agricultural scenarios and climate change on surface water quantity and quality provides useful information for planning effective water, environmental and land use policies. Despite the significant impacts of agriculture on water quantity and quality, limited literature exists that describes the combined impacts of agricultural land use change and climate change on future bioenergy crop yields and watershed hydrology. In this study, the soil and water assessment tool (SWAT) eco-hydrological model was used to model the combined impacts of five agricultural land use change scenarios and three downscaled climate pathways (representative concentration pathways, RCPs) that were created from an ensemble of eight atmosphere–ocean general circulation models (AOGCMs). These scenarios were implemented in a well-calibrated SWAT model for the intensively farmed and tiled Raccoon River watershed (RRW) located in western Iowa. The scenarios were executed for the historical baseline, early century, mid-century and late century periods. The results indicate that historical and more corn intensive agricultural scenarios with higher CO2 emissions consistently result in more water in the streams and greater water quality problems, especially late in the 21st century. Planting more switchgrass, on the other hand, results in less water in the streams and water quality improvements relative to the baseline. For all given agricultural landscapes simulated, all flow, sediment and nutrient outputs increase from early-to-late century periods for the RCP4.5 and RCP8.5 climate scenarios. We also find that corn and switchgrass yields are negatively impacted under RCP4.5 and RCP8.5 scenarios in the mid- and late 21st century.

Short summary
Current water quality problems due to intensification of corn in agricultural watersheds is expected to be exacerbated by the projected change in climate further in the 21st century. Therefore, there is an urgent need to develop alternative biofuel cropping systems and/or implement effective management practices to counteract future water quality problems that could develop from relying on extensive production of row crops in Corn Belt region watersheds.