Influence of Land Use Change on Grant River Hydrology, Grant County, Wisconsin

Abstract

Over the past two centuries, widespread agriculture has been significantly altering the landscape. It is known that agriculture can significantly alter hydrologic processes and increase soil erosion. While corn is the most common crop in the United States, soybean agriculture increased rapidly in the late 20th century. However, in Grant County, WI the increase began in the 1990s (USDA). Soybeans are associated with soil degradation, resulting in increased surface runoff and soil erosion. Even though soybean cropping is becoming increasingly more popular, a paucity of research has been conducted to identify the potential significance that increased surface runoff and soil erosion will have on hydrologic processes. This thesis examines potential impacts of shifts to increased soybean planting in the SW Wisconsin’s Grant River watershed where instrument records for water and sediment yields span pre- and post-1990 years of cropping practices. Overall, it was found that soybean agriculture has yet to have noticeable effects on the Grant River hydrology. This is most likely because of land use management practices that were introduced around the same time as soybean agriculture became popular in the Grant River watershed. Included in these new conservation practices are various tillage techniques and USDA programs such as the Conservation Reserve Program (CRP), Grassland Reserve Program (GRP), and Conservation Reserve Enhancement Program (CREP). Additionally, cattle grazing intensity in the watershed has been reduced. In order to fully conclude the impacts of soybean agriculture on the landscape, agricultural plots should be studied as well as hydrological changes in a smaller watershed than the Grant River.