Water Quality and Movement in Agricultural Landscapes

Water quality refers to the physical, chemical, and biological characteristics of surface waters and groundwaters that determine their suitability for use by humans and aquatic life. Both natural and managed landscapes provide an important ecosystem service by maintaining water quality, which is key for water supply, recreational use, aesthetic values, and biodiversity, including fish and wildlife habitat. The upper U.S. Midwest is a region endowed with abundant groundwater, lakes, and wetlands as a result of a glacial topography and humid climate. Within this region lies the Kellogg Biological Station Long-Term Ecological Research site (KBS LTER) in southwest Michigan, situated in a heterogeneous, largely rural landscape (Fig. 11.1). The region in the vicinity of KBS is ideal for comparative study of how water quality changes as water moves through landscapes and how the transport of nutrients via water movement through watersheds is affected by land use and land cover, human activities, and biogeochemical transformations in surface water bodies. Agricultural influences on water quality are of particular interest in the U.S. Midwest, where nutrient export from farmland to groundwaters, lakes, and streams can lead to high nitrate in drinking water supplies and to surface water eutrophication (i.e., excessive algal and plant growth). Water-quality work at the KBS LTER has two major goals. The first is to improve our understanding of how water quality changes as water flows across the landscape, including the effects of natural processes as well as changes ascribed to agricultural row-crop management. A second goal is to examine how the movement of water through streams and wetlands may lead to changes in water quality that include retention or removal of nutrients of concern for eutrophication, and to investigate the specific processes responsible for the changes. Although the information presented is largely from the KBS region, it is generally applicable to landscapes with intensive agriculture. In this chapter, I discuss the main effects of row-crop agriculture on water quality, as illustrated by findings from the KBS LTER and from studies in the KBS Hamilton, S. K. 2015. Water quality and movement in agricultural landscapes. Pages 275-309 in S. K. Hamilton, J. E. Doll, and G. P. Robertson, editors. The Ecology of Agricultural Landscapes: Long-Term Research on the Path to Sustainability. Oxford University Press, New York, New York, USA.