Agriculture Reference
In-Depth Information
11
Water Quality and Movement
in Agricultural Landscapes
Stephen K. Hamilton
Water quality refers to the physical, chemical, and biological characteristics of sur-
face 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 wet-
lands 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 eutrophica-
tion (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 move-
ment of water through streams and wetlands may lead to changes in water qual-
ity 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 qual-
ity, as illustrated by findings from the KBS LTER and from studies in the KBS
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