Ecological Characteristics of County Drains in the River Raisin, Michigan

Abstract

Agricultural drainage is widely implemented throughout the U.S. to improve land drainage and increase crop productivity, affecting as much as 50% of cropland area in Midwestern states. Many of the headwater streams of this region are managed under state laws by drainage districts, county drain commissioners or similar entities. The ecological condition of these streams is sparsely documented but considered poor. I evaluated ten stream reaches, each of which contained a segment managed under the Michigan Drain Code and an unmanaged segment (“natural”), using a paired reach sampling design. Habitat quality was significantly lower for seven of nine rapid assessment metrics and for overall habitat quality. Other physical characteristics including woody debris, substrate particle size and sinuosity were all greater in natural reaches. In comparison to natural reaches, county drains were significantly incised and were nearly straight in planform. Biological assessment using macroinvertebrates indicated slightly improved scores in natural reaches but differences were not significant for most metrics. A regression of biological metrics against habitat quality that included data from a wide variety of streams within the watershed reveals poorer biological condition in both stream types than would be expected from habitat alone, suggesting that these systems are challenged by additional stressors.