Alteration of the natural flow regime and its effects on the Crystal River.

Abstract

Alterations to the natural flow regime, such as those caused by dams or impoundments, affect lotic ecosystems on multiple levels. Decreased flow downstream, and increased levels of sedimentation and stream width upstream cause numerous changes in the physical parameters, which in turn affect the macroinvertebrate communities and the riparian vegetation. To study the effects of the Crystal River dam in northern Michigan on the areas immediately upstream and downstream from the dam, we took a variety of physical measurements, sampled macroinvertebrates, and surveyed the riparian vegetation. We found significant differences in temperature, dissolved oxygen, depth, flow, light, macroinvertebrate ratios, tree communities, and the diameter at breast height of Thuja occidentalis between the upstream and downstream sites (p< O.O5). While it is difficult to ascertain how much of these differences are due to the presence of the dam, it appears evident that the dam has had an effect on the stream ecosystem in this region.