Time-Scales for Ecological Change in Regulated Rivers
River impoundment causes dramatic changes in the physical, chemical and biological characteristics of the river downstream; changes which are not only confined to the lotic system but also extend to the riparian and flood-plain systems, and, in some cases, to the near-shore zone. Dams interrupt the pattern of downstream transfers involving water, sediments, organic matter, nutrients etc., and river regulation has reduced the diversity-enhancing effects of increasing physical heterogeneity from low-to middle-order streams (Ward & Stanford 1983). However, one fundamental problem in the development of a general model of system response to river regulation is the failure of many studies to consider observed changes within an appropriate time-scale (Petts 1984). This paper describes a conceptual model which provides a temporal framework for the interpretation and assessment of spatial patterns of change within regulated rivers.
KeywordsRegulate River Invertebrate Density Lotic Ecosystem Transient System Glen Canyon
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