Glasgow, Jamie. 1999. Effects of river regulation on the growth and condition of resident salmonids in western Washington. M.S.
In free flowing rivers in Western Washington, peak flow events establish channel morphologies by aggrading and scouring substrate, and repositioning large woody debris within the channel. Thus, they determine the physical template upon which biological processes occur. River regulation by water storage dams may substantially alter this physical template with subsequent impacts to the biota. When dams buffer high flow events, downstream reaches may exhibit riparian encroachment producing changes in LWD recruitment, water temperature as a result of shading, and the dynamics of carbon input, all of which have implications for instream biota. Additionally, the regulation of rivers by water storage dams directly alters the temperature regime of the downstream flow, thereby affecting the growth rates and life histories of the biota downstream. The timing and rate of the development of aquatic insects, critical components of salmonid diets, is largely driven by water temperature. As a result of discharge and temperature alterations, the abundance and composition of food available to fish as drift may be modified by river regulation.
The objectives of this study are to determine if the modification of discharge and temperature regimes by the water-storage dam on the South Fork of the Tolt River in Western Washington has influenced instream habitat, invertebrate drift, and ultimately the growth rates and condition of resident salmonids.