A Preliminary Investigation of Bottom Fauna and Invertebrate Drift in an Unregulated and a Regulated Stream in Alberta

Abstract

A preliminary investigation of two mountain streams in Alberta was undertaken during 1968-69, in order to assess the effect of fluctuating stream flows on standing crops and drift of benthic organisms. One of these, the Kananaskis River, was subject to flow regulation for hydroelectric purposes, while the other, a tributary, Lusk Creek, was not. Several environmental factors known to affect these phenomena were also investigated. The life histories of some of the Ephemeroptera and Plecoptera, and emergence patterns of some Plecoptera in addition to a study of insect distribution at and below the surface of the substrate have been reported elsewhere (Radford & Hartland-Rowe 1971a, b, c). Except for studies by Neel (1963), Pearson & Franklin (1968), and Pearson, Kramer & Franklin (1968), little work has been done on rivers whose flow is regulated. Pearson & Franklin (1968) note that sudden flow increases caused rapid rises in the catastrophic drift of Baetis sp. and Simuliidae and found that artificial reduction of stream discharge also caused an increase in the drift, with virtually all bottom-dwelling forms being affected, as also did Minshall & Winger (1968). Neel (1963) states that daily fluctuations in reservoir releases discourage littoral stream life and may reduce a stream's carrying capacity for many organisms. Sedentary forms of insects, clams and fixed oligochaetes find survival very difficult under such conditions, but most insects (especially those making long mating and egg-laying flights) are apparently able to cope with controlled, fluctuating discharges. Also, the normal annual temperature cycle of streams can be disrupted under regulated flows since reservoirs delay the rise in river temperature in the spring and its decline in the autumn, because more time is required for their relatively great volumes of water to approach air temperature. Rawson (1948) undertook a biological investigation of the Kananaskis River after completion of the Upper Kananaskis Lake reservoir (Interlakes Dam), but before construction of the Lower Kananaskis Lake reservoir (Pocaterra Dam). He found a 'rich and varied fauna' (no quantitative data are given) in stream samples obtained below the Lower Kananaskis Lake. This was the only previous study of the benthic invertebrates in the Kananaskis River.