Abstract As demand for water increases in Wyoming, water diversion from high mountain areas is being considered more often. Instream flow assessment methods are based on summer and fall flows, but low base-flows extend into winter. Little is known of winter conditions in high mountain streams or the instream flow requirements during winter. The objectives of this study were: (1) to describe winter habitat conditions on streams at elevations above 8,000 feet, (2) to determine the effect of decreasing elevation on the amount of potential habitat excluded by ice, (3) to verify brook trout use of stream habitats at elevations above 8,000 feet, and (4) to determine brook trout winter habitat associations in such streams.
Above 9,000 feet, snow insulated the study streams and habitat exclusion by ice was minimal. As elevation decreased, snow depths increased and ice formation increased. Ice depths and the amount of ice-excluded habitat were greatest at the lowest study site (7,500 feet). Stream conditions were harshest and most variable at mid-elevation sites (8,300-8,800 feet) where the streams were partially ice and snow covered and subject to anchor ice formation.
Brook trout remained active in streams above 9,800 feet throughout the winter. Current velocity was the most important variable governing habitat selection of adult brook trout with the fish showing preference for areas with a mid-stream velocity of less than 6 inches/second. Water depth and substrate did not appear to influence trout distribution under deep snow. Flowing water is needed during winter in high mountain streams for incubating trout eggs, enabling young-of-year trout survival and preserving stream invertebrate production.
Water Resources Publications List
Water Resources Data System Library | Water Resources Data System Homepage