DISTINCT REGIMES: THE HYDROLOGY AND GEOMORPHOLOGY OF TWELVE TRIBUTARIES TO THE SALMON RIVER

Increases in surface temperatures caused by climatic warming threaten the availability of water resources within snow-dominated catchments by altering the phase of precipitation input, decreasing seasonal snow accumulation and causing earlier spring runoff. In effort to understand climatic signals in streams and possible changes in water availability we are documenting the hydrologic regimes for twelve tributaries to the Salmon River. Monitoring sites cover three distinct elevation bands that correspond to unique climatic regimes; high (2200 – 3200 m), mid (1000 – 2200 m), and low (400 – 1800 m). Low elevations within the basin typically receive rainfall as their dominant precipitation input, mid elevations are mixed, receiving rain and snow and high elevations primarily receive snow. By meeting objectives we are able to: 1) Identify the current hydrographs for streams within each elevation band, providing a baseline from which any possible future change can be detected. 2) Project possible hydrologic changes in mid to high elevation basins if climate does warm by using the classic “space for time” substitution; low elevation catchments provide a good analogue for the possible hydrologic evolution of mid and high elevation basins. 3) Test the hypothesis that disparate hydrologic regimes result in unique stream morphologies. 4) Through the use of hypsometry constrain topographic characteristics that influence a basin’s sensitivity to rising snow lines. Basins that have a large percentage of their total area in a small range of elevation are susceptible to changes in hydrology. Winter-time snow cover estimates project the Teleher Creek Basin (a low elevation basin) to be 75% covered by snow-pack under current conditions. If snow lines rise 100 m in elevation, the basin would experience a 35% reduction in snow cover. If snow lines increase 200 m, there would be a 65% reduction from 75% to 10% covered. Preliminary hydrologic data indicate that there are differences in hydrographs among basins of disparate elevations and interestingly, there seems to be either, a departure from the classic hydrologic relationship that discharge scales with drainage area (i.e. more drainage area equals more discharge) or the timing of peak annual discharge for streams in low elevations is significantly offset from those in high elevations.