Water in a Changing Climate: Montana's Flathead Indian Reservation, 1961-2100
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The Confederated Salish and Kootenai Tribes of the Flathead Indian Reservation (MT) have observed drastic changes in the quantity and quality of the water resources of the reservation over the last decades, which is threatening the Tribes’ traditional lifestyle and cultural identity. This research evaluates the impacts of climate change, specifically air temperature changes, on the snowpack conditions and stream/river temperatures between 1961 and 2100. Statistical downscaling served as a means to obtain local-scale projections of air temperature and snow water equivalent from course-resolution global climate models. A non-linear logistic function was also used to estimate water temperature time series based on air temperature. The observed data indicate an increment in both air and water temperatures and a reduction of the duration and amount of snowpack due to a later snow accumulation in fall and an earlier snowmelt in spring. According to the estimated data, this tendency is expected to continue or intensify in the future. The magnitude of the change and the monotonicity of the trends vary according to the climate scenario, variable, season, spatial scale, and specific location considered. Based on an intermediate scenario, by the end of the XXI century, air and water temperatures will averagely increase by 4.2°C and 1.9°C, respectively, whereas the annual snow water equivalent maximum and the snowpack duration will decrease, on average, by 46% and 66 days, respectively. In general, higher elevation areas are associated with less steep and less consistent trends than those found at lower elevations. Also, summer is predicted to experience the largest increase in both air and water temperatures. The findings of this research can guide the development of climate change adaptation and water resource strategic plans for the reservation.