Quantifying climate change impacts on low flows of small high mountain watersheds: A nonstationary approach

Study region: The Utah Wasatch Mountains along the eastern Great Basin and the western Rocky Mountains. Study focus: Changes in seasonal precipitation patterns and summer evaporation rates due to increases in temperatures will have severe impacts on low flows of the mountainous watersheds affecting downstream water availability and thus impacting ecosystems and drinking water supplies under future climate change. Reliable prediction of climate change impacts on future low flows needs to consider both the extremity of climatic variables and the physical characteristics of the watersheds. This study analyzes low flows of small mountainous watersheds addressing nonstationarity of climatic parameters and estimates the impact of climate change on low flow, combining nonstationarity and outcome of a physically distributed hydrologic model. MACA statistically downscaled climate data have been used as inputs to the DHSVM model to estimate future low flows for both near term (2036-2044) and distant future (2091-2099) under RCP4.5 and 8.5 scenarios. New Hydrological Insights for the Region: Nonstationary models with time (5 watersheds) or temperature (2 watersheds) as the covariate in the location-scale provided the best performance. This study demonstrated that RCP4.5 has more severe impact on the low flow frequency and volume in the near future than RCP8.5. In contrast, the effect of RCP8.5 is more dominant on the low flow regimes in the distant future than RCP4.5.

Automated summary

This study analyzes the low flow of small mountainous watersheds in Utah's Wasatch Mountains and estimates the impact of climate change on them. The study finds that future temperature increases will result in changes in the frequency and volume of low flows, with RCP4.5 having a more severe impact than RCP8.5.