Methods

Snow and runoff regimes are simulated using models created with the Cold Regions Hydrological Modelling platform, CRHM (Pomeroy et al., 2007). These models were developed and evaluated with basin observations as per Fang et al. (2013), Rasouli et al. (2014, 2015) and Rasouli (2017), and then used to assess the sensitivity of the hydrological response to climate change in each of the three mountain basins by perturbing the model forcings.
The sensitivity experiments use the CRHM basin models, driven with perturbed forcings, to simulate outputs such as snowpack and coverage dynamics, and the timing and magnitude of runoff to capture the snow hydrological response to climate model outputs for the future. The sensitivities of interest are the hydrological responses to increases in air temperature and changes in precipitation that use the observed time series of air temperature and precipitation perturbed changes in the ranges projected by climate models under the Special Report on Emissions Scenarios (SRES) A2 (business-as-usual) and the Representative Concentration Pathways (RCPs) of global change for those basins. Rather than simulations based upon individual climate models, this linear sensitivity analysis provides an assessment of the scale of alteration of the hydrological cycle in mountain basins by climate change. This approach illustrates how the combination of changes in air temperature and precipitation might induce hydrological changes in these basins. Knowing how combinations of warming and precipitation changes induce future hydrological change in mountain basins from northern to mid-latitudes can be used to assess possible impacts of climate change.