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Study region: The Nagqu River Watershed in the Qinghai–Tibet Plateau. Study focus: A computational unit is the basic spatial unit employed in distributed hydrological models (DHMs), which combines the spatiotemporal distributions of meteorological variables and physical parameters denoted within a region to reveal the characteristics affecting the water cycle of watersheds. However, the current methods developed for spatially divided regions into computational units fail to consider the physical meaning and impact of climate change in montane altitudinal zones (MAZs), which significantly affects alpine watersheds. This study proposes a method for assigning the computational units of alpine DHMs according to one-period MAZ that explicitly account for physical meaning and climate change. New hydrological insights for the region: The benefits of the proposed altitudinal discretization method are verified by applying it to construct a DHM based on the water and energy transfer processes in large river basins (WEP-L) models. The results obtained using the WEP-L, SWAT model and the new regional division method (denoted as the WEP-C model) that applies the proposed altitudinal discretization method are compared. The results demonstrate that the simulation accuracy of the daily and monthly streamflows and daily soil moisture from the alpine watershed is improved by the use of the proposed altitudinal discretization method, which provide guidance for further DHM development and can be applied to other hydrological models.

Climate change will affect hydrological cycle and water resources in the Alps. Here we sketched potential future (2045-2054) hydrological cycle under prospective climate change scenarios within an Alpine river of Italy: Serio (ca. 300 km2). Therein, hydrology is highly dependent upon snow cover cycle, very likely to be affected by climate changes. We set up and validated a hydrological model able to mimic water resources regime of the river. We then use downscaled future temperature and precipitation from two general circulation models GCMs to feed the hydrological model and obtain projected hydrological regimes, at flow sections at different altitudes within the catchment. The scenarios and storylines from the adopted GCMs differ from one another with respect to projected precipitation and temperature amount, but agree upon decrease of the former and increase of the latter. All hydrological scenarios agree upon prospective shrinkage of seasonal snow cover due to increased temperature, and upon prospective increase of Fall and Winter stream flows as due to increased liquid precipitation. Lower discharges are projected during Spring and Summer, in view of decreased rainfall and snow cover at thaw, and the CCSM3 model provides shifting of thaw season to one month earlier. Higher catchments are more impacted because Winter flows increase more proportionally.