Partitioning the contributions of cryospheric change to the increase of streamflow on the Nu River

Abstract

Over the past few decades, the Nu River Watershed (NRW), which originates in the Qinghai–Tibet Plateau and covers an area of 113,414 km2, has experienced increased streamflow, temperatures, and precipitation along with cryospheric degradation. To determine the mechanism of increase of the observed streamflow composition, a distributed hydrological model (WEP-C) was developed to investigate the streamflow composition and its changes in the NRW from 1979 to 2019. During this period, glaciers, snowmelt, permafrost, groundwater, and precipitation accounted for 3.2%, 13.4%, 0.8%, 10.4%, and 72.2% of the NRW streamflow, respectively. The streamflow of the watershed increased at a rate of 1.36 mm/year. Among the contribution rates to the increase of streamflow, glaciers increased at a rate of 0.28 mm/year and snowmelt decreased at a rate of −0.53 mm/year. Additionally, permafrost meltwater, groundwater, and precipitation increased at a rate of 0.03 mm/year, 0.60 mm/year, and 0.98 mm/year, respectively. Thus, this study provides an understanding of the composition and change of streamflow in the Qinghai–Tibet Plateau and similar watersheds, wherein the cryosphere plays an important part in the hydrological cycle.