Significant reduction of river discharge in the mountainous basins of Uzbekistan over the last decades

Abstract

Snow is the main hydrological component, and its contribution plays a key role in runoff formation in Uzbekistan, Central Asia. However, climate change has altered snow accumulation dynamics over the past two decades. This study investigated the impacts of seasonal changes in snow on river runoff in the Pskem and Uradarya Basins over the past 22 hydrological years (2001–2023), considering air temperature and precipitation variations. In-situ data from meteorological and hydrological stations in the study areas were used to examine the trend dynamics during the study period. Pearson’s correlation analysis was applied to examine the statistical relationship between the winter snow accumulation and summer discharge. The statistical significance of the trend dynamics was tested using the Mann-Kendall test. The results revealed a significant reduction in snow accumulation over the study period and the number of overall snowfall days, with a marked decline observed in recent years. Consequently, the contribution of seasonal snow to river runoff has markedly decreased, leading to a reduction in the discharge volume during the vegetation period. A reduction in discharge volume in both basins over the past 22-year period (2001–2023) was statistically confirmed based on in-situ data.