Snow as an Important Natural Reservoir for Runoff and Soil Moisture in Northeast China

As one of the major agricultural regions in the world, water scarcity problems in Northeast China have drawn much attention recently. Because of cold and long winter period, snow is an important component in the hydrological system. Yet few studies have been conducted to systematically assess its role. This study quantified the effects of snow on runoff and soil moisture in the entire region in a 30-year time period (1982-2011) for the first time. A water and energy budget-based distributed biosphere hydrological model with improved snow physics after calibration and validation is employed. A Standardized Snow depth Index (SSdI) is also proposed to quantify snow variations. Result shows that snow contributes 11% to runoff annually on average and 66% and 33% in April and May (main months for crop planting). Soil moisture could decrease by at least 20% in March-May if there would be no snow, and the major agriculture area suffers more than other regions. We also found that SSdI is indicative of standardized soil moisture index and standardized runoff index in spring, particularly useful for supporting water management in agriculture. These results indicate that snow performs like an important reservoir: redistribute water resources among months. This study provides unique insights into the importance of snow in the entire region. The results improve the awareness of the importance of snow to water resources management and indicate that it is worth paying attention to snow in water resources management in this region.