Analysis of Detailed Lake Variations and Associated Hydrologic Driving Factors in a Semi-Arid Ungauged Closed Watershed

Abstract

Lakes are key factors in maintaining ecosystems in semi-arid regions. However, due to data shortage, most studies used remote-sensing data and water-balance models to analyze lake variations in semi-arid ungauged closed watersheds, resulting in the oversimplified assessment of lake variations and their associated hydrologic processes. This study aimed to enhance the understanding of the mechanisms behind the water supplement and consumption of lakes and reveal the influences of hydrological processes on lake variations in such watersheds. Physically based and lake-oriented hydrologic modeling, remote-sensing technology, and results from previous studies were comprehensively integrated to achieve the research objective. The Hongjiannao (HJN) watershed in Northwest China was selected as the study area of this research. The calibration and validation results demonstrated that remote-sensing data and results from previous studies indeed guaranteed the accuracy of the lake-oriented model. Further hydrologic and statistical analyses revealed the linkage between lake variations and their associated hydrologic processes, and the mechanisms behind the linkage. Specifically, rainfall and snowmelt were found to be the most stable sources of HJN Lake, particularly in dry years. Due to the differences in recession rates, groundwater inflow was more stable than upstream inflow and inflow from the contributing area of HJN Lake. The correlations between hydrologic processes and the storage variation of HJN Lake varied significantly at daily and monthly time scales, which can be explained by the generation mechanisms of these processes. This study provided valuable guidance for water resources management and ecosystem protection in the HJN watershed and can be further applied for hydrologic simulations in other similar watersheds.