Abstract
Lake area, water level, and water storage changes of terminal lakes are vital for regional water resource management and for understanding local hydrological processes. Nevertheless, due to the complex geographical conditions, it is difficult to investigate and analyze this change in ungauged regions. This study focuses on the ungauged, semi-arid Gahai Lake, a typical small terminal lake in the Qaidam Basin. In addition to the scant observed data, satellite altimetry is scarce for the excessively large fraction of outlier points. Here, we proposed an effective and simple algorithm for extracting available lake elevation points from CryoSat-2, ICESat-2 and Sentinel-3. Combining with the area data from Landsat, Gaofen (GF), and Ziyuan (ZY) satellites, we built an optimal hypsographic curve (lake area versus water level) based on the existing short-term data. Cross-validation was used to validate whether the curve accurately could predict the lake water level in other periods. In addition, we used multisource high-resolution images including Landsat and digital maps to extract the area data from 1975 to 2020, and we applied the curve to estimate the water level for the corresponding period. Additionally, we adopted the pyramidal frustum model (PFM) and the integral model (IM) to estimate the long-term water storage changes, and analyzed the differences between these two models. We found that there has been an obvious change in the area, water level, and water storage since the beginning of the 21st century, which reflects the impact of climate change and human activities on hydrologic processes in the basin. Importantly, agricultural activities have caused a rapid increase in water storage in the Gahai Lake over the past decade. We collected as much multisource satellite data as possible; thus, we estimated the long-term variations in the area, water level, and water storage of a small terminal lake combining multiple models, which can provide an effective method to monitor lake changes in ungauged basins.
Highlights
The results show that the area and water level of Gahai Lake have increased over the past 45 years, but in recent years, the trends of the two indicators are significantly different
This reflects the topographic characteristics of the Gahai Lake basin, and indicates that it is difficult to accurately determine the variations in lakes based on lake area or water level alone
The water level of relatively small lakes such as the Gahai Lake is difficult to be accurately determined because it offers few elevation points and a high proportion of outliers
Summary
As a key part of terrestrial water resources, lakes play an important role in runoff regulation, water supply, and the ecological balance of the basin [1,2,3]. The TP is a region with a relatively dense distribution of lakes, and the evolution of lakes in this area and the effects of climate change have attracted significant attention [5,6,7]. Located in the northeast part of the TP, the Qaidam Basin is characterized by many semi-arid and arid inland lakes with a fragile ecological balance. Most of these lakes are in a natural state; the temporal
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