The GF-7 satellite is equipped with China 's first operational earth observation laser altimeter and sub-meter optical stereo camera. High-precision laser altimetry data and sub-meter-level optical imagery data enable 1:10,000-scale stereoscopic mapping without ground control points, offering unique application advantages in large-scale spatial infrastructure construction for digital twin water resources management and water level monitoring of lakes and reservoirs. In the study, Miyun Reservoir is taken as the main research area. The GF-7 laser altimetry data and stereo image are used to extract the reservoir water level and the surrounding digital surface model(DSM), and the application practice analysis is carried out. The results show that the absolute error of reservoir water level extracted based on laser altimetry data is less than 0.15 m, which is equivalent to the accuracy of the same type of foreign data. Based on the digital surface model, the water surface range prediction result F1 is higher than 0.85, and the water volume change monitoring error is less than 3%, which can meet the requirements of related hydrological analysis applications. The relevant conclusions are of reference value for promoting the application of domestic GF-7 satellite laser altimetry and stereo image data in water conservancy, and better assisting the construction of basin level digital twin water conservancy.