The potential of GRACE gravimetry to detect the heavy rainfall‐induced impoundment of a small reservoir in the upper Yellow River

Artificial reservoirs are important indicators of anthropogenic impacts on environments, and their cumulative influences on the local water storage will change the gravity signal. However, because of their small signal size, such gravity changes are seldom studied using satellite gravimetry from the Gravity Recovery and Climate Experiment (GRACE). Here we investigate the ability of GRACE to detect water storage changes in the Longyangxia Reservoir (LR), which is situated in the upper main stem of the Yellow River. Three different GRACE solutions from the CSR, GFZ, and JPL with three different processing filters are compared here. We find that heavy precipitation in the summer of 2005 caused the LR water storage to increase by 37.9 m in height, which is equivalent to 13.0 Gt in mass, and that the CSR solutions with a DDK4 filter show the best performance in revealing the synthetic gravity signals. We also obtain 109 pairs of reservoir inundation area measurements from satellite imagery and water level changes from laser altimetry and in situ observations to derive the area‐height ratios for the LR. The root mean square of GRACE series in the LR is reduced by 39% after removing synthetic signals caused by mass changes in the LR or by 62% if the GRACE series is further smoothed. We conclude that GRACE data show promising potential in detecting water storage changes in this ∼400 km2 reservoir and that a small signal size is not a restricting factor for detection using GRACE data. Plain Language Summary Changes in water resource, which are strongly correlated with the sustaining development of society and economy, are attracting wide public concerns. Building of dams and reservoirs is a main way for humans to control the water resource. The changes in water volume (i.e., changes in mass) will cause a gravity increase or decrease, which could be detected by gravity satellites in the space on the condition that the gravity signal is large enough. Up to now, space gravity is only used to study water volume changes in the Three Gorges Reservoir, which is the largest hydroelectric power station in the world. Here we demonstrate that the potential of applying space gravity measurements to detect the hydrologic regime of another reservoir in a much smaller size, the Longyangxia Reservoir, located in the upper stream of the Yellow River, China. Key Points Intense precipitation in 2005 caused the Longyangxia Reservoir to experience increases of 37.9 m in water level and