Simulation of the Dynamic Water Storage and Its Gravitational Effect in the Head Region of Three Gorges Reservoir Using Imageries of Gaofen-1

Abstract

The construction of a high-resolution dynamic water storage model, driven by the mass load of the huge water storage of the Three Gorges Reservoir (TGR), is the necessary basic data for accurately simulating changes in the geophysical field, e.g., gravity, crustal deformation, and stress. However, previously established models cannot meet the needs of accurately simulating the impoundment effects of TGR, because these models were simplified and approximated and did not consider the variation of river boundaries caused by water level changes. In this study, we combined high-resolution Gaofen-1 (GF-1) satellite imageries and real-time water level in front of the dam and extracted 31 river boundaries of the head region of TGR between the lowest (145 m) and the highest (175 m) impoundment stages based on the Normalized Differential Water Index (NDWI) and threshold segmentation from Otsu method. Developed dynamic water storage model based on higher-resolution GF-1 data can show the true river boundary changes more exactly, especially in local areas. Compared to the previous approximate models, the model that we constructed accurately depicts the boundary distribution information of the different impoundment stages. Moreover, we simulated TGR-induced gravitational effects based on the high-precision forward modeling of the dynamic water storage model (i.e., considering changes of dynamic water area and water level). The theoretical modelled results are consistent with in situ gravity measurements with the difference mainly within 10 μGal. Our results indicate that water storage variations of TGR mainly affect the gravity field response within 1000 m of the reservoir bank with its maximum amplitude up to several hundred μGal. The dynamic water storage and its simulation results of gravitational effects can effectively eliminate the impact of surface water load driven by the TGR under human control and greatly improve the signal-to-noise ratio of regional gravity observational data. Thus, this work will be beneficial in the application of geophysical and geodetic monitoring aimed to comprehensively track the local and regional geological structural stability, e.g., artificial reservoir induced earthquake and landslide.

A Comparison Method for 3D Laser Point Clouds in Displacement Change Detection for Arch Dams

“…TLS is widely used in all types of topographic surveys [17][18][19][20][21], landslide monitoring [22][23][24][25], deformation monitoring [26][27][28][29], and surface reconstruction [30,31], and provides a new method for measurement work in water-conservancy projects' construction, operation, and management. Extracting dam displacement information from TLS data is a challenging and important task that is critical to displacement detection using TLS technology [1,[32][33][34][35][36]. Wan [37] monitored the extrusion sidewall of concrete-faced rockfill dam based on TLS by drawing the displacement field model.…”