﻿ 三峡库首区蓄放水重力效应模型的构建与观测
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 大地测量与地球动力学  2024, Vol. 44 Issue (8): 867-872  DOI: 10.14075/j.jgg.2023.11.133

### 引用本文

LI Hui, LIU Ziwei, JIANG Ying, et al. Construction and Observation of Gravity Effect Model of Water Storage and Release in the Head Area of the Three Gorges Reservoir[J]. Journal of Geodesy and Geodynamics, 2024, 44(8): 867-872.

### Foundation support

Scientific Research Fund of Institute of Seismology, CEA and National Institute of Natural Hazards, MEM, No. IS202226326; The Spark Program of Earthquake Technology of CEA, No.XH23054C.

### Corresponding author

LIU Ziwei, PhD, professor, majors in gravimetry and digital signal processing, E-mail: lzw@eqhb.gov.cn.

### About the first author

LI Hui, postgraduate, majors in gravimetry, E-mail: lihui21a@mails.ucas.ac.cn.

### 文章历史

1. 中国地震局地震研究所，武汉市洪山侧路40号，430071;
2. 武汉引力与固体潮国家野外科学观测研究站，武汉市洪山侧路40号，430071;
3. 防灾科技学院信息工程学院，河北省三河市学院街465号，065201

1 模型构建

 $g_{P_z}(x, y, z)=\int_{x_1}^{x_2} \int_{y_1}^{y_2} \int_{z_1}^{z_2} \frac{G \Delta \rho}{r_0^3} z \mathrm{~d} x \mathrm{~d} y \mathrm{~d} z$ (1)
 $r_0=\sqrt{x^2+y^2+z^2}$ (2)

 $\begin{array}{l} {g_z} = - G\Delta \rho \left| {\begin{array}{*{20}{c}} {}\\ {} \end{array}} \right.\left| {\begin{array}{*{20}{c}} {}\\ {} \end{array}} \right.\left| {\begin{array}{*{20}{c}} {}\\ {} \end{array}} \right.x{\rm{ln}}(y + {r_0}) + \\ y{\rm{ln}}(x + {r_0}) - z{\rm{arctan}}\frac{{xy}}{{z{r_0}}}\left| {\begin{array}{*{20}{c}} {{x_2}}\\ {{x_1}} \end{array}} \right.\left| {\begin{array}{*{20}{c}} {{y_2}}\\ {{y_1}} \end{array}} \right.\left| {\begin{array}{*{20}{c}} {{z_2}}\\ {{z_1}} \end{array}} \right. \end{array}$ (3)

2 不同蓄水位重力效应的空间分布

 图中深蓝色为精细化提取的水体边界；右下图为三峡库首区(巴东县-秭归县)水体边界提取范围情况，左上图为提取水体边界的部分细节情况 图 1 长江三峡地区及库首区水体边界提取结果 Fig. 1 Extraction of water body boundary in the Three Gorges area and the head of the reservoir

 图 2 三峡库首区水体建模示意图 Fig. 2 Schematic diagram of the water body modeling in the head area of the Three Gorges reservoir

 图 3 三峡库首区不同蓄水位模拟重力效应空间分布 Fig. 3 Spatial distribution of simulated gravity effect in the head area of the Three Gorges reservoir at different storage levels

 图 4 距三峡库区6 km范围内不同蓄放水位对岸边产生的重力效应 Fig. 4 Gravity effect on the bank at different storage and release levels within 6 km from the Three Gorges reservoir area
3 gPhone重力仪实测重力变化

 图 5 秭归站重力变化、库首区水位和降雨量的对比 Fig. 5 Comparison of gravity change, water level in the head of reservoir and rainfall at Zigui station

 图 6 茅坪站重力变化、库首区水位和降雨量的对比 Fig. 6 Comparison of gravity change, water level in the head of reservoir and rainfall at Maoping station

Harnisch等[24]研究认为，地下水和降雨量对局部重力变化可造成10 μGal以上的影响。对比秭归站与茅坪站及周边地区的降水量信息发现，地表重力观测对周围陆地水效应非常敏感，尤其是在发生大降雨事件时。重力效应可以在降雨后迅速发生变化，但在重力数据的表现上会有短暂的滞后效应。

4 结语

1) 三峡库首区蓄放水引起的重力效应非常明显。靠近河道，重力效应变化越大；远离河道，重力效应变化减小。随着蓄放水高度的增加，重力效应逐渐增大，河道支流的重力效应也明显增加。当蓄放水位升高5 m时，离岸2 km范围内存在10~20 μGal的影响；当蓄放水位升高30 m时，离岸5 km范围内存在30~40 μGal的影响。

2) 三峡库首区蓄放水与gPhone重力仪观测的重力变化情况具有良好的相关性。分析秭归站和茅坪站gPhone重力仪观测数据与库区蓄放水位、降雨量发现，三者呈现良好的相关性。秭归站和茅坪站记录的重力变化幅值为40~50 μGal，共同验证了三峡库首区数值模拟结果的准确性。

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Construction and Observation of Gravity Effect Model of Water Storage and Release in the Head Area of the Three Gorges Reservoir
LI Hui1,2     LIU Ziwei1,2,3     JIANG Ying1,2,3     ZHANG Xiaotong1,2     ZHOU Hao1,2
1. Institute of Seismology, CEA, 40 Hongshance Road, Wuhan 430071, China;
2. Wuhan Gravitation and Solid Earth Tides, National Observation and Research Station, 40 Hongshance Road, Wuhan 430071, China;
3. School of Information Engineering, Institute of Disaster Prevention, 465 Xueyuan Street, Sanhe 065201, China
Abstract: Using high resolution remote sensing images, we accurately extract the water body boundary of the head area of the Three Gorges reservoir. A precise discretized numerical model is constructed for the water body to simulate and calculate the gravity effect of the head area of the Three Gorges reservoir at different storage and release water levels. We finely preprocess the continuous observation data of the gPhone 101 gravity gravimeter at Zigui station in 2017 and the gPhone 113 gravity gravimeter at Maoping station in 2019 to 2021. The results show during the water storage process from 145 m to 175 m, the simulation values of gravity change on the bank at different storage levels (distance is 5 m) are 0 to 28 μGal, 0 to 47 μGal, 0 to 60 μGal, 0 to 97 μGal, 0 to 170 μGal, and 0 to 210 μGal, respectively. There is an effect of 10 to 20 μGal within 2 km from the bank at the time when the storage level is elevated by 5 m. When the water storage level increases 30 m, there is an effect of 30 to 40 μGal within 5 km from the bank. The gravity residuals mainly reflect the hydrological gravity effect information, the gravity residuals at Zigui station recorded about 40 μGal of gravity change, and the gravity residuals at Maoping station recorded about 50 μGal of gravity change. The gravity change trend and the water level change show very good consistency, verifying the accuracy of the model simulation results, and provides a reference for the stability monitoring of the head area of the Three Gorges reservoir and its banks.
Key words: head area of the Three Gorges reservoir; gPhone gravimeter; gravity effect; numerical simulation; mobile gravity