Long-Term Water Storage Changes of Lake Volta from GRACE and Satellite Altimetry and Connections with Regional Climate

Shengnan Ni,Clark Wilson,Xiaogong Hu,Jianli Chen

doi:10.3390/rs9080842

Abstract

Satellite gravity data from the Gravity Recovery and Climate Experiment (GRACE) provides a quantitative measure of terrestrial water storage (TWS) change at different temporal and spatial scales. In this study, we investigate the ability of GRACE to quantitatively monitor long-term hydrological characteristics over the Lake Volta region. Principal component analysis (PCA) is employed to study temporal and spatial variability of long-term TWS changes. Long-term Lake Volta water storage change appears to be the dominant long-term TWS change signal in the Volta basin. GRACE-derived TWS changes and precipitation variations compiled by the Global Precipitation Climatology Centre (GPCC) are related both temporally and spatially, but spatial leakage attenuates the magnitude of GRACE estimates, especially at small regional scales. Using constrained forward modeling, we successfully remove leakage error in GRACE estimates. After this leakage correction, GRACE-derived Lake Volta water storage changes agree remarkably well with independent estimates from satellite altimetry at interannual and longer time scales. This demonstrates the value of GRACE estimates to monitor and quantify water storage changes in lakes, especially in relatively small regions with complicated topography.

Highlights

Terrestrial water storage (TWS) plays a key role in global and regional water cycle, and represents the sum of all water stored above and below Earth’s surface, including water in lakes, rivers, man-made reservoirs, wetlands, soil and groundwater reservoirs
We investigate long-term TWS variability in the Volta River basin (VRB), with a focus on Lake Volta, using Gravity Recovery and Climate Experiment (GRACE) RL05 solutions and satellite altimetry lake level measurements
We examine the possible connections between GRACE TWS

Summary

Introduction

Terrestrial water storage (TWS) plays a key role in global and regional water cycle, and represents the sum of all water stored above and below Earth’s surface, including water in lakes, rivers, man-made reservoirs, wetlands, soil and groundwater reservoirs. Lake storage is an important TWS component, providing moisture to the atmosphere through evaporation, serving as a climate modulator by absorbing and releasing heat [2], and providing water for agricultural irrigation, domestic and industrial consumption, and hydropower generation. Located completely within Ghana, Lake Volta collects discharge from the numerous rain-fed tributaries within the Volta River basin (VRB), supplies hydroelectric power to Ghana and neighboring. Countries, and is a source of water for irrigation within the basin. The water storage in this and neighboring countries, and is a source of water for irrigation within the basin.

Results

Discussion

Conclusion