Abstract
The hydrological budget of a region is determined based on the horizontal and vertical water fluxes acting in both inward and outward directions. These integrated water fluxes vary, altering the total water storage and consequently the gravitational force of the region. The time-dependent gravitational field can be observed through the Gravity Recovery and Climate Experiment (GRACE) gravimetric satellite mission, provided that the mass variation is above the sensitivity of GRACE. This study evaluates mass changes in prominent reservoir regions through three independent approaches viz. fluxes, storages, and gravity, by combining remote sensing products, in-situ data and hydrological model outputs using WaterGAP Global Hydrological Model (WGHM) and Global Land Data Assimilation System (GLDAS). The results show that the dynamics revealed by the GRACE signal can be better explored by a hybrid method, which combines remote sensing-based reservoir volume estimates with hydrological model outputs, than by exclusive model-based storage estimates. For the given arid/semi-arid regions, GLDAS based storage estimations perform better than WGHM.
Highlights
Eighty-seven percent of Earth’s open freshwater is stored in reservoirs, 2% is stored in rivers and the remaining 11% in swamps [1]
The study demonstrated that the estimated reservoir flux agrees very well with the remote sensing-based Lake Mead volumetric variation (Figure 5 left), showing 90% correlation with the in-situ and 81% with the remote sensing-based estimates (Figure 10 bottom)
The vertical flux is always negative, which means that evaporative loss from the reservoir is greater than precipitation, and the sum is significantly less in the total flux
Summary
Eighty-seven percent of Earth’s open freshwater is stored in reservoirs (here, the term reservoir includes both lakes and man-made reservoirs), 2% is stored in rivers and the remaining 11% in swamps [1]. Water storage can be regularly quantified by applying: ground-based observations, hydrological modeling and remote sensing [2,3]. This study evaluates the potential of hybrid products in a reservoir-dominated region by combining model outputs, ground-based data, and remote sensing data. The hybrid storages combine the ∆SW from remote sensing-based reservoir volume estimates with ∆SWE and ∆SM from hydrological model outputs. In few of the previous studies, the GRACE signal was compared with the combination of storages; for example, Famiglietti et al [7,8] combined in-situ surface storages with other datasets, de Paiva et al [8,9,10] combined multiple remote sensing data and model outputs at a larger scale but the spatial resolution of the surface water bodies was 250 m. This study investigates the impact of reservoir variability on the GRACE signal at a small scale and validates the reservoir volume variability estimated at 30 m spatial resolution from remote sensing methods [11]
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
