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.
Highlights
Because the Shuttle Radar Topographic Mission (SRTM) Digital Elevation Model (DEM)’s lower spatial resolution may result in large uncertainties and does not provide the information of seasonable water boundary lines [9], combining it with high resolution satellite imageries is of benefit to tack water boundary lines at different water levels, establishing a more accuracy and dynamic water storage model
The simulation of the gravitational effect generated by the water storage change is an essential step to effectively distinguish causes of the local and regional geological structural stability from superposed signals
The gravitational effffects on the surface in the head region of Three Gorges Reservoir (TGR) are computed, for which SRTM DEM is employed to approximate the surface with a ground resolution oof abboouutt 3300 mm
Summary
Determining the Earth’s surface hydrological processes of terrestrial water storage or human1in. dInutcreoddwucattieornstorage is considered a recent interest because the processes reflect the information of hicrSmfwilfnmereooiuovnsofrovmpoemecrdemrrlolereadDmvuioeYrntnoeennhfai-gaittcidetrteicnnhihstnmorlhiddaeigmminmennuertingpasceahontetesothfeticeedtnousetymnrucignvpoCwewycdooneicchocdtamidelhoarfretessrellneesisordsrongnfmcruftqpEaheslcfniptasealYlnloyuorndrriigrmeetcocgrahnhascdeeoage’neasasfttnecsniyec[Yasotghp1asiflnacsl]ueuitty.yntcidolrrvTacclgfocyeCollahitoeltzncrhesrnsaeeoeseontTplifcarRanddhhrochrgieemhrlagvyiqlsrerneeeedeaeierddsnrgdnnirtgGgeob-tiiaacmstnlaoaoosattsriif[apgtorgivl1hdYnaeiane]ecercae.csa(geinoiFpTnltRnefgtyiehesgteitmprttrezs(uisriireeocan.reoTleradenRsotcv.hpeti,-wei1ocrmrrav~si)eeiecaef,s1resalirlrei7utt(dssyrT5bGcweeboaGt(maoueonsaticRre.ciafteenghare)wt.reioeru,t(ioesseanFf~ssnrtcieot1tReCgrihrbfr7erueitheces5athsrluhittleleenerwmalevwriaa1raveepYt,g)alwiloe,creoa)tniiooesnanwsricvtrntg1oee(aer4ct[Tnsr2etrz2i5seierGs0e,lnerc3ee0moRsRugr]v8f.vsl)i,etraavttohleSthiont)eihnefliierrdroniesaenslncbCcge1aiweatn2cr7he[sgt2a05itiittne,t0honhho3emsa8n.ee]errt,,. the water level of the reservoir is perennially controlled in the periodic fluctuation between 145 m and 175 m for meeting the needs of flood control and irrigation in its lower reaches of the Yangtze River basin. Because the SRTM DEM’s lower spatial resolution may result in large uncertainties and does not provide the information of seasonable water boundary lines [9], combining it with high resolution satellite imageries is of benefit to tack water boundary lines at different water levels, establishing a more accuracy and dynamic water storage model. Satellite imageries with high spatio-temporal resolution can provide detailed information for target identification. They are frequently used for the monitoring of river basin evolution [17,18], in hydrodynamic process modeling [19,20], and in the analysis of characteristic changes of water bodies [21,22,23]. An accuracy water storage model of the TGR represents a good opportunity to detailly investigate gravitational responses in this process [3]
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