Monitoring of local deformations and reservoir water level for a gravity type dam based on GPS observations

Abstract

• It is possible to monitor the structure of a dam using space-based remote sensing. • GPS data can be used for compute displacements and reservoir water level. • Determination of displacements using GAMIT/GLOBK for the N, E and U components. • Computation of daily reservoir level measurements based on GNSS reflectometry. • The deformation of the dam in the North component is related to the reservoir level. In order to find a possible relation between the reservoir level and the deformation of the Sanalona dam, the horizontal and vertical displacements for a period of 3.5 years using GPS observations were calculated. The GAMIT/GLOBK scientific software was used for the relative processing of GPS observations and annual speeds over the dam of −6.77 mm/yr, −9.95 mm/yr and −1.62 mm/yr were calculated for the N, E and U components, respectively. In addition, the GNSS reflectometry inversion technique was applied to determine the daily reservoir level of the dam, the values obtained were compared with the real reference values of graduated rulers in situ. The GNSS-R achieved a correlation coefficient ( ρ ) of 0.97 with a root-mean-square error (RMSE) of 1.36 m and a regression slope of 0.932 m/m. The deformation in the x Dam component obtained a greater relation with the reservoir level due to the thrust force generated on the crest. The results demonstrate that it is possible to use a GPS antenna to carry out two monitoring processes together on a dam: (1) determination of displacements and (2) calculation of reservoir level.