A method for constructing reservoir area-storage-elevation curve using sentinel-1 radar remote sensing image

Reservoir elevation-area-storage (Z-F-W) curves are used for regulating discharge during the flood season and allocating water supply in the dry season. According to the latest statistics of the Directorate of Water Resources, Vietnam has about 6636 reservoirs, of which the Z-F-W curves of 474 reservoirs have been already identified and the remaining 6162 reservoirs have no information on the Z-F-W relationship. In order to regulate or allocate water in these reservoirs, operators assume a linear relationship between the area or storage and elevation, varying from the dead to normal water level. By mean of this method, calculated area and storage are subject to large errors but they are still used to operate the reservoirs. In fact, even the reservoirs attributed with the Z-F-W relationships, but the relationships may not be stationary as the reservoirs were built a long time ago with continuous sediment deposition and erosion processes that altered the reservoir bathymetry; as a result, these relationships also require corrections. This paper introduces a method for constructing the Z-F-W curves of the reservoir with the capacity larger than one million cubic meters in Ha Tinh province of Vietnam using Synthetic Aperture Radar (SAR) Sentinel-1 remote sensing image. The scope of the paper includes such steps as (i) pre-processing Sentinel-1 image; (ii) developing image interpretation algorithms for automatic processes for determining the reservoir area using backscattering points of radar image polarization on dry, moist and wetland; (iii) eliminating noise and correcting pixel values which represent water but they are interpreted as not water and vice versa; (iv) implementing methods to validate the interpretation results of the reservoir Z-F-W relationships: conducting field survey to determine the boundary of water surface by Global Positioning System (GPS) and comparing with that determined using image interpretation, method of comparing the values of reservoir capacity which are determined based on reservoir Z-F-W curves with the values of reservoir storage which are interpreted from images, then determining interpretation errors and methods for overlaying the interpretation results with super high resolution optical images at the same time. The study results are fundamental for further completion of the method for constructing the Z-F-W curves using free satellite images and opening a new solution for such needs as flood mapping, water resource inventory and so on. � 2020 40th Asian Conference on Remote Sensing, ACRS 2019: "Progress of Remote Sensing Technology for Smart Future". All rights reserved.