High-Resolution Mapping of Rainwater Harvesting System Capacity from Satellite Derived Products in South India

Indian Rainwater Harvesting System (RHS) is an essential source of irrigation water in upstream agricultural areas. It is composed of hundreds of thousands of Small Reservoirs (SR) often disconnected from any perennial rivers. This study aims at quantifying the RHS Maximum Water Storage Capacity (MWSC) in the Telangana State, South India. The true bathymetries of 545 dry SR, located from Sentinel-2 (SENT-MWAE) and Landsat Maximal Water Area Extent (GSW-MWAE), are extracted from four Very High Resolution (VHR) Pleiades Digital Elevation Model (DEM). The average water depth at full capacity ranges from 22 cm to 4.6 m (average 1.3 m, std 0.6). The MWSC estimated within the Pleiades ground-coverage, for 62% of the total SR, accounts for 37.2 mm on average. The estimated capacity highly depends on the MWAE data source, varying from 5 to 30%. The Telangana RHS MWSC based on the RHS GSW-MWAE (1.6% of the Telangana area) is estimated at 29.7 mm +/− 9 mm. This capacity seems small compared to the large dam capacity (113mm for 126 registered dams in Telangana), but matters in upstream areas, far from irrigated command areas, to complement local groundwater pumping (from 62 to 295 mm). These preliminary results show the high interest of VHR DEM to evaluate uncertainties derived from MWAE products and medium to high resolution DEM to map water storage in RHS.