Assessing Current Tank Storage State from Multi-mission Satellite Observations to Support Water Management in Southern India

Abstract:

Small reservoir tank structures across South India form part of a complex ancient traditional water distribution system that has historically supplied irrigation to cropped fields during the dry-season. Despite their historical significance and the critical need for water storage in an agrarian dominated country with unpredictable rainfall, thousands of tanks have fallen into a state of disrepair. Our current understanding of these systems lacks knowledge about their functional state. To understand tank functionality, spatially explicit and temporally dynamic frequent high-resolution surface water (SW) estimates are needed. Building from an existing surface water monitoring approach (Vanthof and Kelly, 2019), the aim of this study is to assess large-scale dynamics of tank water storage state at a basin scale. This is achieved by using multi-date and multi-sensor satellite images (Landsat-8, Sentinel-1, Sentinel-2, PlanetScope) for three years (2017–2019) covering the northeast monsoon (Sept.–Dec.). SW observations from optical-infrared and radar remote sensing systems are used to estimate tank SW areas for three monsoon seasons and converted to volumes using empirical rating curves developed for the region from Vanthof and Kelly (2019). Annually, tanks were categorized as ‘tanks with water’ or ‘tanks without water’. For the ‘tanks with water’ category, two indicators were calculated: annual temporal period of water storage and the rate of storage loss. Results show that hundreds of tanks do not store water despite precipitation inputs to the system. For tanks with water, further analysis reveals variability among tanks for both indicators. Results show that multiple EO observations offer exciting opportunities to apply data-driven approaches to complement more traditional physically-based hydrological understanding.

Vanthof, V., & Kelly, R. (2019). Water storage estimation in ungauged small reservoirs with the TanDEM-X DEM and multi-source satellite observations. Remote Sens. of Environ., 235, 111437.