Mapping surface area changes in three reservoirs on the island of Trinidad between 2017 and 2023 using Sentinel-1 SAR imagery

Abstract. Rapid urbanization and climate change have the potential to negatively affect water availability in the coming decades. The Caribbean region is particularly at risk since, among other factors, large water storage facilities are not as abundant as in larger nations. It is imperative therefore, that water resources in the small island nations of this region are efficiently monitored and managed. Recent open-source, satellite earth-observation data and processing capabilities have presented additional tools for managers to better regulate water and water infrastructure. In this study, we use Synthetic Aperture Radar (SAR) data from the Sentinel-1 satellite to map surface area changes in three reservoirs on the island of Trinidad using a Google Earth Engine (GEE) framework. Sentinel-1 data was processed using GEE to produce average reservoir surface area calculations for each season (wet and dry) of each year for the period 2017-2023. The resultant reservoir surface area values were cross referenced against average seasonal precipitation values obtained from the CHIRPS (Climate Hazards Group Infra-Red Precipitation with Station data) database. The SAR-derived reservoir surface area values were also compared against reservoir surface area values and reservoir ‘lake level’ values for 2017 – 2023 obtained from the Water Resources Agency (WRA) of Trinidad and Tobago. Results showed that the approach used in this study can be integrated into existing water resource monitoring frameworks, particularly for the larger reservoirs, to improve efficiency at little to no additional cost.