Reservoir Water Surface Area Estimation Using Sentinel-1 and Sentinel-2 Imagery

There are approximately 17,080 agricultural reservoirs distributed across South Korea, and maintaining these reservoirs requires significant costs and time.Accordingly, time series tracking of water surface area changes using satellite imagery has been proposed as a more efficient and economical method for managing reservoirs.This study analyzes reservoir surface areas using Sentinel-1 Synthetic Aperture Radar (SAR) and Sentinel-2 Multispectral Instrument (MSI) imagery and assesses the applicability of satellite data for reservoir maintenance.Sentinel-1 SAR analysis results show that except for Maengdong (0.58) and Gui (0.62), the Split and Merge technique demonstrated a correlation above 0.7.The Region Growing technique showed correlations above 0.7 for all reservoirs, while the threshold-based method maintained correlations above 0.7 for most reservoirs, except for Gui (0.68).Sentinel-2 MSI imagery was analyzed using Modified Normalized Difference Water Index (MNDWI), NDWI, and multi-band/multitemporal NDWI approaches.MNDWI showed correlations above 0.7 only in select reservoirs, such as Maengdong, while NDWI demonstrated correlations above 0.7 for most reservoirs, except Gui (0.57) and Seongju (0.59).The multi-band/multi-temporal NDWI method exhibited correlations above 0.7 for all reservoirs except Seongju (0.52).This demonstrates the feasibility of monitoring reservoir surface area changes using satellite data and suggests its potential as a tool for supporting priority decisions in reservoir maintenance.