Geographia Technica, Vol 20, Issue 2, 2025, pp. 269-282
LINKING TROPHIC STATE INDEX TO HIGH RESOLUTION SATELLITE IMAGERY DATA OF MRICA RESERVOIR, BANJARNEGARA – CENTRAL JAVA
Yoga Candra DITYA 
, Muhammad RAMDHAN , Siswanta KABAN , Gema WAHYUDEWANTORO , Suryo KUSUMO , Agus Djoko UTOMO , Sigid HARIYADI , Majariana KRISANTI , Luky ADRIANTO
ABSTRACT: The increasing eutrophication of inland water bodies necessitates efficient, spatially extensive, and timely monitoring methods. This study investigates the utility of high-resolution PlanetScope satellite imagery for assessing the trophic state of the Mrica Reservoir in Banjarnegara, Central Java, Indonesia. Field measurements of Secchi Disk Depth (SDD), Total Phosphate (TP), and Chlorophyll-a (Chl-a) were collected at six observation stations and used to calculate Carlson’s Trophic State Index (CTSI). These values were then correlated with satellite-derived vegetation indices—Normalized Difference Vegetation Index (NDVI) and Red Edge NDVI (RdEdNDVI). Polynomial regression analysis showed strong correlations between NDVI and TP (R²= 0.975) as well as between RdEdNDVI and Chl-a (R² = 0.959), confirming the potential of these indices to estimate key trophic indicators. Spatial mapping of CTSI indicated that the reservoir ranged from eutrophic to hypereutrophic, with the most degraded conditions observed near the outlet area. The findings underscore the effectiveness of remote sensing for detecting spatial variability in water quality, particularly when field sampling is limited. While challenges such as cloud cover, spectral limitations, and sampling resolution persist, this integrated approach offers a scalable and cost-efficient framework for reservoir monitoring. The study highlights the potential for replicating this method across similar freshwater systems in Indonesia to support sustainable water resource management.
Keywords: Trophic State Index (TSI), PlanetScope, Remote Sensing, Water Quality Monitoring, Mrica Reservoir
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