Document Type : Research Paper
Authors
1
Doctoral Program of Environmental Science, Universitas Negeri Padang, Indonesia
2
Department of Civil Engineering, Faculty of Engineering, Universitas Negeri Padang, Indonesia
3
Department of Geography, Universitas Negeri Padang, Indonesia
4
Department of Civil Engineering, Universitas Negeri Padang, Indonesia
10.30772/qjes.2026.171243.1981
Abstract
Lake Maninjau, West Sumatra, Indonesia, is under pressure from floating net cage aquaculture, shoreline settlements, agricultural runoff, and domestic activities. This study mapped the spatial distribution of pH and Total Suspended Solids (TSS) using an integrated Geographic Information System (GIS), Ordinary Kriging, and Sentinel-2 MultiSpectral Instrument (MSI) Level-2A imagery. Field sampling was conducted at 30 sites on 18 October 2025, and a cloud-free Sentinel-2 image acquired on 20 October 2025 was processed through Google Earth Engine. The Normalized Difference Turbidity Index (NDTI) and Normalized Difference Water Index (NDWI) were extracted to support spatial interpretation. Measured pH ranged from 5.8 to 8.2, while TSS ranged from 10 to 75 mg/L. Low pH values were concentrated near shoreline settlements and aquaculture areas, whereas high TSS values occurred near agricultural inflows and floating net cage zones. Cross-validation showed acceptable pH kriging performance, with RMSE = 0.896, MAE = 0.628, and R² = 0.755. TSS kriging showed weaker performance, with RMSE = 57.17 mg/L, MAE = 38.94 mg/L, and R² = -0.018. Integration with Sentinel-2 indices showed a strong relationship between TSS and NDTI (R² = 0.84, RMSE = 6.2 mg/L, r = 0.92, p < 0.01), while pH and NDWI showed a weaker relationship (R² = 0.69, r = 0.74, p < 0.05). The results indicate that Sentinel-2 imagery is more effective for optically active parameters such as TSS than for chemical parameters such as pH
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