LAND USE AND LAND COVER CHANGES IN THE DAVAO RIVER WATERSHED: IMPLICATIONS FOR WATER QUALITY

Joel S. Pardillo; Cherry Fe B. Madrigal; Jake Rowell Mangin; John Michael L. Palmes

doi:10.5281/zenodo.21510626

Abstract

Land use and land cover (LULC) changes have become major drivers of watershed degradation, influencing the physical, chemical, and biological characteristics of river systems. This study assessed the relationship between land use, land cover, and water quality in the Davao River Basin from 2018 to 2025 using Geographic Information Systems (GIS), and correlational analyses. Land use and land cover maps were generated through supervised classification in QGIS, while water quality data for biochemical oxygen demand (BOD), dissolved oxygen (DO), pH, total suspended solids (TSS), chloride, and fecal coliform were obtained from secondary sources. Results showed that forestland remained the dominant land cover but declined by 7.92% in 2020 and 0.59% in 2023, whereas built-up areas increased by 5.72% in 2023 and agricultural land recovered by 11.52% after a previous decline. Water quality assessment revealed that chloride concentrations exceeded the DENR Class B standard of 250 mg/L only in 2024, reaching 290.79 mg/L, while all other annual chloride values remained within the standard. Pearson correlation and linear regression analyses indicated significant relationships between selected land use and land cover classes and several water quality parameters (p < 0.05), demonstrating that changes in landscape composition influence river conditions. The findings underscore the importance of sustainable land use planning, forest conservation, and integrated watershed management to protect water quality and support long-term environmental sustainability in the Davao River Basin.

Keywords

Land Use, Land Cover, Water Quality, Davao River Watershed

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