Consequences of LULC dynamics on the water quality in Mananga forest reserve, Metro Cebu, Philippines

ABSTRACT This study investigates the influence of land use and land-cover changes on water quality within the Mananga River Watershed Reserve, Metro Cebu, Philippines, over three distinct time periods: 2010, 2015, and 2020. The watershed supplying around 40% of Metro Cebu's water found significant land-use shifts due to urban expansion and declining forest areas. Using geographic information system-based analysis, the research correlates land cover data with water quality parameters. It identifies brushlands/shrubs, perennial crops, annual crops, and built-up areas as dominant land uses. Findings show perennial crop areas correlate positively with dissolved oxygen levels, while grasslands are linked to higher nitrate levels, indicating agricultural pollutants. Closed and open forests are vital for water quality, showing negative correlations with various pollutants. The study links forest cover loss and increased built-up areas to poorer water quality, threatening crucial sources like the Jaclupan Dam. This is the first study to quantify land-use change impacts on water quality in Metro Cebu, providing key insights for urban watershed management. Recommendations include sustainable land management practices such as enrichment planting, preventing encroachment, promoting organic farming, and implementing soil and water conservation technologies. Limitations related to topography and agricultural practices’ influence on water pollution are acknowledged.