Authors : John Camilo E. Naraval; Carl Dave Duyan; Dr. Joel S. Pardillo

Volume/Issue : Volume 11 - 2026, Issue 4 - April

Google Scholar : https://tinyurl.com/2taz2m4j

Scribd : https://tinyurl.com/3t653czk

DOI : https://doi.org/10.38124/ijisrt/26apr2163

Note : A published paper may take 4-5 working days from the publication date to appear in PlumX Metrics, Semantic Scholar, and ResearchGate.

Abstract : This study analyzes the spatial trends and temporal variability of water quality in the Talomo River Watershed, Davao City, Philippines, using Geographic Information Systems (GIS). A descriptive-quantitative approach was applied to evaluate key parameters across 14 monitoring stations from 2019-2024, including Biochemical Oxygen Demand (BOD), Dissolved Oxygen (DO), fecal coliform, Total Suspended Solids (TSS), nitrate, phosphate, pH, temperature, color, and chloride. Results show that average BOD levels reached up to 9.02 mg/L (Station 7), exceeding the standard of 5 mg/L, while DO ranged from 6.31–8.37 mg/L, remaining above the minimum threshold. Fecal coliform concentrations were critically high across all stations, with values reaching 158,675.91 MPN/100 mL, far beyond the allowable 100 MPN/100 mL. TSS values peaked at 155.98 mg/L, exceeding the 65 mg/L limit in several upstream stations. Nitrate concentration reached 13.58 mg/L at Station 1, surpassing the 7 mg/L standard, while chloride peaked at 2,427.11 mg/L, indicating localized contamination. In contrast, pH (7.80–8.30), phosphate (0.06–0.27 mg/L), temperature (23.48–28.54°C), and color remained within permissible limits. Spatial analysis using IDW revealed pollution hotspots in upstream and midstream sections. The findings emphasize the need for targeted watershed management and improved wastewater control strategies.

Keywords : GIS, Inverse Distance Weighting (IDW), Water Quality, Talomo River Watershed, Philippines.

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