Ambient Water Analysis of Cagayan de Oro River, Philippines

Cagayan de Oro River is one of the rivers that drain the northern central region of Mindanao, and urbanization has given rise to problems with its ambient water quality. A cross-sectional, correlational study was carried out to assess the physicochemical parameters and total coliform count of the river and evaluate it against applicable national standards. Spectrophotometric analyses showed that mercury (Hg) and nitrate (NO3-) concentrations were below the maximum limit. The amounts of dissolved oxygen (DO) and total dissolved solids (TDS) across the sampling spots were also observed to be acceptable. Except for samples taken upstream, pH and water temperature readings were within the recommended range. Phosphate (PO4-3) concentrations and total coliform counts had significantly exceeded allowable limits.  TDS was positively correlated with both water temperature and PO4-3 concentration, while an increase in pH is associated with decreasing water temperature.  Spatial variation in DO and TDS was not observed in this study; however, water temperature from upstream was relatively lower and more alkaline. The study has established that Cagayan de Oro River is not fully compliant with the national water quality guidelines for Class A water bodies.  This finding points to the fact that the river has been vulnerable to both natural and human-related threats.

Keywords: River water quality, physicochemical parameters, total coliform, spatial variation, spectrophotometric analysis