Scientific Findings Raise Alarm Over Water Safety in Cotabato City
COTABATO CITY, BARMM — A comprehensive scientific study has issued a stark warning over the worsening condition of the Rio Grande de Mindanao, revealing that the river faces a high risk of organic pollution that could endanger aquatic ecosystems, public health, and the livelihoods of thousands of residents. Published in the international journal Nature Environment and Pollution Technology in 2023, the research found strong biological evidence that sections of the river flowing through Cotabato City are experiencing serious environmental stress caused by untreated waste and nutrient overload.
Algae Reveal Hidden Pollution
Unlike conventional water testing that relies mainly on chemical measurements, the researchers employed Palmer’s Algal Pollution Index, a globally recognized biological tool that uses algae as natural indicators of water quality. Led by scientists from Notre Dame University–Cotabato City and Mindanao State University–Maguindanao and funded by the Ministry of Science and Technology–BARMM, the study analyzed algal diversity alongside physicochemical water parameters. Algae respond rapidly to environmental changes, making them reliable “early warning systems” for detecting pollution long before it becomes visible to the public.
Four Rivers Under Scientific Examination
The study examined four major rivers in Cotabato City—the Rio Grande de Mindanao, Matampay, Esteros, and Tamontaka—through systematic sampling conducted in August 2022. All rivers are classified by the Department of Environment and Natural Resources (DENR) as Class C waterways, intended mainly for fishing, agriculture, and recreation. Researchers collected water samples from three monitoring stations per river and tested them for dissolved oxygen, biological oxygen demand, pH, nitrates, and total dissolved solids, while algal samples were examined under laboratory microscopes to determine species composition and density.
Rio Grande Found at High Risk
Results showed that the Rio Grande de Mindanao registered a Palmer pollution index score of 18, placing it in the “high probability of organic pollution” category. The river was found to contain several pollution-tolerant algal genera, including Euglena, Nitzchia, Navicula, Oscillatoria, and Synedra, all known to thrive in waters contaminated by organic waste. Their presence strongly suggests the influx of untreated sewage, domestic wastewater, agricultural runoff, and decaying organic matter into the river system. Scientists warned that continued exposure to these pollutants could worsen water quality and accelerate ecosystem decline.
Warning Signs in Other Waterways
While Matampay, Esteros, and Tamontaka rivers did not reach critical pollution levels under Palmer’s index, the study identified troubling indicators. The Esteros River recorded high biological oxygen demand, exceeding DENR standards and signaling heavy organic waste loads that consume oxygen needed by aquatic life. Matampay River, meanwhile, showed low dissolved oxygen levels, another sign of environmental stress. Researchers cautioned that these conditions, if left unchecked, could escalate into severe ecological problems.
Threats to Communities and Livelihoods
The Rio Grande de Mindanao plays a vital role in the social and economic life of central Mindanao, supporting fisheries, irrigation systems, household water use, and transportation. Thousands of families living along its banks depend on the river for survival. Organic pollution threatens not only fish populations and biodiversity but also food security and public health, increasing the risk of waterborne diseases and economic losses for fishing and farming communities.
Urban Growth and Environmental Pressure
Cotabato City lies between the Rio Grande and Tamontaka rivers and serves as a catch basin for floodwaters from the Ligawasan Marsh. Rapid urbanization, population growth, and limited wastewater treatment facilities have intensified pressure on these waterways. The study noted that scientific monitoring in the area has historically been limited, making this research one of the first detailed assessments of river health in the city.
Scientists Call for Immediate Monitoring and Action
The researchers stressed that the findings represent only a snapshot based on one sampling season and warned that pollution levels may worsen during rainy periods when runoff increases. They recommended year-round monitoring, expanded sampling stations, and the integration of algae-based indicators into government water quality programs. The study also urged local governments and regulatory agencies to strengthen wastewater treatment, enforce environmental laws, and improve solid waste management systems.
A Narrow Window to Save a Vital River
While the Rio Grande de Mindanao has not yet reached extreme pollution levels, scientists emphasized that the current warning signs should not be ignored. Without immediate intervention, organic pollution could intensify and cause irreversible damage. The researchers concluded that the river’s condition reflects the broader environmental challenges facing rapidly growing urban centers and warned that protecting Mindanao’s largest river now is crucial to safeguarding the health, livelihoods, and future of the communities that depend on it.