Polluted Rivers and Groundwater Crisis in Southeast Asia’s Mekong, Chao Phraya, and Citarum

Rivers are the lifeblood of Southeast Asia’s ecosystems, economies, and communities, yet some of the region’s most vital waterways—the Mekong in mainland Southeast Asia, the Chao Phraya in Thailand, and Indonesia’s Citarum River—are besieged by severe pollution from industrial waste, untreated sewage, and agricultural runoff. This contamination threatens human health, biodiversity, and food security, underscoring an urgent environmental and governance challenge.

Mekong River: A Shared Lifeline Under Threat

The Mekong River, which flows through China, Myanmar, Laos, Thailand, Cambodia, and Vietnam, supports over 60 million people, providing water for drinking, farming, fisheries, and industry. However, rapid industrialization, urban expansion, and intensified agriculture have resulted in elevated levels of pollutants entering the river. Industrial effluents, heavy metals, pesticides, and untreated sewage are key contaminants, exacerbated by lax enforcement and insufficient wastewater treatment across the basin.

Chemical runoff from farms includes nitrogen and phosphorus compounds, which contribute to eutrophication and harmful algal blooms, affecting aquatic ecosystems and fisheries crucial to millions of livelihoods. Upstream damming has altered water flow and sediment transport, compounding the stresses induced by pollution. The degradation of water quality in the Mekong basin poses public health risks, including waterborne diseases and exposure to toxic substances.

Chao Phraya River: Thailand’s Water Quality Crisis

The Chao Phraya River is integral to Thailand’s agriculture, industry, and urban water supplies, including Bangkok. The river has suffered chronic pollution due to discharge from factories, municipal sewage, and runoff laden with pesticides and fertilizers from intensive farming. Poorly treated or untreated sewage remains a major pollution source; only about 30 percent of the population is connected to municipal sewage systems, the rest relying on septic tanks often leaching contaminants into groundwater and nearby waterways.

Pollution levels in the Chao Phraya have led to declines in fish populations and disruption of aquatic ecosystems, threatening food security. The odour and discoloration of the water have also increased, impacting tourism and public well-being. Efforts to upgrade wastewater treatment infrastructure continue, but rapid urban growth and industrial activities outpace remediation.

Citarum River: Indonesia’s Toxic Challenge

The Citarum River, running through Indonesia’s West Java province, is widely regarded as one of the world’s most polluted rivers. Approximately 2,000 factories, predominantly textile manufacturing plants, discharge an estimated 20,000 tons of waste and 340,000 tons of wastewater daily into its waters. The river, spanning 300 kilometers and relied upon by 25 million people, provides water for agriculture, domestic use, and industry despite being heavily contaminated.

Industrial pollutants include lead, mercury, chromium, zinc, and a variety of organic toxins. These contaminants have caused a drastic decline in fish populations—up to 60% loss since 2008—and widespread health problems among communities reliant on the river. Plastic waste and untreated domestic sewage contribute further to the degradation.

The Indonesian government has launched ambitious cleanup initiatives, including a seven-year plan to restore the Citarum, but enforcement remains inconsistent, and illegal "ghost drains" continue to channel untreated industrial wastewater directly into the river. Communities living along the riverbanks disproportionately suffer from skin diseases, respiratory problems, and disruptions to agriculture and fisheries.

Common Drivers and Consequences

Across these rivers, the intersection of weak regulatory enforcement, inadequate infrastructure, rapid urbanization, and economic activities drives pollution. Industrial zones often discharge untreated waste legally or illegally; agricultural runoff laden with fertilizers and pesticides leaks into waterways; and many urban and rural communities lack access to proper sewage treatment, causing raw sewage to flow into rivers and groundwater.

The consequences are multifaceted. Human health is jeopardized by contaminated drinking water and exposure to toxic substances, manifesting in skin diseases, cancers, and gastrointestinal illnesses. Aquatic biodiversity and fisheries—the primary protein source for millions—are in decline. Sediment and nutrient balance disruptions threaten agricultural productivity and food security. Economically, pollution inflates public health costs, damages tourism, and diminishes industrial productivity.

Towards Sustainable Solutions

Addressing this crisis calls for integrated water resource management across sectors and borders. Investment in modern wastewater treatment, strict industrial pollution controls, and enforcement against illegal discharges is essential. Agricultural best practices that minimize chemical runoff can protect rivers and groundwater. Public-private partnerships and community engagement enhance transparency and compliance.

International cooperation is particularly vital for transboundary rivers like the Mekong, involving coordinated monitoring, data sharing, and policy alignment. Innovative technologies such as satellite pollution tracking can improve governance.

Ultimately, ensuring clean rivers and safe groundwater is critical not only for environmental integrity but for the health, livelihoods, and resilience of Southeast Asia’s growing populations. The Mekong, Chao Phraya, and Citarum rivers symbolize both the challenge and the imperative to restore the region’s water lifelines for present and future generations.