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Restoring the flow:

Imus-Ylang Ylang-Rio Grande Rivers

By IW:LEARN

October 31^st, 2025

A river remembered

At 70, Mr. Reynato Robles, a river ranger, recalls the glory of the river he grew up with. He remembers a time as a young fisher, when the river teemed with fish and seashells, and families could earn a living without leaving the riverbanks.

“Back then, the river was clean and children could swim in it.”

He recalls his youth in Libis sa Nayon during the 1960s. Today, pollution and flooding have made survival harder. Yet like many Caviteños, Reynato persists. His story reflects both the struggle and the hope of communities bound to the Imus–Ylang Ylang–Rio Grande Rivers.

South of Metro Manila, the bustling capital of the Philippines, lies Cavite, a province balancing breezy highlands, rapid industrial growth, and crowded coastal towns. One of the province’s major river systems is the Imus–Ylang Ylang-Rio Grande Rivers —a network of three rivers that once sustained ten cities and municipalities.

Mr. Reynato Robles, a river ranger who has witnessed the river’s journey from its former glory to its deterioration. Photo by John Castillo/PEMSEA.

Flowing from the cool highlands of Tagaytay, Amadeo, and Silang, through the midstream centres of Dasmariñas, General Trias, and Imus, down to the coastal towns of Bacoor, Rosario, Noveleta, and Kawit before draining into Manila Bay, the rivers irrigated farmlands, nourished fishing communities, and served as natural drainage and transport routes.

Large stretches of the river basin are now degraded, unable to support aquatic life. Domestic wastewater and solid waste, siltation, flooding, and water scarcity are among its pressing challenges. But the story is not only about decline. Local and national governments, communities, non-government organizations, and private companies are exploring solutions - from river rangers and flood basins to mangrove restoration. Slowly, the river’s story is shifting: from deterioration to renewal and restoration.

From green highlands to growing towns

The river begins in the uplands of Tagaytay, winding past Amadeo and into Silang, where cool breezes and green banks conceal an undercurrent of vulnerability. The soil here is prone to erosion and landslides. Tourism has flourished nonetheless, with homestays, cafés, and resorts drawing visitors to Tagaytay’s wide vistas.

But Mr. Maynard Ambion of Amadeo Municipal Environment and Natural Resources Office (MENRO), warns of tourism’s ecological costs.

“The growing number of private resorts is one of the contributors of water issues we closely monitor,” he says, noting that any new development must secure permits and clearances from the Local Water District and the National Water Resources Board.

In Amadeo and Silang, the Ylang Ylang River still flows – narrow, shaded, and partly hidden by dense greenery.

Informal settlements line its banks, with residents using the river to wash clothes. The water, however, is far from clean. Improper waste disposal persists despite regular garbage collection.

To address the problem, the local government of Amadeo transports residual waste to a sanitary landfill in a neighboring province, while biodegradable waste is composted and used as organic fertilizer in farms. Plans are underway for the establishment of a materials recovery facility and installation of trash traps that intercept waste before it drifts downstream.

Recent storms have only deepened the strain. “The tropical storm Crising (international name: Wipha) in July 2025 caused heavy erosion along the riverbanks,” explains Mr. Ron Adarlo of Amadeo MENRO. To reduce risks, the province is reinforcing river setbacks by establishing buffer zones along riverbanks to protect residents.

Midstream: where the river meets the city

As the river reaches Dasmariñas and General Trias, green banks give way to concrete, crowded homes, and floodwalls. Here, at the center of Cavite’s most populated areas, untreated sewage, domestic waste, and encroaching settlements place immense pressure on the waterways.

River rangers on the frontline

In General Trias, Mr. Winston Santillan leads a team of river rangers trained by the Department of Environment and Natural Resources (DENR) and employed by the General Trias local government. Every weekday, they wade through floating debris and vegetation along the river, a relentless and strenuous task.

Mr. Winston Santillan, a river ranger with the General Trias local government, leads a team that conducts daily clean-ups along the Imus– Ylang Ylang–Rio Grande Rivers. Photo by John Castillo/PEMSEA.

“The most common waste we recover is plastic packaging and Styrofoam,”

shares one of the river rangers.

But plastic is not the only problem. Without proper sewage systems in nearby neighborhoods and businesses, fecal contamination worsens, with fecal coliform levels in the midstream areas of the river reaching 16,000,000 most probable number (MPN) per 100 milliliters (1)– far exceeding the standard limit of 200 MPN per 100 milliliters. Untreated wastewater discharges from industrial and commercial establishments further degrade water quality.

To address this, Mr. Kenneth Castillo of General Trias City Environment and Natural Resources Office says that the city government is working to install sewage treatment plants in all 33 barangays and amend its septage policy. Plans include incorporating septage fees into household water bills to ensure compliance. Partnerships with private companies and NGOs are also helping rehabilitate the river through programs like Adopt-an-Estero, where these partners sponsor clean-up efforts in designated areas.

Sorting out Cavite’s trash

At the provincial level, the Office of the Provincial Environment and Natural Resources Officer (OPENRO), headed by Ms. Anabelle Cayabyab, has been strengthening solid waste management systems across Cavite. Their initiatives cover household waste disposal, sanitation services, and stricter enforcement of environmental regulations.

Cavite’s Provincial Ordinance No. 2013-021 promotes eco-friendly alternatives, such as reusable bags, and sets guidelines for proper waste segregation, recycling, and disposal.

Plastic waste remains one of the river’s major pollutants, clogging waterways and worsening floods. Photo by Orange Omengan/PEMSEA.

Flood management measures

The Imus–Ylang Ylang–Rio Grande Rivers is also prone to flooding, particularly in the low-lying areas of Bacoor, Imus, and Noveleta. To reduce these risks, the national government through the Department of Public Works and Highways (DPWH) with support from Japan International Cooperation Agency (JICA) has implemented the Cavite Industrial Area Flood Risk Management Project.

Completed in 2021, the Imus Retarding Basin is the country’s first facility of its kind. Spanning 35 hectares, it is designed to temporarily store excess rainwater and river overflow, helping to minimize flooding downstream. Nearby, the Bacoor Retarding Basin covers nine hectares and is divided into two storage ponds connected by a sluiceway, a channel fitted with gates that regulate the controlled release of water from one section to another.

“During the tropical storm Crising in July 2025, flooding in nearby communities was lessened thanks to the basin,”

says Engr. Sevino Cabral of DPWH Flood Control Management Division.

“The debris line shows just how high the water rose,”

he adds.

Downstream at a crossroads

As the river nears Rosario, Kawit, Noveleta, and Bacoor, challenges multiply. Quarrying contributes to siltation, while urban sprawl adds layers of solid waste. To keep the waterways navigable, the DPWH conducts annual dredging.

In Rosario, industrial discharge mixes with household waste, similar to what is observed in other highly urbanized areas. Informal settlements press against the riverbanks, often ignoring buffer-zone regulations, such as the Water Code of the Philippines (Presidential Decree 1067), which mandates easements of three meters in urban areas.

A portion of the mangrove area in Kawit, Cavite, which serves as a sanctuary for waterbirds and adds greenery to the urban landscape. Photo by Orange Omengan/PEMSEA.

In Kawit, road expansions once claimed swaths of mangroves. Today, 50 hectares are managed by the local government to restore lost cover and strengthen coastal defenses. Heavy rains, however, continue to carry garbage downstream, threatening the mangrove ecosystems.

In Barangay San Rafael, Noveleta, members of the Mangrove Farmers Association sustain their livelihoods by selling seedlings to companies sponsoring tree-planting drives. Supported by the DENR and the Philippine Coast Guard, this small-scale, biodiversity-friendly enterprise shows how communities link conservation with livelihood.

But waste is relentless.

“Most of the trash here comes from upstream,”

says Ms. Melody Gaguit of the Mangrove Farmers Association.

“Last July 2025, even a refrigerator was washed into our mangroves after typhoon Crising hit our area.”

Despite the odds, the association continues its work, replanting and selling seedlings, as part of efforts to restore the river and sustain the members’ livelihoods.

Ms. Glenda Alcantara sells seashells harvested from the brackish waters of Manila Bay along the roadside in Kawit, Cavite. Photo by Orange Omengan/PEMSEA.

Harvesting a living

Downstream, along Marulas Road in Kawit, seashell vendors line the roadside with harvests from the brackish waters of Manila Bay. According to the locals, their trade is affected by the bay’s water quality.

“Poor water quality affects our shellfish.”

says Ms. Glenda Alcantara, who has sold along the roadside for 20 years.

A seashell vendor sells seafood harvested from Manila Bay along Marulas Road in Kawit, Cavite. Photo by Orange Omengan/PEMSEA.

“Sometimes the brackish water turns milky, murky, and smells of chemicals. It’s better now since a big commercial polluter was shut down in 2024.”

For vendors like Glenda, the health of the river and bay directly determines daily earnings, with each storm and every influx of trash threatening their livelihoods.

Imus River in Barangay Kaingen in Kawit, Cavite. Photo by Orange Omengan/PEMSEA.

Integrated river basin management and the path forward

Plastic and solid waste remain as the river’s most stubborn pollutants, clogging waterways from upland creeks to coastal areas. In addition, untreated domestic and industrial wastewater, recurring flooding, and water scarcity are other pressing issues along the river basin.

Currently, the river basin is experiencing a water deficit of 106.053 million cubic meters per year, which is projected to increase to 382.640 million cubic meters per year by 2040 (2). To address this, the local government has implemented measures such as imposing a moratorium on land conversion in upstream areas, reforestation, and other water conservation initiatives.

The Imus–Ylang-Ylang–Rio Grande (IYRR) Rivers was designated as a Water Quality Management Area (WQMA) through DENR Administrative Order No. 2 in 2013 as part of the implementation of the Philippine Clean Water Act. An IYRR WQMA Action Plan covering the period 2016-2025 outlining strategies and actions to address pollution from domestic, institutional, commercial, industrial, and recreational sources provides opportunities for the IRBM Project to build on and contribute to its implementation and in the preparation of the Action Plan for 2026-2035.

Ylang Ylang riverbank in Amadeo, Cavite. Photo by Orange Omengan/PEMSEA.

The implementation of the Action Plan is overseen by a Governing Board, co-chaired by DENR-EMB Region IV-A and the Provincial Government of Cavite. Members of the Governing Board include representatives from relevant national government agencies, provincial and city or municipal governments, non-government organizations, the private sector, civil society organizations, and academia.

The Integrated River Basin Management (IRBM) Project is a regional initiative funded by the Global Environment Facility, implemented by the United Nations Development Programme Bangkok Regional Hub in partnership with ASEAN, and executed by the PEMSEA Resource Facility. This collaboration supports Cavite’s local governments in applying a “Source-to-Sea” approach -- linking upstream, midstream, and downstream cities and municipalities under one integrated management system.

A State of River Basin (SORB) Reporting System is being established for IYRR with the preparation of the baseline SORB Report consolidating information on the governance and management practices in the river basins and identifying gaps and priority issues requiring management interventions.

The flow towards revival

The Imus–Ylang Ylang–Rio Grande Rivers may no longer teem with the abundance that Reynato once knew, but its story is far from over. Across Cavite, river rangers, mangrove stewards, fisherfolk, artists, and local officials are restoring the river’s vitality by removing debris, nurturing mangroves, and promoting cleaner, sustainable livelihoods.

With sustained partnership, coordinated planning, and strengthened governance, the river can once again sustain farms, fisheries, and families. As Cavite grows, the river’s journey offers hope that progress and conservation can coexist, and that its waters.

A view of the Imus River near the retarding basin, filled with vegetation, in Barangay Anabu 1-A, Imus City, Cavite. (Photo courtesy of the Provincial Government of Cavite).

About the project

Supported by the Global Environment Facility, the Integrated River Basin Management(IRBM) Project is working to set up functional management mechanisms in priority river basins of six ASEAN countries to reduce pollution and sustain freshwater environmental flows as well as adapt to climate change vulnerabilities. The regional Project is being implemented by the United Nations Development Programme Bangkok Regional Hub, and executed by Partnerships in Environmental Management for the Seas of Seas Asia, in collaboration with ASEAN.