---
title: who depends on the matanza-riachuelo
canonical_url: https://ensurance.app/guide/who-depends-on-the-matanza-riachuelo
markdown_url: https://ensurance.app/guide/who-depends-on-the-matanza-riachuelo.md
subtitle: "about 4.7 million people in the basin, and a city that drinks the estuary those waters reach"
category: ensurance
---

# who depends on the matanza-riachuelo

*about 4.7 million people in the basin, and a city that drinks the estuary those waters reach*

The Matanza-Riachuelo is the river along the southern edge of Buenos Aires. In the upper basin the stem is called the Matanza. In the last stretch it is the Riachuelo. It is a lowland river with little slope, and the main course runs 64 kilometers, southwest to northeast, until it discharges into the Río de la Plata.

If you live in Lanús, Avellaneda, La Matanza, or the southern comunas, that stem is the edge of the map you already use. It is a boundary more than an amenity: a river the city's sewage has used, which the people along it still meet. ACUMAR's basin characteristics, using the definitive Census 2022, count **4,703,058** people there. They depend on that river still functioning as a river.

The city around them depends on a different water. Drinking water for the concession is taken from the Río de la Plata, the estuary this river joins, not from the stem itself. Same metro. Two waters. Naming who depends means keeping them apart.

## who the basin count is

The basin covers about **2,047 km²**. That area, the 64 km stem, and the census population are the figures on ACUMAR's characteristics page, and they are the figures this series uses. The authority's own documentary center still says about 2,200 km² and about 6 million people. Those older lines are still sitting on that page. They are not the count here.

Fourteen partidos of the Province of Buenos Aires sit inside the basin: Almirante Brown, Avellaneda, Cañuelas, Esteban Echeverría, Ezeiza, General Las Heras, La Matanza, Lanús, Lomas de Zamora, Marcos Paz, Merlo, Morón, Presidente Perón, and San Vicente. So does all of Comuna 8 of the Ciudad Autónoma de Buenos Aires, and parts of Comunas 1, 3, 4, 5, 6, 7, 9, and 10. The Province as a whole is a different geography. These partidos are in the story because the river is.

ACUMAR reads that census figure as about 10 percent of Argentina's population, on a small piece of the map. When the sewer does not take the flow, the street and the river do. For a person who lives there, the dependency is concrete: less sewage in the street, and a river that is still a river.

If the basin is where you sleep, you are already in the 4,703,058.

## who is on the tap

[What Buenos Aires depends on](/guide/what-buenos-aires-depends-on?from=guide) is the estuary staying treatable. Intake towers take raw water from the Río de la Plata. **AySA** treats it at three surface plants. The company names two of them: General San Martín and Juan Manuel de Rosas. The public count of surface plants is three. The third plant is left unnamed.

The 2023 sustainability figures put average treated water at **6,219,234 m³/day**. Well water is **13%** of production. The wells are part of the system. The tap is the estuary.

The concession covers **3,363.51 km²**. **15,103,199** people live in the concession area. **11,351,535** of them are served with potable water. **9,497,481** are on sewer service. All four figures are that 2023 set. The concession is a wider map than the basin. A ratepayer on AySA's tap may never stand on the Riachuelo and still drink water taken from the estuary the Riachuelo enters. A household on the upper Matanza may sit outside the potable-service count and still live on the river. Adding the two populations would double-count the overlap and produce a number nobody published.

If you pay an AySA bill, your dependency is the shore the towers stand in. Turbidity, a spill, and whatever the southern river still delivers to the estuary all arrive at the same plants. The plants can treat a bad day. They were sited on this estuary.

## the operator is not the authority

AySA — Agua y Saneamientos Argentinos — is the metropolitan water and sewer company. It runs the Plata plants. It runs the Riachuelo system: the collector, the outfall, and the treatment plant. The office that already operates the tap and the big sewer job is AySA.

The Ley de Bases declares the company subject to privatization, and AySA began a reorganization. That is a corporate fact from the company's April 2025 results note. No sale is recorded here, and no buyer is named. The operator of record is still AySA.

**ACUMAR** — Autoridad de Cuenca Matanza Riachuelo — is the basin authority Law 26.168 created for the Nation, the Province of Buenos Aires, and the City. It plans and controls sanitation in the basin through PISA, the basin sanitation plan. ACUMAR does not treat your drinking water, and it does not run the surface plants. AySA is the operator. ACUMAR is the statute.

The Supreme Court's 2008 judgment in *Mendoza* ordered the cleanup. In October 2024 the Court ended its supervision of that case. On 14 August 2025 it rejected appeals and reaffirmed the close. Execution stays with ACUMAR. The Court leaving is not the river recovering. The 4,703,058 people did not receive a different river in the week the file closed.

## what the works are leaning on

A World Bank paper from August 2025 says the Riachuelo system was in testing, and that the testing already reduces overflows. The works are real. The paper does not call the outfall finished.

The same record treats the tannery sector as a major industrial source. A park for those shops was finished in October 2023. The industrial plant that would treat their load was not the operating fix in the June 2025 snapshot: physical progress stood at 90 percent on 30 June 2025, and the paper said full operation still required tanneries to relocate, which would take years. That is a load. Households on an unfinished sewer and shops still sending effluent are two ways the stem gets used as a pipe.

The works depend on the river remaining a river. A collector that moves sewage out still needs a mouth, a bank, and a direction of flow. The plant assumes the stem is still there. While the test runs, people on the bank live with both: pipes going in, and a river still carrying what the pipes have not taken.

A southeast storm can reach you by a different path. When that wind holds the Plata up, the city's drains cannot empty, and the highest remaining flood risk sits over the Matanza-Riachuelo. The wind and the industrial load are separate hazards. [What a sudestada does to the city](/guide/what-a-sudestada-does-to-buenos-aires?from=guide) is the wind. The estuary — a river meeting the sea, not a tank behind the plants — is [its own account](/guide/the-plata-is-an-estuary-not-a-tap?from=guide). The Paraná is only the parent outlet, already mapped as [parana-river.basin](/parana-river.basin?from=guide). This series stays on the southern river and the intakes.

## three dependencies

| who | depends on | the figure |
|---|---|---|
| Basin residents | the Matanza-Riachuelo still working as a river, including with less sewage in the street | 4,703,058 people, Census 2022 |
| Ratepayers on the intakes | the Río de la Plata staying treatable where the towers stand | 11,351,535 people on potable service, inside 15,103,199 in the concession area (2023) |
| The Riachuelo works | the river remaining a river the pipes can leave | collector, outfall, and plant in testing (2025) |

You cannot move a resident off this stem, a ratepayer off this estuary, or the works off the mouth they were built to relieve.

:::johnson
**the basin is counted on the river. the tap is counted on the estuary that river reaches.**

Census 2022 puts 4,703,058 people in the basin. AySA's 2023 figures put 11,351,535 people on potable service. Same metro. Two waters. The works in testing are the third party, and they lean on the river still being there.

[see how a utility funds the water it already runs →](/solutions/utilities?from=guide&topic=matanza-riachuelo)
:::

## beside the pipes, not instead of them

AySA is already running the plants and testing the system. ACUMAR is already the authority the Court handed execution back to. What is still open is a shared hold on the living condition of the stem, and of the intake shore, while the pipes do what pipes do.

The estuary, the towers, and the Matanza-Riachuelo are there whether or not anyone buys a certificate. **Ensurance** is how the utility that already runs the tap can fund that living water. The funding is not the river, not a second concession, and not a claim that the water is clean. It does not stand in for the collector.

A certificate is that funding, named for the thing it funds. The line `matanza riachuelo` is in ideation under [parana-river.basin](/parana-river.basin?from=guide). [Co-create it](/specific/create?mode=suggest&agent=parana-river.basin&name=matanza%20riachuelo&from=guide): you propose the line, a person reviews it, and the parent agent receives it. Water as a condition, rather than as a single pipe, already has a live home at [clean-water.ensurance](/clean-water.ensurance?from=guide).

If you operate the system, the services that match this exposure are named on the [utilities](/solutions/utilities?from=guide&topic=matanza-riachuelo) page: source watershed investment for the shore the intakes use, and sewer overflow restoration for the river the overflows have used. What a year of that partnership looks like, for the company that already runs both, is [who already pays for the riachuelo](/guide/who-already-pays-for-the-riachuelo?from=guide).

## questions people ask

### who depends on the matanza-riachuelo?

People in the basin, first: 4,703,058, the definitive Census 2022 count ACUMAR publishes. Then the ratepayers on the Plata intakes, because this river reaches the estuary their tap comes from: 11,351,535 people on potable service in AySA's 2023 figures, inside 15,103,199 in the concession area. Then the works. A collector, an outfall, and a plant in testing depend on the river remaining a river.

### is the riachuelo the city's drinking water?

No. Drinking water is taken from the Río de la Plata through intake towers and treated at three surface plants. AySA names General San Martín and Juan Manuel de Rosas. The Matanza-Riachuelo meets that estuary. It is the southern river.

### how many people live in the matanza-riachuelo basin?

4,703,058 people, across about 2,047 km², on a main stem of 64 km. That is ACUMAR's characteristics page and the definitive Census 2022. The documentary center still shows about 6 million people and about 2,200 km². The characteristics figures match the census. The older pair is a different sentence, still on the documentary center.

### who runs the water, and who has the basin?

AySA runs potable water and sewer, including the plants and the Riachuelo system. ACUMAR is the basin authority under Law 26.168 and coordinates PISA. It does not treat the drinking water. Since October 2024, reaffirmed on 14 August 2025, execution of the Mendoza cleanup sits with ACUMAR. The end of court supervision is not a recovered river.

### can the river be funded beside the works?

The line `matanza riachuelo` is in ideation under [parana-river.basin](/parana-river.basin?from=guide). [Co-create it](/specific/create?mode=suggest&agent=parana-river.basin&name=matanza%20riachuelo&from=guide): a person reviews the suggestion, and the parent agent receives it. [clean-water.ensurance](/clean-water.ensurance?from=guide) is the live water instrument you can open now. If you run the plants, start from [utilities](/solutions/utilities?from=guide&topic=matanza-riachuelo).

## what you can do with this

If the basin is your neighborhood, you are already in the census the authority publishes. The works in testing are the public effort next to you. The river is still the thing you live with.

If you run the plants or the sewer, you are already the operator this water depends on. Fund the living estuary and the living river beside those pipes: the [utilities](/solutions/utilities?from=guide&topic=matanza-riachuelo) page for that work, [clean water](/clean-water.ensurance?from=guide) for the outcome that already exists, or a conversation that starts from this basin.

[talk to someone who can help →](/contact?from=guide&topic=matanza-riachuelo)

## sources

[ACUMAR, características de la cuenca](https://www.acumar.gob.ar/institucional/que-es-acumar/caracteristicas-de-la-cuenca2/) — the 64 km main stem, about 2,047 km², 4,703,058 people on the definitive Census 2022, the fourteen partidos and the city comunas, and the page's reading of that population as about 10 percent of Argentina.

[ACUMAR documentary center, La Cuenca](https://centrodocumental.acumar.gob.ar/la-cuenca) — the older lines, about 2,200 km² and about 6 million people. Cited so the conflict is visible. Not used as the current figure.

[AySA, nuestros números](https://www.aysa.com.ar/Quienes-Somos/nuestros-numeros) — 2023 sustainability figures: concession area 3,363.51 km², 15,103,199 people in the concession area, 11,351,535 on potable water, 9,497,481 on sewer service, three potable plants, average treated water 6,219,234 m³/day.

[AySA, agua potable](https://www.aysa.com.ar/Que-Hacemos/Agua-potable) — intake towers, surface plants named General San Martín and Juan Manuel de Rosas, a total of three, and well water at 13% of production.

[AySA results note, April 2025](https://www.aysa.com.ar/usuarios/Novedades/2025/04/resultados_superavit_operativo) — the Ley de Bases declares AySA subject to privatization, and the company began a reorganization.

[World Bank paper, August 2025, P105680](https://documents1.worldbank.org/curated/en/099082025172028148/pdf/P105680-60a8b946-e924-4105-8690-a2f3d85c639a.pdf) — the Riachuelo system in testing, overflows the paper says testing already reduces, the tannery sector as a major industrial source, the park finished in October 2023, and the industrial plant at 90% physical progress on 30 June 2025 with relocation still ahead of full operation.

[Infobae, 14 August 2025](https://www.infobae.com/judiciales/2025/08/14/la-corte-ratifico-el-cierre-de-la-causa-riachuelo-y-dio-por-concluida-su-supervision-del-saneamiento/) — the Court rejected appeals and reaffirmed the close of its supervision. Used only for that close.

[ACUMAR, causa Mendoza](https://www.acumar.gob.ar/institucional/causa-mendoza/) — the authority's page on the 2008 judgment and the case it still executes.

## the series

- [what buenos aires depends on](/guide/what-buenos-aires-depends-on?from=guide)
- [who depends on the matanza-riachuelo](/guide/who-depends-on-the-matanza-riachuelo?from=guide)
- [the plata is an estuary, not a tap](/guide/the-plata-is-an-estuary-not-a-tap?from=guide)
- [a sudestada stacks the plata against the drains](/guide/what-a-sudestada-does-to-buenos-aires?from=guide)
- [who already pays for the riachuelo](/guide/who-already-pays-for-the-riachuelo?from=guide)