How Lesotho Works | Water to South Africa Explained

Why does Lesotho send water to South Africa? The two countries operate the Lesotho Highlands Water Project, a long-term arrangement to move water from Lesotho’s highland rivers towards South Africa’s Vaal River system, which helps supply the economically important Gauteng region. The project also supports hydroelectricity generation in Lesotho and includes payments, infrastructure and commitments agreed between the two governments.

How does the Lesotho Highlands Water Project work? Water is collected in highland reservoirs, transferred through engineered tunnels and routed to where it is needed. Katse and Mohale dams are parts of the completed first phase. Polihali Dam and a new water-transfer tunnel are part of Phase II, which was still under construction in October 2026—not an already finished extension.

This guide follows a drop of water through Katse, Mohale, the ‘Muela power station, the Ash River and the wider supply system. It also explains water royalties, electricity generation, local communities, environmental questions and project progress. For the broad country overview, read How Lesotho Works | Government, Highlands Water and Economy.

Lesotho’s water project at a glance

Project: Lesotho Highlands Water Project (LHWP), a cross-border water and hydropower programme.
Original agreement: Treaty signed by Lesotho and South Africa in 1986.
Phase I: Includes Katse Dam, Mohale Dam, tunnels and the ‘Muela Hydropower Station; completed and inaugurated in the early 2000s.
Phase II: Includes Polihali Dam and a long new tunnel connecting Polihali with the Katse system.
South African destination: The bulk-water system serving the Vaal/Gauteng region.
Lesotho benefits: Treaty-based payments, power generation and related infrastructure; these come with costs and responsibilities.
Construction status as of 1 October 2026: LHDA listed Polihali Dam at 56% and its transfer tunnel at 60% completion.

The simplest way to understand the project is to imagine the highlands as the source, reservoirs and tunnels as the connectors, and the cities and communities at the receiving end as the users. None of these pieces works alone.

Why is water from Lesotho useful to South Africa?

Lesotho is a mountainous country entirely surrounded by South Africa. Its highlands receive precipitation that feeds river systems. South Africa’s Gauteng region contains large concentrations of homes, commerce and industry, and dependable bulk-water infrastructure helps support those activities.

The two countries have different geographical strengths and needs. Lesotho has highland water resources; South Africa has major demand in the Vaal-linked supply system. Engineering allows part of the water to move across a watershed and a national border under a long-term agreement.

This does not mean that Lesotho has unlimited water. Rainfall varies, river systems have ecological needs, and households within Lesotho still require their own reliable water services. A country can participate in a major export or transfer system and still face local access challenges. Bulk-water infrastructure and village water distribution are related but distinct tasks.

What was agreed in the 1986 treaty?

The 1986 treaty established the framework for the Lesotho Highlands Water Project between Lesotho and South Africa. It governs a shared undertaking in which water is delivered and hydropower benefits Lesotho. Later agreements set out the arrangements for subsequent phases.

The two-country structure matters. One government cannot simply treat the project as a domestic dam while ignoring downstream users or the other country’s rights. Engineering, water delivery, money, oversight and community commitments require institutions that work across the border.

The Lesotho Highlands Development Authority (LHDA) is a primary source for project descriptions and progress. Its pages explain the project’s origins, physical infrastructure, power-generating role and current works. For detailed treaty interpretation, readers should consult the governing legal agreements rather than relying on a simplified article.

Where does the water actually go?

A useful mental map traces the principal Phase I route.

Highland rivers: Water reaches reservoirs in Lesotho’s highlands.
Mohale to Katse: A connecting tunnel links the Mohale and Katse systems, enabling transfers between the reservoirs.
Katse Reservoir: Katse is a major storage and transfer centre in the network.
Katse to ‘Muela: Water is conveyed through a long tunnel towards the ‘Muela hydropower installation.
‘Muela: Flowing water drives turbines to generate electricity, subject to operating conditions.
Ash River outlet: After the delivery tunnels, water reaches the Ash River in South Africa and continues through the receiving river and supply system.
Regional users: The wider Vaal system supports water supply to Gauteng and other connected users.

This is a simplified learning route. Actual operations include gates, levels, maintenance, environmental-flow obligations and different conditions across seasons. Water moved for the project does not bypass every treatment plant and arrive directly at someone’s kitchen tap.

The official LHDA Phase I technical description sets out the Katse, Mohale, ‘Muela and Ash River connections.

What is Katse Dam and why is it important?

Katse is one of the project’s central highland reservoirs. Its dam stores river water and its intake and transfer arrangements connect it to the wider tunnel network. The project is more than an impressive concrete wall: it includes engineers, gauges, operations staff, access infrastructure and continuous monitoring.

Large reservoirs allow some separation between when rain falls and when water is needed. But storage is never infinite. Reservoir operators must also manage safety, environmental conditions, changing inflows and the demands placed on the system.

The key point is that Katse is a hub. It links natural catchments, engineered storage, water-transfer infrastructure and power generation. Students learning geography can trace the catchment; students learning physics can study pressure and gravity; students learning economics can study long-term water agreements.

What does Mohale Dam add?

Mohale is a second major reservoir of Phase I. It is linked to Katse through a long connecting tunnel. This increases the project’s flexibility and ability to use water from more than one part of the highland catchment system.

It is easy to imagine two isolated lakes. The engineered reality is closer to a connected network. Water levels, transfer capacity, maintenance schedules and operating decisions determine how the reservoirs support one another.

That is why comparing dams only by height or storage capacity misses the wider purpose. The question is not simply, ‘How big is the dam?’ It is, ‘What useful, reliable connection does the dam provide, and at what environmental and social cost?’

How can the same project provide electricity to Lesotho?

As water moves from higher elevations through suitable infrastructure, its flow can turn turbines. At the ‘Muela hydropower station, turbines drive generators that produce electricity. The water can then continue along the delivery route towards South Africa.

According to LHDA’s Phase I description, the ‘Muela station has three turbine-generators rated at 24 megawatts each, for 72 megawatts of installed capacity. Installed capacity, however, does not mean that the station generates 72 megawatts every minute of every day. Output depends on water availability, operating requirements and technical conditions.

This is one of the most educational features of the programme: a water transfer can provide more than one service. Yet every use brings constraints. Hydropower operation, water delivery and river management must be coordinated rather than treating the water as a free and unlimited source of energy.

Is Lesotho selling water like a commercial product?

People often say Lesotho sells water to South Africa. That is a convenient shorthand, but it can mislead if it makes the arrangement sound like an ordinary supermarket sale.

The project is governed by an international treaty and associated agreements. Payments to Lesotho include water royalties or treaty-based financial arrangements, alongside wider project responsibilities and costs. Readers should not infer a simple bottle-by-bottle price from the phrase ‘selling water’.

Royalties are financially important, but they are not the project’s only effect on the economy. Construction employment, roads, skills, procurement, power infrastructure, maintenance and environmental obligations also matter. A complete economic picture asks where the benefits go, what public spending they support, and who bears the consequences of land and livelihood changes.

LHDA’s project reporting includes information on water royalties and project operations, and is a better starting point for dated financial figures than a general statement about a fixed yearly income.

What is Phase II and why is Polihali Dam being built?

Phase II is the next major stage of the Lesotho Highlands Water Project. It includes the Polihali Dam, associated infrastructure and a water-transfer tunnel connecting Polihali to Katse. The programme is designed to expand the amount of water available for the agreed cross-border transfers.

Polihali is not just a second name for Katse. It collects water in a different reservoir area and needs a new transfer connection to the established project system. The planned works also require roads, bridges, power connections, communications, contractor facilities and arrangements for affected communities.

A major dam therefore changes more than a stretch of river. It changes road networks, land use, construction access, local movement, public services and future maintenance demands. The LHDA Phase II overview describes those wider components.

Does the Polihali–Katse tunnel work by gravity?

The planned transfer tunnel carries water from Polihali towards Katse by gravity, using the elevation difference and the tunnel’s engineering design. The approximately 38-kilometre tunnel is a central part of Phase II.

Gravity can move substantial quantities of water, but the system still needs gates, monitoring, safe tunnel construction, reservoir operations and maintenance. A tunnel does not become self-managing simply because there is no pump pushing the water for the main transfer.

South Africa’s Department of Water and Sanitation reported the launch of major tunnel-boring work at Polihali in April 2026. That was a construction milestone, not the completion of the water-transfer route.

How far had Phase II progressed by October 2026?

According to the official LHDA site update dated 1 October 2026, Phase II’s advance infrastructure was reported at 99%, Polihali Dam at 56%, and the Polihali transfer tunnel at 60%. The same update listed the major bridges as complete.

These figures describe reported construction progress on that date. They are not a guarantee that exactly the same percentages hold today or that water transfer has begun. Later progress reports can change the numbers, and physical completion still has to be followed by testing, commissioning and safe operation.

The LHDA’s project documentation has described targeted future water-delivery dates. Treat old target dates as planning milestones, not as evidence that construction was completed on schedule. Readers seeking an opening or commissioning date should check the newest official announcement.

How much more water is Phase II intended to deliver?

LHDA’s Phase II project explanation describes a reference supply of about 780 million cubic metres a year and an intended increase towards roughly 1,270 million cubic metres a year as the project expands. These are programme-scale reference and target quantities, not proof of what was actually metered in a particular week of 2026.

The numbers are easier to understand when connected to demand. Cities need water every day. A large annual quantity is a planning measure that allows governments and utilities to design reservoirs, tunnels and distribution capacity. Real deliveries still depend on rainfall, stored water, operations and environmental obligations.

If a headline gives only the target increase, it leaves out the very important question of how, when and under what constraints that target will be achieved. Engineering programmes need actual measured performance once commissioned.

Do local communities automatically benefit from the water project?

No. A large national project can create jobs, roads, bridges and revenue while also disrupting homes, farmland, grazing areas and community connections. Some benefits are national and long-term; some costs are local and immediate.

The Phase II programme includes compensation, resettlement and livelihood-restoration commitments. The LHDA project information recognises that construction and reservoir development may cause physical or economic displacement. It sets out mitigation measures intended to restore or improve affected households’ living conditions.

The test of a development project is not simply whether compensation is promised. It is whether processes are transparent, people can participate meaningfully, grievances are addressed, and households can sustain their livelihoods after construction workers leave.

Can a community near a reservoir still lack piped water?

Yes. Being physically close to a large dam does not automatically give a household a treated-water connection. Bulk transfer, local treatment, village distribution, maintenance and affordability are different layers of infrastructure.

This is an important lesson for students. The presence of an impressive national asset should never be mistaken for automatic access to a service by every person living nearby.

What happens to rivers, fish and downstream ecosystems?

A dam alters the timing, location and movement of water. It can affect sediment, aquatic habitats, river flow, land and livelihoods. The type and extent of impact depend on the project, its operating rules, mitigation measures and ecological conditions.

Responsible analysis asks what flows must remain in affected rivers, how environmental monitoring is carried out, how communities are consulted and what remedies are available if an expected outcome does not materialise. A water project can produce genuine public value while still imposing significant environmental and social costs.

The right question is not whether a dam is automatically good or automatically bad. It is whether benefits, risks and obligations are assessed honestly, and whether the people affected have practical ways to be heard.

What if there is a drought in the Lesotho highlands?

Drought can reduce inflows into reservoirs and place pressure on the wider supply system. Reservoir storage and connected infrastructure create flexibility, but they cannot manufacture rainfall.

Water managers must consider current storage, inflows, environmental requirements, delivery commitments and long-term climate variability. A full reservoir one month is not a promise of unlimited supply in future years.

The project therefore belongs in the broader conversation about water conservation, catchment protection, demand management and resilience. New dams are only one component of dependable regional water supply.

A worked example: follow one drop from the highlands to a city

Imagine a fictional drop of rain falling in a Lesotho highland catchment. It flows towards a river and, under suitable conditions, reaches a reservoir. It is stored alongside water from many other rainfall events. Operators manage how water is released or transferred through the engineered system.

The water moves through the linked reservoirs and tunnels. As part of the journey, it can help drive a turbine at ‘Muela. It then travels towards the Ash River outlet in South Africa and enters downstream water systems that ultimately support users. Before reaching a home, actual public water supply requires additional conveyance, treatment and distribution.

Now imagine something fails. Too little rain reduces inflow. A tunnel needs maintenance. A water-treatment facility has a fault. A neighbourhood pipeline breaks. The same person at the end of the chain may experience a shortage, but the cause could lie at very different stages.

This is an educational illustration, not a hydrological simulation. It shows why good water management starts by tracing the chain rather than blaming the nearest visible dam.

How does Lesotho’s project compare with Singapore’s water planning?

Lesotho and Singapore solve different geographical problems. Lesotho uses highland rivers and cross-border agreements to supply water to a neighbouring country’s major demand centres. Singapore combines local catchment, imported water, NEWater and desalination to diversify its supply.

Neither model can simply be copied into the other’s landscape. Both show why a tap is only the last stage of a much larger system. Storage, treatment, conveyance, financial arrangements, maintenance and the trust between institutions determine whether water reaches people.

For another country-system view, visit How Singapore Works and How South Africa Works | Government and Economy. Water connects geography, infrastructure and public decision-making in each setting.

Frequently asked questions about Lesotho’s water

Why does Lesotho transfer water to South Africa?

The countries agreed to a project that uses Lesotho’s highland water resources to support the Vaal/Gauteng supply system while providing treaty-based benefits, infrastructure and hydropower opportunities to Lesotho.

Does South Africa own the water in Lesotho’s rivers?

A cross-border treaty governs specified project rights and obligations. It does not mean that a simplistic statement about one country owning every river in another is accurate.

Which dams are already operational?

Katse and Mohale are established components of Phase I, along with the linked tunnels and other infrastructure.

Was Polihali Dam finished in October 2026?

No. LHDA’s 1 October 2026 update reported Polihali Dam at 56% and its transfer tunnel at 60% construction progress.

Does the water flow through a power station?

The Phase I transfer system includes the ‘Muela hydropower station, where flowing water can generate electricity before continuing towards South Africa.

How much power can the ‘Muela station generate?

Its installed generating units are rated at three times 24 megawatts, giving 72 megawatts of installed capacity. Actual output varies with operating conditions.

Is the water exported in bottles?

No. The Lesotho Highlands Water Project is a bulk-water transfer system using dams, tunnels and river infrastructure.

Are water royalties the same as profit?

Not necessarily. Treaty-based royalty receipts are one financial element; project costs, public spending, maintenance and broader economic impacts need separate accounting.

Will bigger dams eliminate drought risk?

No. Storage improves flexibility but cannot remove the effects of rainfall variability, catchment conditions, operating constraints or rising water demand.

Do households in Lesotho automatically receive water from the project?

No. Household supply depends on separate local networks, treatment, distribution, maintenance and access arrangements.

Official sources and verification routes

The progress figures quoted above were reported by LHDA as of 1 October 2026. Planned targets, actual measured deliveries and commissioning dates should always be kept separate. This article is a learning guide, not a substitute for operational or legal project documentation.

Continue the How Countries Work series

Read How Lesotho Works | Government, Highlands Water and Economy, Understanding the Education System of Lesotho, and the How Countries Work collection.

The larger lesson is that a water project is not only a reservoir. It is a long chain of rainfall, mountains, tunnels, electricity, law, communities, environmental responsibilities and taps. A good system works when the entire chain remains connected—and when the people along it are not forgotten.

How Lesotho Works | Why Does Lesotho Send Water to South Africa? Katse, Mohale and Polihali Explained