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By Annonciata Byukusenge
Samuel Ochieng has fished Lake Victoria for twenty-three years. He knows the water by its moods, the silver mornings, the sudden storms, and the way the Nile perch used to run so thick a man could feel them pressing against the hull of his boat. He does not know what is happening beneath him.
Below the surface of the world’s largest tropical lake, and the second-largest freshwater lake by area on earth, something is quietly failing. Scientists call it hypoxia. Fishermen in Mwanza, Kisumu, and Entebbe have another name for it, when they have a name at all: empty water.
Roughly 40% of Lake Victoria’s lake floor is now a dead zone, a deposit of water so empty of oxygen that virtually nothing can survive there. It is not a projection. It is not a forecast drawn from a climate model. It is the condition of the lake today, and it is expanding.
A crisis hidden in plain sight
The announcement that five East African nations will gather in Mwanza this week for the inaugural Lake Victoria Day, a regional forum organised by the East African Community’s Lake Victoria Basin Commission, has drawn attention to a body of water that sustains more than 45 million people across Burundi, Kenya, Rwanda, Tanzania, and Uganda. The forum’s theme, Shared Waters, Shared Future, gestures toward cooperation. What the official program does not dwell on is the scale of what is already lost.
The State of the Basin Report 2025, released alongside the forum materials, documents a fishery that has declined by more than 50% in two periods. Kenya’s Winam Gulf, which wraps around the city of Kisumu and hosts the Lake Victoria Basin Commission’s own headquarters, is rated critical for pollution. Tanzania’s Mwanza Gulf, which will host this week’s ceremonies, requires more than 100 million dollars in infrastructure investment just to begin addressing its environmental problems. Uganda’s Murchison Bay, where Kampala’s wastewater meets open water, has pushed the cost of treating drinking water at the Ggaba plant to an additional 135,000 dollars every single month.
These are the numbers that have made it into the reports. The dead zones, mostly, have not.
What Hypoxia Does
When oxygen disappears from deep water, the lake floor becomes chemically hostile to most forms of aquatic life. Fish abandon these zones. Bottom-dwelling organisms that form the base of the food chain collapse. Decomposition slows and then stalls, allowing phosphorus and nitrogen to build up in the sediment rather than cycling back into the water column in forms that support life.
Eventually, the anoxic layer releases those nutrients in a burst, feeding algal blooms at the surface that block sunlight, consume more oxygen as they decay, and drive the dead zone deeper still. It is a self-reinforcing loop. The lake is not simply being polluted from the outside. It is beginning to poison itself from within.
Lake Victoria was always small by the standards of great lakes; its average depth is around 40 meters, and low tropical lakes are integrally vulnerable to stratification, the separation of warm, oxygen-rich surface water from cooler, oxygen-starved water below. What has changed is the speed and severity of that stratification. Warmer air temperatures, driven by climate change, reduce the seasonal mixing that once refreshed the deep water. Nutrient loading from the rivers that drain into the lake, the Kagera, the Nzoia, the Nyando, the Mara, and the Mirongo, has accelerated, feeding algal growth faster than the lake can absorb it.
The result is a lake that is functionally shrinking. Not in surface area. In a volume that can support life.
Five countries, five pressures
Each of the five partner states brings its own particular damage to the lake, and each pays a price shaped by its geography.
In Burundi, which sits at the headwaters of the Kagera River system, the problem begins with fire. More than 74% of the population lives on less than three dollars a day, and most cook with firewood and charcoal. Deforestation in Burundi’s steep highlands strips the soil, and every rainy season delivers another load of sediment and agricultural runoff into the river system that eventually reaches the lake. Burundi has only 77 megawatts of installed renewable energy, the lowest in the basin, and electricity reaches just 12% of its people, the lowest figure in the region by a wide margin. The country’s groundwater monitoring systems are, according to the Basin report, almost nonexistent. The headwaters of a lake that 45 million people depend on are being watched by almost no one.
Rwanda has a different story; the basin’s strongest performer is in water access, sanitation, and climate governance. Kigali’s Nyandungu Eco-Park, a wetland restoration project in the middle of a fast-growing city, is held up in the basin report as a model that other countries could replicate. Rwanda has the region’s most ambitious greenhouse gas reduction target, 38% by 2030, and has built advanced river flow sensors across the Akagera basin.
The challenge the report identifies is not Rwanda’s domestic performance. It is whether a country of 14 million people can translate its institutional credibility into regional influence, persuading upstream and downstream neighbors to take commitments as seriously as Rwanda does.
In Kenya, the contradictions are sharpest. The Lake Victoria Basin Commission itself is headquartered in Kisumu, on the shores of Winam Gulf, the most polluted bay in the lake, rated critical in every meaningful indicator. Fish landings from Kenyan waters have dropped by 50% over the past twenty years. Mercury contamination near Kisumu threatens water life, the health of pregnant women, and children.
The Nzoia and Nyando rivers carry heavy loads of sediment and agricultural runoff into the lake. Kenya invested 70 million dollars in water treatment upgrades and has the highest electricity access in the basin at 76%, but the gulf directly outside the commission’s window is choking.
In Tanzania, scale is both an asset and a liability. Tanzania holds the largest share of the lake’s surface area and operates the largest fishing fleet: more than 25,000 small boats working water that is producing less with every passing season. Nile perch exports through Mwanza generate significant foreign exchange, but the fishery is under sustained pressure from overfishing and pollution simultaneously.
The Mirongo River carries untreated wastewater and solid waste directly into Mwanza Gulf. The Kagera River, flowing through Rwanda, Burundi, and Tanzania before reaching the lake, brings sediment and runoff from three countries into water that Tanzania must share with four others. Climate-related losses between 2020 and 2024 reached 1.26 billion dollars, the second-highest total among the five nations.
In Uganda, the stakes take on a dimension no other country in the basin faces. Uganda controls the lake’s only outlet, the Victoria Nile at Jinja, which means that every hydropower dam downstream of the lake, supplying electricity to much of East Africa, depends on the lake maintaining both its volume and its water quality. Murchison Bay’s pollution is not only a public health problem. It is an energy security problem. Around 15,000 fishing boats work in Ugandan waters, and the port infrastructure at Port Bell and Jinja, the arteries of regional lake trade, needs major investment that has not yet arrived.
What the forum will and will not do?
The Mwanza gathering runs from 18 to 21 May. The Stakeholders’ Forum on 18 and 19 May will feature presentations on the Lake Victoria Basin Water Information System and the LVBC Strategic Plan. The Development Partners Round Table on 20 May will convene ministers and international funders around investment priorities. On 21 May, the inaugural Lake Victoria Day will be formally declared, an annual marker, the commission says, of collective regional commitment to the lake’s future.
Technical releases are scheduled: the State of the Basin Report 2025, the Lake Victoria Basin Water Information System, and the integrated water resources management strategy running to 2050.
Whether any of these moves at the speed the dead zone requires is a different question.
The basin report calls for restoring Winam Gulf; enforcing pollution controls along river catchments; protecting wetlands in Uganda and Tanzania; upgrading ports; investing in Kampala’s wastewater system; revising Uganda’s outdated rules for managing the Victoria Nile outflow; and expanding water monitoring in Burundi’s upper catchments, a country that, as the report notes with some care, receives less technical and financial support, relative to its basin-wide impact, than any of the other four.
None of these recommendations is new. Several have appeared in previous regional plans. The gap between agreed commitment and practical action is itself documented in the same report that calls for closing it.
The number nobody quotes.
Back on the water, Samuel Ochieng and the 15,000 or so fishermen working Ugandan waters, and the 25,000 working Tanzanian waters, and the thousands more spread across Kenya, Rwanda’s small shoreline, and Burundi’s banks, are operating on a lake where four out of every ten square meters of floor offers nothing. No food. No refuge. No future for the fish that once defined what this water meant.
Forty-five million people live in the basin. They drink from it, eat from it, ship goods across it, generate electricity from its rivers, and in places like Kisumu, Mwanza, and Kampala, build cities along its banks. The lake is not dying in a way anyone can see from the shore. It is dying at the bottom, in the dark, in the silence that falls when oxygen leaves and nothing comes back to fill the space it leaves behind.
