The Yala Swamp at the mouth of the Yala River covers about 175 square kilometres (68 sq mi) along the northern shore of Lake Victoria.^[1] The swamp contains 1,500 hectares (3,700 acres) Lake Kanyaboli, a freshwater deltaic wetland with an average depth of 3 metres (9.8 ft), which is fed by the floodwaters of the Nzoia and Yala rivers and by the backflow of water from Lake Victoria.^[2]

In the past the Yala River flowed through the eastern 20% of the Yala Swamp into Lake Kanyaboli, then into the main swamp, and then through a small gulf into Lake Victoria. Today the eastern part of the swamp has been drained, and the river flows directly into the 8,000 hectares (20,000 acres) main swamp. It is cut off from Lake Kanyaboli by a silt-clay dyke. Lake Kanyaboli now receives its water from the surrounding catchment area and from back-seepage from the swamp.^[3]

Lake Kanyaboli provides a refuge for several species of fish, some of which are no longer present in Lake Victoria.^[2] The introduction of the Nile perch (Lates niloticus) to Lake Victoria caused an ecological disaster which threatens to destroy the ecosystem of the lake. In the past the lake fishermen caught hundreds of species of fish, many of which were endemic. Today they rely on the Silver cyprinid (Rastrineobola argentea) locally known as "Omena" or "Dagaa" among East African communities, the Nile Perch and the Nile tilapia (Oreochromis niloticus). In 1988 the World Conservation Union listed hundreds of the endemic fish species as Endangered. Some of these fish are still thriving in Lake Kanyaboli, including several unknown Haplochromis species, Singida tilapia (Oreochromis esculentus) and Victoria tilapia (Oreochromis variabilis).^[4]

Lake Kanyaboli is among hundreds of ecosystems which are facing extinction threats in the country. Like its cousin oxbow lake in the Rift Valley, Lake Kamnarok, a game reserve which is currently at the edge of losing its value, Lake Kanyaboli is also underway to become an history. In early May, 2023, the lake broke all its dykes following the heavy rains in the region and lost its water at alarming rate for more than one week. The water swept everything on its way, destroying thousands of acres of farms and leaving hundreds of families homeless. According to the Nation Media report, the lake lost more than 50% of its volume, and if urgent action is not taken, then the lives of the communities that rely on it would be adversely affected.^[5]