Why Rift Valley, Nyanza lakes are overflowing
Geological activities deep into the earth’s crust are triggering overflow of lakes in Rift Valley and Nyanza regions aided, partially, by human activities.
According to a report compiled by a special team put together by the government to look into the effects of rising water levels in 17 water bodies in 13 counties, the situation has caused a crisis with 75,987 households displaced and 379,935 people requiring urgent humanitarian assistance.
The document titled ‘Rising Water Levels in Kenya’s Rift Valley Lakes, Turkwell Gorge Dam and Lake Victoria Report 2021’ prepared with the help of the United Nations Development Programme (UNDP) indicates that Rift Valley is in the midst of a geological shift that started in 1996 and is expected to last between 25 to 40 years.
The task force further established that climate change, deforestation, intensified and irresponsible land use resulting in degradation and thus, higher rainfall runoff from land, and less percolation of it into the groundwater systems were also leading to larger volumes of water flowing directly and rapidly from the land surface into the lakes.
A team of 49 experts that comprised geoscientists, meteorologists, ecologists, geologists, seismologists, environmental scientists and physical planners further established that water seepage into underground aquifers in affected areas had been hampered by silt that clog fault lines and increased water supply because of runoff brought about by land degradation.
The taskforce singled out loss of lives and livelihoods, increased human-wildlife conflicts, injury, an outbreak of disease, legal issues, safety and security concerns and ecological or environmental degradation as the major negative outcomes of rising lakes.
Affected lakes include Lakes Victoria in Nyanza, Turkana in the North Rift and Magadi in the South Rift.
The unprecedented increase in water levels has also been witnessed in the freshwater lakes of Naivasha and Baringo and the saline lakes of Solai, Olbolosat, Elementaita, Nakuru, Bogoria and Logipi.
The mandate of the task force was also to establish the causes, the socio-economic impacts of rising water levels at Turkwel Gorge dam.
According to Jackson Kinyanjui, a geo scientist and a member of the technical team that conducted the study, tectonic shifts have also affected the Nyanzian Rift where Lake Victoria’s waters are rising.
He said tectonic activities influenced underground permeability, which had an impact on the subterranean outflow and ground water table.
“Most of the Rift Valley lakes discharge their waters through underground channels.
Tectonic activity may plug the cracks between the tectonic plates, slowing the lake’s natural underground discharge and forcing the water up, leading to an overflow.
Warming of Indian ocean
When the reversehappens (widened cracks) the water drains underground at a high rate and the lakes start to dry up but the situation has been accelerated by deforestation, which has resulted in siltation and floods,” Kinyanjui said in an interview.
He observed that warming of the Indian Ocean’s dipole, which he linked to higher-than-average rainfall during the East African Short Rains (EASR) between October and December, plays a major role in the phenomenon.
The Indian Ocean dipole is the difference in sea-surface temperatures in opposite parts of the ocean.
Temperatures in the eastern part of the ocean oscillate between warm and cold compared with the western part.
Kinyanjui added: “It is also important to note that rising water levels in the affected lakes with ecosystems in Baringo, Busia, Homa Bay, Kajiado, Kisumu, Marsabit, Migori, Nakuru, Narok, Nyandarua, Siaya, Turkana and West Pokot counties over the past 10 years have coincided with warmest global temperatures recorded in earth’s history.”
The findings revealed that Lake Turkana has risen 10 per cent from its normal 7,485.4 to the current 8,265 square feet disrupting livelihoods of 12,392 people.
Scientists’ had projected in 2019 that the construction of the Gilgel Gibe III Dam in Ethiopia would lower the levels by 2-10 metres (6-33 feet) and increase salinity by more than 50 per cent.
At least 30,186 people living on the shores of the lake have been displaced in Kerio, Kangatotha, Kalokol and Lake Zone wards. Fishing village of Kalokol and hundreds of manyattas that served as homes to the fishing community have been swallowed up by the waters.
“Water backflows within Lake Turkana and its surrounding areas rendered the settlements uninhabitable with several homes, institutions, health facilities and worship centres marooned while 19 lives were lost following attacks by crocodiles,” the report reveals.
The Turkwel Gorge Dam recorded its highest historical levels since it was commissioned in 1991 enlarging from 18.9 to the current 59.27 square kilometers.
Kinyanjui said the task force has recommended close monitoring of lake levels to avert future crises through the establishment of close monitoring of meteorological patterns as well as a rapid assessment of the impacts of rising lake levels on biodiversity and food security.
He also called for immediate humanitarian assistance and creation of awareness on climate change among others.
For medium and long-term interventions, the task force proposed the creation of buffer zones, drilling and installing groundwater monitoring boreholes as well as carrying out research on tectonic movements and development of county spatial plans among others.
The team of experts established that the rising water levels in Lake Baringo have claimed 139.98 square kilometres of riparian land increasing its size to 228.06 square kilometres submerging Loruk, Kambi Samaki, Loboi, Salabani, Ng’ambo and Ol Kokwe Island health facilities thus hindering access to medical services for people living in the area.
“The affected populations are at risk of contracting water-borne diseases as well as respiratory infections because of the cold.
As Lake Solai increased in size by more than 50 per cent from 5.7 to the current 13 sq-km the task force 86 landowners lost over 2,625acres of land to flooding.
These included Solai Roiyobo Farm (2,000 acres), Kampi Ndege Scheme (20 acres), Kasururei Farm (200 acres), Kale Farm (126acres), Arus Farm (20 acres) and Tuiyotich Farm (260 acres).
Lake Victoria though not in Rift Valley displaced 37,140 households. Of these, 8,922 are in Busia, 3,250 in Siaya, 13,800 in Kisumu, 7,752 in Homa Bay and 3,416 in Migori.
In Lake Magadi, increased siltation has been recorded with 30 per cent of the lake being covered by silt, hindering trona mining affecting livelihoods of 50,000 people and 600 employees that work for Tata Chemicals Magadi Ltd.
“UNDP and the government should move to secure broad-based ownership and support to a comprehensive programme that will seek to sustainably manage this situation,” says the report.
At Lake Bogoria, the waters have risen by 10 per cent in surface area, submerging geysers and hot springs displacing families, inundating hospitals, business premises and schools and eating away some 360 hectares.
“The entrance to the Lake Bogoria National Park at Loboi and Maji Ndege village are completely submerged. Traditionally River Mpirrich would flow to Lake Bogoria from Ilemane swamp.
Today, the reverse is happening with the water flowing from Lake Bogoria, back to the swamp by the same river,” Kinyanjui pointed out
Lake Nakuru was the first of the Rift Valley lakes to burst its banks. It increased its area from 40.4 sq km in January 2010 to a high of 68.18 hectares in October 2020, an increase of 70.28 per cent swallowing its entry gates, driveways and pushing its borders to private lands.
The same was witnessed in Lake Naivasha, which previously occupied a total area of 112.66 square-kilometres in 2010 to the current 173 square-kilometres where 1,500 households at the Kihoto Settlement and Kamere beach have been displaced.
“The fisher-folk at Lake Naivasha have lost their livelihood due to beaches getting submerged.
There have also been reports of human-wildlife conflict where hippos that now graze closer to human settlements are attacking humans.”
The report also revealed that Lake Olbolosatt located in Nyandarua County recorded the highest rise in water levels by 186.59 per cent after enlarging from 18.2 to 52.16 square kilometres between 2012 and 2020. The alkalinity levels of the lake were also affected.