New Report: Increased rainfall cause of flooding in Kenya’s Rift Valley lakes

Increased rainfall in Kenya’s Rift Valley Lakes’ catchment zones is the main cause of the rising water levels in the water bodies according to new research findings.

A study conducted jointly by the Technical University of Kenya (TUK) and University of Natural Resources and Life Sciences (HyWa-BOKU) in Vienna, Austria indicates that mean annual rainfall for 2010−2020 period increased by up to 30 percent in the Rift Valley region due to the effects of climate change on rainfall patterns.

According to the study dubbed ‘Hydroclimatic analysis of rising water levels in the Great rift Valley Lakes of Kenya’ though actual evapotranspiration in Rift Valley (the process by which water is transferred from the surface to the atmosphere by evaporation) also increased over the period, it was to a lesser extent compared to rainfall.

The report published in the ‘Journal of Hydrology-Regional Studies’ indicates that, data collected through Integrated Catchment Response (ICR) system revealed that in the period 2010−2020, rainfall increased by an average 30 percent in the Lakes Baringo, Bogoria and Solai catchments.

In Lake Nakuru, Elementaita and Naivasha, rainfall increases, though lower, amounted to 21 and 25 percent respectively.

“These results illustrate that changes in catchment properties due to human activity influences or changes in underground permeability are not essential in explaining the lake levels rises. Minor changes in the water balance are necessary to trigger the lakes’ level rises, since an increase of only between 0.4 and 2 percent of mean annual effective rainfall leads to swelling of the water bodies,” reads part of the report.

The Principal Investigators included Luke Olang from TUK’s Department of Biosystems and Environmental Engineering and Centre for Integrated Water Resources Management (CIWRM-TUK) and Mathew Hermegger and Gabriel Stecher both from Institute for Hydrology and Water Management, University of Natural Resources and Life Sciences (HyWa-BOKU), Vienna, Austria.

Their findings are a sharp contrast to various research outcomes by geologists, geophysicists, ecologists and environmentalists from the Ministry of Environment and Natural Resources, Kenya Wildlife Service (KWS), Kenya Electricity Generating Company (KenGen), Geothermal Development Company (GDC) and research institutions that have ruled out increased rainfall as a trigger of the phenomenon.

Most scientists who have studied the phenomenon have cited three factors: climate change, siltation caused by human activities and geological activities and tectonic shifts.

Kenya’s Rift Valley lakes have received global attention due to rising water levels baffling authorities and scientists, who appear not to have satisfactory explanations as rains have not fallen in huge volumes over the past few years.

Lakes Nakuru, Naivasha, Baringo, Ol’ Bolossat and Bogoria have expanded to levels not seen in 75 years. The phenomenon is replicated across Lakes Solai, Elementaita, Kamnarok and Oloiden.

Messrs Olang, Hermegger and Stechers who analysed and documented water level fluctuations, the causes, and the socio-economic impacts of rising water levels in Lakes Baringo, Bogoria, Nakuru, Solai, Elementaita and Naivasha revealed that the lakes recorded a rise in water levels of between 123 percent and 21 percent covering some 110,000 hectares of land.

The report shows that Lake Solai in Nakuru County recorded the highest rise in water levels by 123 per cent.

Lake Solai swelled from 5.7 to 12.71 square kilometres during the phenomenon that hit the lakes across the country between 2012 and 2020.

The alkalinity levels of the once-salty lake were also affected.

Another water body that was adversely affected by the phenomenon was Lake Baringo in Baringo County whose water levels according to the scientists rose sharply by 59 percent.

The size of the lake also increased from 128.1 to the current 203. 6 square kilometres.

Researchers in the study recommended close monitoring of the lakes 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.

“The major effects included increased human-wildlife conflicts, loss of lives and livelihoods, injury, an outbreak of diseases, legal issues, safety and security concerns, and ecological or environmental degradation,” the report notes.

In the wake of their swelling, the waters from the lakes destroyed social amenities including learning institutions, health facilities, markets, fish landing and processing facilities, once-thriving hotels, curio shops, resorts and lodges, electricity lines, water supply and sanitation units as well as road networks in several areas.

The raging waters from Lake Nakuru have invaded Kenya Wildlife Service (KWS) rangers’ homes, forcing some to relocate with the floods submerging offices in the park and displacing more than 700 families in the nearby Mwariki village.

Lake Baringo has expanded from 236 square kilometres in 2015 to about 270km square kilometres, posing a threat to adjacent homesteads and institutions.

More than 15 schools bordering the lake may need to be relocated after water levels rose drastically, swallowing adjacent structures.

Among the affected schools are Salabani Secondary, Ng’ambo Girls, Lake Bogoria Girls, Ng’ambo Primary, Sintaan, Leswa, Lorok, Loruk Loropil, Noosukro, Kiserian, Sokotei and Salabani primary schools.

Separately a task force appointed by the Ministry of Environment and Natural Resources established that climate change was the main cause of the rising water levels in the lakes.

“This was coupled with cases of deforestation that has resulted in run-offs resulting in larger volumes of water and siltation in the lakes, geological activities that control runoff and flows into the rift valley is also a contributor,” states the report.

According to the report Lake Baringo had submerged a conservation area of 130 square kilometers after its increased water volumes occupied 260 square kilometers from the previous 176 square kilometers. Rongena and Lokorosi islands have been submerged, while Ol-Kokwe Island has been split into two.

In Lake Bogoria the rising levels have totally submerged the geysers and hot springs while flamingo populations at the water body had dropped from 1.5 million birds to less than 100,000 due to altered ecological balance after the water body expanded from 34 square kilometers to 45 square kilometers.

It has submerged major roads leading to the Lake Bogoria Park and adjacent structures, including Loboi dispensary and Lake Bogoria Girls’, which is on the verge of being swallowed up completely.

The rising water levels in Lake Naivasha have affected the quantity and quality of water, leading to death of fish. Kihoto, Karagita, Kamere, Kasarani and Kwa Muhia estates have also been submerged.

Greater inflow of fresh water into some of the lakes has destabilized their already fragile ecology, harming the resilience and distribution of certain water species.

An independent probe commissioned by the Kenyan government and the United Nations Development Programme (UNDP) last year showed that rising water levels had generated a humanitarian crisis, with about 75,987 households in 13 affected counties and 379,935 people requiring urgent assistance after they were displaced from their homes.

According to the report, while tectonic activities are a natural phenomenon, increased siltation as a result of poor land practices aggravated the situation of the lakes in Rift Valley.

It indicates that changes in land use practices have led to increased runoff, causing larger volumes of water to flow directly and rapidly from the land surface into the lakes.

The report cites human activities as a threat to freshwater ecosystems – mainly deforestation and excessive drawing of water from lakes, rivers, wetland systems and groundwater.

“Since the East African region is an active tectonic belt characterized by extensional stress-regime, it is anticipated that a myriad of tectonic forces continue to shape the present rift geometry including the segmentation of rift lake basins,” the report says.

The report, based on research from 2010 to 2020, established that Lake Turkana increased by 10 percent from 7,485 square kilometres to 8,230 square kilometres while Nakuru rose from 40km² to 68km².Over the years, rising water levels in Lake Baringo have claimed 139km² of riparian land and about 3,087 homes.

In Lake Nakuru, at least 677 families were affected, including 325 households in Baruti East sub-location and 352 in Mwariki. The Nakuru sewerage works were also submerged. In Parkview sub-location, about 70 acres of land were also swallowed up.

At Lake Naivasha, the areas affected include the Kihoto settlement, Kamere beach and several hotels. More than 1,500 households were also displaced, with several structures and power transformers submerged, posing a serious hazard to the community.

There have also been reports of human-wildlife conflicts, with hippos now grazing closer to human settlements and frequently attacking residents.

The report established that the Kihoto and Karagita areas were the most populated and rising waters have heightened security issues. Furthermore, rising water levels have hurt business for tourist hotels, wiping out jobs.

By August 2020, 264.8 hectares of land and 170 households in Nakuru County had been affected by rising water levels and a significant proportion of the acreage affected is around Lake Naivasha, the Ministry of Agriculture said.



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