26 April 2018

Kenya: Mystery of Half-Empty Ndakaini Dam Despite Heavy Rains

Photo: Joseph Kanyi/Daily Nation
An image of Ndakaini Dam in Murang'a County taken on April 24, 2018.

Nairobi residents will continue grappling with water rationing as mystery of lack of water at Ndakaini Dam despite heavy rains at the Aberdares deepens.

While meteorological reports indicate that the Aberdares region had received heavy rains of more than 100mm in the past few weeks - enough to have recharged the aquifers and perhaps fill the 70 million cubic metre dam - Ndakaini remains the only dam in Kenya that has not benefited from the ongoing rains.

The implication of this is that six million city residents will be at the mercy of water vendors.

Lately, water vending has turned out to be a multimillion shilling venture, with new bowsers criss-crossing city estates selling water.

WATER CARTELS

Ndakaini Dam Coordinator Job Kihamba, while taking the Nation crew on a tour of the dam, denied reports that there are cartels leaking the dam's water to create an artificial shortage.

"There is no outlet that the water can flow out from. Even Nairobi City Water and Sewerage Company has been forced to shut supply from the dam to allow the water levels to rise," he said.

"At the moment, the city is relying on Sasumwa and Ruiru Dams to supply water to Nairobi."

It is a paradox since both Sasumwa and Ruiru dams rely on the same Aberdare water catchment and are by far smaller than Ndakaini.

The mystery on what has happened at Ndakaini is deeper since Nairobi Water has been running without a board since August last year.

This is after the Raphael Nzomo-led board was suspended by Governor Mike Sonko following a workers' strike.

RATIONING

The workers had downed their tools after the board refused to renew the contracts of Managing Director Philip Gichuki, Commercial's Stephen Mbugua, Finance's Johnson Randu and HR Director Rosemary Kijana over non-performance claims.

A Nation's fact finding mission found that Ndakaini is only a third full with only 23.6 billion litres of water.

With that, officials manning the dam say they cannot guarantee that Nairobi will have full supply of water.

"What we can guarantee is that the dam will not fill fully even with the rains.

"But if the levels can reach 60 per cent, we will be good to go until for the next season. Nevertheless, the rationing will continue because the population is high," Mr Kihamba said.

SEEPAGE

The main rivers that drain into Ndakaini are Thika, Githika and Kayuyu.

Thika contributes 50 per cent, Githika 30 per cent and Kayuyu 20 per cent of the water at the reservoir.

A meteorological station at Tuthu in Murang'a - in the same geographical area as Ndakaini - recorded more than 100 mm of precipitation, which is characterized by heavy rains and flooding.

"If the catchment area is receiving rainfall and the dam is not keeping water, the only possible explanation is that it has serious cracks and that Nairobi Water officials have poor gauging networks downstream. They could have now known what is happening," a meteorologist based in Nairobi said.

Ndakaini is a 70m earth fill embankment, but at the bottom is a grout curtain built during the construction to contain possible seepage and spills.

FLOODS

The weatherman's data shows that Aberdare, where the dam sources water from, has received a cumulative 397 millimetres of rain compared to other areas like Murang'a Town, which has received up to 532 millimetres.

"Generally, this is the normal amount for the highlands but the reason we are experiencing floods in lower parts is because they have received more rain.

"With such heavy rains in lower parts, one would expect highlands to receive more rains but that is not the case," Murang'a Meteorological Department Director Paul Murage said.

But if the Aberdares is receiving "normal amount", why Ndakaini is not benefiting from the two-months of long rains is yet to be answered.

The Gitabiiki, Kanegenaga, Githika, Thika and Kayuyu tributaries that drain into the dam draw water from Gatare and Kimakia forests in the Aberdare Ranges.

Naturally, tributaries are smaller and have less water than main streams.

Additionally, the tributaries source their water from saturated ground and water table through capillarity.FOREST COVEROfficials say following prolonged dry seasons, the water table sank deeper, which means it takes relatively longer for the rain water to seep through the soil into the small streams.

They claim that Ndakaini Dam is a victim of its location since it is built on high grounds, which have received the least amount of rainfall compared to other areas.

Another explanation is that Ndakaini is suffering from the effects of degradation of the forest cover in the Aberdares.

Environmental Compliance Institute Executive director Gerry Opondo said the water catchment could have suffered degradation, leading to more surface run-off.

"When it rains in the area, water percolates into the ground due to the dense forest cover in the water tower before emerging as small springs, which then join to form smaller streams that feed the dam," Mr Opondo said.

"If you cannot trace it to either degradation or failed rains, then what is it?" He said.

RAINFALL

The Kenya Meteorological Department's March-April-May long rains outlook forecast "near normal to above-normal" rainfall in most parts of central Kenya, where the Aberdares water catchment falls.

The forecast pointed out that some counties in the region --Nyandarua, Nyeri, Kiambu, Murang'a, and Kirinyaga -- were likely to receive near-normal rainfall.

The forecast indicated that most parts of central Kenya are likely to experience slightly enhanced rainfall in May and that the Seven Forks dams along the Tana would "experience good inflows due to the enhanced rainfall in the catchment areas, according to a report by the Meteorological Department Director Peter Ambeje.

While other dams are getting good inflows, water levels at Ndakaini Dam only started rising in the last one week, and the intake has been relatively low.

KENGEN

Residents living in the upper areas of Ndakaini note that for the last three years, the four tributaries have not attained maximum water levels.

"In the past, the rivers were so huge but in the last three years things have changed. There is no rain and what is left are just small streams," Mr Peter Kigoori, a resident of Kimangu, said.

At one of the inlets, Nation found that water was yet to reach the level where culverts that drain water into the dam are set, meaning no water is flowing to the dam from that particular inlet.

Meanwhile, while Nairobi residents brace for continuous rationing, KenGen has announced it has increased production of cheap hydropower after all its dams, including Turkwel in Turkana filled up.

KenGen Managing Director Rebecca Miano said the overflowing dams would boost power generation and ensure stability of supply.

Kenya

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