Puzzle of Ndakaini Dam’s low water levels despite rainfall

This photo shows the dropped water level at Ndakaini Dam in Gatanga, Murang'a County, on April 25th, 2018. [Kibata Kihu/Standard]

The low water levels in Nairobi’s main water reservoir despite the heavy rains is puzzling.

Residents and environmentalists have questioned if there was sabotage at Ndakaini Dam in Murang’a to create an artificial water shortage in the city.

It is not clear why the dam is still at 30 per cent capacity despite the heavy rains in the region, yet other reservoirs that rely on the same catchment area are overflowing.

The Seven Forks Dams in Embu County, which also get water from the Mt Kenya and Aberdare catchment areas, are flooded.

KenGen CEO Rebecca Miano in a press briefing on Tuesday said the level of Masinga Dam had risen to 1,045.86 metres against a maximum level of 1,056.50 metres (see separate story).

Even more puzzling is the fact that while Ndakaini is at 33 per cent, the other two dams that provide water to Nairobi - Sasumua and Ruiru - are full, yet all three get their water from the Aberdares.

Still ration

The Nairobi Water and Sewerage Company (NWSC) has announced that it will continue to ration water to households in the city, at least until levels in Ndakaini Dam rise.

The paradox that despite the heavy rainfall, Nairobi still faces the prospect of running out of water is not lost on the residents.

In Murang’a, the villagers around the dam are also puzzled by its low levels. 

The reasons for the abnormally low levels vary depending on whom you ask. Some attribute this to the destruction of the Aberdare Forest catchment for the rivers that feed Ndakaini.

Yesterday, The Standard team visited the dams on a fact-finding mission and noticed that the water levels in nearby rivers was high.

The water agency insisted that the dam had not been fully replenished since 2017, when levels were at their lowest.

“Under normal circumstances, cumulative rainfall amounts in the Aberdares catchment that feed the reservoir are up to between 1700 and 2000 mm. In 2017, cumulative rainfall was about 700mm, which was too low,” the agency said yesterday. 

Logically, if the rainfall was inadequate last year, then the heavy rainfall over the past month should be sufficient to refill the dam.

Curiously, Ndakaini was low two weeks ago, at just 30 per cent.

Since March 2017, the dam has been at 21 per cent and the level rose by only nine per cent in more than a year.

This has puzzled the residents of Ndakaini area in Gatanga constituency.

All trees cut

“I can’t understand how this is possible. It has been raining consistently for the past month but the level stays the same,” Winnie Mukunya, who operates an inn a short distance from the dam, said.

“You should go up to the forest and see if there are any trees left. They have all been cut down,” she added. 

Erastus Kairu was of the same opinion - that destruction of catchment areas was choking the rivers that feed Ndakaini.

“It might not be raining in the forest due to all the destruction and that’s why the rivers do not have water,” he offered.

According to NWSC, rivers Thika, Githika, Kayuyu, and Gitabiki, which drain into Ndakaini, have not attained their optimum volumes.

“We only measure the levels in rivers Thika and Githika and they have increased in the past week. We are hopeful that as the rainfall peaks in May they will be higher,” one of the officials charged with monitoring the levels of the rivers said.

The NWSC acting managing director, Nahason Muguna, said the dam started recharging four days ago and that level had registered at 34.24 per cent, holding 23,968,903 cubic metres of water.

Poor rains

“A lot of rainfall has fallen in Nairobi and the southern part of the Rift Valley and eastern regions, but there are poor rains in the catchment areas of the Aberdares,” he said.

Mr Muguna denied claims that the dam had secret gates that could have been used to drain water.

“We have not opened any other gates. It will make no sense to reduce water in the dam at this particular time,” he said.

In fact, he said, the outlet to Ngethu was closed on Sunday after the levels of River Chania increased significantly.

Ndakaini makes up 20 per cent of the water being treated at Ngethu while the rest comes from River Chania and the Kiama and Kimiakia streams.

Slow recharge

It supplies the Ngethu treatment plant when the water levels in the river are low.

Nairobi, Muguna said, had a demand of 770 million cubic metres daily, yet the supply was 525 million cubic metres.

He said when the rains started on February 28, the facility had 20 million cubic metres, calculated at 27 per cent.

He added that there had been a slow recharge and that it was hoped that by end of next month, the dam would have achieved 50 per cent storage.

“Supply for Nairobi is sourced from Thika River which is recharging Ng’ethu treatment plant for onward transmission to Nairobi consumers,” he said.

The Standard learnt that by April 16, Ndakaini had a 21.98 million million cubic metres of water, Sasumua in Nyandarua 11.02 million, and Ruiru Dam 2.7 million.