Rain, rain everywhere, but where is the water?

By MUNGAI KIHANYA

The Sunday Nation

Nairobi,

29 April 2018

Kenya is indeed a peculiar country. When we have a long dry spell, our dams dry up and we have no water and no electricity. When we get heavy rains, our pipes and power lines are broken by the floods and we have no water and no electricity. Damned if we do, damned if we don’t!

The recent heavy rains have elicited one important question: where is all the water? Unfortunately, Kenyans will never let facts get in the way of a good story. “The water and power cartels have given orders for the dams to be emptied so that they can continue extorting us.” That’s a good story…

The fact is that on 24^th April, the Kenya Electricity Generating Company (KenGen) released two statements. The first one announcing that, due to the heavy rains, they were now operating the hydro power stations at full capacity.

The second one was a safety alert to the people living downstream on the River Tana. Kiambere Dam, the last one on the Seven Forks Complex, has filled up to maximum capacity and the spillway has been opened to allow excess water to run off.

In short; don’t believe that story going around in the social media that the dams are only 23 per full. It is not true!

What about drinking water: why isn’t Ndakaini Dam overflowing? On the same day that KenGen was making its announcements, the Nairobi Water Company released a water rationing program! No information has been published about the levels of the Ndakaini reservoir.

Nevertheless, data from the Athi Water Services Board shows that Ndakaini Dam has a storage capacity of 70 million cubic metres. Since one cubic metre is equivalent to 1,000 litres this works out to 70 billion litres.

Ndakaini supplies water at the rate of 430 cubic metres (430,000L) per day. So, if there was no rain at all and the dam was operated at maximum capacity, it would run for 162 days continuously before drying up. That is, about five and half months.

The dam has a water catchment area measuring about 70 square kilometers and data from the Kenya Meteorological Department indicates that this region is expected to get a total of about 400mm of rainfall during the current rain season.

Now one millimetre of rainfall is equivalent to one litre of water per square metre. Also, one square kilometre is equal to one million square metres. So 70sq.km = 70 million sq.m.

Therefore; the catchment area for Ndakaini Dam is expecting to get a total of 70 x 400 = 28,000 million litres. In other words, 28 billion litters Even if all this water flowed into the dam, and none was collected by the local community or the Nairobi Water Company, it still wouldn’t fill up!

But Nairobi has seen heavy flooding; where is all the water going? The flood waters of Nairobi drain into the Athi River and head straight down to the Indian Ocean. There is no dam on this river.