Brace yourself: water rationing is here to stay!

By MUNGAI KIHANYA

The Sunday Nation

Nairobi,

06 May 2018

There is a new talk in town: “After the spirited campaign against the water cartels of Nairobi, Ndakaini dam has miraculously started filling up!” This story was triggered by a report in the mainstream media quoting the acting Managing Director of Nairobi Water Company, Nahashon Muguna, saying that the reservoir’s level was rising.

Mr. Muguna said that the dam was receiving water at the rate of 7 cubic metres per second adding that the inflow is expected to reach the peak of 9 cubic metres per second in the coming days.

Now, 7 cubic metres is equal to 7,000 litres. Therefore, the daily inflow rate is 7,000 x 60 seconds x 60 minutes x 24 hours = 604.8 million litres. That is a very large amount of water; or is it?

Ndakaini supplies water at the rate of 430 million litres daily. Now that’s an interesting number: given that Nairobi has a population of about 4.3 million, it turns out that each resident is assigned 100 litres daily! Are you getting your 100L?

If we subtract 430 million litres from the 605 million that is flowing into the dam, we are left with 175 million litres of unused water. If the inflow rate improves as expected to 9 cubic metres per second, the unused balance will go up to about 225 million litres daily.

If we continue accumulating the water at this rate (200 million litres per day on average), how long will it take to fill the dam? Ndakaini has a capacity of 70 million cubic metres, that is, 70 billion litres. At the time of the news report, it was at 37% full, that is 26 billion litres. Thus, it still had room for another 44 billion litres.

At 200 million litres daily, the dam will need another 220 days to fill up. That is, more than seven months of this kind of weather…up to December!

Unfortunately, we just 30 more days remaining in the current rain season. So, we should only expect to add another 6 billion litres (200 million x 30 days). That will raise the dam to about 32 billion litres. In other words, it will only rise to about halfway (46%) by June.

After that, the water extraction rate will start to exceed that of inflow and the dam level will begin to go down again.

Still, suppose I am wrong and the dam does indeed fill up before the end of this rain season; that will NOT cure the water shortage problem of Nairobi. The reason is that the water pipes and pumps in place can only supply 430 million litres daily while the demand is over 600 million litres. So, the water rationing programme is here to stay!

Perhaps we should consider splitting the water company into two separate entities: one to focus on water collection and storage, the other to distribute to consumers. That’s what we did to electricity and it solved the shortage problems.