L. Victoria is overflowing: why not pipe the water to Nairobi?

By MUNGAI KIHANYA

The Sunday Nation

Nairobi,

24 May 2020

Media reports about the increase in water levels at Lake Victoria have sparked the age-old idea piping it to Nairobi. This might not solve Nairobi’s water problems since they nothing to do with availability of sources!

Nonetheless, it is good to find out what it would take to fetch water from Lake Victoria and pipe it to Nairobi. The first question is: how much water does the lake have and how much of it belongs to Kenya?

It is estimated that the lake has about 2,400 cubic kilometres of water. How much it that? Well; imagine a square plot of land measuring one kilometre on each side. Now, picture a perimeter wall that goes up one km…then fill it with water! That’s ho large one cubic kilometre is. L. Victoria has 2,400 such cubes. Ponder upon that for a moment…

Now; one kilometre is equal to 1,000m; therefore, one cubic kilometre is equivalent to 1,000 x 1,000 x 1,000 = 1,000,000,000, or one billion cubic metres. So, the lake has about 2.4 trillion cubic metres of water.

A quick look at the map of East Africa reveals the only a small portion of L. Victoria is Kenyan territory. It is actually just 6 per cent; thus, we can lay claim on this fraction of the total volume of water.

This is 6 per cent of 2,400, or 144 cubic kilometres of water. In other words, 144 billion cubic metres. To put that volume in some perspective, compare it to our biggest dam (Masinga); it has a capacity of 1.56 billion cubic metres. That is, our share of water in L. Victoria is almost 100 times the quantity in Masinga dam…and over 2,000 times the quantity in Ndaikini!

In view of this, why not fetch the water from the lake and pipe it to Nairobi? Well; one fact that is usually ignored is that, at 1,795m above sea level, Nairobi is at a higher altitude than L. Victoria (1,135m)!

The city is 660m higher than the lake, therefore, the water would need to be pumped continuously. How much energy would be required to do this work?

Nairobi gets about 432 million litres each day from the Ng’ethu Water Works: suppose we want to double that with supply from L. Victoria.

This means pumping 5,000 litres per second over a height of 660m. This would require a series of pumps with a combined output of 33 megawatts (33MW)!

In one hour, these pumps will deliver 18 million litres of water, or 18,000 cubic metres and consume 33,000 units of electricity. The power cost comes to about Sh660,000 per hour; or Sh36 per cubic metre of water.

Currently, Nairobi residents pay about Sh40 per cubic metre for water. It flows by gravity from the mountains – no pumping is required. The electricity bill alone to fetch water from L. Victoria would add Sh36 to this cost – almost doubling the price. And we haven’t included the project finance costs yet. Do you think it is a feasible option?