There is more underground water in Turkana than in the lake

 By MUNGAI KIHANYA

The Sunday Nation

Nairobi,

22 September 2013

So, exactly how much water was discovered in Turkana County recently? Some reports said 250 billion litres while others put it at 250 billion cubic metres. Which is which?

Well it is 250 billion cubic metres; but how much is that in simple English?

A cubic metre is the volume occupied by a box measuring 1m-by-1m-by-1m. Since we are more accustomed to litres, it might help to convert it to these units. We start by defining a litre in terms of cubic dimensions.

Now every motorist knows that a 2,000cc engine is also called a 2-litre one. What many might not know is that one litre is the volume occupied by a cube (or, box) measuring 10cm-by-10cm-by-10cm. When you multiply 10 x 10 x10, you get 1,000; hence this is 1,000 cubic centimetres – the “cc” stands for “cubic centimetres”.

If these one-litre boxes are arranged in a straight line, how many would be needed to make one metre? Well, a metre has one hundred centimetres… but, on second thought, that’s the wrong way to say it. The correct statement is that one centimetre is one-hundredth of a metre. The metre is the standard while the centimetres are its subdivisions.

Any way, 100cm divided by 10cm is equal to 10. Therefore, 10 one-litre boxes will make a one-metre line. So, 100 boxes would cover a 1m-by-1m square on the ground – that is, 10 x 10 = 100.

And if 10 such layers are stacked up on top of each other, they would rise to a height of 1m. In total, there would be 100 (boxes per layer) times 10 layers, equals 1,000 boxes altogether.

But this arrangement occupies 1m-by-1m-by-1m; that is, one cubic metre. Therefore, it turns out that one thousand litres make one cubic metre.

So, the volume of water discovered under the Turkana desert is 250,000 billion litres, or 250 trillion litres! Now that’s another large number but it shouldn’t be difficult to comprehend for the average Kenyan: After all, our national budget crossed the trillion-shilling mark a couple of years ago!

Still, 250 billion cubic metres, or 250 trillion litres of water remains an unfathomable quantity. So let’ try to put it in the right perspective. First, such large volumes are better expressed in cubic kilometres. Knowing that there are 1,000m in 1km, it is easy to evaluate (following steps similar to those above) that one billion cubic metres make one cubic km. Thus the underground water in Turkana is 250 cubic km.

Imagine an area measuring 10km-by-10km – that comes to 100 square km. Now suppose that a deep hole was dug over this whole area…to a depth of 2.5km. That hole would be 250 cubic km…. now fill it with water!

By comparison, the nearby Lake Turkana is about 290km long and 30km wide. Its total surface area is about 6,400square km – of course it is not rectangular in shape! The water has an average depth of 30m and this makes a total volume of about 200 square km.

At 250 cubic km. the recently discovered water under the desert is more than that in the lake. Think about that.