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Harare's underground water
Jackie Cahi
September 19, 2009

On our property in Harare we are very careful with our water. For the past year or so we have been supplying water also to our neighbours. They are a self organized group - just one of many local initiatives that are emerging out of necessity. But we are literally being 'undermined- by another neighbour who is now sucking water from next to the local streambed and selling it.

I live in Greendale, an area of Harare that has had no municipal water for a couple of years now. Our bananas and lemons grow in gray water run-off from the bath and shower. We use the bath water to flush the toilet. When we first moved in we installed a rainwater tank to collect drinking water from the roof, and used that even when there was a municipal supply. (Its always been much cleaner.) We garden carefully. Half our large plot is given over to indigenous trees and shrubs that don-t need year round water. We mulch our vegetables and flowers to keep the moisture in the earth. And over the years by being careful, by planting more trees, by watching our land, we have attracted more moisture into our garden. We are lucky enough to have a borehole but we want to look after the ground water. We have made swales and planted grasses to keep the ground water with us. Our ecologist friends tell us we are successful. Our garden is healthy. Our borehole gets replenished. The cycle is in balance.

Three times a week 5 households line up on the other side of our fence to collect water in containers. They each take perhaps 100 litres -Monday, Wednesday, Friday - 500 litres each day. 1500 litres per week. Modest enough for washing and cooking, drinking and cleaning..

But water is being shipped out of our street on a large commercial scale. Early in the morning - well before dawn - I hear the bowser making its first trip of the day. It-s the last thing I hear at night too. The heavy trundle up our potholed road as another 10 000 litres leaves our area. When I walk my dog in the morning I see the bowsers loading up. It-s a constant worry to me as I visualise the huge quantity of water being sucked out of the ground and exported to other parts of this dry city. I can hear the bowser now. It seems like it never stops.

How much per day if each bowser load is 10 000litres? (It would take 6 weeks for our combined households to use up one bowser load.) 10 trips a day is 100 000 litres! Every day! Even Sunday. I start doing the sums. Its almost 3 million litres per month. Put it into cubic metres which is how we are billed by the city for the water that we don-t get - this 3000 cubic metres per month.

Surface water has dried up all over the city. Our little stream is one example. When my mother was a child, 60 years ago, this stream was navigable. She and her brother used to go fishing in it in a small boat. Even 20 years ago our children could still catch fish in it, (though by then it was no longer navigable.) It had a name. It flowed into the Mukuvisi. It was part of Harare-s waterways. Now it is clogged with reeds and rubbish.

Groundwater originates as surface water and in the Harare area it is estimated that only 5% of the mean annual rainwater reaches the groundwater reservoirs. I worry about what-s happening to our underground water all over the city. When I first expressed my concern to the neighbour I was told not to worry. That they were tapping in to an underground aquifer, a separate underground source, and my borehole would not be affected. (And of course if it was then I could get water from them!)

There is a widespread misconception that an aquifer is a flowing underground river. Unfortunately in Harare there is nowhere where this can be true. According to geologist friends the underlying geology of the city does not allow for large underground aquifers. The secondary aquifers that can exist are generally small in extent and cannot give large sustained yields. Particularly in the Greendale and Rhodesville area aquifers are erratic and water is restricted to fracture and fissure zones with limited storage capacity.

"Groundwater is a poor relation of surface water; it lies out of sight, out of mind". We can see what-s happening on the surface - when a stream dries up, or when a tree is chopped down. We can-t see what-s happening underground. Our first hint is when the borehole runs dry and this year domestic boreholes are drying up earlier in the season than usual. And this after good rains. Obviously we are taking out much more than we are putting back in.

Ground water is not an inexhaustible resource. Correct use of a groundwater reservoir should ensure that there is a reasonable balance between the volume pumped and the volume that be replaced. It-s a useful resource if well managed - i.e. used modestly and used locally. But our neighbour is extracting massive quantities and trucking it away from its location. The water doesn-t come back into the ground here. We are not talking about irrigation where only a certain percentage is lost to evaporation and the rest seeps back into the ground. This water has gone from our neighbourhood. Gone from the tree roots. Gone from the water table.

He is not the only one of course. Water barons have sprung up all over Harare and are delivering tons of water to households and industry. All you need is a couple of lorries and a pressure pump, unfettered access to local ground water and you-re in business. But how is any of this sustainable in the longer term - even the medium term. And what do we do as residents of the city? As people and households who need water?

In many cities (especially in the USA) groundwater formed the chief stages of early urban development and through misuse, reservoirs have been seriously and probably irretrievably depleted. What do we do to help our city to keep alive?

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