IS NAIROBI SINKING?

The current policy of  Nairobi Water and Sewerage Company NWSC is to rely solely on surface water, but it is likely that the use of groundwater will in future be critical in providing adequate service levels for the growing urban population and as a strategic reserve in times of drought. Groundwater, from water wells, is mainly used by large private operators such as industry and hotels to supplement Nairobi Water and Sewerage Company (NWSC) supply. Annual reading is the responsibility of NWSC and is used as a basis for levying waste water charges.The drilling of boreholes started in the 1930's – and the number of water wells in greater Nairobi increased from fewer than 10 in 1940 to almost 2,000 in 1997 and further increased to 2,250 in 2001 as a result of the drought. Over-exploitation of groundwater resources is likely to become an emerging issue. The increase in demand for water has led to unregulated exploitation of groundwater and it is thought this might lead to undesirable effects such as the lowering of the water table. For instance, during the 1999/2000 drought the criteria of 800 m-separation distance for sinking boreholes was ignored and this could have long lasting effects. While there might not be any immediate threat of land subsidence, there is the potential risk of local infrastructure and building damage. Nairobi was once a swampy area and the presence of clay and silt layers in the shallow subsoil, and of unconsolidated fractures and cooling joints, may be potential sources of subsidence. The problem has occurred elsewhere in the world: thus, Mexico City sunk by more than 10 meters in the last 70 years from over-exploitation of groundwater.
 That said What if Nairobi suddenly became a Venice?  We could end up like this

or maybe we could become like some parts of India

 maybe not. But we could do with another Mombasa or not again.

source: (UN Habitat 2000 in UNEP/DRSRS undated).

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