VULNERABILITY OF NAIROBI AQUIFERS DUE TO OVER ABSTRACTION OF
GROUNDWATER RESOURCES
ABSTRACT
This report covers the City of Nairobi and its environs; it covers an area of approximately 260
kilometer square and it is on the sheet 148/4 and bounded by the latitudes 250000 to 270000 E
and longitude 984900 to986200 S. The area under study has the highest concentrations of
boreholes than any other place in Nairobi in the whole country. The areas covered by this report
are as follows; Nairobi Central Business District, Upper Hill and Kilimani area, Eastleigh,
Karen, Embakasi West Lands and the surrounding areas.
The area covered by this report is the most well developed part of the country in terms of
buildings, road network and telecommunications and it is the capital city of the country. This
area is also the with the greatest population density in the whole country. The city of Nairobi
and its environs is a water conservation area, the area was gazetted as a conservation area under
the terms of the water ordinance act way back in 1951 by the British colonial government and
the amendment of the same was done in 1957 and 1960 and it has been undergoing several
amendments to date. The government through the Water Resources Management Authority
(WRMA) and the Catchment Area Conservation Committee (CACC) controls the developments
of ground water resources within the water drainage area. Although there has been control over
the developments of ground water resources since 1951 to date, numerous number of boreholes
have been drilled within this groundwater conservation area. The water table within these areas
has drastically gone down as more and more boreholes are drilled. As the density of boreholes
increases more abstraction of water will take place and thus lowering of the water table. If the
rate of discharge from the aquifer is greater than the rate of recharge, the water table will
obviously go down. At the moment deep boreholes have good yields of groundwater than the
shallow ones. Deep boreholes needs more money to drill and pumping water from deep
boreholes also needs more energy to pump water from it.
The aquifers are recharged by surface water which infiltrates in to the ground and percolates
deeper in to the ground water reservoirs after the rains. The rivers, streams and water channels
which receive water from the surface runoff also acts as recharge zones for the ground water
within the basin. There are boreholes for ground water monitoring purposes within these areas
covered by the report and also the intensity of water abstraction, Electric conductivity and the Ph
of water. The monitoring exercise is carried out on monthly basis with the main aim of
monitoring the behavior of water rest levels as the water is discharged from the boreholes and
also as it is recharged from the surface water. The information obtained from this exercise
together with the information on the volume of water abstracted also done at the same time is
used for groundwater management and development within the area.