Abstract:
Water is the source of life covering 70% of the Earth surface. However only a small
portion of this precious natural resource is fit for human consumption. We mapped
various point and non-point sources of pollution within Nairobi River Basin and
Mbagathi Sub-basin, with aim of taking an inventory for future clean ups and protection
of the basins. The water from the basins flow to Tana River basin downstream of Nairobi
and Mbagathi Rivers. Nairobi River Basin (NRB) is traversed by several rivers that
include; Ngong/Motoine, Nairobi, Mathare, Kiu, Riara, Ruiru and their tributaries. This
research was conducted through field assessment by taking GPS coordinates of possible
pollution points downstream of the suspected area of pollution. Insitu physiochemical
analysis of COD, TDS, EC, BOD, T ALK and TSS done and samples were taken for
analysis of heavy metals and pesticides. QGIS version 2.6 with the shapefiles of Kenya
water basins, Kenya major rivers and tributaries, wetlands, protected areas and forests
and major towns were used in mapping of these points within the basins. There were
high values of physiochemical parameters in the mid catchment, TDS of 6146, COD of
4314 and high traces of heavy metals in the mid catchment, pesticides in the upper and
lower catchments. It was therefore concluded that much of the pollution in Nairobi and
Mbagathi sub basin emanate from poor management and handling of waste water and
from anthropogenic activities such as settlements/build up areas and Agriculture.
Pollution is mainly from sewer line discharges, effluents from the Water Services
Providers, solid waste disposals and industrial effluents at the middle catchment,
sediments and pesticides/herbicides from farming activities within the upstream and
downstream parts of the sub catchments.
