This study investigated the anthropogenic activities in Lake Naivasha Basin and how they are influencing the
quality of water resources. The poor quality of water in the lake is seen from the presence of water hyacinth (Eichhornia
crassipes) and is a reflection of nutrient rich waters. The water hyacinth in Lake Naivasha is associated with major
negative economic and ecological impacts. The intensity of land use within the basin was mapped from multispectral
Landsat satellite imagery of 1986 (TM) and 2000 (ETM) and SPOT imagery 10 m (resolution) of 2007. From interpreted
data, the surface area of the Main Lake has decreased from 134.9 km in 1986 to 117.5 km in 2007 (12.9%); that of
papyrus and wetland grasslands along the lake shore decreased from 54.6 km to 34.3 km (37.2%) and that of the
horticultural and irrigated farms increased by 103.3% from 45.1 km to 91.7 km in the same period, placing great
pressure on both the quality and quantity of the lake’s water resources. Information obtained from the Fisheries
Department in Lake Naivasha show that the fishery production declined from 513 to 110 tons in the period considered.
The Naivasha Municipal Council records indicate a 30% decline in the water it supplies to Naivasha Town from 10,000
m3
to 7,000 m3
in the same period despite the increase in population. The decline was attributed to many factors among
them the presence of water hyacinth and the decline in water quantity due to increased human activities.
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