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Water cooperation for sustainable utilization:
Lake Naivasha, Kenya
Professor David M. Harper, Dr Nic Pacini, Dr Caroline Upton, Dr Ed H. J. Morrison, Mr Richard Fox, and Mr Enock Kiminta
F
resh waters around the world are critical for human welfare
yet widely degraded. Lake Naivasha is the world centre for
irrigated cut flowers, accounting for over 70 per cent of
Kenya’s flower exports (US$400 million) and 3 per cent of its gross
domestic product. Some 5 km
2
of commercial farms are irrigated
from lake and groundwater, supplying 40 per cent of the European
Union market, 25 per cent of which is direct to UK supermarkets.
Lake Naivasha and its basin
Lake Naivasha is the most well-known freshwater resource in Kenya
after Lake Victoria, because the land around it was subdivided early
in colonial history and sold to settlers unlike the other freshwater
lake, Baringo, which has remained as government land occupied by
three indigenous communities. Naivasha has long been famous for
its aquatic bird diversity, and is popular with residents of Nairobi
for weekend escapes and tourists on their way to major destinations
such as the Maasai Mara National Reserve. Mid-twentieth century
tourist guidebooks describe it as ‘one of the world’s top 10 bird-
watching sites’ and ‘the most beautiful of the Rift Valley lakes’. Such
abbreviated descriptions barely do justice to an ecosystem once as
spectacular as this.
Anthropogenic changes in the twentieth century
A commercial fishery was opened in the lake in the second
half of the twentieth century after several earlier introduc-
tions of piscivorous American large-mouthed bass and
herbivorous East African native Tilapia species. The former
is believed to have exterminated the only native species, a
small endemic tooth-carp, by the 1960s, representing the
first detectable impact on the lake’s ecology by humans.
By the time this endemic fish had disappeared, the first
of several exotic species had arrived by chance. A floating
fern originally from South Africa, named ‘Kariba Weed’
because of its dramatic impact on the Kariba reservoir on
the Zambezi, was recorded in the shallow lagoons in the
1960s. The exotic with worst impact of all, the Louisiana
Crayfish, was deliberately introduced in 1970 by the
Fisheries Department to diversify the commercial fishery.
It ate every native species, plant or animal, beneath the
water surface that could not escape by swimming. The
fishery for it, which exported to Europe, collapsed after
about six years and has never recovered. The Water
Hyacinth, a flowering floating plant also from South
E
conomic
D
evelopment
and
W
ater
Water Ambassadors training on lake ecology at Lake Oloidien, an alkaline lake supporting lesser flamingoes beside Lake Naivasha
Image: Nic Pacini