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13.2.9 Tanzania
Report No 678-F-001
METSI CONSULTANTS: SUMMARY OF MAIN FINDINGS FOR PHASE 1 DEVELOPMENT
Tanzania has initiated some IFA activities, and the new Water Policy has adopted the principle of a reserve from
the RSA Water policy. Water resource projects presently coming into operation have not all had IFAs. The Lower
Kihansi Hydropower Project on the Kihansi River, Rufiji Basin, was commissioned in July 2000 and is expected to
lead to a loss of wetland habitat and the possible extinction of several threatened endemic species, including the
Spray Toad. The EIA was limited to the effects of inundation and did not address the effects on the downstream
river system in Kihansi Gorge. A constant bypass release averaging 2 m 3 s -1 (~12.5% of MAR) has been
guaranteed and is being supplemented by an artificial sprinkler system. A 2-year flow release experiment
involving a range of small to high flows will be used as a basis for establishing an IFR before a final water right is
granted.
13.3. ASSESSMENT OF INSTREAM FLOW REQUIREMENTS IN THE REST OF AFRICA
The Sahelian Wetlands Expert Group is a network of 100 specialists comprising hydrologists, water engineers,
biologists, physicists, pedologists, planners, human and animal health experts, ecologists, sociologists, legal
experts and agro-foresters working in the Sahelian region of West Africa. Its primary goal is to improve the
management of water in this region. Guidelines and a manual have been developed for use by planners and
decision makers in West Africa. Projects include the successful introduction of artificial flood releases from dams
to the Diawling National Park on the Senegal River in Mauritania, and the Waza Logone wetlands on the Logone
River in Cameroon, which restored biodiversity and the associated livelihoods of communities dependent on the
floodplains.
In Nigeria, an economic valuation of the Hadejia-Nguru wetlands has found that the waters from the Hadejia-
Jamare River basin, which are dammed to provide irrigation for cereal crops, could more productively be used to
sustain the wetlands. The Hadejia-Jamare River Basin Development Authority is experimenting with managed
flood releases.
In Ghana, the Akasombo Dam on the Volta River has changed downstream flows to the extent that the coastlines
of Togo and Benin have eroded at a rate of 10-15 m a year due to trapping of sediments. No IFAs have been
done although flows for irrigation and domestic water abstraction have been addressed. There is a growing
awareness of the need for IFRs following the impact of high dry-season or constant flows on Egeria populations
and Bilharzia in the Volta Estuary.
The Manantali Dam on the Senegal River in Mali was designed to provide irrigation to the Senegal River Basin,
and to generate electricity for Mali, Mauritania and Senegal. The Diama Dam, 50 km upstream of the mouth of
the Senegal River, was built to prevent salt water from intruding into the river delta as a result of the construction
of the Manantali Dam and to aid navigation. IFAs were not done before the dams were built. Since their
construction there has been an increase in the prevalence and extent of urinary and intestinal Bilharzia
(transmitted by Bulinus sp.) in the Senegal River basin, and upstream aquatic weed (Salvinia molesta)
infestations have become a major environmental problem. A study of the environment in the valley was
undertaken in 1978 but no EIA relating specifically to the dam impacts appears to have been conducted. The
biodiversity of the deltaic ecosystems downstream of Diama Dam in the Diawling National Park has declined.
Managed flood releases from the Diama Dam were introduced in order to restore the downstream delta. Floods
are released to guarantee the hydraulic conditions necessary to maintain 50,000 ha of floodplain agriculture
below the Manantali Dam, although during drought years, this figure is not always achieved.
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