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Report No 678-F-001
METSI CONSULTANTS: SUMMARY OF MAIN FINDINGS FOR PHASE 1 DEVELOPMENT
13.2. ASSESSMENT OF INSTREAM FLOW REQUIREMENTS IN SOUTHERN AFRICA
13.2.1 Lesotho
This report describes the IFA carried out for the rivers below existing and planned LHWP Dams using the DRIFT
methodology to develop scenarios for decision-making. Each scenario describes a possible future flow regime,
and the consequences for river health and for subsistence users of the rivers. This has been the largest and most
comprehensive IFR assessment to date in Africa and involved an international team of 27 scientists from 19
disciplines over a 2-3 year period. The consequences of each of four flow scenarios has been predicted on the
basis of existing knowledge and twelve months of fieldwork, during which time the specialists collected river data
specific to their field of expertise. The input of each specialist team has been integrated using the DRIFT
methodology to produce the scenarios of predicted consequences.
13.2.2 South Africa
IFAs have been researched and implemented in South Africa for over 10 years, and were initiated in the mid-
1980s by the DWAF to manage the health of aquatic ecosystems. Habitat-simulation methods were found
unsuitable for several reasons and the BBM was developed as an approach where time, finances and biological
data were limited. This approach has to date been used to determine comprehensive IFRs for more than 20 rivers
in South Africa and was the basis upon which environmental protection of aquatic resources was built into the
South African Water Act of 1998, recognized at the time of promulgation as one of the most advanced in the
world.
The South African Water Act recognizes only two rights to water, which have to be met before any other water
demand is catered for. These are jointly called the Reserve. The 'Basic Human Needs Reserve’ allocates water
per capita for basic drinking, washing and cooking purposes, while the 'Ecological Reserve’ recognizes the need
to protect the health of the aquatic systems that are the basis of water and other linked resources. The Reserve is
determined for all rivers on which development is proposed and is currently being estimated for the Thukela River
in Kwazulu-Natal.
13.2.3 Swaziland
IFR determination in Swaziland commenced with the Maguga Dam on the Komati River, the fourth largest dam in
southern Africa (behind Kariba, Cohora Bassa and Katse). The Komati River has been subjected to a
comprehensive IFA, using the BBM.
13.2.4 Mozambique
Limited environmental flow studies have taken place in Mozambique. A basic desktop assessment has been
done for the Joint Inkomati Basin Study for the water departments of South Africa, Swaziland and Mozambique.
The retention of Zambezi River floods by the Cohora Bassa Dam has impacted on downstream river ecosystems,
resulting in losses of fisheries, agriculture and grazing and causing floodplain recession. Although no formal IFAs
have yet been undertaken in the country, interest in implementing IFRs is growing and proposals have been
made for an extensive research programme for the rehabilitation of the Zambezi delta, which would involve reestablishment
of a flood regime for downstream rivers and subsistence economies.
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