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Report No 678-F-001
METSI CONSULTANTS: SUMMARY OF MAIN FINDINGS FOR PHASE 1 DEVELOPMENT
Article 7(18) of the Treaty refers to the welfare of local people in the Project area and states “The LHDA shall
effect all measures to ensure that members of the local communities in the Kingdom of Lesotho, who will be
affected by flooding, construction works or similar project-related causes, will be able to maintain a standard of
living not inferior to that obtaining at the time of first disturbance: provided that such Authority shall effect
compensation for any loss to such member as a result of such project-related causes not adequately met by such
measures.”
Article 15 of the Treaty addresses similar concerns and states “'The Parties agree to take all reasonable
measures to ensure that the implementation, operation and maintenance of the Project are compatible with the
protection of the existing quality of the environment and, in particular, shall pay due regard to the maintenance of
the welfare of persons and communities immediately affected by the project”.
1.4. WATER TRANSFERS AND RIVER FLOWS
Phase 1 of the LHWP was designed to maximise the amount of water that would be transferred from Lesotho to
the RSA with minimal amounts to be released through the structures to the downstream river channels. The
Treaty-defined releases (termed ‘compensation flows’ at the time the Treaty was signed) of 0.5 m 3 s -1 through
Katse Dam to the Malibamats’o River and 0.3 m 3 s -1 through Mohale Dam to the Senqunyane River represent
values that were computed to exceed annual minimum flows in nine out of every ten years of record (at the time
the Treaty was negotiated). The ecological basis for these selected values was not stated. Earlier environmental
evaluations considered that negative impacts would be mainly limited to the proximal reaches of downstream
rivers and would be mitigated by flows from unregulated downstream tributaries. The Treaty minimum releases
represent about 2.6% of the overall long-term combined yield of the Malibamats’o and Senqunyane rivers
(measured at the sites of the respective dams).
The need to determine more realistic and defensible releases to downstream rivers was identified in 1994 when
the Phase 1B environmental impact assessment was initiated. The World Bank, one of the international agencies
providing funding for the LHWP, emphasised the importance of determining instream flow requirements (IFR) on
a scientifically justifiable basis, while international NGOs identified the absence of instream flow assessments as
a weakness in LHWP planning. Estimation of IFRs for the lower Matsoku became a key concern in project
justification in late 1996.
1.5. PREVIOUS STUDIES
A study (LHDA 648) of the instream flow requirements (IFR) of the river reaches within Lesotho downstream of
dams and weirs of the LHWP was conducted between 1997 and 2000 by Metsi Consultants, a joint venture
between SMEC International of Australia and Southern Waters Ecological Research & Consulting of South Africa.
The study area included the Malibamats’o River downstream of Katse Dam, Matsoku River downstream of the
Matsoku Weir and the Senqunyane River downstream of Mohale Dam. All three of these structures are part of
Phase 1 of the LHWP. The study also included the mid- and lower Senqu River downstream of the confluence
with the Malibamats'o River. In addition to being downstream of Phase 1 structures, these reaches would be
affected by the proposed Mashai Dam on the Senqu River, which would be the main component of a Phase 2
development of the LHWP.
The IFR assessment utilized the DRIFT (Downstream Response to Imposed Flow Transformations) methodology,
and focussed primarily on eight IFR sites, each selected as representative of a particular river reach. For each
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