Background
The Western Cape System Analysis Study, conducted between 1989 and 1995,
assessed the future growth of water demands in the greater Cape Metropolitan
Area and surrounds and studied options for meeting or moderating these demands.
One of the options considered was the development of Skuifraam Dam and the
Skuifraam Supplement Scheme for the upper reaches of the Berg River.
As part of the pre-feasibility investigation of Skuifraam Dam, the instream flow
requirements (IFR) for the Berg River at various sites along its length were
identified on the basis of motivations for flows to drive a range of biological
and physical processes in the river. These flows were identified during a series
of workshops, held in 1992 and 1993, and subsequently refined in 1996. At the
end of 2001, another workshop was held to re-visit certain of the flood
requirements of the refined IFR. In each case, motivations for particular flow
regimes for ecosystem maintenance were made on the basis of best available
knowledge, but it was acknowledged that much work is necessary to deepen
scientific understanding of the relationship between desired or essential
ecological processes and a particular flow magnitude or its frequency, and thus
increase the sophistication of how the effects of different levels of flow
modification are quantified. In this respect, a programme to monitor the effects
of the artificial flow regime imposed by the construction of any dam would need
to be established in order to:
· confirm compliance with the IFR,
· verify the nature and accuracy of the changes to the ecosystem that were
predicted as a result of the dam,
· determine the effectiveness of the environmental flow releases (the IFR) in
terms of their predicted effects on ecosystem processes, and
· facilitate the implementation of adaptive management where undesirable and/or
unpredicted changes in ecosystem characteristics are detected. Such adaptive
management would seek to minimise the impacts of these changes.
Prior to construction of a dam, however, the baseline ecological, physical
/chemical, hydrological, hydraulic and social conditions of the river system,
including its associated groundwater, estuarine and floodplain components, would
need to be established, to allow clear identification of future changes as a
result of implementation of the IFR, as well as to guide the post-construction
monitoring programme itself.
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