Metsi Consultants - DWA Home Page

Report No 678-F-001
METSI CONSULTANTS: SUMMARY OF MAIN FINDINGS FOR PHASE 1 DEVELOPMENT
4.2.2 Ecosystem Responses to Overall Reduced Flow Releases
Biophysical consequences and explanations linked to each flow reduction level within a scenario were assessed
in combination to create a single description of an overall ecosystem response for each river reach within each
scenario. These are summarized further in Sections 5 to 8. The levels of impact can be interpreted as changes in
the river from present-day (near natural) conditions, or for IFR Site 2 (immediately downstream of Katse Dam) an
estimated near-natural condition, as follows:
None: The river will stay in approximately the same condition as at present.
Negligible: 0-10% change, either in most subcomponents or most important subcomponents, of the riverine
ecosystem.
Low: 10-20% change.
Moderate: 20-40% change.
Severe: 40-80% change.
Critically severe: 80-100% change.
4.3. DESIGNATION OF SEVERITY RATINGS USED FOR SOCIO-ECONOMIC CONSEQUENCES
Social impacts were assessed on a scenario-specific basis, i.e., the method required the identification of a
comprehensive modified flow regime and assessment of its biophysical consequences before social impacts
could be determined.
4.3.1 Cultural and Subsistence Use of River Resources
Impacts on cultural and subsistence use of river resources were assessed using the predicted biophysical
changes, the critical nature of the usage (i.e., the importance of the resource for the livelihoods of the affected
populations), the number of households harvesting the resource, the frequency of usage, and the availability of
alternative resources. The resulting social impact was then ranked for each resource on a four-point scale, using
expert opinion, as follows:
None: No appreciable change expected.
Low: The resource is not important or, if important, its quantity is predicted to change by < 20%.
Moderate: The resource is important, and its quantity is predicted to change by 20-50%.
Severe: The predicted biophysical change is > 50% and the resource is considered to be essential for the
livelihoods of the affected populations.
4.3.2 Public and Animal Health
The impacts on public and animal health were assessed on the basis of biophysical changes that could influence
people’s health, the wide range of factors influencing health and data, and on the extent of river use by members
of the PAR and their livestock. Most of the diseases considered already occur in Lesotho and there is a risk of
contracting them even in the absence of the LHWP. Thus, for health assessment, both a baseline probability and
a future probability of contracting a disease or facing a health risk were considered. The predicted future
probability was inclusive of the baseline probability of contracting the disease. Further, if the dams are expected
to make a difference to health risk, this difference is reflected by adding the extra probability to the baseline
probability. For each type of impact, a baseline probability (i.e., the present-day probability that someone in the
community or a domestic animal would contract the disease or face the health risk), and a future probability were
identified using the following scale:
19