10.2.1.4. Impacts and Vulnerability
Sensitivity analyses of major rivers of the continent indicate that these rivers
are sensitive to climate change. Magadza (1996) examined changes in water storage
in Zimbabwe's main water storage facilities during the 1991-1992 drought
cycle. During this period, the mean temperature averaged 2°C above the long-term
seasonal mean, and seasonal Penman evaporation exceeded the long-term seasonal
mean by more than 30%—peaking at just less than 90% in February at the
Kutsaga station. During this drought cycle, stored water resources dwindled
to less than 10% of installed capacity.
Urbiztondo (1992) simulated the response of Lake Kariba power-generating capacity
to various climate change scenarios. His results indicate that with no significant
change in precipitation, the lake would regulary fail to meet installed generating
capacity if the temperature rose by 4°C. During dry years, generating capacity
would decrease by as much as 50%. Even during wet years, maximum generating
capacity would barely exceed 50% of installed capacity.
Economic impacts from curtailment of hydropower generation from Lale Kariba,
as a result of the 1991-1992 drought, were estimated to be US$102 million
loss in GDP, US$36 million loss in export earnings, and loss of 3,000 jobs (Benson
and Clay, 1998). The direct impacts on agriculture and the knockon impacts also
were quite severe. These limited estimates provide a window on potential economic
impacts of climate change-mediated water resources changes in the medium term
(i.e., into the middle of the 21st century—a time span within the planning
window of economic development strategies).
With an estimated error of about 8%, the Gambia River flow has been shown to
be very sensive to climate change. Based on the results of river flow responses
and vulnerability analysis, climate variables alone can cause a 50% change in
runoff in the Gambia River catchment (Jallow et al., 1999). In general,
a 1% change in rainfall will result in a 3% change in runoff (Manneh, 1997).
On the whole, this translates into saltwater intrusion into the Gambia River
by 40 km at times of maximum intrusion. However, the flushing action of freshwater
flow of the river will keep the saline/freshwater interface at an equilibrium,
oscillating between 90 and 290 km. The rate of saline water intrusion during
dry seasons would increase from about 20 km per month in January to about 40
km per month in April and May.
10.2.1.5. Adaptation
Likely changes in precipitation and discharge regimes call for a wide range
of adaptations. Broadly, these adaptations would include:
- Refinement of early warning sytems to enable timely remedial measures
- Shared basin management, necessitating international agreements
- Water-use strategies—especially demand management—in industry,
settlements, and agriculture
- Intensified monitoring to improve data reliability
- Intensive research into energy usage and alternate renewable energy at household
and industrial levels
- Intensive research into design of infrastructure facilities, such as roads
and telecommunications, to withstand extreme events
- Intensive research into flood control management technology
- Innovation in building designs (e.g., to minimize urban flooding)
- Research into and commencement of coastal defense facilities
- Research into adaptive agricultural startegies
- Reserarch into environmental flow requirements.
Although there are now subregional climate change scenarios for the African
region, the quality of such scenarios varies with the intensity of historical
data and the spatial distribution of monitoring stations. There is an urgent
need to intensify the density of monitoring stations to improve climate change
scenarios. The cost of rehabilitating stations that are in disrepair is not
beyond the financial capability of African states. Appreciation of the strategic
importance of these facilities and a sense of ownership of climate change concerns
needs to be reawakened.
It has been noted that practically all of the major river basins of Africa
include several states. In recognition of this fact, the past decade has seen
the development of international river basin mangement protocols—such as
the Southern Africa Development Community (SADC) Protocol on Shared Waters,
the Niger Basin Authority, and several others, including the more recent Lake
Victoria Fisheries Authority. The United Nations Environment Programme International
Environmental Technology Center (UNEP-ITEC) have emphasized the river basin
as the fundamental unit of management (UNEP, 2000). We recommend that these
international basin authorities be strengthened in terms of finance and human
resources and that their perspectives should embrace near- and long-term climate
variability and climate change issues in their work plans. Most important is
that the legal framework for such river basin authorities should be robust to
ensure equity in access to and accountability for water supply and water quality
management. Failure to take these concepts on board could lead to water resources-related
conflict.
In general, the African continent lacks technical strategies to optimize water
resources. A few countries (e.g., South Africa and Zimbabwe) have begun to develop
strategies for optimum use of water resources—using, for example, water
pricing and demand management tools. Crop-watering technology is primitive and
wasteful in most cases. Few industrial and household water-usage strategies
incorporate water reuse. During drought periods, management authorities have
resorted to supply restrictions, such as the 3-day supply per week in Mutare
during the 1991-1992 drought. Water supply shortages conventionally are
addressed through construction of more impoundments. Magadza (1996) remarks
that in severe drought periods there would be a multiple failure syndrome of
water storage facilities, especially where individual reservoirs are dedicated
to defined communities. Although supply structures (banning of garden hoses)
and construction of storage reservoirs are practical options, demand management—which
reduces consumption per unit of product output—has proved increasingly
to be a water-saving strategy that can allow communities to enter a drought
cycle with adequate supplies.
Whatever strategies are adopted for optimizing water usage, successful development
of such strategies is contingent on reliable meteorological and hydrological
information. In many instances, application of hydrological models on a basin-wide
scale is restricted by data density. Reliable impacts assessments and near-term
predictions depend on robust databases. For example, flood propagation and thus
flood warning capability, which are real-time processes, are a function of the
density of measuring points. Similarly, crop yield forecasts could be made spatially
more accurate by improving the intensity of climatic measurements.
Over the past half-century, Africa has invested heavily in hydroelectric power
schemes. Recent drought episodes and demand escalation have highlighted the
vulnerability of even the largest hydroelectric plants to climate variability
(Magadza, 1996). This assessment has shown that future water resources, especially
in the subhumid to semi-arid regions of the African savanna and subtropics,
will be more restricted. Research into other forms of renewable energy and energy-use
efficiency in industry and households is an essential inverstment in a more
energy-secure future. At the regional level, energy resource sharing is a necessary
strategy. Individual states must have trust and confidence to invest in neighboring
countries for overall regional energy security.
Populations that live in flood-prone areas need to consider strategies for
early warning procedures for flood events; strategic planning in the location
of human habitations to minimize flood impacts; and strategies for robust protocols
for alleviating impacts of drought events to minimize loss of human life, economic
assets, and societal norms. On the other hand, early warning systems can be
effective if impacted areas are accessible in the worst-case scenario, to enable
either evacuation or relief supplies delivery.
Although there are major reservoirs on most large African river basins, these
reservoirs were not designed for flood control. However, synchronization of
operations of reservoirs that are located in the same basin can alleviate flood
impacts. Nevertheless, there is a need to consider purposely building flood
control facilities in some of the flood-prone areas of Africa, similar to those
found on the Danube, which reduce flood crest intensity by sequestering floodwaters
into temporary storage facilities along the river. This could be a subject of
directed research for each African basin.
Research into coastal defense systems is an immediate need. Several African
coastal areas already are experiencing sigificant coastal impacts. Coastal management
infrastructures are likely to entail intergenerational investment programs in
which each extent generation must make its contribution to minimize long-term
costs. If our generation abrogates our responsibilities to future generations,
we will impose immense costs on our posterity.
To minimize sensitivity to climate change, African economies should be more
diversified, and agricultural technology should optimize water usage through
efficient irrigation and crop development. Considerable advances have been made
in agricultural industries of southern Africa, particularly in South Africa
and Zimbabwe.
As water resource stresses become acute in future water-deficit areas of Africa
as a result of a combination of climate impacts and escalating human demand,
there will be intensifying conflict between human and environmental demands
on water resources. Because maintanance of healthy ecosystems is an underpinning
to economic sustainability, there is need in each water basin management unit
to identify and factor into development projects the need for environmental
flows.
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