Climate Change in the Basin

Climate change will have considerable impacts on the southern Africa region and the Kunene River basin. The changes expected are principally changes in:

• Temperature;
• Precipitation; and
• Evaporation.

The resulting impacts are described below generally in terms of:

• Water Supply impacts;
• Hydropower impacts; and
• Agricultural impacts.

Regional Impacts of Climate Change

As a result of increasing concentrations of Greenhouse Gases (GHGs), it is predicted that global temperatures will increase by about 2.0–3.5º C if CO₂ concentrations double from pre-industrial levels. Higher temperatures will lead to changes in precipitation and atmospheric circulation, which are hard to accurately predict with existing atmospheric models (IPCC 2001).

There is growing evidence of changes in temperature, precipitation and streamflow over many parts of southern Africa (Warburton and Shulze 2005; Hewitson et al. 2005). Using agro-hydrological simulations and climate change models, Warburton and Shulze (2005a) found that potential evaporation appears to have increased over much of the interior of southern Africa in recent decades. These findings support the International Panel on Climate Change (IPCC 2008) findings that temperatures have increased by 0.2°C and 2.0°C between 1970 and 2004.

These temperature changes will have profound effects, both direct and indirect, on hydrology and water resources. Large parts of southern Africa are expected to experience some of the most variable rainfalls and stream flows in the world, presenting major challenges to managers of water resources (Schulze 2005). In fact, the IPCC has identified southern Africa as one of the world's most vulnerable regions to anticipated climate change impacts (IPCC 2001).

Climate change raises serious concerns about the sustainability of current development trends in southern Africa. Global and regional climate models predict warming and drying trends over large areas, which will increase pressure on human welfare, particularly of the poor (MEA 2004). The box below presents the array of cross-cutting environmental and developmental issues related to strategies for mitigating climate change impact within the Kunene River basin.

Climate Change and the Implications for the Kunene River Basin

Temperature changes: Available reports from the region looking particularly at Namibia report a rise in mean temperature over the 20th Century that is three times that of the global average. A temperature rise in the region of between 2° C to 6° C has been predicted for 2100.

Precipitation changes: Regarding specific observations relevant to the Kunene River basin, the following statements can be made:

• Precipitation is generally expected to decrease across all of Angola with the exception of northern areas where these may increase (High Level Conference on Water for Agricultre and Energy in Africa 2008).
• Studies for Namibia suggest much greater variability in rainfall from year to year with a much shorter and more intense rainy season (Government of Namibia 2002).

These will result in changes in the run-off regime of rivers. Decreased precipitation in Angola, particularly in the Upper Kunene where up to 75 % of the flow is generated, will have a marked effect on the entire Kunene basin.

Evaporation changes: Temperature increases will be associated with an increase in the potential evaporation rate, resulting in the overall water balance becoming drier, even if precipitation were not to change (Government of Namibia 2002). Soil moisture is thus expected to decrease and the dune system in the desert is expected to increase (High Level Conference on Water for Agricultre and Energy in Africa 2008).

Water supply impacts: With almost half of the Namibian population living in the north and largely reliant on drinking water from the Kunene (see chapter on Bulk Transfer Schemes) a decrease in water availability will increase competition for water resources from different users. In Namibia, water for drinking water supply is the priority user and as such will have first rights to any water taken from the Kunene for Namibia.

Hydro-power impacts: The 240 MW installed capacity Hydropower Plant at Ruacana could supply nearly half of the electricity needs in 1994 of Namibia. The amount of power generated varies with the strength of water flow and so depends on climate. There are possibilities for further hydropower projects on the Lower Kunene River. The magnitude and reliability of power supply from such projects will be impacted by climate change to a degree that is currently poorly quantified (Government of Namibia 2002).

Irrigation impacts: Plans to vastly expand irrigation areas along the Kunene in Angola along with moderate expansion of irrigation areas in Namibia (see Irrigation Infrastructure) are dependent upon the availability of water for irrigation. Allocations for irrigation are likely to come under pressure in the future as demands from the domestic and other sectors with a higher economic return on water use increase.

Agricultural impacts: Agricultural output in the basin is extremely sensitive to climatic conditions, particularly in the areas with lower rainfall. Periodic droughts cause considerable stock losses and reduce grain production. The uncertainty in future rainfall trends make projection of agricultural impacts very difficult, but certain projections under increased temperatures can be made with confidence.

• Subsistence agriculture: A decrease in soil moisture and increased inter-annual rainfall variability would result in a greater variability in yield of millet (the staple crop in drier areas) and thus decrease food security.
• Commercial cropping: The vulnerability of this sub-sector to competition for irrigation water has already been noted. Maize is the principal commercial crop. One study predicts a small increase in maize yield under future climate change scenarios, although yield quality would be reduced because of shortened growing seasons. Given the projected increase in air temperature, already close to the maximum for maize, a probable decrease in rainfall and increased evaporation, a decrease in maize yield is more likely.
• Livestock farming: The raising of cattle, sheep and goats is practiced in the basin. A trend towards greater aridity would be associated with a shift towards farming with more small stock and game. Droughts are associated with a greater incidence of stock poisoning as stock animals are forced to eat unpalatable or toxic plants that are the first to emerge on overgrazed rangelands. Drought lowers the availability of forage, reduces milk production, growth rates and the health status of livestock. With increased temperatures the incidence of tick-borne diseases may increase, but diseases borne by the tsetse fly may decrease. The expanded use of indigenous livestock breeds may help mitigate this trend. Impacts on household food security in the subsistence farming areas could be dramatic and climate change has the potential to cause significant social disruption and population displacement in these communities (Government of Namibia 2002).