Adaptation Strategies Basin level

Three adaptation strategies were developed at basin level: business as usual, food security and energy. In business as usual, the present water use levels were maintained to assess what the isolated impact of climate change would be. Both future climate

Fig. 9.7. Energy production at Akosombo for the different simulation periods using the Hadley model and A2 and B2 scenarios.

Simulation year

Fig. 9.7. Energy production at Akosombo for the different simulation periods using the Hadley model and A2 and B2 scenarios.

scenarios (Hadley A2 and B2) predict higher rainfall for the Volta Basin. It is not realistic to assume that existing infrastructure will be removed to favour environmental water flows. One could, therefore, see the business as usual adaptation strategy also as the best possible environmental adaptation strategy (CSIR-WRI, 2000).

The second adaptation strategy is the food security strategy. Food production is mainly rain-fed in the Volta Basin but irrigated agriculture is growing quickly. It is difficult to increase the productivity of rain-fed agriculture mainly because investments in labour or agro-chemicals do not pay off when the rains fail. Irrigation is therefore definitely an important means by which local food production can be increased. The present level of irrigation is very low. If Asian-type land use pressures existed in the Volta, probably more than 4% of the total area would be under irrigation. This would correspond with a 100-fold increase with respect to present levels, which is not realistic under present institutional arrangements. Instead, an irrigated area of 1% of the total area is put forward as the irrigation scenario, still an enormous relative increase from the present situation. We expect that most irrigation expansion will take place as small-scale, village-level irrigation.

The third adaptation strategy is the energy strategy At present, the dam at Akosombo is used at unsustainable rates. The pressure to produce more energy is so high that the Volta River Authority (the energy-producing institution) lets too much water through the dam in the hope that next year's rains will replenish the reservoir. When the rains are not so good for a single year, such as happened in 1997/98, there is no buffer and hydropower production comes to a halt. In the business as usual scenario, we used a throughflow of 983 m3/s, which is equal to the average flow over the past decades. In that case, flow demands were only unmet in 1983/84 under the historical scenario, which corresponds with actual disaster years in Ghana in which many forests burned down due to the drought (1983 also was the strongest El NiƱo year on record). In recent years, outflow levels of 1350 m3/s were reached, which are not sustainable. For the energy scenario, it was assumed that the operation engineers will continue searching for more sustainable energy management measures. In practice, this translated into letting all extra runoff water that becomes available under projected future climates run through the Akosombo turbines.

The three adaptation strategies are relatively simple, but it can be stated with confidence that they span most of the realistic 'management space'. The business as usual adaptation strategy is definitely the minimum level of water resource development. The 1% irrigation adaptation strategy implies a very large extension of present irrigated areas and, as such, a maximum in irrigated area to be expected. Perhaps the only somewhat conservative strategy is the energy strategy because it assumes a reduction of the flows through Akosombo. It is, however, the only sustainable energy adaptation strategy because letting more water out from a reservoir than flows in clearly means that one runs out of water quickly.

Additional adaptation strategies that may be developed in the future could include a scenario in which the flows through Akosombo are concentrated in a shorter period in the wet season so that salt is allowed to enter the estuary as used to be the case before building the dam. It has been reported that the lack of movement in the salt front over the year has been the main environmental impact of Akosombo, destroying clam fisheries and increasing schistosomiasis. Thermal power could be used to bridge the dry season energy gap, but would most likely come at considerable financial costs. A second scenario that should be tried in the future is building the Bui Dam. It has many times been proposed to build a dam in the Bui gorge on the Black Volta, which would flood an almost uninhabited flood forest. This would be associated with unknown environmental damage. At present, it seems that a fully fledged Bui Dam would produce electricity at a cost of $0.09/kWh, whereas a thermal plant would produce at $0.07/kWh. A second alternative would be a smaller Bui Dam that would produce at economical costs but may not be interesting from a development-political point of view. Unfortunately, because the Bui Dam is presently in a bidding stage, no information concerning the properties of the dam and reservoir are available.

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