## 6 Discussion  
Statistical extrapolations should be made with some care. The data sets from Mozambique indicate a clear and steady temperature increase from 1974 and the extrapolation done in this paper coincided with models previously presented by IPCC, see for instance [18]. Temperature has a less clear effect on precipitation, but longer periods of drought have been observed in the watersheds of the major rivers in Mozambique, not least at Cahora Bassa.  
The total hydropower potential for Mozambique is approximately 18,000 MW according to Electricidade de Mozambique (EDM) and hydrological studies of the large river basins in the country [1]. The hydropower plants presented in Table 2 are thus only a fraction of the potential hydropower plants available for electricity generation in the country. Mozambique and neighboring countries will need to develop electricity generation further to meet the needs of the population and the economy, as much as possible. The climate change effect, however, reduces the runoff in the rivers and thus the economic value of investment in hydropower plants. The substantial hydropower potential that could be exploited in Mozambique should be investigated. The dramatic growth in demand and supply until 2100 has geopolitical consequences for all countries in southern Africa. The South African share of regional capacity will decrease and hydropower from the Democratic Republic of Congo, Mozambique and Zambia is estimated to increase. The fuel mix will shift away from coal and towards hydropower. Depending on growth assumptions and the economy, the southern African regional power generation capacity will increase from 52 GW to about 1000 GW in 2070, a 20 fold increase [15]. This is approximately the same growth rate as for Mozambique itself. The capex cost for a large hydropower plant is in the range of US$50 per MWh. To build a new plant like Cahora Bassa (with an annual generation of about 15 TWh) could be estimated to cost US$750 million. Assuming that all the hydropower potential in Mozambique was utilized, the total investment cost for these additional 16,000 MW would be in the range of US$8-10 billion. Capital is generally difficult to raise in southern Africa, yet the need for electricity and the willingness to pay for it is high in the region. Increased sustainable power generation will benefit all countries in the southern part of Africa. Therefore, one important step to facilitate an expansion of the hydropower generation in Mozambique is to increase the economic collaboration with the neighboring countries and increase the electricity transmission capacity within and between the countries. The joint European electricity market may possibly be one inspiration for the southern African countries on how to organize the supply and transmission. Central for the southern African countries is probably to continue collaboration and develop mutual organizations to utilize the important hydropower potential of the watersheds.  
When investigating potential hydropower projects in Mozambique, it is necessary to take into account that the climate change effects on river runoff will decrease the annual capacity of a plant by 10-20% and reduce electricity generation. Particularly in the investment calculations the prolonged pay-off of investments should be considered. The need for sustainable and renewable electricity generation is however urgent in southern Africa and investment projects should therefore be considered carefully in the feasibility phase considering they may need to operate for a longer period before delivering profit to the owners.