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DAM SYNCHRONISATION AND FLOOD RELEASES IN THE ZAMBEZI RIVER BASIN: ANNEX 4 OF FINAL REPORT However, it should be realized a pumping release of 200 m 3 /s during a day decreases lake level by 0.6 mm/day (averaged over the whole Lake). About 5 to 6 mm/day is the evaporation loss when no rain occurs. Therefore, the pumping time required for a 10 cm additional dropdown due to pumping alone is 170 days. If pumping is necessary for only one dry season, the pumping causing 10 cm extra drawdown has limited impact. If pumping is continuous over consecutive years the impacts can be more severe. Kholombidzo Reservoir A Kholombidzo Reservoir High would influence Lake Malawi water levels which the ecology specialists do not consider acceptable. A lower dam (lower then what is currently proposed as the lower alternative) that can store water but not affect Lake Malawi levels, could be acceptable, the ecologists reckon from the Lake Malawi point of view. The impact on the ecosystems functioning downstream depends on the extent to which downstream tributaries stay natural and the operating regime of the Kholombidzo dam. Other investment options The Consultant points out that the proposed Shire-Zambezi River dredging project is potentially much more damaging than a single dam project. The dredging project as proposed would attempt to allow for large-scale barging from Lake Malawi to the Indian Ocean. A prefeasibility has been carried out (Hydroplan Ingenieur, 2006). Depending on which scenario will be chosen, both the Shire and Zambezi will be dredged. Dredging causes turbidity which damages the ecosystem. Mozambique has requested for a full Environmental Impact Assessment to be carried out before further approval of the waterway will be granted. Cost effectiveness Cost effectiveness for flood protection and flow regulation is difficult to assess. All options have to be financed from benefits of power production and the added benefits for flood protection are therefore secondary. Upgrading of Kamuzu Barrage Costs were estimated for the Upgraded Kamuzu Barrage, including refurbishment of the roadway, improved reed island management capabilities, and excluding environmental cost. The 2003 estimates (Norconsult et al., 2003a) were: 8.56 million USD in construction cost invested over a 27-month implementation period; 0.05 million USD in annual operation and maintenance costs over 30 years; and 0.5 million USD in refurbishment costs on mechanical/electrical components after 30 years. From a flood protection, cost effectiveness cannot be confirmed, as the project is evaluated based on a different set of benefits (hydropower, traffic, damage) and it is explained above that the contribution to flood management is limited. The repair of one of the flood gates which is now blocked and improving the ease of operating the gates in times of emergency can add to flood security with little investment. The Norconsult (2003) report assumes a higher maximum operating level of 20 cm and some environmental flows, and with this scenario of operation power production would improve on 14
DAM SYNCHRONISATION AND FLOOD RELEASES IN THE ZAMBEZI RIVER BASIN: ANNEX 4 OF FINAL REPORT average by about 15 MW. In that case, the Benefit/Cost ratio in excess of 5, an Economic Internal Rate of Return of 50 as assessed in Norconsult (2003) may still be valid. Pumping scheme at Mponda Capital costs for Mponda Pumping Scheme were estimated in 2003 in the range of 30-40 million USD, depending on the selected pumping capacity. Operational costs depend very much on the frequency of use. With the interconnector for the electricity grid between Mozambique and Malawi in sight, the investment is not considered cost effective. Kholombidzo Reservoir The costs of the High Kholombidzo hydropower plant and Low Kholombidzo are in the same range (Norconsult 2003): 230 million USD in construction cost invested over a 39-month implementation period; 16 million USD(Low) and 25 Million USD (High) for environmental costs during the construction phase; 2.3 million USD in annual operation and maintenance costs over 30 years and addiitonally 1.8 million USD environmental costs over the first 20 years; and 14 million USD in refurbishment costs on mechanical/electrical components after 30 years. As Norconsult concluded, both the High and the Low Kholombidzo reservoir are highly viable projects in pure power economic terms. To make it cost effective for flood protection, the operating of the dam has to be adjusted, which will affect power generation. Impact on human use The main purpose of the investments is extra storage capacity or extra flow regulation for the benefit of hydropower production, however there are also agricultural impacts and impacts on navigability. See for further detail also Annex 2, Chapter 6. Upgrading of Kamuzu Barrage Apart from the hydropower benefits, upgrading of Kamuzu Barrage is beneficial for traffic over the barrage. Pumping scheme at Mponda Without the power interconnector Malawi-Mozambique, the pumping scheme may be the life line in very dry years for electricity supply in Malawi. However, the additional drawdown of lake Malawi levels may have a negative impact on lake transport infrastructure and fisheries (Norconsult, 2003). Kholombidzo Reservoir In terms of hydropower production, the Kholombidzo reservoir is most beneficial. However, this reservoir is also most debated on the other impacts it may have on flooding of residential area. The High Kholombidzo reservoir is most negatively assessed, as it impacts on Lake Malawi levels. 15
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