The Kenyan government approved construction of High Grand Falls Dam in Mwingi aimed at promoting irrigation and supply clean water in Ukambani and Tana River regions.
Though this is a project aimed making positive impact improving water supply and people’s livelihoods through increased food production through irrigation, flood control and electricity generation it has a number of negative impacts which should not be ignored. Construction of such a dam upstream will reduce the amount of water flowing into Tana Delta from River Tana. This would hasten and exacerbate changes in downstream ecosystem and biodiversity, further disrupting the flooding regime, which has already been disrupted by existing dams; and also affect livelihoods for farmers, fishermen and pastoralists within the Delta who depend on the flooding system of the river for their source of livelihoods.
The Tana Delta also contains unique species and habitats which are not found elsewhere in East Africa. 76% of this biodiversity is wetlands, comprising permanent water bodies; swamp or marsh vegetation; seasonally flooded grasslands; mangrove forests; riverine/floodplain forests; marine sea grass beds; coral gardens and coastal dune habitats. The remaining 24% comprises wooded grassland and bush land associations. It also sustains 2 species of endangered monkeys that are considered endemic to Kenya - the Tana River Crested Mangabey and the Tana River Red Colobus – and several globally threatened bird species, including Basra Reed Warbler and the Malindi Pipit.
To date economic appraisal had considered only the physical costs of dam construction and the financial and economic benefits arising from power generation, and had made little allowance for design options that would mitigate or avert the environmental impacts of flood loss.
It is therefore important to quantify the economic losses arising from loss of flooding downstream as well as the environmental degradation. The need for a holistic planning approach for projects affecting the Tana Delta should be considered. In particular Land Use Planning and Strategic Environmental Assessment.