Competition for water allocation in the Tana River basin

The Tana delta biodiversity and its ecosystem services are linked to the magnitude and duration of the bi-annual flood of the Tana River. These 2 key variables have decreased over the past 25 years following hydropower dam... [ view full abstract ]

The Tana delta biodiversity and its ecosystem services are linked to the magnitude and duration of the bi-annual flood of the Tana River. These 2 key variables have decreased over the past 25 years following hydropower dam construction to meet the urban needs and increased water abstraction for irrigation upstream. Combined with a reduced synchronization between floods and rainfall, and a modification of the local hydrology (shifting of the main flow from the Southern branch of the Tana River to the Northern branch), the reduction of extent and duration of the flooding has reduced the fodder, fish and recession farming production and has led to an increased competition between the farmers and the pastoralists. The construction of High-Grand Falls dam and more large scale irrigation projects upstream will further alter the flooding pattern.
One of the objectives of the GEOPAR Project (2009-2012) was to explore the consequences of the competition for water allocation between the urban and agro-industrial needs and the rural ecosystem downstream. We analyzed the links between floods, ecosystems services provided by the wetlands and human well-being in order to develop prospective scenarios for the future. Two complementary approaches have been used:
In a first step we have studied the link between the prospective dam operation and abstraction upstream, the flooding characteristics (extent, duration, water height, frequency) and their consequences for some key ecosystem services and biodiversity values in the delta. However, if linking hydro-climatic conditions and natural resources availability is a key element, it is not sufficient to explain the impact of future flood scenarios on the livelihoods and well-being of the Tana delta inhabitants.
We have therefore, in a second step, investigated the different economic strategies of the local users under various flood scenarios and evaluated the flexibility of the user practices under extreme scenarios (prolonged drought or high flood scenarios).

With this combined approach, we were able to explore various possible scenarios for the coastal wetlands and highlight the most likely to favour an improvement of human well-being downstream of the dam.