An integrated river basin planning approach – Nyando case study in Kenya

The river basin has long been acknowledged as the appropriate unit of analysis for water resources management and has also been named by the United Nations Conference on Environment and Development (UNCED 1992) as the logical unit for integrated water resources management in Agenda 21, chapter 18. The comprehensive methodology framework for analysis structures the decision making process, starting with the problem identification, through the weighing of various options to the final selection of the most appropriate policy. The integrated planning approach methodology is applied to the 3600 km2 Nyando river basin in western Kenya, one of the sub-basins that drain into Lake Victoria in Eastern Africa. Statistical methods used to check the adequacy and reliability of the available hydrometeorological records revealed existence of trends, inconsistencies and inhomogeneities in some the observational data series. The modular structure of the computational framework consisted of modules for estimation of water demands for irrigation and public water supply, a river basin simulation and allocation model, a module for yield reduction and damages due to agricultural demand shortages and a module for incorporating investments and benefits in a given timeframe, assessing the impacts in terms of economic indicators. Various possible development strategies are formulated and evaluated based on the specific objectives of enhancing social equity, efficient economic growth, environmental conservation and efficient resource allocation and use, through multi-criteria analysis. Performance measures are used to evaluate the alternative strategies in light of the multiple objectives. The economic strategy is found to dominate the other strategies under different stakeholders priorities for the specific objectives, although not robust under all analysis conditions. Institutional arrangements largely determine whether objectives can be achieved in practice. The existing institutional framework for water resources planning and management is outlined together with the desired situation. Remedial actions proposed to fill the gap between existing and desired situation in future are outlined.

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