Optimization and assessment of agricultural water-sharing scenarios under multiple socioeconomic objectives

The allocation of irrigation water to multiple, spatially distinct sites is one of the oldest and most important problems in water resources planning and management. However, past technical investigations have focused almost exclusively on allocation for an optimization objective and have not diagnosed the tradeoffs existing between this objective and other important socioeconomic goals such as equity and security. A common optimization technique is reviewed and adapted to multiple levels of irrigation allocation. The process of spatial distribution is then investigated for five different hypothetical allocation scenarios, which represent various definitions of the objectives of efficiency, equity, and security. A semi hypothetical case study for the Lake Victoria Basin in East Africa is used to illustrate international water and crop production distributional effects of the five water-sharing scenarios. It is found that pursuit of nonefficiency objectives does entail material costs. The magnitude of these costs is variable with the specific policy pursued and the total system allocation level. Pursuit of a single objective, equity, can lead to very different patterns of water allocation and crop production depending on how exactly the political-social idea is defined. Finally, physical limitations of the agricultural system may require an explicit choice between objectives as it is shown that food supply security may not be possible under certain equity-targeted policies.