Scale issues in the governance of water storage projects

In the face of global change, which is characterized by growing water demands and increasingly variable water supplies, the equitable sharing of water and the drought proofing of rural livelihoods will require an increasing physical capacity to store water. This is especially true for the semiarid and dry subhumid regions of sub-Saharan Africa and Asia. This paper addresses the following question: What criteria should policymakers apply in choosing between centralized storage capacity in the form of conventional large reservoirs and large interbasin water transfer schemes and decentralized and distributed storage systems in the farmers' fields and in microwatersheds and villages (tanks, microdams, and aquifers)? This exploratory paper uses an interdisciplinary framework encompassing the natural and social sciences to develop four indicators that are considered critical for understanding the biochemical, physical, economic, and sociopolitical dimensions of the scale issues underlying the research question. These are the residence time of water in a reservoir, the water provision capacity, the cost effectiveness of providing reliable access to water per beneficiary, and the equity dimension: maximizing the number of beneficiaries and compensating the losers. The procedural governance challenges associated with each indicator are dealt with separately. It is concluded that water storage and the institutional capacity to effectively administer it are recursively linked. This implies that if the scale of new storage projects gradually increases, a society can progressively learn and adapt to the increasing institutional complexity.