Water-scarcity patterns : spatiotemporal interdependencies between water use and water availability in a semi-arid river basin

This thesis addresses the interdependencies between water use and water availability and describes a model that has been developed to improve understanding of the processes that drive changes and variations in the spatial and temporal distribution of water resources in a semi-arid river basin. These processes include hydrological processes and water user responses to variations and changes in water availability. The results are relevant for climate change impact assessments and river basin management, in particular for water allocation in semi-arid environments. The Jaguaribe basin in the northeast of Brazil was used as a case study. Concepts from the literature on common-pool resources were applied to analyse the extent to which the physical characteristics of a river basin facilitate or impede sustainable management of water resources in different parts of the Jaguaribe basin. The relationship between water use and water availability in a sub-basin of the Jaguaribe basin was explored. The obtained knowledge was used to design and test a multi-agent simulation approach implemented by using remotely-sensed land use data and survey data on water user decision making. It was found that for the Jaguaribe basin a decrease in rainfall and runoff typically leads to a transition of irrigation water use not only from water-scarce periods to less water-scarce periods, but also from downstream areas to upstream areas. Strategic reservoir operation enables local water managers to offset the effect of decreasing rainfall and runoff with respect to irrigation water use at the sub-basin level, at the cost of further decreasing water availability at the basin level. It is concluded that the theory of common-pool resources and that the concept of downstreamness, introduced and quantitatively defined in this thesis, are helpful in assessing the manageability of water resources in a river basin. Further, a multi-agent simulation approach has proven instrumental in studying interactions between water users and water resources.