These results are inputted into the ES-production models, one for each ES analyzed: intra-basin domestic supply, water transfer to Barcelona, hydropower, irrigation, historical canals, wetlands and river ecosystem maintenance, safeguarding the salt edge away, elver and trout fishing, aesthetics of the waterscape in Girona city, and familiar and freestyle kayaking. The outcomes shed light on several aspects of interest for water management. The model allows visualizing the level of provision of specific ES along the river. The variation of the ES provision along the year comparing dry, humid and normal years or different water management scenarios can also be drawn. In addition, tradeoffs and synergies can be identified comparing the production of different ES under certain conditions.
In relation to potential conflicts in the Lower Ter, our model offers several insights. First, different ES compete for water flows, interfering in spatial coexistence. Hence ES localization pinpoints competition hotspots that could be managed. A good example is Girona city, where hydropower production coexists with tourism and local recreation. Second, modeling ES spots critical moments of competition among ES over the hydrologic year and for rainy, dry and normal years. In spring and summer, demands for irrigation enhance the water availability for kayaking and the preservation of wetlands. Finally changing the priorities among water uses shows which use conditions the provision of the others. In particular, the water transfer to Barcelona drags the bulk of water flows, impacting the production of the rest, especially during dry years. Hydropower production does not particularly threat the river ecosystem when the transfer is low.
The model here presented is a useful tool to understand the complexity of managing rivers that frequently suffer natural droughts and intense human pressures, as the case of the Ter River, in the Mediterranean basin. Multiple stakeholders are involved to incorporate their requirements in terms of water flows and to design management scenarios preferable for them. This paper shows sound tradeoffs in specific stretches and at specific moments, giving an idea of where and when a conflict can break up under the controversial BAU scenario. COM and ECO scenarios appear as management alternatives with the aim at sharing the benefits that a well-preserved river provides. Making these results explicit improves transparency hence facilitates informed negotiation for a better river management.
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