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Advances in the distribution of environmental cost of water bodies through the exergy concept in the Ebro river

Abstract:

The Physical Hydronomics (PH) methodology is a tool to properly calculate restoration cost of water masses in exergy terms, in the framework of the Second Law of Thermodynamics. This methodology makes possible to assess the quality degradation of water as well as the water consumption. An opportunity which that methodology brings up is the development of River exergy profiles which can be represented along the length of the river, for different periods and degradation statuses. Focussing on the Water Framework Directive milestones, fist novelty presented here consist on developing an hypothetical scenario corresponding to the state reached by applying the restoration Plan of Measures, therefore making possible to test their suitability by comparing that scenario with the Environmental Objectives, pursued by the Directive. Together with it, the second most relevant contribution which is presented here is the assessment of restoration cost among diverse water polluters, from physico-chemical parameters of the river according to the exergy degradation provoked individually by each of them. The case study which is developed is the Ebro basin, an Spanish very representative river which flows into the Mediterranean sea. Important differences within the average rainfall values among the diverse areas of the Ebro and changing natural average total water resources are typical from this river. Results shown that quality restoration costs found in the agriculture user resulted to be the highest, in dry years, but quite similar to the ones fund in the urban user in wet years. On the other hand, degradation provoked by the hydroelectric user, never taken into account before in the PH spectrum, resulted to be the lowest, but increases in wet years. Considering changes in flow downstream dams due to their storing and delivering effect, it ranges during hydrologic periods, but it reaches maximum values during wet years. The Plan of Measures proposed by 2015 is enough to fulfil with environmental objectives pursued by the Ebro river Environmental Authorities. Only punctual non-compliances were found during the simulated period. Reposition Cost varied among hydrological years: the more dry the year is, the higher reposition costs. In any case, the total investment cost to put into practice the measures projected in the draft version of the Ebro river management Plan seems to be enough to fulfil the already mentioned Environmental Objectives.