ASSESSMENT OF CLIMATE CHANGE IMPACTS ON THE HYDROLOGIC RISK BY QUANTITATIVE ALTERATION IN THE CATALAN INTERNAL BASINS

The Catalan Internal Basins has a peculiarity in respect of other Mediterranean basins; its total urban demand exceeds the agriculture extractions, so the returns of the wastewater treatment plants have special relevance in the total water balance. Usually, the main quantitative alterations of the hydraulic regime of the rivers are the regulation of reservoirs and the demands. The main objective of this study is to include and evaluate the quantitative pressure of urban discharges on the analysed system, in order to estimate the altered regime risk of water bodies and analyse their evolution in future scenarios of Climate Change. The tool used to achieve these goals is the Rapid Response Environmental Status (R2EA) model. Firstly, from results, the percentage of the volume dumped over the total inflows of each of the bodies is calculated and the simulated period is evaluated. Secondly, the percentage of water extraction is calculated from discharges located upstream of the intake for each of the urban demands included in the model. These indices are calculated for three Climate Change scenarios. The calculated indices analysed show that the water regime alteration by discharges mainly affects temporal water bodies. In addition, a significant risk increase during summer months is identified. Finally, we propose that the water managers should use this approach in order to characterize the vulnerability level by quantitative alteration of aquatic ecosystems.