IWRA Proceedings

AbstractIntroduction Recent climate monitoring and modelling studies revealed a general trend toward drier and warmer conditions in the Mediterranean area, both for the last and forthcoming centuries. Such a climatic evolution would lead to a decrease of water resources likely affecting ecosystems, socio-economic activities and populations. In this study, we aimed to analyse recent and future climate change and its consequences on the water resources of 6 coastal Mediterranean rivers located in southern France. Objectives 1. Examine the major climatic conditions changes for the period 1965 -2004 and its consequences on the water resources in the considered watersheds. 2. Build scenarios on the evolution of the water resources in the 6 considered rivers for the end of the 21st century. Methods Firstly, we collected a comprehensive dataset of hydrometeorological data from climatic and hydrologic stations for the period 1965-2004. A digital elevation model was used to delineate the 15 watersheds according to the geographical position of the considered hydrologic stations. Climatic parameters were spatialised and averaged for each watershed. All reconstituted hydroclimatic data time-series were tested in order to detect significant trends over the study period and the consequences of the changing climatic conditions on the hydrologic variables were examined through correlation analysis and hydrological modelling. Secondly, the climatic change scenarios for the period 2070-2099 produced by the PRUDENCE project were coupled with the GR2M hydrologic model calibrated for the present conditions. This allowed us to provide a first estimation of the possible changes in the water resources that could occur in the studied rivers at the end of the 21st century. Results 1965-2004 was characterised by a temperature increase of about 1.5°C, mainly because of a strong warming during spring and summer. Precipitation did not follow significant changes, except a small decrease in winter in the northernmost watersheds. Water discharge significantly decreased in one third of the watersheds, accounting for an overall decrease of the water resources in this area of about 20%. Increasing losses by evaporation processes due to the temperature increase are likely to be responsible for this. First results of the coupling of climatic and hydrologic models revealed a decrease of the water resources between 20 and 70% for the end of the 21st century, depending on the considered rivers and both the scenarios and climatic models we used. Conclusion Although precipitation in the studied watersheds did not change markedly during 1965 -2004, our results already revealed a significant decrease in the water resources, likely related to the strong temperature increase. According to model scenarios, this temperature increase will also be accompanied by decreasing precipitations and hence still extend the decline of the water resources in the future.