a Multi-Site and Multi-Variable Calibration of the Swat Model to Assess the Impacts of Climate and Landscape Changes Over a Mediterranean Vineyard Watershed.

The impacts of landscape and climate change on watershed dynamics have been largely highlighted in recent decades. From a watershed management perspective, the impacts on the water balance components contribute to affect various ecosystem services. The aim of this study is to assessing the combined effects of landscape and climate changes in a region considered as a "hot spot" of climate change and characterized by a high water resources variability: the Mediterranean basin. Before that, a thorough understanding of the spatial functioning of the watershed is necessary. Given the purpose, the SWAT model was used over the 80 km² Peyne watershed located in the south of France were vineyards are the dominant crop. The Olivettes dam, located upstream allows water supply for irrigation during summer. To meet the study purpose and after an understanding of the watershed functioning based on field expertise and measurements, a multi-site and multi-variable approach was implemented over the period 2007-2017 for evaluating and calibrating the model. The discharge at three stations and the spatialized actual evapotranspiration were used for the calibration, while the evaluation was also carried out on the soil moisture and over the aquifer-river contribution period. Based on this simulation, two climate change scenarios and three landscape change scenarios were implemented on the model over the period 2030-2050 and compared through eco-hydrological indicators. The climate scenarios reflects two possible IPCC climates (RCP 4.8 and 8.5) whereas the landscape scenarios were designed to apprehend possible evolutions of landscape use: urbanization and rural exodus in the first, PDO winegrowing in the second one, and development of local farming in the last one. Based on the actual case, the implementation of climate and landscape scenarios highlight the strong impacts of their combined effects on surface runoff, evapotranspiration and underground water resources. This study highlighted the need for a detailed understanding of the watershed functioning, before assessing the impacts of climate and landscape changes on hydrology and ecosystem services. This first approach could permit the implementation of integrated resource and landscape management tools, that might latter be extended to other Mediterranean watersheds.