Across middle Europe, the Alps cover four sub-climatic regions and play a major role in accumulating and supplying water to the continent. Famously called as the “water towers of Europe”, they host most of the headwaters of the rivers Danube, Rhine, Po and Rhone. Located in the Mediterranean basin, the southwestern Alps are known to be particularly vulnerable to flood, landslide events and summer droughts. Precipitation is expected to decrease by 20-30 % by 2100 threatening water resources. However, large uncertainties remain on future precipitation regimes at a local scale. Climate models spatial resolution do not integrate regional climate heterogeneity and models are calibrated on a short temporal “observations” window (the last century mainly). The Hydro-Alps project aims at providing new perspectives on the history of past local hydrological changes that needs to be considered in order to improve climate projections and strategies to water resources issues. Hydrological changes and chemical weathering will be studied in the southwestern Alps for the pre- industrial period and over several millennia. Valuable information can be provided by microalgae called diatoms which are accumulating through time in the sediments of alpine lakes. They build a cell wall in silica (SiO2) which records lake water chemistry during the shell formation. The project will rely on measurements of oxygen and silicon isotopes from diatoms extracted from lacustrine sediments used as tracers of local hydrological conditions and chemical weathering of the crystalline bedrock. This innovative approach will provide new information on mountainous past climate variability by combining isotopic tracers on same sample and new perspective about long-term changes in the Mediterranean climate. Altogether, the Hydro-Alps project will improve our understanding of climate changes at local scale and will help stakeholders to adapt water resource strategies.
Major accomplishments expected include the coring and water sampling of alpine lakes in the Southwestern Alps, measurements of oxygen and silicon isotopes in diatoms since the last glaciation, integration of results in open access databases, several publications and communication in national and international conferences.
