Isotope hydrology to insight the behaviour of Mediterranean Temporary Ponds: Implications on sustainable ecohydrological management strategies

Mediterranean temporary ponds are very shallow ponds, isolated from permanent water bodies, which undergo a periodic cycle of flooding and drought, and have a characteristic flora and fauna adapted to this alternation. They are identified as one of the worldwide biodiversity hotspots and constitutes therefore a priority habitats according to the Natura 2000 network of the European Union. Despite this protective conservation status, this habitat has suffered continuous degradation and loss, disappearing at a fast rate due anthropogenic impacts and climate pressures. In most cases, temporary wetland disappearance is unintentional and related to a lack of understanding of its hydrological functioning within the watershed.

In this study, we use observations of hydraulic heads, geochemical and isotopic composition of pond and groundwater from the Musella pilote study site (Corsica, Western Mediterranean) to assess the applicability of the isotope hydrology tools for understanding the hydrological behaviour of temporary wetlands and refine their optimal environmental conditions.

By combining together physical and isotope measurements, we demonstrated (i) the main role played by groundwater and subsurface water in the flooding phase of the temporary pond; (ii) the involvement of different water reservoirs in varying proportions over time to maintain the pond filled with water: precipitation, subsurface and groundwater by using d-excess; (iii) the main role played by evaporation in the starting of the drying up phase; and (iv) the connection existing between a geographically isolated wetland and the regional groundwater body.

Results bring the urgent need to consider both surface and groundwater fluxes in wetland’s specific protection statutes. To this aim, we encourage the use of the water stable isotopes to insight the hydrological behaviour of the wetlands in order to have additional cost-effective arbitration elements able to help ensuring their sustainability considering the future consequences of climate change in the Mediterranean region.