Abstract
The Vaccarès Lagoon System, located in the central part of the Rhône Delta (France), is a complex shallow coastal lagoon, exposed to a typical Mediterranean climate and a specific hydrological regime affected by man-controlled exchanges with the sea and agricultural drainage channels. In this article, we report the results obtained by a series of monitoring programs, with different spatial and temporal resolutions. Long-term datasets from 1999 to 2019 with data collected on a monthly basis and a high spatial resolution highlighted the significant spatial heterogeneity in salinity regimes, and helped to determine the long-term evolution of the total mass of dissolved salt. High-frequency surveys allowed to characterize the water levels and salinity dynamics seasonal response to (i) the exchanges with the Mediterranean Sea, (ii) the exchanges with agricultural drainage channels, and (iii) the rain and evaporation. In addition, wind effects on salinity variations are also explored. This work shows how different spatial and temporal monitoring strategies provide complementary information on the dynamic of such a complex system. Results will be useful and provide insight for the management of similar lagoon systems, accommodating for both human activities and ecological stakes in the context of global change.
Highlights
Coastal lagoons are generally defined as shallow water bodies, separated from the sea by a barrier, and connected to the sea by one or more restricted inlets [1,2]
They occupy around 13% of the coastline worldwide and about 5% of the European coast, where they are prevalent around the Mediterranean Sea [3]
Due to variations in rainfall and evaporation from year to year, typical of the Mediterranean climate, to the shallow depths of the Vaccarès Lagoon System, and to the complexity of its hydro-saline functioning, some management objectives may not be met in certain years, creating regular tensions around water management in this area, which is still subject to debate
Summary
Coastal lagoons are generally defined as shallow water bodies, separated from the sea by a barrier, and connected to the sea by one or more restricted inlets (channels, hydraulic structure) [1,2]. Coastal lagoons are complex systems that can exhibit strong temporal and spatial variations in water levels, flows, and salinities. These variations are the result of the interaction between freshwater and seawater inflows, rain, evaporation, and wind-driven forces, which vary over a wide range of time-scales. Using the example of a shallow and choked Mediterranean coastal lagoon, namely the Vaccarès Lagoon System, this article illustrates how combining different types of monitoring programs, with diverse spatial and temporal resolutions, allows the study of hydro-saline variations and provides a first analysis on the influence of the various anthropogenic and climatic stressors. Results are exploited to derive recommendations for the sustainable management of this type of environment on different time scales
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