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Hydrologic modelling of coastal wetlands under the current and future conditions: The case of the Gialova lagoon, Greece

Stockholm University, as a co-lead partner for the Greek MAL2 case in COASTAL, has developed a modelling approach based on coupled water and salt balance equations to estimate currently unknown water exchange fluxes through the Gialova coastal lagoon, Greece.

Increasing pressures on this wetland, similar to other Mediterranean coastal wetlands, due to competing demands for freshwater resources and climatic changes, may result in higher wetland salinity and thus loss of its ecological functions. On the other hand, multiple channels, diffuse surface water exchanges, and diverse groundwater pathways complicate the quantification of different water balance components for this wetland. The developed approach facilitates quantification of both saline and freshwater exchange fluxes, using measured precipitation, water depth and salinity, and estimated evaporation rates.

As a result of such quantification, for the current condition about 40% and 60% of the freshwater inputs to the wetland are from precipitation and lateral freshwater flows, respectively. Approximately 70% of the outputs from the wetland is due to evaporation, with the remaining 30% being water flow from the lagoon to the sea. Under projected drier and warmer conditions, salinity in the lagoon is expected to increase, unless land-based freshwater inputs are enhanced by restoring hydrologic connectivity between the lagoon and the surrounding freshwater bodies.

This restoration strategy would be fundamental to stabilizing the current wide seasonal fluctuations in salinity and maintain ecosystem functionality, but also could be challenging to implement due to expected reductions in water availability in the freshwater bodies supporting the lagoon.

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