Fighting salinization in a coastal lagoon

26 Jun 2012  

The National Park of Circeo, situated about 80 kilometres south of Rome, is one of Italy’s most important wetland ecosystems, characterised by coastal lagoons, dunes and forested areas and an exceptionally high biodiversity. The complex dynamics of this ecosystem, however, make its management a challenging task. DHI helped the National Park Authority to choose the best possible option to fight the increasing salinization of parts of the system.

To limit the increasing eutrophication of the coastal lakes Fogliano and Monaci, Circeo’s National Park Authority, has diverted the nutrient-rich rivers discharging into the lakes. This action, together with other interventions, resulted in a progressive and significant improvement of the water quality of the two coastal lakes. However, the reduced input of fresh water also resulted in an increased salinization. In the summer, the two lakes can become even more saline than the sea itself.

DHI Italia, together with its Italian partner Hydrodata, has been commissioned by the National Park Authority to evaluate the possible actions to improve the environmental situation of the two coastal lakes.

In the first phase, we performed an extensive monitoring of the groundwater, rivers and lakes, together with a detailed mapping the main indicators of the lakes’ quality status. In the second phase, an integrated modeling platform was set up to simulate the water balance including fresh groundwater supply as well as various physical, chemical and biological parameters (water levels, temperature, salinity, dissolved oxygen, phytoplankton, zooplankton, inorganic nitrogen and phosphorus, benthic vegetation).

The model has permitted to study in detail the effects of four possible scenarios of intervention for the two lakes, each one aiming at achieving an optimal compromise between the positive effects induced by the re-introduction of fresh water in the lakes, thus limiting the salinity of the lagoons, and the negative effects induced by the re-introduction of higher nutrient load associated to fresh water. Thereby, we supplied Circeo National Park Authority to choose the optimal plan for salinization management in this precious ecosystem.

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