Subtask Description:
Science Policy Consultations and analysis without using software based DST or DSS tool.

Action points of the implementation:

Thau Lagoon, France

Policy Issue:
Managing the microbiological contamination

Human Activities:
Urban activities, agriculture, shellfish farming, recreational activities.

General Information:
The natural marine heritage of the area is linked to high productivity and biological diversity which involve water management issues, as the variety of the lagoon economic exploitation often creates antagonism and conflicts. Urban and land-use pressures are high and increasing while agriculture is in decline and the phenomenon of agri-urban areas is spreading, causing increasing microbiological contamination effects that have impact to the shellfish farming activity. The main stakeholder concerns are connected to the management of water resources in relation to the population growth and the viability of the traditional activities (shellfish farming and recreational activities).

Example of Implementation:
During the stakeholder forum, the Thau Lagoon team presented the main changes which could be simulated with the model regarding population and land-use evolutions (exploratory scenarios) and regarding management options (strategic exploratory scenarios). The corresponding assumptions had been fixed during the last meeting before the forum. Five specific scenarios were then presented: one exploratory scenario (development toward the West and the consecutive impacts in terms of lagoon sanitary status) and four strategic exploratory scenarios (scheduled improvement of the Wastewater Treatment Plant network, urban street cleaning and focused improvement of pumping stations, combination of the 2 last options).
The deliberation regarding scenarios concerned first the definition of credible evolution of the population and the land use; in particular the distribution of demographic changes over the municipalities of the territory has been further examined, in order to check which municipality is likely to gain (loose) which kind of population (inhabitants, tourists, etc.). In addition to the intrinsic characteristics of one municipality, population changes should depend on external factors of changes, in particular those due to the overall effects that the regional capital Montpellier may have on the land use and spatial planning in the Thau territory.
The stakeholders insisted also that the strategic scenarios should consider additional options. First, it was recommended to take into account that there exist two technologies for urban cleaning: street washing with high-pressure water jets (implemented for the output step meeting) but also waste removal with motorized vacuum cleaners. Second, it was recommended to consider complementary management measures, based on the mitigation of pollution impacts rather than on the avoidance of pollution, which presents an increasing marginal cost: this recommendation concerns in particular the ability to develop safeguard mechanisms for the shellfish farms products during commercial bans of the oysters from the lagoon. At last, it was suggested to present a series of scenarios which consider in a successive way: first, the implementation of the most efficient technical options one by one, second, the implementation of the combination of all these efficient technical options, and third, the implementation of the combination of technical options plus the complementary mitigation measure. This experimental procedure is intended to be complemented with a cost-efficiency analysis of each management measure or combination of measures.

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Figure 5: Modelling approach: coupling the economic and pollution models.

Contact: Remi Mongruel,