Hydrodynamic Circulation and Hydraulic Exchange in the Pappas Lagoon, Western Greece

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Monday 29 june 2015

18:03 - 18:06h at Europe 1 & 2 (level 0)

Themes: (ST) Ecohydraulics and ecohydrology, (T) Hydro-environment, Poster pitches

Parallel session: Poster pitch: 3G. Environment - Ecohydraulic

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The Pappas coastal lagoon lies in Western Greece, embedded in the northwestern coast of the Peloponnese, adjacent to the Gulf of Patras. Protected by the Ramsar Convention and included in the Natura 2000 network, the lagoon is shallow -mean depth c. 1.8 m- has maximum length c. 5 km and average width 1 km. It is connected to the Gulf of Patras with three stable tidal inlets the length and width of which lie within 160-260 m and 25-50 m respectively. The lagoon is subject to extensive fish exploitation and aquaculture. It is naturally eutrophic, but its condition has exacerbated due to human activities in its catchment area. During the last 20 years it has been subject to frequent dystrophic crises followed by mass mortality of fish and benthic fauna, with considerable cost to the local economy. Hydrodynamic forcing is provided by the semi-diurnal tides and the wind action. Constraints on the circulation are imposed by the hydrology (freshwater input) and meteorology (surface heat transfer). To contribute to the understanding of the hydrodynamic circulation of the lagoon and, ultimately, to its management, two- and three-dimensional (2d, 3d) numerical simulations have been undertaken using the MIKE21 and MIKE3 codes. To make the 3d simulations effective, the Papas Lagoon domain is considered in isolation from the Gulf of Patras and time series of the sea surface elevation are provided as boundary conditions at the tidal inlets. These time series are produced by 2d simulations of the entire Gulf of Patras hydrodynamic circulation, including also part of the adjacent seas. To appraise this practice, 2d simulations of the entire Gulf of Patras-Pappas Lagoon system have been compared with 2d simulations of the Pappas Lagoon alone, using boundary conditions at the inlets. The comparison is satisfactory. Results of the 3d simulations compare favorably with the available field measurements and observations. In specific, hydraulic exchange between the Gulf and the Lagoon has been found to of limited importance and the circulation is dominated by the wind and the constraints imposed by the stratification.