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Abstract

In recent decades, the Mar Menor coastal lagoon has experienced a significant deterioration in the quality of its waters. The first source is the intensive agriculture in its watershed, with poor or non-application of soil conservation measures and excessive nitrogenous fertilizers. The second source are the abandoned open-pit mining zones.The aim of this study is, on one hand, to estimate the current nitrogen and sediment inputs to the lagoon and, in the other hand, to evaluate the impact of different control measures in order to select and prioritize the most effective ones. In this way, it will be possible to improve the ecological status of the lagoon. The distributed eco-hydrological model TETIS was used for these two objectives, activating the sediment, nitrogen and crop modules. The model was implemented with a spatial discretization was 5 m at daily time step.The evaluated measures are: reforestation of the mineral extraction zone with coniferous, use of support practices like hedgerows and contouring, adjustment of the applied fertilizer, zones where irrigated intensive crops are replaced by olive trees, shrubs and terracing, and finally, sediment retention ponds.Reforestation and terracing are crucial to reduce the sediment yield and the high erosion rates. Support practices and crop replacements shows a significant reduction in the case of the nitrogen associated to the runoff (water and sediments) which discharges directly into the lagoon. Finally, fertilizer adjustment is the more effective measure to reduce the nitrogen input to runoff and percolation.