Fifty years of eutrophication in the Albufera lake (Valencia, Spain): causes, evolution and remediation strategies

Abstract

[EN] The water quality deteriorated in the middle of the 1970s in the Albufera lake, a shallow Mediterranean coastal lagoon in the east coast of Spain. In few years, the water changed from an oligotrophic status to hypereutrophic as the lagoon received sewage and agrochemicals, lacking adequate sanitation facilities. For more than 40 years, the lake was used as a wastewater treatment plant given the urban development in the surrounding area. It was not until the early 1990s, 20 years after the hypereutrophic state was reached, when the first sanitation facility protecting the lake was implemented: a perimeter intercepting sewer carrying out the sewage to a waste water treatment plant. This paper describes the different engineering solutions and tools implemented to improve the water quality in the Albufera lagoon. We describe the measures and their effects on the water quality as well as their limits. Those are sanitation solutions as sewers, wastewaters treatment plants, stormwater detention tanks, and nature based solutions as constructed wetlands that have been used in these years. In addition, the role of agricultural activity in the water balance (quantity and quality), the importance of sediments management and the use of water quality models in environmental engineering have been assessed. Evidences of the improvement of environmental quality are the decrease of mean clorophyll a concentration from 800 mu g Chl a l(-1) in 1980s to less than 100 mu g Chl a l(-1) currently observed, the increase of water transparency and the recovery of macrophytes within the lake or the presence of winterbirds which disappeared years ago.