SHALLOW LAKES RESEARCH Remote sensing application for the study of rapid flushing to remediate eutrophication in shallow lagoons (Albufera of Valencia) Xavier So `ria-Perpinya ` . Maria R. Miracle . Juan Soria . Jesu ´ s Delegido . Eduardo Vicente Received: 28 August 2017 / Revised: 31 July 2018 / Accepted: 17 August 2018 Ó Springer Nature Switzerland AG 2018 Abstract Albufera of Valencia shallow lagoon expe- riences water clarification about once a year. This study aimed to observe the timing of water clarity events and to detect the associated flow during these periods. Spatial variation in chlorophyll a along the Albufera was observed using remote sensing images. Due to the lagoon’s spatial complexity and the varying water qualities flowing in from more than 60 tributaries, remote sensing was the only approach that could obtain images simultaneously covering the entire lagoon. The data were used to explore the evolution, duration and intensity of the clear-water phase, and the lagoon’s subsequent re-eutrophication. The duration and inten- sity of the clear-water phase varied across the lagoon, but complete water quality renovation occurred in 1 week. Our analysis demonstrates that rapid flushing could remediate the lagoon eutrophication. Keywords Eutrophication  Residence time  Management policy  Remote sensing  Landsat Introduction Lake retention time (also called residence time or flushing time) is a well-established factor that influ- ences lake ecology (Kalff, 2002). Retention time controls in-lake phosphorus concentrations, which affects the amount of phytoplankton (Elliott et al., 2009). Water and nutrient inputs are two key elements in the Albufera current hydrological cycle and are likely drivers of significant changes in the lagoon, such as clear-water phases (CWPs). The hydrology of the Albufera lagoon is regulated by the local water council according with the needs of the surrounding agricultural lands, primarily rice paddies. The lagoon outflow to the Mediterranean Sea is regulated by sluice gates that are located on the outlet canals. From November to the beginning of January, the sluice gates are closed, and the lagoon water level is about 20 cm above the annual average. The pumps that drain the fields during cultivation are turned off, and the fields below lake level are flooded to encourage the decomposition of organic remains. During January and February, there is a higher water renewal rate at the lake. Flooded rice fields are pumped empty, water flows out to the sea through the Albufera open sluice gates, and the lagoon water level Guest editors: S. Nandini, S.S.S. Sarma, Erik Jeppesen & Linda May / Shallow Lakes Research: Advances and Perspectives X. So ` ria-Perpinya `(&)  M. R. Miracle  J. Soria  E. Vicente Cavanilles Institute of Biodiversity and Evolutionary Biology (ICBiBE), University of Vale `ncia, Campus Paterna, 46980 Paterna, Vale `ncia, Spain e-mail: javier.soria-perpina@uv.es J. Delegido Image Processing Laboratory (IPL), University of Valencia, Scientific Campus, 46980 Paterna, Vale `ncia, Spain 123 Hydrobiologia https://doi.org/10.1007/s10750-018-3741-6