Shallow lakes, especially the ones in highly populated areas, are vulnerable for eutrophication. The overload of nutrients to a lake can originate from rivers, runoff of nearby agricultural areas, from air pollution and from sewer systems. These diverse inputs, and the historic load of nutrients in the sediments of the lake that can easily resuspend, make it hard to reduce the nutrient concentrations again. These lakes have in common that they are relatively shallow and not too large and located in populated areas. Eutrophication can lead to e.g. cyanobacterial blooms and generally reduces the biodiversity. Regardless of their eutrophic status, a portion of these lakes is used as drinking water source. Other services typically offered by these lakes are shipping, fishing, irrigation. Because of the potential of toxins originated from cyanobacteria, drinking and irrigation water from these lakes must be checked properly before use. Because of the high chlorophyll concentration, the colour of these lakes is green.
Within GLaSS, the following shallow eutrophic lakes have been selected: