Fish species belonging to the Clupeidae family (such as sardine and herring). The allis shad are among the anadromous species (i.e. which swim up rivers to spawn in the middle part of the rivers). As such, their populations have paid a heavy price to river development (dams without fish pass facilities, extraction of gravel changing the spawning, etc). Their presence is therefore a good indicator of the status of a river development. Two species of allis shad are present (and exploited) in French waters: the allis shad (Alosa Alosa) and twaite shad (Alosa fallax).
Temporary drying out of a watercourse or of a river section.
As part of the monitoring carried out by the National Observatory of Low Water, a watercourse is considered in a dry period when the water is totally evaporated or infiltrated on more than 50% of the reporting station.
Grass strip bordering a plot, mainly located along rivers, which acts as a buffer zone by intercepting and filtering runoff water.
System designed to remove pollution at source. It comprises a kind of wraparound intake roughly connected to a polluted air exhaust system (blowing - suction).