Réservoir de Haute-Vilaine — niveau d’eau

Reading the chart. Hub’Eau limnimetric gauges report hauteur d’eau — water level in metres above the station’s own datum. The absolute number matters less than the trend: a falling level means shrinking launch depth and exposed shoals, a rising one means floating debris and lost beach.

Water levels respond to dam releases (EDF reservoirs in the Alps and Massif Central can move metres overnight), irrigation abstraction, and recent rainfall. For launch decisions, combine the trend here with the wind forecast — falling water plus strong wind makes steep, tired slips and exposed margins.