What the figures show
The figures correspond to all available measurements from the first measurement to the date of the most recent measurement. For satellite measurements, these dates depend on the satellite(s) used, and how long it takes to return above the same point on Earth.
Water heights
The level of lakes and rivers is related to their water supply and its variations; it reflects the amount of water available, and also the flow for rivers. Variations in this height have important impacts on agriculture, fauna and flora, certain energy sources (hydroelectricity, cooling of power plants), the availability of drinking water, and can cause significant damage in case of floods. Their monitoring over several years makes it possible to observe seasonal cycles and more or less extreme variations from one year to the next.