Level - Basin Water Level (m). The first water level must also be the lowest level in the reservoir/basin. Values in this column are interpreted as ABSOLUTE levels if the first stage equals the Basin Invert Datum Level. Otherwise, the first stage MUST equal zero and values are interpreted as stages RELATIVE to the Basin Invert Datum Level.
Storage - Storage (in 1000 cubic metres) corresponding to adjacent left column. Storages must be non-negative. The first storage MUST be zero.