Reservoir levels are reported as elevation above sea level and compared against two references: full pool (the normal maximum) and conservation pool (the managed operating target).
A lake sitting feet below full pool isn't necessarily in trouble — operators draw down ahead of wet seasons for flood storage. Context against the seasonal curve matters more than the raw number.
Gauges from agencies like the USGS and the Army Corps update continuously, so a current reading plus the historical average tells you whether a lake is genuinely low or just seasonally managed.
Try it: current lake levels.