An elevation needs a reference surface, called a datum. Without it, a number such as “6,223 feet” is incomplete. A lake gauge may also report gage height relative to a local reference rather than a geodetic elevation.
NAVD 88, NGVD 29, local project datums, and station gage datums are not automatically interchangeable. The offset can vary by location and method. Subtracting two values that use different datums can produce a convincing but wrong change.
LakeRiverNow keeps the datum attached to each applicable parameter. We do not compare elevations across datums unless a documented, tested normalization exists and the transformed value is clearly labeled. When the datum is uncertain, the interface sends users to the official station metadata instead of guessing.
For reservoir operations, also distinguish observed pool elevation from conservation targets, rule curves, and forecasts. Those are different products with different issue and valid times.