water level

water level (plural water levels)

1. The level of a body of water, especially when measured above a datum line.
   • 1949 September and October, “The "Nord Express"”, in Railway Magazine, page 337:

     There is one feature of interest: at Rendsburg after a not too-easily graded ascent from the plain by means of an embankment, the train crosses the Kiel Canal by a double-track steel bridge 138 ft. above water-level, with, on a clear day, magnificent views over the countryside, and then loops round right, descending to canal level and, parallel with the canal, crossing under the bridge over which it passed a few minutes previously.

2. The level of the water table below ground.
3. The waterline of a ship.
4. An instrument to show the level by means of the surface of water in a trough, or in upright tubes connected by a pipe.
5. (attributive) Of a route that follows a riverbank or shoreline.
   • 1960 October, P. Ransome-Wallis, “Modern motive power of the German Federal Railway: Part Two”, in Trains Illustrated, page 613:

     The water-level route, the whistle and the loud staccato exhaust of this great engine recalled most vividly memories of the New York Central Hudsons highballing along the Hudson River between Harmon and Albany!