Highest_navigable_water_level
Reference water levels
River navigation parameters
The reference water levels are used on inland waterways to define a range of water levels allowing the full use of the waterway for navigation.[1] Ship passage can be limited by the water levels that are too low, when the fairway might become too shallow for large ("target", "design") ships, or too high, when it might become impossible for the target ships to pass under the bridges.[1] The goal of establishing the reference water levels is to balance the safety of navigation and economic value of the waterway[2] (for example, increase of the low level shortens the navigation season but allows the use of larger ships). Reference levels are set up based on statistics obtained from the multi-decadal observations (typically 30 years).[3]