The water level ( WS ) is the height of a natural or artificial water level in relation to a defined mark.
The following is used as the reference height for the water level:
- colloquially the height above sea level
- the river bed (as water depth )
- an arbitrarily defined level zero for the sea and open waters , which is usually set well below the usual water levels in order to avoid negative values. This zero point is connected to the reference height of the respective national survey by leveling
- in hydraulic engineering to the upper edge of a certain discharge barrier (water level at overflow point, upper edge of the embankment )
- the surface of the ground for groundwater . As the first measurement step, the distance between the groundwater level and the corridor edge / top of the well is determined (see also groundwater measuring point )
- a nautical chart zero for shipping
- an arbitrarily defined fixed point to which measurements are taken relatively (e.g. a mill pile )
Designation of special water levels
Decision of the Reich German state offices for hydrology on the designation of the water level and discharge figures.
The board members of the Reich German State Offices for Hydrology, which met in Munich from September 17 to 19, 1925, agreed on the following abbreviations, which are still used today:
NW, MW, HW
- lowest / middle / highest water level of the period under consideration; NW if necessary to be separated into general and ice-free
NQ, MQ, HQ
- lowest / medium / highest flow rate of the period under review
- lowest ever known low water level, possibly to be separated into general and ice-free
- smallest known discharge
- mean lowest / highest water level of the observed period
- mean lowest / highest flow rate of the observed period
- highest known water level: highest flood
- highest ever known discharge
Limit and mean values of the water levels ( W in cm) and runoff quantities ( Q in m³ / sec). Without an addition, the designations refer to the year.
MNW of the year is obtained by determining the lowest water level of each individual year of the annual series under consideration and taking the mean from these values, as is MNQ by finding the smallest discharge volume of each individual year and calculating the mean from these values. In a corresponding way, MNW and MNO are to be understood for one month and in countries that have a fixed division of the year into a winter and summer half-year, MNW and MNO for winter or summer as well. How winter and summer are delimited has to be said. For the values MHW and MHQ, the upper limit values take the place of the lower limit values.
The letters belonging to one of the abbreviations must never be separated from one another. Any time information must be added in the following way, unless it is evident from the table arrangement:
Jan. MW 1901/20
Wi. MNW 1901/20
So. MHQ 1901/20
While the abbreviation of the month names and half-years is indicated by a point, the abbreviations are written without a point.
- High tide - medium tide - low tide
- List of national and international hydrographic and flood services (with links to water level values worldwide)
- Level (water level)
- Zentralblatt der Bauverwaltung: 1925 Volume 43, page 551