Discharge curve
A discharge curve (also: key curve ) defines the relationship between discharge and water level . It is used in hydrological data processing .
The runoff is the central factor in surface hydrology. It indicates how much water (in m³ / s) drains off at one point in the body of water. However, it is usually far too time-consuming to measure it directly. Instead, the water level is measured. This takes place at defined points in the water, at gauges . The water level in cm can be read off the gauge or continuously recorded with a measuring device. This leads to a time series of the water level.
To determine the outflow (Q) from the water level (W), you have to regularly discharge measurement to make. For this purpose, different methods are used to determine how high the discharge is at a level. Together with the current water level, this results in the coordinate pair (w, q).
As soon as you have determined several pairs of coordinates, which can take months or years depending on the size of the body of water, you can use various approaches to lay a compensation curve through the point cloud of the pairs of coordinates, the discharge curve.
Running water in natural waters changes the shape of the channel through which it flows. Floods (e.g. floods) can greatly change its profile. Since the body of water can then be deeper or wider, the water level will be different with the same discharge. But this does not apply to all water levels. For example, a slope may have been washed away that is only under water when the water level is high. Then discharge measurements with a small W remain valid, while those with a capital W have to be recreated. After every flood it is therefore necessary to measure again. With hydrological expertise, a new discharge curve is then created from the current point cloud.
Over the years, you get a family of discharge curves, each of which is valid over time.
See also
- Hydrograph (Q / t diagram)