- Station name: Marlow Lock (downstream)
- Station ID: 7396
- River name: River Thames
- Typical range: 2.02m to 3.23m
- Highest level on record: 4.73m on 10 February 2014
- Site datum: 22.77mAOD (what does this mean?)
How are river levels measured?
The Environment agency uses a network of monitoring stations across the country. Each one has its own datum - a height in metres fixed relative to mean sea level. This height is expressed as metres above ordnance datum (mAOD). The river levels we provide for each monitoring station are all relative to its site datum.
If we didn't do this, we'd show some very high measurements, which could cause confusion. By using a local site datum, the river levels are easier to understand, especially by users familiar with the data from a particular monitoring station.
A river's height above ordnance datum can be seen by adding the site datum to the river level.
How often are river levels measured?
We use measuring stations like this one to collect water level data, usually once or twice a day. We collect data more frequently when there's a greater risk of flooding. That's why the graph might show a short time lag since the last measurement.
How might river levels affect flood risk?
This is the usual range of river levels at this station, based on historical data.
This means that flooding is possible because river levels at this station are currently higher than usual.
Many factors can influence the possibility of flooding - river levels are only one indicator. Always check if there's a flood warning in place at a particular location.
This means that river levels at this station are currently lower than usual.
Drought or water management measures may be in place. Please check for the latest information on water resources and restrictions in your area.