| Source | Active Monitoring Stations | Active Monitoring Stations with Current Data | Active Monitoring Stations with Stale Data | Data Reliability | Latency | Inactive Monitoring Stations |
|---|---|---|---|---|---|---|
| Environment Agency (England) | 3,455 | 3,383 | 72 | 97.9% | 20 minutes | 389 |
| Scottish Environment Protection Agency | 351 | 345 | 6 | 98.3% | 35 minutes | 72 |
| Natural Resources Wales | 230 | 228 | 2 | 99.1% | 5 minutes | 8 |
| Great Britain Total | 4,036 | 3,956 | 80 | 98% | N/A | 469 |
Data is defined as stale if the most recent update from the data source is more than 24 hours old. Most active stations are normally updated more quickly than that, but there are some monitoring stations which are only updated two or three times a day and where a single missed reading can therefore create a significant time gap from the most recent reading. This is a feature, not a bug - the reporting interval for some stations is deliberately increased when there is a low risk of flooding in order to conserve battery life on the gauge. So just because the latest river level is a few hours old doesn't necessarily mean that there's a problem. But if a monitoring station has gone more than a day without any updates at all then there probably is a problem - every active station should normally get at leaast one update every day.
Data reliability is the percentage of active monitoring stations with current (non-stale) data. This is usually somewhere in the 90s (often 100 for the smaller agencies); anything below around 85% indicates a potential problem somewhere.
Latency is the difference between the timestamp of the most recent data obtained from our sources and the time that the data was last pulled from those sources. Under normal circumstances this should not be more than an hour, although under times of heavy demand it can be longer.
Inactive stations are those which no longer appear in the lists of monitoring stations supplied by the data source. They are maintained here for archive purposes only so that the long term graphs and data downloads remain available. They are not included in the data reliability and latency stats.