Updated: Added briefing notes to support users of the data.
River-level data which is updated several times an hour is available from http://flooddata.alphagov.co.uk. The content of these files is defined in the Hydrometric data feed user manual. This is a demonstration data feed that will be replaced by an application programming interface (API) soon. Groundwater level data for England can also be found on http://flooddata.alphagov.co.uk.
The flood alerts API provides access to Environment Agency data including a list of flood alerts and warnings.
The API, river-level, and groundwater level data is published under the Open Government Licence v2 and will be available in this form until May 2014.