September was a predominantly unsettled month with low pressure systems bringing persistent and sometimes heavy rainfall, particularly to the west, including the first named storm of the winter 2017/18 season, Aileen.
Soil Moisture Deficits generally decreased during the month and soils mostly remained wetter than average for the time of year. River flows were generally in the normal range or above across the UK, with some western catchments registering more than twice the September average. However flows in the less responsive rivers in southern England were below normal and in some cases were notably low. Reservoir stocks generally increased relative to average and were substantially above average in some impoundments in northern England and Northern Ireland.
The assessment is contained in the latest monthly hydrological summary for the UK, an authoritative analysis of the country's water resources status. The monthly summaries are produced by the National Hydrological Monitoring Programme, operated by the Centre for Ecology & Hydrology in conjunction with the British Geological Survey.
Summary author Katie Muchan said, "Following the wet summer and early autumn, the short-term water resources outlook is healthy with above average reservoir stocks and SMDs across much of the UK. However, groundwater levels generally continued their seasonal recession and remained below normal or notably low across much of the Chalk in south-east England, reflecting longer-term rainfall deficiencies. The long-term outlook is very dependent on recharge over the winter half-year, which will commence from a below-normal baseline in these areas."
The monthly summary is a look back at hydrological events occurring in September 2017. Latest information on flood warnings is provided by the Environment Agency, Natural Resources Wales and Scottish Environment Protection Agency (flood warnings for Northern Ireland are not available).
The Centre for Ecology & Hydrology jointly operates the National Hydrological Monitoring Programme (for the UK) in conjunction with the British Geological Survey. NHMP scientists produce the UK Monthly Hydrological Summary which assesses rainfall, river flows, groundwater and reservoir levels. They also operate the UK’s National River Flow Archive.
The NHMP also has a remit to analyse major flood and drought events in the UK and analyse long-term trends in UK hydrological data. The UK Monthly Hydrological Summary is normally published on, or before, the tenth working day, of the following month. A Hydrological Outlook for the UK is also available, and is updated monthly. The latest Outlook can be viewed here.