Background and Data Sources

The National Hydrological Monitoring Programme (NHMP) was started in 1988 and is undertaken jointly by the Centre for Ecology & Hydrology and the British Geological Survey. The NHMP aims to provide an authoritative voice on hydrological conditions throughout the UK, to place them in a historical context and, over time, identify and interpret any emerging hydrological trends. Such information is essential for improved water management strategies and its dissemination helps to increase public understanding of hydrological and water resources issues. 

This is accomplished through regular monthly and annual bulletins, occasional reports on floods and droughts, and engagement with the media. Hydrological analysis and interpretation within the programme is based on the data holdings of the National River Flow Archive (NRFA; maintained by CEH) and National Groundwater Level Archive (NGLA; maintained by BGS), including rainfall, river flows, borehole levels, and reservoir stocks.

The NHMP is run with the cooperation of the Met Office, and the principal Measuring Authorities of the Environment Agency (England), Natural Resources Wales, the Scottish Environmental Protection Agency, and the Rivers Agency (Northern Ireland).

Data sources

The NHMP depends on the active cooperation of many data suppliers. This cooperation is gratefully acknowledged.

Rainfall 

Rainfall data are provided by the Met Office.  To allow better spatial differentiation the rainfall data for Britain are presented for the regional divisions of the precursor organisations of the EA, NRW and SEPA.  The areal rainfall figures have been produced by the Met Office National Climate Information Centre (NCIC), and are based on 5km resolution gridded data from rain-gauges.  In addition to Met Office rain-gauges, the majority of the full rain-gauge network across the UK comprises rain-gauges operated by the EA, NRW, SEPA and Northern Ireland Water.  The Met Office NCIC monthly rainfall series extend back to 1910 and form the official source of UK areal rainfall statistics which have been adopted by the NHMP. The gridding technique used is described in Perry MC and Hollis DM (2005)*, available at http://www.metoffice.gov.uk/climate/uk/about/methods

* Reference: Perry, M, & Hollis, D (2005) The generation of monthly gridded datasets for a range of climatic variables over the UK. International Journal of Climatology, 25, 1041-1054. doi: 10.1002/joc.1161

Long-term averages are based on the period 1971-2000 and are derived from the monthly areal series.

The regional figures for the current month in the hydrological summaries are based on a limited rain-gauge network so these (and the associated return periods) should be regarded as a guide only.

The monthly rainfall figures are provided by the Met Office NCIC and are Crown Copyright and may not be passed on to, or published by, any unauthorised person or organisation.

Soil Moisture

The Hydrological Summary and other NHMP outputs may also refer to and/or map soil moisture data for the UK.  These data are provided by the Meteorological Office Rainfall and Evaporation Calculation System (MORECS).  MORECS provides estimates of monthly soil moisture deficit in the form of averages over 40 x 40 km grid squares over Great Britain and Northern Ireland.  The monthly time series of data extends back to 1961.

River Flow and Groundwater Levels

River flow and groundwater level data are provided by the regional divisions of the EA, NRW, SEPA, the RA and the Northern Ireland Environment Agency. In all cases, the data are subject to revision following validation (extreme high and low flow and level data in particular may be subject to significant revision). The NRFA and the NGLA provide the historical perspective within which to examine contemporary hydrological conditions.

Reservoir Stocks

Details of reservoir stocks are provided by the Water Service Companies, the EA, Scottish Water and Northern Ireland Water.

Terms and Conditions

Some of the features displayed on the maps contained in the reports are based on the following data with permission of the controller of HMSO:

  1. Ordinance Survey data. © Crown copyright and/or database right 2005. Licence no. 100017897.
  2. Land and Property Services data. © Crown copyright and database right, S&LA 145. 
  3. Met Office rainfall data. © Crown copyright.

All rights reserved.  Unauthorised reproduction infringes crown copyright and may lead to prosecution or civil proceedings.

Text and maps are © NERC (CEH) 2015 unless otherwise stated and may not be reproduced without permission.

National Hydrological Monitoring Site Map

The NHMP uses a subset of the NRFA gauging stations, NGLA index wells, and reservoirs for its analyses.  The map below shows these sites, alongside rivers and major groundwater aquifers:

Location Map