Hydrological summary image
Hydrological Summary

Hydrological Yearbook cover 1995
Hydrological Yearbook

2010-2012 Drought and Transformation Report
2010-2012 Drought and Transformation

National Hydrological Monitoring Programme

The National Hydrological Monitoring Programme (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 and National Groundwater Level Archive, including rainfall, river flows, borehole levels, and reservoir stocks.

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

Amongst the NHMP outputs are:

Press and Media enquiries should be directed to the CEH Press Office.


The NHMP was started in 1988 and is undertaken jointly by the Centre for Ecology & Hydrology and the British Geological Survey. The programme relies on the active co-operation of measuring authorities throughout the UK.


The National Hydrological Monitoring Programme (NHMP) uses a subset of the National River Flow Archive gauging stations, National Groundwater Level Archive index wells, and measuring authority and water company reservoirs for analysis within its monthly Hydrological Summaries. This map shows these sites, alongside major groundwater aquifers.

Data sources

River flow and groundwater level data are provided by the regional divisions of the Environment Agency, Natural Resources Wales, the Scottish Environment Protection Agency, the Rivers Agency and the Northern Ireland Environment Agency. Details of reservoir stocks are provided by the Water Service Companies, the Environment Agency, Scottish Water and Northern Ireland Water.

Most rainfall data are provided by the Met Office, National Climate Information Centre (NCIC). To allow better spatial differentiation, most regional rainfall figures for Britain are presented for the regional divisions of the precursor organisations of the Environment Agency, Natural Resources Wales and SEPA.

For historical comparisons of national and regional rainfall totals the NCIC monthly series are normally used but for England and Wales the homogenised E&W rainfall series developed by the Climatic Research Unit (University of East Anglia) and currently updated by the Hadley Centre may be used.