The Historic UK Water Quality Sampling Harmonised Monitoring Scheme (HMS) data contains statistics for a series of water quality sampling sites including annual means, maximum and minimum values for each Region for specified determinands from 1975 onwards.
The sampling network includes 230 sites, which are mainly located at the tidal limits of major rivers or at the points of confluence of significant tributaries. The information held within the HMS includes data on: oxygen and ammonia, nutrients, list II metals and pesticides. Annual mean concentrations have been calculated for each HMS site. The data show the annual averages of the site means in each region, with each site given equal weight irrespective of the number of samples taken - an average of all the samples would give a greater weight to the sites at which samples are most frequently taken. In order to give an indication of the range of values at different sites within each region, figures are also given for the maximum and minimum site mean for each region. The data also includes for the UK average, the 10th percentile and the 90th percentile of the site means for the whole of the UK. For each determinand in each year and the 10-percentile and the 90-percentile of the site means in each region.
The Harmonised Monitoring Scheme (HMS) was established to provide an archive of water quality data for the UK. It is used to provide information for international obligations, including the long-term trends of some determinands and the estimation of riverborne input of selected determinands to the sea.
Chemical and Physico-chemical data is collected via site-specific surveys