Harmonised monitoring scheme
The Harmonised monitoring scheme is a long term river water quality monitoring scheme in the UK [1]. The term is also used to refer to the long term data sets produced by the scheme.
It was set up in 1974 with the establishment of a network of sites across the UK. Most sites were at the downstream freshwater limits of the larger rivers although some of the largest rivers also included additional locations below major tributary confluences. Before inclusion of any location in the survey, homogeneity testing was carried out to characterise quality variations laterally and vertically within the river section chosen. For each designated point a specific sampling location was identified based on the results of the homogeneity exercise.
The scheme is administered by the Environment Agency in England and Wales and by SEPA in Scotland and involves routine monitoring at 230 sites.