A summary of regional water quality for Eastern UK rivers

Abstract

Variations in water quality and chemical loads are described for UK rivers draining to the North Sea. These variations are related to regional differences in geology, climate, land use and population distribution. The study uses water quality data collected under the Harmonised Monitoring Scheme. Regional maps of average concentrations and tables of loads, concentrations and loads per unit area are used to present the data. For all the examined determinands, industrial and domestic inputs cause significant increases in river concentrations. For some, such as nickel, ammonium, orthophosphate, lindane and dieldrin, industrial/domestic inputs dominate all other sources. For others, there are comparable inputs from diffuse sources from either mine contaminated sediments (e.g. zinc, lead and copper to the North) or from weathering of bedrock (e.g. calcium to the South, because of the dominance of limestones and calcareous clays). Even for determinands such as nitrate, which are widely recognised as having diffuse sources, industrial inputs can be very significant. For many substances around 60–80% of the total riverine load to the North Sea (as measured at the tidal limits between the Tweed and the Yare) is derived from the Humber rivers, even though this region supplies only a half of the flow. The Aire and Don contribute particularly high loads relative to their catchment area. The much larger Trent, which provides about a fifth of the flow from the LOIS region, also carries substantial loads and it contrasts strongly with the Tweed which carries almost as much water, but only a fraction of the load. Northern rivers generally contribute low loads of most determinands, the exception being for metals such as iron, lead and zinc, which account for over a third of the total North Sea input from the UK. East Anglian rivers provide only 8% of total flow and are generally a relatively minor source of materials. Most significant inputs from the East Anglian region are for calcium, nitrate, sulphate and orthophosphate.