Water Quality
Rising in the Cambrian Mountains, the river Wye flows 152 miles, crossing the Wales/England border, before joining the Severn Estuary at Chepstow. For most of its length the river is both a Site of Special Scientific Interest (SSSI) and Special Area of Conservation (SAC). Atlantic salmon are one of the listed species for which the river is famous and an indicator of the rivers well being.
More than half the river is failing to meet pollution targets, a Natural Resources Wales study has revealed. Comparison of nutrient concentrations in the Wye against targets, indicated widespread failures, some of them large in magnitude. Fourteen water bodies passed their targets, 28 failed and three were unknown.
R W Edwards & M P Brooker’s 1982 book The Ecology of the Wye suggests water quality of the Wye is largely related to soil structure and the underlying geology of the catchment, which determines the potential source of most materials (except sulphate and sodium, much of which are atmospheric in origin, and phosphate which is derived from sewage), and to the pattern of rainfall, infiltration and run-off which determines the leaching and dilution of such materials.
The nature of land-use influences not only the amount of run-off, but it also modifies water quality. Chemical inputs are further influenced by discharges of sewage effluent, acid rain and biological processes, producing temporal variations. Water chemistry is also characterised by seasonal changes, particularly in the lower catchment where concentrations of nutrients and chemicals are likely to be are substantially higher than the upper catchment. Alkalinity (pH) and the concentrations of total dissolved solids (EC/TDS) and the major ions, such as calcium, magnesium, sodium, potassium and bicarbonate are generally lowest during the winter and highest during the summer.
In July 2020, WSA volunteers began an 18 month project to monitor water quality on the Wye and its tributaries, given the concerns over the visible impact of diffuse pollution in the form of algal blooms. This monitoring concentrated on phosphates (see phosphate-sampling ), pH, EC/TDS, water temperature, with a limited study of nitrate and ammonia.
Water Quality Monitoring Elements
To understand why we do a chemical analysis of a river, it is important to understand EQS (Environmental Quality Standards). These have been set by the EU for Priority Hazardous Substances under the Water Framework Directive (WFD). This includes providing a standard limit for pollutants such as nitrate. The standard maximum contaminant level for nitrate is 10 ppm (parts per million). EQS provide a base line for how we assess whether a river is in good health or not. For example, a nitrate level that exceeds 20 ppm (parts per million) would need to be reported to NRW/EA.
Complimenting, and in addition to, our original study of phosphates we have broadened research to include other water quality parameters such as Ammonia, Nitrates, Electrical Conductivity and pH to our monitoring.
As with Phosphates we are adding science and knowledge by a line of communication with Cardiff University, establishing, together with Gwent Angling Society, Ross Anglers, and environmental groups such as, Friends of the Upper Wye [FoUW], Campaign for the Protection of Rural Wales (CPRW) environmental collaborative research aimed at empowering citizen scientists to monitor water quality. and this data is collected with the same smartphone app allowing volunteers to add their samples to our online database at EpiCollect