Revisions to Joint Nature Conservation Committee (JNCC) monitoring guidance have required Natural Resources Wales (NRW) to review its conservation objectives for river Special Areas of Conservation (SACs) in Wales, notably with respect to phosphorus where targets have been substantially tightened. This data was created to identify compliance with the revised phosphorus targets for Welsh river SACs. Phosphorus concentration data were extracted from the NRW water quality database (KiWQM), for a three-year period from January 2017 to December 2019 for all sample points within water bodies in the nine SACs designated for one or more river features. These were Afon Gwyrfai a Llyn Cwellyn; Afon Eden – Cors Goch Trawsfynydd; Meirionnydd Oakwoods (Afon Glaslyn); Afon Teifi; Afon Tywi; Afonydd Cleddau; River Dee & Llyn Tegid; River Usk; and River Wye. In total, 125 water bodies (river sections) were in scope. Data were excluded where (i) detection limits were inadequate to assess compliance with the target or (ii) where the sample exceeded the recommended holding time of three days prior to analysis. Outliers in the data were identified and, if they were considered likely to be causing a failure on their own, data from other nutrient pollution indicators (biochemical oxygen demand, nitrate and ammonia) were checked to corroborate possible pollution events. The data consists of two products: 1. An Excel spreadsheet summarising results and 2. An ArcGIS layer consisting of the WFD catchment area water bodies, clipped to the Welsh border and excluding water bodies not overlapping with river SAC boundaries.
