Assessment of water quality in protected rivers in Wales

This report assesses the compliance of Wales’ river SACs in relation to targets for seven water quality attributes:

  • Dissolved Oxygen
  • Biochemical Oxygen Demand
  • Total Ammonia
  • Unionised Ammonia
  • Trophic Diatom Index
  • pH
  • Acid Neutralising Capacity

Failures to meet water quality targets were reported in the River Dee, Afon Eden, Afon Gwyrfai, Afonydd Cleddau, Afon Teifi, River Usk and River Wye SACs.

In terms of this assessment, the SACs with the most target failures were the Afonydd Cleddau, River Usk, River Wye and Afon Teifi.

The majority of failures were for Biochemical Oxygen Demand (41% of assessed water bodies failed to meet the target) and Trophic Diatom Index (45% of assessed water bodies failed to meet the target).

A small number of failures are reported for Dissolved Oxygen and Total Ammonia, and one failure each for Unionised Ammonia and Acid Neutralising Capacity.

No failures were reported for pH.

The report identifies recommendations to address water quality failures in our protected rivers.

Targets and methods of assessment

The targets and methods of assessment are set at a UK level by the Joint Nature Conservation Committee and form part of the conservation objectives for the riverine SAC features.

The assessment was carried by dividing each SAC into waterbodies, which are individual stretches of river. A total of 119 (of a possible 127) water bodies were assessed for one or more attributes.

Water quality data from a three-year period (1st of January 2017 – 31st December 2019) were used to assess compliance with the targets.

This period was used to be consistent with the Compliance Assessment of Welsh River SACs Against Phosphorus Targets, which complements this report.

There are nine SACs in Wales with riverine features:

  • River Dee and Bala Lake
  • Afon Gwyrfai a Llyn Cwellyn
  • Coedydd Derw a Safleoedd Ystlumod Meirion (Afon Glaslyn)
  • Afon Eden - Cors Goch Trawsfynydd
  • Afon Teifi
  • Afonydd Cleddau
  • Afon Tywi
  • River Usk
  • River Wye

You can find the Core Management Plans for each SAC by visiting our protected site search page and reading the attached documents.

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