Understanding the sources of phosphorus in our rivers

Too much phosphorus in our rivers can cause algal blooms which in turn affect the amount of oxygen available in the water and can harm wildlife.

As a result, its presence in our rivers is now subject to a lot of attention, with more and more people and organisations who care about our rivers wanting to know where it comes from, and what the solutions are.

That is why Natural Resources Wales and Dŵr Cymru Welsh Water (DCWW) are working together on research which will evidence what the different contributing factors are to phosphorus levels in our rivers. The reports focus on our rivers designated as Special Areas of Conservation.

The modelling approach will be used to develop plans for future wastewater investments to help ensure SAC rivers achieve water quality targets. See Natural Resources Wales / Compliance Assessment of Welsh River SACs Against Phosphorus Targets.

To understand Dwr Cymru’s contribution to the phosphorus load to the rivers, and to assess any improvements we may need to make to our wastewater treatment works’ discharges, we have updated and re-calibrated our water quality models using the regulator and industry standard tool known as SAGIS (Source Apportionment Geographical Information System). This was a joint exercise run in collaboration with our environmental regulator.

Dwr Cymru are pleased to publish key documents on our website relating to this modelling work and communicate the investment Dwr Cymru is planning which will support the collaborative efforts to restore them to favourable conservation status whilst supporting the economic development Wales needs to be a thriving community.

Cover Letter

Phosphorus Programme Cover Letter Feb 2023

161kB, PDF

SAC SAGIS reports

Updating the SAGIS Afonydd Cleddau Model 2023

313kB, PDF

Updating the SAGIS River Dee Model 2023

485kB, PDF

Updating the SAGIS Afon Teifi Model 2023

428.5kB, PDF

Updating the SAGIS River Usk Model 2023

375.4kB, PDF

Updating the SAGIS Upper Wye Model 2023

589.7kB, PDF

Updating the SAGIS River Tywi Model 2023

2.9MB, PDF

Updating the SAGIS River Gwyrfai Model 2023

1.6MB, PDF

Updating the SAGIS Meironydd Oakwoods Model 2023

3.2MB, PDF

Updating the SAGIS River Eden Model 2023

2.6MB, PDF

SAC Phosphorus Load Overview Maps

Afonydd Cleddau Phosphorus Load Overview

3.1MB, PDF

River Dee Phosphorus Load Overview

7.9MB, PDF

Afon Teifi Phosphorus Load Overview

5.3MB, PDF

River Usk Phosphorus Load Overview

7.6MB, PDF

Upper Wye Phosphorus Load Overview

10.3MB, PDF

Phosphorus Programme List

DCWW Phosphorus Programme List

51.3kB, XLSX

Collaboration Information

Collaboration on Phosphorus Reduction Schemes Guidance

200kB, PDF

Appendix 1 Phosphorus Reduction Interactive

261.1kB, PDF

SAGIS data

Sector source apportionment data for all failing SAC river basins in DCWWs operational area

39.6kB, XLSX