Guidance and tools to calculate nutrient budget for developments within Special Areas for Conservation (SAC’s) river catchments.
Documents
Nutrient budget calculator: guidance , file type: PDF, file size: 1 MB
Nutrient budget calculator , file type: XLSX, file size: 9 MB
Nutrient budget calculator: frequently asked questions , file type: PDF, file size: 372 KB
Details
The Nutrient Budget Calculator for Wales is used to calculate phosphorus and nitrogen mitigation requirements for development within the catchment for rivers that are SACs and some marine SACs.
There are nine SAC rivers in Wales. Nutrient budgets for development need to be calculated in seven of these river catchments which fail nutrient water quality targets. Nutrient budgets are also required within freshwater catchments of three failing marine waterbodies.
Nutrient budgets are required in these catchments:
- River Gwyrfai and Llyn Cwellyn
- River Teifi
- River Tywi
- River Cleddau and areas around inner Milford Haven
- River Dee & Bala Lake
- River Usk
- River Wye
- River Lougher
Nutrient budgets are not required in the following catchments, but the calculator exists for these should developers want to demonstrate nutrient outputs for their development:
- River Eden, Cors Goch Trawsfynydd
- Meirionnydd Oakwoods and Bat Sites (the Afon Glaslyn)
Nutrient budgets are required around Cemlyn Lagoon but the catchment is currently not included in the calculator.
You can find further guidance on completing the calculator in this instructional video.
For any queries or issues with the calculator please email: decisionsbranch@gov.wales
Wastewater Treatment Works permit figures updated on 7 July 2025.