Nutrient Management in Planning and Development
Further Information and Questions
What are nutrients, and why are they affecting our rivers?
Nutrients occur naturally in the environment in various forms, including phosphate, nitrate, nitrite, and ammonium. These may exist in inorganic, organic, particulate, or dissolved states. While nutrients are essential for plant and animal life, excessive concentrations in rivers can cause significant ecological harm.
When nutrients accumulate, they can trigger eutrophication, a process that severely disrupts river health.
Excess nutrients feed algal blooms, which block sunlight from reaching aquatic plants. As plants die, microbes feed on the decaying matter, consuming oxygen in the process. This depletes oxygen levels in the water, leading to the suffocation of fish and other aquatic life. In severe cases, eutrophication can collapse entire ecosystems, resulting in ‘dead zones’ where little or no life survives.
The main sources of nutrient pollution are:
- Agricultural runoff (fertilisers, slurry, and manure)
- Wastewater discharges (sewage, food waste, detergents)
Dŵr Cymru Welsh Water has undertaken a review of phosphorus sources across Wales to better understand the relative contributions of different sectors and inform mitigation strategies. You can access the source apportionment data here.
Any development within or upstream of a SAC river catchment that would lead to an increase in foul wastewater, surface water discharge, or population numbers is likely to be affected. This includes:
- New housing
- Tourist accommodation
- Employment or commercial developments with increased occupancy or usage
- Agricultural intensification
- Extensions or conversions that increase wastewater loading
You are unlikely to be affected if your proposal:
- Does not result in any increase in foul or surface water discharge
- Is outside the hydrological catchment of an SAC
- Involves purely internal works or changes of use that do not generate additional wastewater
- Is already consented and not subject to re-application
You will need to:
- Use the All Wales Nutrient Budget Calculator to assess nutrient impact
- Submit a Habitat Regulations Assessment (HRA) screening form
- Propose appropriate mitigation measures where required
- Engage with the planning authority as early as possible to clarify information needs
In most cases, if there is no increase in occupancy or wastewater, your development may not require further nutrient assessment. However, this must be clearly demonstrated as part of the planning application.
Yes, if the change of use results in an increase in foul wastewater or overnight accommodation, it is likely to require a HRA. This will depend on the existing use, new use, and number of occupants.
Yes. You can:
- Join a citizen science group monitoring water quality – contact the NMB crichards@carmarthenshire.gov.uk
- Support local and national initiatives on river health
- Reduce nutrient runoff from your own property (e.g. through SuDS, careful use of fertilisers, appropriate drainage)
Nutrient mitigation refers to actions taken to reduce or offset nutrient pollution generated by development. These can include constructed wetlands, buffer strips, SuDS, or upgraded treatment systems. They must be effective, enforceable, and secured for the long term.
Nutrient offsetting allows developers to fund or deliver mitigation off site, rather than on the development plot. This can include agreements with landowners to create wetlands, plant riparian buffers, or reduce agricultural nutrient loading in the same catchment.
Nutrient neutrality means that the total nutrient load after development is no greater than it was before. This is the legal threshold for development in failing SAC catchments under the Habitats Regulations.
Yes, solutions include:
- On-site SuDS, treatment and separation infrastructure
- Future off-site mitigation or offsetting agreements
- Future participation in nutrient credit schemes or nature-based investment platforms
- Collaborative delivery with landowners and local authorities
Farmers play a critical role in nutrient management. If you are within a SAC catchment, you can:
- Take advantage of local support programmes and funding for on farm improvements
- Reduce nutrient loss through soil health, wetland creation, buffers, or infrastructure upgrades
Contact the Nutrient Management Board or Council officers for tailored advice – lecarrington@carmarthenshire.gov.uk
This is a method used to determine whether the soil at a development site can safely absorb wastewater or surface water. It is required when proposing a non-mains drainage solution, such as a soakaway or package treatment plant.
An HRA is a legally required process used to assess whether a proposed plan or project could have adverse effects on the integrity of a European-designated site (SAC or SPA). If there is a likely significant effect, further assessment and mitigation will be needed.
