Poole Harbour Nutrient Neutrality Calculator

Stuck behind a Poole Harbour nutrient condition?

New homes draining to Poole Harbour have to be nitrogen-neutral. The harbour is one of the most heavily affected catchments in the country, and it reaches well inland across Dorset along the Frome and Piddle — so plenty of sites nowhere near the water still fall inside it.

If your site drains to Poole Harbour SPA / Ramsar, the planning authority can't grant permission until you've shown the scheme is nutrient neutral — that it won't add nitrogen to a catchment that's already overloaded. NutrientMonkey gets you the number: build the assessment on screen, watch your budget in kg/year update as you go, and export the planning-ready report when it's right.

Which nutrient applies here

Poole Harbour is a nitrogen-led catchment: excess nitrogen drives algal growth that smothers the harbour’s internationally important mudflats and saltmarsh. That matters, because the methodology and the credits differ by nutrient — and neighbouring catchments often differ. NutrientMonkey flags the Poole Harbour catchment for nitrogen and locks the tool to match, so the assessment is right from the start.

Credits in the Poole Harbour catchment

Poole Harbour has an official credit price of around £3,250 per kg of nitrogen/year. One credit is 1 kg/year. Buying permanent credits only, the number you need is your governing budget — the greater of the pre- and post-2030 figures, floored at zero; where a 2030 permit change applies, a cheaper split of temporary credits (valid to 1 April 2030) plus permanent is also possible. The calculator shows these live so you can see roughly what mitigation will cost before you commit. Prices change — always confirm the current figure with the scheme.

There are two providers here. Alongside Natural England, Dorset Council runs its own credit scheme and now sells both temporary and permanent nitrogen credits — currently £406 per kg N/year for a temporary credit (valid to 1 April 2030) and £1,840 per kg N/year for a permanent credit, plus a £360 administration fee per transaction. One credit is 1 kg of Total Nitrogen per year and credits can be bought in fractions down to 0.01 kg. The council’s figures are usually cheaper than the Natural England price above, so it is worth comparing both — and always confirm the current price with the provider.

How the Poole Harbour calculator works

1. Pick Poole Harbour from the catchment list — it's pre-flagged for nitrogen.
2. Enter the dwellings & waste water — occupancy, water use (125 or 110 l/p/d plus NE's allowance) and the drainage route (septic, package plant or mains permit).
3. Add land use & SuDS — current vs future land cover and any sustainable drainage, with editable export coefficients for the Dorset catchment values.
4. Export when ready — a branded, planning-ready PDF with the budget in kg/year and every input documented.

Honest about what it is

This is a nutrient-methodology assessment built to support your Poole Harbour planning application — fast, clear and ready to discuss with your case officer. The official Natural England catchment calculator remains the statutory tool, and your figures should reproduce in it; the report states this plainly. Want it handled end to end? That's what we're here for.

Frequently asked questions

In a different catchment?

NutrientMonkey covers every Natural England catchment.

Also in the Dorset area:

• Chesil & the Fleet N & P

Or jump to another part of the country:

• Solent N
• Tees (Teesmouth) N
• Lindisfarne N
• Stodmarsh N & P
• The Broads N & P
• River Wensum N & P
• Hornsea Mere N & P
• Oak Mere N & P
• Rostherne Mere N & P
• West Midlands Mosses N & P
• River Clun N & P
• River Avon (Christchurch) P
• Somerset Levels & Moors P
• River Itchen P
• River Axe P
• River Camel P
• Derwent & Bassenthwaite P
• River Eden P
• River Kent P
• River Lambourn P
• River Lugg P
• River Mease P
• Esthwaite Water P
• Peak District Dales P
• Roman Walls Loughs P

Or go back to the main NutrientMonkey calculator.

Wider planning support

Nutrient neutrality is rarely the only condition on a scheme. Our energy statements service and the wider SAP & compliance team cover the rest of the planning and Building Control picture — get a quote and we'll talk it through.