Nutrient neutrality

Natural England's assessments during 2019/20 suggest that more than 3000 hectares of the inter tidal parts of Chichester Harbour, which is the subject of several European designations, is now classified in an "unfavourable - declining" condition. Natural England's Condition Review of Chichester Harbour sites (opens new window) was published in February 2021. 

Water quality is a contributing factor to the build-up of excess nutrients in the Harbour causing metrification (algal growth) which impacts on the Harbour's ecology and conservation. Sewage from new development using waste water treatment works or an on-site package treatment plant that discharges to Chichester Harbour contributes to the excess nutrients in the Harbour (albeit in small amounts relative to other sources) and therefore needs to be considered in line with the Habitats Regulations. This means that before agreeing to a proposal (such as a planning application or a development plan) the authority needs to undertake a Habitats Regulations Assessment. The authority must be satisfied that the proposal will not have any adverse impact on the protected site or sites. Certain types of new development will now need to be nutrient neutral to avoid detrimental harm to the Harbour's ecology and conservation.  

Guidance

As part of the information needed to determine planning applications, if a relevant proposal (primarily those involving an overnight stay) is likely to discharge into Chichester Harbour, then a nitrogen budget will need to be prepared and submitted with the planning application. Natural England's Guidance sets out when and how nutrient neutrality must be achieved with catchments maps to clarify the areas that are affected. Natural England and DEFRA have published Guidance (opens new window) on achieving nutrient neutrality which includes a methodology for calculating the "nutrient budget" of proposed development.  

The Rivers Trust and Constructed Wetland Association have set up a Constructed Wetlands Hub (opens new window) where specific details around designing and constructing wetlands for nutrient neutrality can be found. In particular, the Natural England Framework for Wetland Mitigation Proposals has been produced by Natural England working with the Rivers Trust and the Constructed Wetland Association, to guide anyone interested in submitting a proposal for wetland designed to deliver nutrient neutrality.

Framework Approach for Responding to Wetland Mitigation Proposals (PDF, 2 MB)

Southern Water has produced a helpful info graphic providing a broad overview of the issues of nitrates in Chichester Harbour, and this is also available to view.

Southern Water - Protecting Langstone and Chichester Harbours from nitrogen pollution (PDF, 260 KB)

Joint working

We are a working with the Partnership for South Hampshire (PfSH) and other authorities affected by the issue of nutrients to deliver mitigation schemes through the Solent Mitigation Partnership (opens new window) . Information about other potential mitigation schemes is available on the PfSH website (opens new window) .