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The Partnership

The Downs and Harbours Clean Water Partnership is taking action to tackle diffuse water pollution issues affecting the quality of ground, surface and coastal waters in West Sussex and East Hampshire. The Partnership is focused on reducing the amount of polluting nutrients, particularly nitrate, currently entering the water environment. 

Working Towards a Cleaner Water Environment
Press the links below to find out more:

Free Advice & Grants for Farmers and Landowners to protect water quality + Farmer Working Groups

Advice for oil tank owners

Support and information specifically for Equestrian Establishments

 Portsmouth Water Biodiversity Grant Scheme-APPLICATIONS OPEN FOR 2023/24

Contact Information and meet the team page

Check out what we're currently doing and for latest updates!

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The Downs and Harbours Clean Water Partnership is a forward-thinking initiative between Portsmouth Water, Catchment Sensitive Farming and the Environment Agency. 

Partnership Aims 

The partnership aims to:

  • Protect and improve the water quality for all by safeguarding groundwater sources used for public water supply.

  • Reduce pressures on the ecology of local rivers such as the Meon, Wallington, Ems and both River Lavants.


  • Reduce algal growth in the Portsmouth, Chichester, Langstone Harbours and Rive Hamble estuary.

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Partnership Area

The Downs and Harbours Clean Water Partnership project area runs from east of Southampton to Bognor Regis. The area includes vital rivers, public water supply aquifers and coastal areas.

The Geology of the area is unique due to the Karstic nature of the Chalk Aquifer.
We aim to ensure that the rivers, lakes, groundwater and coastal waters of East Hampshire and West Sussex are protected and improved for current and future generations to enjoy.
Public Water Supply Aquifer

Portsmouth Water abstracts groundwater found within the Chalk rock (aquifer) of the South Downs to supply public drinking water in the area.


Around 85% of the water comes directly from groundwater, sourced from boreholes or springs, with the remaining 15% being derived from the River Itchen - itself being groundwater fed.

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Coastal areas

These include:

  • Portsmouth Harbour - Site of Special Scientific Interest (SSSI), Special Protection Area (SPA) & RAMSAR

  • Langstone Harbour - Site of Special Scientific Interest (SSSI)

  • Chichester Harbour - Site of Special Scientific Interest (SSSI) 

  • Chichester & Langstone Harbours - Special Protection Area (SPA) & RAMSAR Solent Maritime - Special Area of Conservation (SAC).

These semi-enclosed harbours are particularly affected by the excessive algal growth resulting from elevated nitrate levels in water and estuarine sediments. However, as a result of all the reductions in nutrients that have occurred over the last 20 years, we are now seeing reduced amounts of algae in several Solent estuaries, plus other encouraging signs of recovery. Efforts to sustain this improvement are ensured through continued catchment management work.


Rivers in the Downs and Harbours area are predominently fed or influenced by groundwater. These rivers are the:

  • Hamble

  • Meon

  • Wallington

  • Lavant (Hants)

  • Ems

  • Lavant (West Sussex)

  • Lavant

  • Aldingbourne, Pagham and other rifes

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