The Partnership

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

The Downs and Habours 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. 


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. 

Harbour pic 2.JPG

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.
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. As a consequence, large areas of coastal SSSI and Natura 2000 sites in the Eastern Solent are in unfavourable and declining condition.

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.

Public Water Supply Aquifer

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