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; and 

  • reduce algal growth in the Portsmouth, Chichester, Langstone Habours and Rive Hamble estuary.


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.

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


  • Hamble

  • Meon

  • Wallington

  • Lavant (Hants)

  • Ems

  • Lavant (West Sussex)

  • Lavant

  • Aldingbourne, Pagham and other rifes


Public Water Supply Aquifers

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.

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.

Working with farmers

The Partnership works closely with agriculture by promoting a voluntary uptake of best management practices, so to reduce the impact of their activities on land and water environments. The emphasis is placed on a catchment-sensitive farming approach to reduce the loss of soil, nutrients and pesticides.

Working with equine holdings

We work together with equestrian owners to reduce excessive nutrients and other losses to groundwaters, rivers and harbours by promoting best land management practices and offering free specialist advice on pasture, soil and manure management. 

Further information please take a look at our awareness leaflet.

Working in partnership

We work together with several catchment partnership to deliver shared projects and schemes to maximise benefits on a catchment scale.