Poole harbour catchment information

Poole Harbour catchment information


The Poole Harbour catchment is one of three sub catchments in Dorset, located in the south west of England. The main rivers flowing into the Harbour include the Rivers Frome, Piddle, Sherford and Corfe and when combined with all of their tributaries cover a total land area of around 820 km2.

Both the Frome and Piddle rivers are located in picturesque rural catchments. Their nationally recognised chalk streams/rivers are important for the salmon and trout fishing. Both rivers rise in the Dorset Downs and flow through the chalk lands and across clay and gravel deposits to enter Poole Harbour.

There are many smaller streams that drain over the tertiary beds near Poole Harbour, these include the River Sherford and Wareham Forest Stream. The urban area of Poole is located to the north of the Harbour and is heavily populated. The coastal town of Wareham is located to the west of the harbour, and the Isle of Purbeck area lies to the south west of the harbour.

Map showing watercourses in  the Poole Harbour Catchment
Map showing watercourses in the Poole Harbour Catchment
Beach in the Poole Harbour Catchment
Beach in the Poole Harbour Catchment

Environment and landscape

The area contains many sites of local, regional, national and international importance, with a range of habitats supporting a variety of species.

A substantial proportion of the area is within the Dorset Area of Outstanding Natural Beauty (AONB) which works in partnership to conserve and enhance the natural beauty of almost half of Dorset's countryside (1128km2).

A large part of the catchment is also within the Wild Purbeck Nature Improvement Area (NIA) which is being led by the AONB. The NIA is trialling a partnership approach to deliver enhanced wildlife habitats and community engagement at a landscape scale. It covers the lower part of the catchment but will promote land management advice and habitat creation throughout the Poole Harbour catchment.

Tourism is one of the predominant industries in Dorset, one of the primary reasons tourists are drawn to Dorset is the attractiveness of the county's coast and countryside.


There are approximately 250,000 people living in the borough of Poole and 50,000 people (Dorset County Council, 2011) living in the more rural upper catchments and county town of Dorchester. It is anticipated that the local population within the catchment will rise by a further 25,000 by 2035 given that the population is predicted to increase by 10% in this period.

The effects of sewage from a rising local population need to be considered, with particular focus given to the affects this will have on Poole Harbour. Summer visitors can increase the population significantly, and are predicted to increase waste discharges by a further 13% in Dorchester and 80% in Wareham (using Wessex Water estimates for 2035).

Wessex Water is the main public drinking water and sewage treatment provider in the catchment although there are also private water supplies and private sewage treatment (including septic tanks).

Public water supply is sourced from the chalk aquifer. Waste water is returned through sewage treatment works and septic tanks to the aquifer, rivers and direct to Poole Harbour.

Farming and the environment

Over 75% of the land within the catchment is used for agriculture which is almost equally divided between arable and pasture; this is on par with the national average. Cereals are dominant over the chalklands with much dairy and beef farming in the west and in the lower floodplains.

Farming now accounts for approximately 5% of Dorset’s economy with the annual gross output equating to £306 million and the GVA reaching £112 million (NFU, South West). There are over 5,974 people directly employed in agriculture in Dorset which equate to 9.8% of the South West’s farm workers.

Poole Harbour

Poole Harbour is one of the largest and shallowest natural harbours in the world, with an area of approximately 38km2. The harbour is of exceptional ecological value and is protected by a multitude of conservation designations. Central to the ecological value are the intertidal mudflats, sandflats and marshes (80% of area at low water) and the diversity of the shoreline ranging from reed and marsh to sand and shingle. The main freshwater inputs to the harbour are the rivers Frome, Piddle, Corfe and Sherford.

The harbour is highly eutrophic and there is a very clear ecological disturbance from the excess of nutrients in this system.

Find out more about the PHCI catchment plan.