Mersey Estuary Environment

The River Mersey originates at the confluence of the River Tame and the River Goyt in the town centre of Stockport, Greater Manchester. It flows west, towards Liverpool, passing through South Manchester towards Warrington, where the river becomes tidal at Howley Weir and the Upper Estuary starts. It widens to form the Inner Estuary at Runcorn. Here is the confluence with the navigable River Weaver.

The Mersey Estuary continues through the ‘Narrows’ a straight narrow channel with depths of up to 30m driven by a change in geology. It forms the Outer Estuary, a large area of inter-tidal sand and mud banks as it flows into Liverpool Bay on the Irish Sea.

The length of the river is 110km of which the Estuary is 26km in length. The total area drained by the river and its tributaries is 4680km2...read more

Natural Features of the Estuary

The Estuary is sheltered and comprises salt and brackish marshes, intertidal sands, mudflats, rocky shores and boulder-clay cliffs. There are 122km of shoreline behind which lies a mixture of urban, rural and industrial environments. A feature of the Mersey Estuary is its narrow mouth - unlike most estuaries which tend to become progressively wider near the sea.

Large parts of the Mersey Estuary and Liverpool Bay are European-Community-designated Special Protection (SPA), Ramsars or Special Areas of Conservation (SAC). The Mersey Estuary is rich in wildlife, particularly overwintering birds. It is used regularly by at least 1%, in each case, of the UK's golden plovers, shelduck, teal, pintails, dunlins, black-tailed godwits and redshanks... read more 

The Estuary has a deep and variable bedrock profile. There is  also a “tunnel valley” under the Estuary above Birkenhead - this was formed by meltwater flowing beneath the glacial ice sheets under great hydrostatic pressure. This valley contains isolated, overdeepened depressions where the bedrock can be 70 - 80m below ground level... discover more

Water Quality

Water quality in the Mersey Basin generally and the Mersey Estuary specifically has improved significantly in recent years. Massive investment in infrastructure by the water company United Utilities, enforcement of regulation by the Environment Agency, the closure of the worst polluting industries and co-ordinated action led by the Mersey Basin Campaign over a twenty five year period all contributed. Salmon have returned to the Mersey...read more 

Climate change and flooding

Climate change in the Northwest of England is expected to bring warmer temperatures, heavier rainfall, more frequent extreme conditions and sea level rise. High, medium and low scenarios have been developed by the UK Climate Impacts Programme...read more

Climate Change Northwest partners are actively exploring the problems and opportunities presented by climate change in the region...read more

Most of the shoreline of the Estuary is protected by flood defences. Flood risk assessments indicate that the greatest threat of flooding occurs at Warrington...read more

The Shoreline Management Plan is currently in its draft form. There is a general policy of ‘holding the line’. The exception is naturally eroding cliffs where there is a policy of no active intervention...read more

Sediments and dredging

Although the river contributes little in the way of deposits, sediment from Liverpool Bay is slowly accumulating in the Estuary. Despite this, the locations of sandbanks and channels, though still subject to change, are more stable than they were 30 years ago. Dredging has decreased over time and is now limited to to the channels to Eastham Docks and the entrance to the Manchester Ship Canal. 

Wildlife and conservation

The Mersey Estuary is rich in wildlife particularly over-wintering birds. Large parts of the Estuary and Liverpool Bay are European Community designated Special Protection Areas (SPA), Ramsars or Special Areas of Conservation (SAC). The Estuary is used regularly by at least 1%, in each case, of the UK’s golden plovers, shelduck, teal, pintails, dunlins, black-tailed godwits and redshanks...read more

There are four individual Sites of Special Scientific Interest (SSSI) in the Estuary region - New Ferry, Mersey Estuary, the Mersey Narrows and the North Wirral Foreshore - this is in Liverpool Bay, a potential SPA. The designation of these SSSIs relate mainly to the birds found there...read more

Marine planning

The European Water Framework Directive requires Member States to adopt river basin management plans. The responsible authority in England and Wales is the Environment Agency. The first  River Basin Management Plan for the Northwest Region has been adopted by Ministers. This includes the Mersey Basin. The Estuary qualifies as a heavily modified water body with unsatisfactory quality though there has been very substantial improvement in recent years...read more

Marine Plans that are intended to guide decisions in the marine environment are in the process of being developed with stakeholder engagement. The government’s Marine Policy Statements and Marine Plans are the responsibility of the new Marine Management Organisation (MMO).

Marine planning

Built Environment and Heritage

Liverpool’s World Heritage status is one of 850 cultural or natural World Heritage sites including The Great Wall of China. he Liverpool World Heritage Site includes a substantial part of Liverpool's historic waterfront and docks. It does not include all of the city centre, nor all of the heritage assets in the city, but what it does include is a contiguous area, dominated by historic buildings and structures with a strong link to Liverpool's maritime mercantile heritage. The designation was made on the basis that the site is “the supreme example of a commercial port at the time of Britain’s greatest global influence”.

Liverpool World Heritage Homepage

Irish Sea Coastal Observatory

Real time data and monitoring and information on many aspects of the Irish Sea including wave heights, currents, tidal sea levels, temperature and much more can be found at the Natural Environment Research Council’s Irish Sea Coastal Observatory...read more

Coastal Observatory, Liverpool Bay, Irish Sea (UK) | Project summary