Status: Purely descriptive
Water circulation is the natural movement and mixing of water. Common features which effect the pattern of circulation are the temperature and salinity of sea water. These factors alter the waters density and allow, for example, warmer water to circulate above colder water, and freshwater from rivers will float above salty seawater. Tides are also a major factor in water circulation, however circulation can also be altered by rivers entering the estuary, as well as weather focussed phenomenon such as rain, wind, storms, and air pressure.
The Solway Firth is one of Scotland’s major estuaries with an area of around 300km2. Being on the west side of Scotland/England the Firth includes the boundary between these two UK countries and follows roughly the same orientation as the Isle of Man throughout the majority of its area, in a southwest/northeast direction. As the Solway narrows it orientates to a more East/West direction, before splitting into the River Eden and the Channel of River Esk. These are just two of the rivers which feed into the Solway, others include the Scottish; Annan, Nith, Dee, and Cree, and the English; Waver, Wampool, and the Sark which forms the beginning of the Scottish/English land border as it progresses inland.
‘Hydrological conditions’ such as the salinity and sea surface temperature of the marine area around the UK are assessed in relation to meeting the high level UK ‘Good Environmental Status’ (GEnvS) objective that; “The nature and scale of any permanent changes to hydrographical conditions resulting from anthropogenic activities do not have significant long term impacts on UK habitats and species” (Department for Environment, Food and Rural Affairs, 2019). Hydrological conditions are one of eleven ‘descriptors’ used to describe what GEnvS will look like in the Marine Strategy Framework Directive. These descriptors help member states interpret GEnvS for their waters. As of the recent, 2019, updated assessment for the UK Marine Strategy Part One, GEnvS was continuing to be achieved for hydrological conditions in the UK.
Image; Tidal sign. © N. Coombey/ Solway Firth Partnership.