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What is a watercourse? Understanding its definition and implications for construction professionals

One of the questions we are most frequently asked during our interactions with construction sector professionals is: what exactly is a watercourse?


The answer of course isn’t as straight forwards as we’d like, it really depends on the context and where you are in the UK.


The legislative bits


The Rivers (Prevention of Pollution) Act 1951 defines a water course as “any channel through which water flows” and it also includes “those rivers which are dry for part of the year”.


However, that’s not really the answer our clients are looking for as their concern generally relates to engineering design and/or pollution prevention.


England and Wales


From an engineering context, across England and Wales, there are two types of ‘watercourses’: main rivers and ordinary watercourses. A main river will be clearly defined on an Environment Agency/Natural Resource Wales map. An ordinary watercourse is every river, stream, ditch, drain, sluice, sewer (other than a public sewer) and passage through which water flows, and which does not form part of a main river.


They don’t even need to transport water. Some act purely for storage to prevent water from collecting elsewhere and seasonal flows may also make watercourses appear dry. In times of heavy rainfall these play an important role in accommodating flood water.


When is engineering works authorisation required?


Authorisations may be required from statutory bodies for engineering works on any of the water courses mentioned above.


With regards to pollution control, the Environment Agency recognises the need for controls when discharging pollutants to what they define as surface waters, which includes: rivers, streams, estuaries, lakes, canals or coastal waters, and discharges that may impact ground water conditions.


In Scotland


In Scotland, in an engineering context, notification to the environmental authority, in this case SEPA, is not necessary if the surface water does not feature on a 1:50,000 scale map. However, you do need to abide by the General Binding Rules for that activity. If it does feature, a registration, simple or complex licence is required for certain activities.


In a pollution control context SEPA reference the water environment which includes all surface and groundwater, rather than the term ’watercourse’.



Still have questions?

For definitive guidance about what constitutes a watercourse and what steps should be taken to protect it, Naturally Compliant can help. Please get in touch with Simon Knott at,


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