From the Guardian, typically Anglocentric, today:

England’s rivers are likely to remain in a poor state for years to come because the government is failing to put in place EU clean water laws post-Brexit, the watchdog has found.

When Britain was a member of the EU, the government was required to follow the water framework directive (WFD), standards for waterways that have been credited with cleaning up Europe’s dirty water.

Since Brexit, the UK (sic) is no longer required to match EU regulations, and has its own watchdog, the Office for Environmental Protection (OEP).

Under the WFD, all rivers are supposed to attain “good” ecological status by 2027. In 2019, the last time full water assessments took place, just 14% of rivers were in good ecological health and none met standards for good chemical health.

Under their worst-case assessment, just 21% of surface waters will be in a good ecological state by 2027, representing only a 5% improvement on the current situation. This would break the Environment Act, which aims to improve air and water quality, protect wildlife, increase recycling and reduce plastic waste.

https://www.theguardian.com/environment/article/2024/may/09/englands-rivers-to-remain-in-poor-state-as-eu-laws-ignored-post-brexit-says-watchdog

Scotland has its own water watchdog – the Water Industry Commission for Scotland (WICS). We all know that because the Scottish press, even the UK Telegraph, delight in exposing jaw-dropping expenses and eye-watering golden goodbyes, there.

Anyhow, doing the actual testing and providing the data for WICS, Sepa, 18 May 2023 (new report imminent) reported that Scotland is at 87% for the 2027 target.

So, without any direct comparison possible with the above figures from England, it still looks certain that our water courses are far more likely to be clean.

Source:

https://beta.sepa.scot/news/2023/scotlands-water-quality/#:~:text=Date%20published%3A%2018%20May%202023&text=%E2%80%9CScotland’s%20water%20quality%20is%20at,waters%20rated%20as%20’excellent’.