England's drinking water risk index soars with three companies responsible

Risk arising from water quality incidents soared by more than 300% in England during 2018 while in Wales it fell 42% according to the latest Drinking Water Inspectorate’s (DWI’s) reports from the chief inspector on England and Wales.

The Event Risk Index (ERI) for the combined public water sectors of England and Wales increased in 2018 to 783 from 241 in the previous year according to the DWI report. For Wales alone the ERI fell from 55 to 32. Southern Water, Thames Water and Bournemouth Water were responsible for the increase in national ERI in 2018 with the coliform detection at Southern Water’s Testwood works the largest single contributor accounting for more than 30% of it.

The DWI also reported national performance against another drinking water quality measure, the Compliance Risk Index (CRI), with England showing a “marginal increase” deteriorating from 3.62 in 2017 to 3.86 in 2018. The report for Wales showed a fall in performance from 2.63 to 4.15.

The ERI – introduced in 2017 – provides a measure of risk attributable to individual events such as treatment failures. by assigning values to the significance and duration of an event, the number of consumers potentially affected and the quality of the company’s response. Similarly the CRI – introduced in 2016 – puts a number on the significance of a failure in compliance to standards in (say) the level of iron, again along with consumers at risk and the company’s response.

In 2018, the figure for public water supply compliance in England with the European Union Drinking Water Directive was 99.95% while in Wales it was 99.997% – “largely unchanged since 2004” in both instances.

The DWI’s chief inspector, Marcus Rink (pictured) said in his letters to water minister, Thérèse Coffey, and Wales’ environment minister, Lesley Griffiths AM, the CRI and ERI were introduced in recognition of the water quality in England and Wales each being among "the best in the world" and that "new, innovative methodology was required to focus on the few areas which matter to the water industry and consumers alike.”

Ofwat has introduced the CRI as a common performance commitment for PR19 and the it has made ERI available as an asset health performance commitment for PR19, should companies wish to be measured by it .