- Drinking Water 2024 – Summary of the Chief Inspector’s report for drinking water in England
- Foreword
- Water supplies and testing
- Compliance with water quality standards
- Water quality events
- Asset health and service reservoir integrity
- Consumer contacts
- Water safety planning and risk assessment
- Perfluoroalkyl and polyfluoroalkyl substances (PFAS)
- Audit programme completed by the Inspectorate
- Enforcement, transformation and recommendations
- Lead in water
- Materials in contact with drinking water (Regulation 31)
- Security and Emergencies (SEMD)
- Network Information systems (NIS)
- Research publications
- Raw water data
- Whistleblowers
- Working with stakeholders
- Annex A – Number of tests carried out by companies
- Annex B – Compliance with standards
- Annex C – Compliance failures and events
Raw water data
Treated water regulation has long mandated efforts to ensure the safety of our drinking water. This is the overarching purpose of the Inspectorate, which has been analysing and reporting the quality of water around England and Wales since 1990. The regulations define safe ranges of chemicals in the water, and enforces action where companies fail to meet these requirements post-treatment. In 2024, this ranks the UK as joint first country in the world for drinking water quality, with an EPI Score of 100.0 for sanitation and drinking water. However, there is no official regulation on safe levels of pre-treatment raw water.
In the past century, water quality stressors have been primarily anthropogenic, with increasing freshwater demand and the polluting consequences of the urban, industrial and agriculture sectors. With climate change driving the increase in frequency and severity of extreme events such as storms and floods, inland water quality is set to continue worsening beyond these human factors. This will further strain treatment works and threaten drinking water supplies, and thus, there is a need for a more comprehensive quantification of raw water quality, to understand past and current trends through data.
In 2024, the Inspectorate commissioned a research project in association with the University of Cambridge to analyse the raw water dataset currently held by the Inspectorate to see what insights could be generated. The dataset currently comprises of:
- ~22.1 million total samples;
- ~13.5 million are groundwater
- ~8.4 million are surface water
- 764 parameters;
- 3,258 sites.
The project aims to deliver a tool which can be initially used for prediction of a small set of parameters to enable effective analysis with the potential to expand the number of parameters at a later stage.
A better understanding of the evolving distributions of different chemicals across the country will facilitate data-driven prediction of contamination risks and potential for polluted drinking water. Understanding how these propagate through treatment works could enable the prevention of these events, enabling water suppliers to handle transient increases in chemical levels in raw water. The DWI has been collating monthly raw water quality data collected by water companies since 2009, but has thus far been mostly focusing on monitoring and analysing compliance data from treated water. Analysis of this raw water dataset will support the Inspectorate in assessing the action, or lack thereof, of water suppliers in these cases. It will also help identify hotspots and highly stressed areas that might begin to struggle to provide drinking water up to regulatory standards in future.
The project continues into 2025 with the aim to complete the interactive tool focusing on the initial small number of parameters selected, with ideas around future work to expand this analysis to cover a more extensive range.