1. guardians of drinking water quality DRINKING WATER INSPECTORATE Water supply & sanitation after flooding events Dr Jim Foster Deputy Chief Inspector (Science & Strategy) Drinking Water Inspectorate London, UK. IPR/101-66CA British Geological Survey. © NERC 2007. A ll r ights reserved.

2. guardians of drinking water quality DRINKING WATER INSPECTORATE Wettest May – July period since records began (250yrs) –> 4 times the average rainfall –1 months rainfall in a 24hr period 13 people died Major disruption to essential services >50,000 premises flooded £billions in damage Cause? –Higher sea temperatures in the Atlantic Ocean –Jet stream stronger & further south than normal Summer 2007 Floods

3. guardians of drinking water quality DRINKING WATER INSPECTORATE IPR/101-66CA British Geological Survey. © NERC 2007. A ll r ights reserved. Flood defences are normally modelled on a “1 in 100yr flood event” i.e. the worst predicted flood in 100yrs Summer 2007 was > 1 in 150yr flood event Sewerage systems overwhelmed in many areas > 300 sewage treatment works flooded 6 water treatments works shutdown Mythe WTW (Gloucestershire) –WTW shutdown due to site flooding –No piped water supply to 340,000 consumers –Full recovery of the supply system took 16 days –Alternative supplies provided by tankers, temporary tanks (bowsers) & bottled water Impact on water supply & sanitation

4. guardians of drinking water quality DRINKING WATER INSPECTORATE Responders need to better understand each others roles –Multi-agency response to a major emergency Clearly define responsibilities for water supply operations –Return of piped supplies was delayed by activities of other organisations Clearly define responsibilities for informing the public –Inappropriate advice was initially given to consumers Value of a quality-driven recovery plan –Defined sampling plan and acceptance criteria  confidence in water safety Importance of post-incident health surveillance –No evidence of any direct impact on public health from water supply problems - controls were effective –Indirect health effects (stress & anxiety) of impacts of flooding are ongoing Lessons learnt - response & recovery of drinking water supplies

5. guardians of drinking water quality DRINKING WATER INSPECTORATE Lessons learnt - water safety plans have a key role in adaptation “Catchment to tap” –Catchment: rethink vunerability assessments don’t rely on history, forecasts are short-term Plan for more extreme events – rethink assumptions Rainfall levels, flood levels, deterioration in raw water quality –Treatment works: assess local risks & have a plan in place –Distribution: assess risks & mitigation measures, e.g. Access to service reservoirs controls to prevent contamination by “backflow” –Consumers: assess risks in & from buildings in advance, understand human behaviour in extreme events, prepare clear information & advice