Performance Indicators for drinking water quality – ESC workshop Proposed indicator is: “Percentage of population receiving drinking water meeting the [E. coli or turbidity] standard”... Expressed as a proportion of population receiving drinking water from that supplier.

Explanatory detail “ Complies with the standard” means each zone whose annual compliance results comply with the standards for E. coli and turbidity, based on the compliance monitoring program. A zone is a water supply locality (town or suburb) where the water has common characteristics.

Where did it come from? Desire to tie in with standards (applies to the water, not samples) Move away from global % of samples and snapshots population Focus on main matters of public interest: –E. coli (microbiological quality) –Turbidity (physical or aesthetic quality)

Example calculation E. coli standard is 98% of samples over twelve months with zero result If the result is 98% or greater, the zone complies for that year If the result is below 98%, the zone doesn’t comply for that year

Example continued... If all zones comply, then result is 100% - desired (and expected) outcome! If some zones don’t comply, then they are added up and weighted by population to arrive at an overall figure for that supplier – zones require undertakings.

Example continued... Water supplier has 40 zones supplying 100,000 people in total One zone is 91% for E. coli and fails to comply; it supplies 500 people: Result is 99,500 / 100,000 = 99.5% Means that almost all customers (99.5%) received a supply that met the E. coli standard for that year.

Example continued... Water supplier has 70 zones supplying 100,000 people in total Four zones fail to comply, supplying 2,000, 3,000, 4,000 and 1,000 people: Result is 90,000 / 100,000 = 90.0% Means that 90% of customers received a supply that met the E. coli standard for that year.

Comments Standards must be met ALL YEAR for zone to comply – desired outcome It is recognised that most people living in zones that do not comply may well receive satisfactory water most of the time, however,... the hurdle is based on demonstrating continuous good performance, not partial good performance

Comments Zones that do not comply must be identified under legislation with undertakings and in annual report Non-potable supplies excluded Chemical standards excluded Separate indicator for metropolitan interface points – hurdle is higher upstream of customer taps