An adequate supply of good quality water is essential to Jersey's sustainable wellbeing. About half of the Island is farmed, making Jersey’s natural water resources vulnerable to pollution from the use of fertilisers and pesticides. As a result, Jersey’s surface and ground water resources have some of the highest concentrations of nitrate in Europe. Ensuring that the public water supply meets regulatory requirements can require costly treatment by Jersey Water. This indicator tracks the average annual nitrate (mg/l) level using weekly samples from surface streams at 31 different sites. It is the headline indicator as nitrate levels in ground water are also closely monitored.

In 2022, the average annual nitrate (mg/l) level in surface streams across Jersey was 44.3 mg/litre. Variables such as weather conditions, use of automated potato planting and fertiliser application rates mean that the longer-term trend is more significant than changes from one year to the next.