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Groundwater monitoring

​Groundwater

Groundwater is water below the ground in the saturation zone and it constitutes about 70% of the world's freshwater. It represents an extremely valuable source of freshwater for:

  • drinking
  • domestic use
  • agricultural use
  • industrial use

Approximately 10% of Jersey residents rely on private borehole supplies for drinking water and domestic use. Visit our private water supplies page for more information.

The importance of groundwater

As well as playing a vital part in human activities, groundwater has an important role in our environment. It supports rivers and wetlands, especially through drier months when there is little direct input from rainfall. The flow of groundwater into rivers as seepage through the river bed can be essential to the health of wildlife and plants that live in the water.

Monitoring of Jersey's groundwater

The Environmental Protection Team monitors both quality and quantity of groundwater.

Quality

Currently, 46 sites are monitored for quality twice a year. Field analysis is carried out at each site for:

  • pH
  • conductivity
  • temperature
  • alkalinity

The collected samples are then sent to the Laboratory of the Official Analyst to the States of Jersey for chemical analysis.

Pesticide analysis

Additional samples are taken from 8 of the sites, which are then sent to a UK laboratory for pesticide analysis.

The issue of nitrate in Jersey's groundwater was highlighted by the initial BGS study, as they found that 60% of the samples taken had concentrations of nitrate greater than the EC maximum admissible concentration (MAC) for drinking water. Since 1990 there has been an overall steady decline in the number of samples that have exceeded 50mg/l of nitrate. However, 30% of samples still exceed the EC MAC.

November 2018 field and chemical data

May 2018 field and chemical data

November 2017 field and chemical data

November 2017 pesiticide data

May 2017 field and chemical data

May 2017 pesticide data

November 2016 field and chemical data

November 2016 pesticide data

May 2016 field and chemical data

May 2016 pesticide data

November 2015 field and chemical data

November 2015 pesticide data

May 2015 field and chemical data

May 2015 pesticide data

Quantity

The Island currently measures water quantity at 23 sites across the Island. Data for some of the sites goes back to 1993.

Groundwater leaflet​​

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