Reservoirs would be expected to be 86% full in August, but levels have dipped to 77% capacity.
While water restriction measures are not planned, they may be put in place if dry weather continues, particularly if a dry winter is on the way.
Guernsey Water managing director Steve Langlois said Guernsey must never think it is immune to water shortages.
‘Our approach to restrictions would be to apply them on a voluntary basis for homes initially, then businesses,’ he said.
‘Any decision to take this next step would consider many different factors such as water resource level, demand for water, weather, and the time of year. Mandatory restrictions would come later if necessary. This staged process allows us to see how successful islanders have been in reducing their demand for water before any further steps are taken.’
A raw water network of pipes is used to move stored water, which is separate from the drinking water network, between the island’s 14 reservoirs. The process ensures that the St Saviour’s, Kings Mills and Juas reservoirs have a constant supply of water, and makes space for more water to be collected when rain does come.
In the UK, Southern Water, South East Water and Thames Water have introduced hosepipe or sprinkler bans following recent record-breaking temperatures.
In France, French Prime Minister Elisabeth Borne has warned that the country is facing the most severe drought ever recorded there, and Jersey has entered its second absolute drought of the summer, following less than a millimetre of rainfall in July.
But Guernsey is in a better position.
‘We are benefitting from the foresight of people that invested in increasing our ability to capture and store more water. This has put us in a better place right now than many across Europe, where water restrictions are already in force,’ said Mr Langlois.
Immediate questions being faced by Guernsey Water are how much rain will fall between now and next spring and how much water the island will use in that time.
‘Guernsey must be self-sufficient when it comes to the public water supply, so it is right that we have invested in capturing and storing enough water to cope with the dry weather we have experienced so far this year,’ said Mr Langlois.
‘We have experienced droughts in the past that would still require water restrictions if they were repeated today. Our plans suggest that on average this could happen once every 20 years.’
The future use of Les Vardes quarry, which is currently being used by Ronez, will be discussed in the States next year as part of the Government Work Plan. Guernsey Water has previously said the quarry is important for future water storage security.
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