Gore District Council is searching for the reasons behind a sudden drawdown from Mataura's reservoir, which is jeopardising the town's water supply.
The council has imposed level four water restrictions on the town - which bans sprinklers, garden irrigation systems and both unattended and handheld hoses - after the reservoir dropped to critical levels.
Gore's waters asset manager, Matt Bayliss, said the reservoir started haemorrhaging water at midday Friday and levels dropped to 45 percent of capacity yesterday afternoon.
Mr Bayliss said the drawdown from the reservoir is constant and throughout the night, suggesting there is a major leak in the network.
He said it should be obvious considering the volume of water lost and wants anyone who has noticed a lake or flow of water on to their own or neighbours' property to contact the council.