South Canterbury's groundwater is being investigated by Environment Canterbury scientists.
About 75 wells between Timaru and the Waihao River will be examined as part of research into the age and chemistry of the deep water sources.
''We will be focusing on a particular sub-surface group of gravelly rocks, called the Cannington Gravels, which are quite porous and hold groundwater,'' ECan groundwater quality team leader Carl Hanson said.
''The research work we are doing is quite significant in size and scope.
''We're focusing on the deep groundwater to gain a better understanding of how it's replenished, and what the effects of taking water will be on the environment and other groundwater users.''
ECan has identified the wells it would like to sample in the study. Institute of Environmental Science and Research (ESR) scientists will collect the samples.
''ESR will be contacting landowners directly for permission to access and sample groundwater from their private wells,'' Mr Hanson said.
''Without the co-operation of private landowners this work wouldn't be possible, and we appreciate their support.''
The water will be sampled from depths of down to 200m. Results will be shared with landowners. In 2007, a water sample from deep groundwater within the Cannington Gravels near Waimate was dated as being more than 20,000 years old.
''We have few age samples of deep groundwater. This research will give us an increased understanding into the origin and movement of deep groundwater in South Canterbury and will assist in setting appropriate management regimes,'' Mr Hanson said.
The sampling will be finished before Christmas. Once results come back from the laboratory, the data will be interpreted and presented in a technical report next year.