Marlborough District Council has embarked on a study into the long term outlook for water supplies on the Wairau Plains, which are in decline.
Council scientist Peter Davidson said there were signs that aquifers on the plains are recharging at levels of up to a metre below those seen in the early 1980s.
He said record low levels have been recorded over the past three summers and everything was pointing to that scenario being repeated this summer.
He said scientists were trying to work out how much of the drop was due to natural processes and how much to human intervention.
He says it was possible flood control measures to contain the Wairau River may have changed how the aquifer is recharged, along with natural changes in the river bed.