The most important source of groundwater is from the deeper aquifer under artesian conditions.

Since 1970s the water supply for the Karaikudi residents relies on this deeper aquifer.

But the critics say the risk to the deeper aquifer is too great.

Some of the water in very deep aquifers may not have entered them as rain.

The draw-down of water from the deep aquifer was gradual at first, accelerating in the late 1980's and throughout the next 15 years.

Other communities in Waukesha County also draw from the same deep aquifer as the city.

A few hundred gallons of spilled water would be a drop in the bucket that might never reach a deep aquifer.

In the background, the Swift's drill sighed softly as it cut its way to a deep aquifer.

They feared that the deeper aquifer would be contaminated if everyone drilled through the clay, he said.

The other half comes from deep aquifers, most of which contain nonrenewable water.