However, the U.S. has more than 1,400 billion gallons of usable water daily, about 80 percent of which is from streams and lakes, while 20 percent comes from groundwater, he said.

"That should be plenty, given that the total U.S. needs only about 400 billion gallons a day, but the water supply is not uniform around the nation. The East is water-rich; the West is water-scarce."

Though the nursery/landscape industries are high users of the water -- some 31 percent of available supply when added to traditional agriculture irrigation needs -- the majority of water use, some 49 percent, is used for thermoelectric power, Pawlow said.

Since 1990, recycled water use increased by 36 percent and is still rising, plus conservation, increased efficiency and productivity, and new technology have helped to partially offset the increasing demand for water.

But water needs are expected to increase, especially in areas with the least capacity to handle more, he said.