Study: Groundwater Role in Nation’s Water Supply Increases

Groundwater’s role in the nation’s water supply increased slightly from 2000 to 2005 at the same time groundwater withdrawals decreased--an indication that our nation may be better managing freshwater resources, said National Ground Water Assn. (NGWA) Executive Director Kevin McCray.

According to U.S. Geological Survey (USGS) data released last month, daily groundwater withdrawals declined 4% between 2000 and 2005. The USGS estimates that, for all purposes, the nation pumps 79.6 billion gal per day of fresh groundwater, down from the 83.3 billion per day (bgd) in the survey’s 2000 estimate.

However, as a percentage of the nation’s total water supply, groundwater rose from 24% to just more than 26%.

“Perhaps as a nation we are learning to be better managers of our available freshwater resources, conjunctively balancing the use of groundwater and surface waters,” McCray said.

The USGS data shows that agricultural irrigation, historically the largest purpose for which the nation pumps groundwater, remained in its leadership position, although at lesser levels than in 2000. The USGS estimates agricultural irrigation uses about 53.5 bgd, down nearly 8% from the 2000 estimates.

“With local moratoriums or other restrictions placed on groundwater extraction for agricultural irrigation around the nation, it is not a total surprise there would be an accompanying decline in groundwater extraction,” McCray said.

Groundwater for public supply declined from 15.98 bgd in 2000 to 14.6 bgd in 2005. As a segment of the nation’s total groundwater withdrawals, the public water supply use dropped from 19% to 18%.

“Between 2000 and 2005 there was a decline of 2,643 community water systems using groundwater--a change of 6%, at least as tabulated by the U.S. Environmental Protection Agency,” McCray said. “But the population served groundwater by those systems increased by 3.7 million, or more than 4%.”

The estimates of groundwater use for individual household supply by use of private water well systems show a slight uptick, moving from 3.5 bgd to 3.7 bgd. An examination of U.S. Census housing statistics show that during the years between 2001 and 2005 there had been a decrease of just under 1% in the number of households served by individually owned private water well systems. However, when looking at 2007 compared to 2001, there was a slight increase.

Based upon the Survey’s estimates for 2005, some 43.8% of the nation’s population depends upon groundwater for its drinking water source when accounting for groundwater use for drinking water from public supply systems and from individual household water well systems. Using 2000 estimates, the percentage was 45.9%.

Source: NGWA