The water issue in my area- the bread basket of the world- is not going to get better. I copied the entire article as it is a very important assessment of our aquifer. Unfortunately, this is not the only American aquifer under threat.
The Ogallala Aquifer, also known as the High Plains Aquifer, is a vast yet shallow underground water table aquifer located beneath the Great Plains in the United States. One of the world's largest aquifers, it covers an area of approximately 174,000 mi² (450,000 km²) in portions of the eight states of South Dakota, Nebraska, Wyoming, Colorado, Kansas, Oklahoma, New Mexico, and Texas.
The Ogallala Aquifer was depleted at a rate of 26 cubic km (21 million acre feet) per year in 2000, which is slightly greater than the historical discharge rate of the Colorado River. As of 2005, the total depletion amounted to 253 million acre-feet (312 cubic km). Some estimates say it will dry up in as little as 25 years.
http://en.wikipedia.org/wiki/Ogallala_AquiferFeds document shrinking San Joaquin Valley aquiferCalifornia's San Joaquin Valley has lost 60 million acre-feet of groundwater since 1961, according to a new federal study. That's enough water for 60 Folsom reservoirs.
This is among the findings in a massive study of groundwater in California's Central Valley by the U.S. Geological Survey. It helps shed light on the mysteries and dangers of California's groundwater consumption, which is mostly unregulated.
According to the study, groundwater pumping continues to cause the valley floor to sink, a problem known as subsidence. This threatens the stability of surface structures such as the California Aqueduct, which delivers drinking water to more than 20 million people.
The Central Valley is America's largest farming region; it's also the single-largest zone of groundwater pumping. About 20 percent of groundwater pumped in America comes from under the Central Valley, said Claudia Faunt, the study's project chief.
In the Sacramento Valley, the study found groundwater levels have remained stable. Virtually all of the groundwater loss has occurred in the San Joaquin Valley, where aquifer levels have dropped nearly 400 feet since 1961, she said.
The current drought has aggravated this problem.
"In most years, especially in the San Joaquin Valley, the groundwater pumping exceeds the recharge," said Faunt, a USGS hydrologist. "With recent times, those groundwater levels have dropped back down close to historical lows."
The study is part of a project by the USGS to update groundwater data around the country that dates to the 1980s. USGS chose to begin in the Central Valley because the region is so important to the nation's food supply. The study took five years and cost $1 million.
California is the only state in which groundwater use is almost completely unregulated. California well owners are not required to report pumping or consumption patterns.
The study relied, in part, on indirect measurements. State monitoring wells provide a peek at regional groundwater behavior. Researchers also tapped into more than 8,500 well-drilling records dating back to 1900, as well as land-use patterns and surface water recharge data.
After 1900, when large-scale farming began in the Central Valley, water tables dropped significantly as wells were drilled to feed crops. Aquifers eventually dropped about 400 feet compared with pre-1900 levels. This was part of the impetus to build the state and federal canal systems in the 1960s that divert water from the Sacramento-San Joaquin Delta. Switching farms to this new surface water supply allowed aquifers to recover.
Then drought came in the late 1970s, and surface water diversions were cut back, as they have been during the current three-year drought. In both periods, farmers relied more heavily on groundwater, and aquifers declined again.
Between 1961 and 2003, the period covered by the new study, groundwater levels in the San Joaquin Valley fluctuated depending on drought, Faunt said. The current drought has caused aquifers to drop again by nearly 400 feet, to near the historic low.
"Overall, there's a loss in groundwater," she said, amounting to about 60 million acre-feet since 1961.
An acre-foot of water is enough to serve two average California households for a year. That groundwater lost from the San Joaquin Valley was enough for every California household for 10 years.
One consequence has been land subsidence over vast areas of the San Joaquin Valley. The most severe drop is about 29 feet near Mendota, which occurred before the canals were built, said Al Steele, an engineering geologist at the state Department of Water Resources in Fresno.
"That's a three-story building, almost," he said.
The land generally does not recover from this subsidence, and the compacted aquifer often loses its ability to store water.
It was assumed that subsidence had stopped after about 1970. But both Steele and Faunt said it has continued because of periodic droughts.
This threatens the 444-mile California Aqueduct, built in part to address groundwater shortages in the San Joaquin Valley.
As the Associated Press reported last week, officials recently learned that the canal may be subsiding due to modern groundwater pumping. As land subsides, the canal drops with it. This slashes the canal's water capacity by creating low spots, which reduce flow rate. It also could crack the structure.
"There's incomplete data that shows subsidence during periods when there is increased groundwater pumpage is alive and well," Steele said. "It's still occurring."
He said Caltrans land survey data shows highways 198 and 152 near Fresno have subsided "a number of feet" in the past four decades. How much the canal has subsided is unclear.
To find out, DWR hired USGS to monitor the canal by satellite.
The new USGS study also includes a mathematical modeling tool that can help water officials manage groundwater. This could help target the best locations for new groundwater banking projects and also could prevent land subsidence.
Officials could use the model to determine where and when groundwater pumping most threatens the canal. The state could then manipulate surface water delivery in those areas to prevent groundwater pumping.
Another option might be to stop farming in threatened areas.
http://www.sacbee.com/ourregion/story/2020696.htmlReaders who are interested in the full USGS report can obtain it for free as a pdf at
www.usgs.gov The citation is USGS Professional Paper 1766, 225 pages.