Some Utah County residents are worried that the valley's inhabitants have borrowed more than they can pay back.
In the past few dry years, Utah County has drawn heavily on its underground water reserves. Experts say if levels get too low, the storage system will be permanently damaged, but they believe there is no cause for alarm yet."Water between the underground sand and gravel supports a large proportion of the weight of the land," Jim Wells, assistant state engineer for the Utah Lake-Jordan River area, said. "If you took too much water out, the overlying material would press down and the surface would subside.
"We have been taking more water out than was put back in by nature for the last few years. The water level has dropped about 15 feet over three or four years. A few wet years would bring the levels back up.
"The effects on the earth are only irreversible when you get compaction and lose storage space, and we are not aware of any subsidence in Utah County yet."
Subsidence occurs when portions of the land surface begin to sink. Settling can cause expensive damage to buildings on the compressed land, as well as reducing underground water storage area.
About 30 million acre feet of water is under Utah County, but only a third of that is recoverable, Wells said. The rest of the water is too tightly held to be extracted. (An acre foot is the amount of water it takes to cover 1 acre with a foot of water - 325,900 gallons.)
Farmers in the Vineyard area, partly in Orem and partly unincorporated, have noticed the levels of well water dropping over the past few years. They fear the level of underground water is dropping too low for their wells to reach, and perhaps low enough to threaten subsidence similar to what has occurred in Florida, Texas and southern Utah.
"We are taking out more water than nature is putting back in," said Rulon Gammon, spokesman for the Vineyard residents. "It is creating problems for Vineyard, but soon it will create problems for everyone."
Engineers believe Vineyard's problem is a local one, possibly caused by pumping of large municipal wells in nearby cities. Large wells can drain an area faster than water can move through the sand and gravel of the aquifer to refill it. Earth surrounding nearby wells can be also be drained.
Northern Utah County alone has an estimated 4,000 wells. Some are pumped all year, but most are pumped only in the dry summer months when water from the mountain snowpack is gone.
The Wasatch Front's supply of groundwater is much greater than the contents of the Great Salt Lake and Utah Lake combined, according to U.S. Geological Survey information.
Groundwater has many advantages over surface water. It is a more dependable source of water during droughts. It is generally available where needed; surface water may need to be moved great distances from the source to where it is needed.
Groundwater is less vulnerable to contamination and pollution and to upset caused by a natural disaster, such as an earthquake, that might shift waterlines.
But although water cannot leave the Earth, it could leave the spots where Utah needs it.
"The Earth has a finite supply of water that recycles," Joe Gates, chief investigator for Utah's U.S. Geological Survey office, said. "Water evaporates from the oceans, moves through the air, then rains down onto the ground and into streams. Water removed from the ground in great quantities would stay in this system but might not re-enter the ground in the same places or in the same quantities."
Gates said large-scale pumping could also contaminate underground reserves.
"Most pollution is in shallow water, and wells usually pump from deep reserves. If we pump too much, we could draw shallow waters down, and send with it the contamination. We've been pretty lucky, the way towns have developed."
Groundwater moves downward near the mountain recharge area, Gates said. Shallow water contaminated there would travel down and contaminate deeper reserves. Luckily, the area near the mountains is usually residential, so unless the residents use lots of chemical fertilizers, there is not much threat, he said.
Further into the valley, underground structure makes water travel upward, Gates said. Pollution from industry and landfills may contaminate shallow water, but that water doesn't mix with deeper reserves.
"A landfill near the mountains would create a problem.
"It's a very complicated system; all water supplies are interrelated. But we have been really lucky, the way Utah's valleys have developed. There are problems in isolated areas, but over the state as a whole, there hasn't been a drastic drop in groundwater quality."
Gates said tests have found evidence of contamination in Utah.
"There is an artesian well in a park near downtown Salt Lake City that people have used for years. Our tests showed the quality was stable until the 1960s, about when we started salting the roads. Now the well has more chloride. It's still not much, but it's double what was there 25 years ago."
But Gates said there is no evidence enough water has been removed from the ground to make changes in flow directions or to threaten subsidence.
"Ideally, we would not take more out than is put in over the long term. That is the trick. But water levels go up and down in isolated areas in different years. Overall, there is no indication of a long-term drop in Utah County's underground water levels."
Gallons of water used to produce various items
Wheat for loaf of bread 301.2
Tank op gasoline 401.7
Pound of beef 4,016.6
Ton of alfalfa 200,830
Source: "Encounter with Our Earth, Canfield Press, 1975