Eight trillion gallons of water per year — 12 million acre-feet — for more than three years.
That’s how much water California has lost so far, says Jay Famiglietti, senior water scientist for NASA’s Jet Propulsion Laboratory at the California Institute of Technology. He is also a professor of earth system science and civil and environmental engineering at the University of California.
For perspective, Famiglietti explains that 38 million Californians use about 10 million acre-feet of water per year for domestic and municipal use.
Worse yet, approximately two-thirds of California’s annual water loss is groundwater. As the state’s historic drought lingers, Famiglietti told participants at the recent annual meeting of the National Institute of Animal Agriculture, “We will be shifting to 100% groundwater.”
That’s notable, because the California water crisis serves as a microcosm of emerging reality across the nation and around the world. Fresh groundwater availability has declined for decades as population and water use increase, but few pay much attention unless it affects them directly.
Distinguishing between surface water and groundwater, and between freshwater and saline water, matters greatly in understanding the global water crisis and the one emerging in the U.S.
Surface water, as the name implies, is water existing in lakes, rivers, streams and the like. When these supplies run short, groundwater reserves — collected and retained by the earth — make up the deficit in many areas. Groundwater sources include aquifers and soil moisture.
Fresh water accounted for 86% of total water withdrawals in 2010, according to Estimated Use of Water in the U.S. 2010, a report from the U.S. Geological Society (USGS) — 75% of that from surface water. Saline water withdrawals were mostly seawater and brackish coastal water used for thermoelectric power.
U.S. water usage declines
Total water usage in the U.S. is decreasing even as the population increases, according to the same USGS source.
Total freshwater and saltwater use in the U.S. in 2010 was estimated by USGS at 355 billion gallons per day, which was 13% less than in 2005 and the least since 1970. USGS has conducted these studies every five years since 1960. Thermoelectric power and irrigation continue to be the primary water users.
Incidentally, livestock account for 1% of total usage. Keep in mind, that’s water for direct consumption. The livestock category excludes on-farm domestic use, lawn and garden watering, and irrigation water use.
Although total water usage in the U.S. declined, groundwater continues to be siphoned off at unsustainable rates. The cumulative depletion of groundwater in the U.S. from 1900 to 2008 of 1,000 cubic kilometers is about twice the volume of Lake Erie, according to the report Groundwater Depletion in the U.S. (1900-2008), from USGS. The report evaluates long-term cumulative depletion volume in 40 separate aquifers or areas and one land-use area.
“This large volume of depletion represents a serious problem in the U.S., because much of this storage loss cannot be easily or quickly recovered and affects sustainability of some critical water supplies and base flow to streams, among other effects,” according to the report.
The individual depletion assessments can be lumped into broader categories to help illustrate the magnitude of the problem. The three individual systems that represent the largest contributors to groundwater depletion in the U.S. from 1900-2008 are principal aquifers: the High Plains Aquifer (340.9 cubic kilometers), the Mississippi embayment aquifer system (182.0 cubic kilometers) and the Central Valley aquifer system of California (144.8 cubic kilometers).”
“The losses in Lake Powell and Lake Mead, as big as they are, the groundwater losses are six or seven times bigger — and that’s because there is no management and because no one is really paying attention,” Famiglietti says.
“Although groundwater depletion is rarely assessed and poorly documented, it is becoming recognized as an increasingly serious global problem that threatens sustainability of water supplies,” according to the USGS groundwater report. “Groundwater withdrawals in the United States increased dramatically during the 20th century — more than doubling from 1950 to 1975.”
Dust in the garden
Domestically, the salt in the domestic groundwater wound comes with the fact that some of the nation’s most agriculturally productive regions rely on groundwater.
California’s Central Valley, overlaying the Central Valley aquifer system, is one of the most productive agricultural regions in the world. It provides 8% of all food produced by the U.S. in terms of value (2002), Famiglietti says. It accounts for one-sixth of all irrigated land in the U.S. and accounts for one-fifth of U.S. demand for groundwater. The Central Valley Aquifer is the second-most pumped aquifer in the U.S. Groundwater depletion and subsidence have been documented here for decades.
Subsidence is a term used to describe ground sinking as groundwater is removed below it, like letting the air out of a bike tire, Famiglietti explains. Land in parts of California’s Central Valley is sinking as much as 1 foot per year. Imagine the challenges posed to infrastructure, including bridges, pipelines and aqueducts.
Producers in the High Plains are likely more familiar with the Ogallala Aquifer, which is the primary geologic formation within the High Plains aquifer system. The Ogallala Aquifer underlies the Great Plains in eight states, according to USDA. It supports nearly one-fifth of the wheat, corn, cotton and cattle produced in the U.S. It has served as the main water supply in the High Plains for years. Also according to USDA, it is being depleted at an unsustainable rate.
Agricultural productivity in both of these massive regions depends mightily upon the irrigation these aquifers provide. Plus, the climate in these areas appears to getting drier, rather than wetter, over time.
Whether or not mankind contributes to climate change is the source of all kinds of heated debate, not the fact that climate change occurs; logic and data say it’s been in a state of constant flux since time began.
“Climate models suggest that the wetter areas of the world are getting wetter, and the dry areas of the world are getting drier,” Famiglietti says. He explains the most credible science is telling us there are changes in freshwater availability, and also changes in the water cycle in terms of increased frequency, and intensity of floods and drought.
Looking at records going back to 1962 in the Central Valley, for instance, there is some groundwater recovery following drought, but even heavier usage in the next drought and so on.
In simple terms, draw a line coast to coast to split the United States into northern and southern tiers. By and large, the northern half is getting wetter and the southern half is getting drier. That’s based on data from NASA’s Gravity Recovery and Climate Experiment (GRACE) from 2002 to 2104. Water-storage changes are most negative in California, the South-Central Plains (worst is Texas and Oklahoma, but also New Mexico, Colorado and Kansas). Wetter areas include the Northern Plains and the Corn Belt.
“We’ve [California] been in overall decline for a long period of time, actually since we began pumping groundwater,” Famiglietti says. He explains that history indicates some groundwater recovery during wet periods, followed by more severe groundwater depletion in the next drought — more groundwater is depleted than recovered.
“This is happening all over the world,” Famiglietti says. He explains that groundwater accounts for as much as 33% of all water withdrawals globally. “Ironically, groundwater is poorly managed and monitored in many regions around the world, so that global water security is at far greater risk than is currently acknowledged,” Famiglietti says.
“Cumulative total groundwater depletion in the United States accelerated in the later 1940s and continued at an almost steady linear rate through the end of the century,” according to the USGS groundwater report.
Authors of this report also emphasize, “All of the quantitative calculations underlying the estimates of groundwater depletion are based on limited observed data, and assumptions and parameters values that contain uncertainties.”
That’s where GRACE comes in. Twin satellites launched in 2002 fly in line about 137 miles apart in a polar orbit about 310 miles above the earth. GRACE is a joint partnership between NASA in the U.S. and the German Aerospace Center in Germany.
Famiglietti explains that GRACE satellites continuously map the earth’s gravitational field by measuring groundmass via the gravitational tug on the two satellites. The more mass there is, the heavier the ground, and vice versa. The difference is water. In simpler terms, Famiglietti likens GRACE to a scale in the sky that tracks changes in water availability around the world.
“We can see areas gaining or losing water — changes in all of the surface water, snow, soil moisture and groundwater together,” Famiglietti explains. It doesn’t measure absolute amount, but change. Advanced computer models are also used to predict how freshwater availability may change in the future.
Until GRACE came along, groundwater data came mostly from USGS monitoring wells scattered across the U.S. The USGS Active Groundwater Network includes more than 20,000 wells measured at least once in the past 13 months.
Based on GRACE data, areas losing the most water are ice sheets in Greenland and Antarctica, and glaciers in places like Alaska and Patagonia. There are a lot of other red spots — places losing groundwater over time — in areas with aquifers, such as those in the U.S. mentioned earlier.
“Unfortunately, in those alpine regions of the world where the glaciers are melting, we will be seeing very serious water shortages in the future, and they will also drive food shortages and power shortages; we’re seeing it already in places like China and India,” Famiglietti explained in an earlier TED Talk.
“Ultimately, water will be limiting in all respects unless we learn to do a lot more with a lot less, and learn to reuse and reuse more and more, and to manage our way to a sustainable water future,” Famiglietti explains.
No one can simply end the growing water crisis here and around the world. “It’s too big. It’s too complex. We can’t beat it down or conquer it. We’ve passed too many tipping points with respect to climate change, population growth and human behavior to able to turn this very complicated situation around,” Famiglietti says.
“But, I firmly believe with shared vision, with the leadership and commitment of governments — our government and those around the world — and with public and private partnerships, if we work together, we can manage our way to ensure a sustainable water future.”
Editor's Note: Next in the series: The battle for societal understanding