7 March 2018
By Scott Tyler, AGU President-elect Hydrology Section and Professor in the Department of Geological Sciences and Engineering and adjunct Professor in the Department of Civil and Environmental Engineering at University of Nevada, Reno
This week marks the 19thannual National Groundwater Awareness Week, established in 1999 by the non-profit National Groundwater Association to bring public awareness to the water “beneath our feet.” The themes of this year’s awareness are “Tend, Test and Treat,” referencing the need to recognize the value and potential vulnerability of groundwater, the necessity of monitoring groundwater – both its quality and quantity – and finally to use our science and engineering to produce water that is appropriate for use. Surprisingly, the science of groundwater, or hydrogeology to many, is quite a “new” scientific and engineering discipline. While the earliest civilizations relied upon springs and aquifers, it is only in the last 100 years or so that the study of groundwater became a specialization unto itself. This in spite of the fact that groundwater is relied upon by more than 40% of the US population.
“Tending” to groundwater, i.e., managing groundwater resources requires a bit more creativity than monitoring the stage or level of a reservoir or river. The visuals of a bathtub ring around the local reservoir or flooding of a major river are pretty obvious indicators of the state of the water supply. But the old saying, “you don’t miss water until the well goes dry” is perhaps rather fitting for our perception of groundwater; it is out of sight, difficult to measure and always seems to be there! But that is beginning to change.
Groundwater has long been considered “drought proof” since aquifers respond much more slowly than to lakes, rivers and reservoirs to changes in rain and snowfall. But, after decades of accelerated mining of groundwater, what was once seen as a nearly unlimited resource, aquifers around the U.S. are showing signs of distress. While it used to be rare to see a center-pivot irrigation outside of arid states like Texas and Arizona; you can now see these systems – which draw on groundwater – being used to irrigate corn and soybeans in “wet” states like Michigan and the many of the nation’s major agricultural regions. I spoke with Dr. David Hyndman from Michigan State University, where he has been witnessing this shift in strategy in his own backyard as well as in the rest of the country. His team’s work on Central and Southern High Plains Aquifer (covering parts of Colorado, Kansas, Oklahoma, Texas and New Mexico) now clearly document that the current rate of groundwater extraction for agriculture is unsustainable as the pumping of groundwater is outpacing infiltration, but also as a result of our warming climate that is driving up the evapotranspiration demand of existing crops and croplands. Their modeling suggests that drops of as much as 60% in corn production are possible in this agriculturally rich region in the next 50 years. While the western U.S and parts of Central High Plains have regulated groundwater withdrawals to varying degrees, most of the “new” areas of groundwater-dependent agriculture have little to no experience or regulations on how to “tend” to groundwater supplies.
This trend is not unique only to North American as it is occurring on almost every continent on Earth. The shift to an increasing reliance on groundwater is pushing agriculture, and perhaps some cities, into a much more “brittle” operational mode. This was borne out in the most recent California drought. Beginning in the 1990’s California agriculture began looking away from agricultural systems that could allow fields to remain fallow during years of surface water drought. Thanks to the development of relatively unregulated groundwater drilling, growers instead moved to perennial crops and orchards that demands irrigation every year. As the drought progressed and groundwater levels began to fall, farmers had to race each other to deepen their wells. As with all races, this groundwater race had winners and losers with some farms failing as the resource diminished. To coin a phrase from the world of finance, groundwater is fast becoming the “lender of last resort” for many farms and municipalities in the US and around the world.
This week gives all of us at AGU and beyond, the opportunity to think how we “tend” to our groundwater whether as consumers of food produced with groundwater from around the world or locally in our own homes and communities where we may rely on groundwater for drinking. While it may not be the most fascinating cocktail party topic (groundwater hydrology falls somewhere between plumbing and rocket science), everyone drinks water and almost half of which is extracted from groundwater. You will find that most people do really want to know where their water comes from and, from an AGU earth and space science perspective, what is both above their heads and beneath their feet!