In a previous post, I discussed some of the issues of agriculture and water use in California. Though constantly stricken with water scarcity issues, California is a large agricultural supplier, with most of its operations concentrated in the Central Valley. In talking about agriculture and water use in California, it is impossible not to touch on issues of groundwater depletion.
Groundwater sits below the earth’s outermost surface, usually stored in rock formations called aquifers. When in abundance, it is relatively easy to drill a well into an aquifer and pump fresh water out of the ground. However this is no longer the case in the U.S. Groundwater is what you would call a common good or resource, meaning that if you dig a well on your land you are allowed to extract from it as much as you want. However, relying too much on that source of water has proved problematic. The Central Valley is a perfect example of everything that can go wrong when you over-pump groundwater.
The most obvious detriment of over-pumping groundwater is that the water is bound to run out. Well owners might not realize that the water they are pumping was stored there over thousands and thousands of years. It can quite simply run out if they are not careful to allow as much water to seep back into the aquifers as they are taking out. Groundwater also serves to “hold” the ground or soil at its normal level. If you extract all the water from underground, that support will no longer be there and the ground “subsides” or sinks. In some parts of the Central Valley, the land surface is sinking as much as a foot per year.
Land subsidence is problematic for a host of reasons: for example, land sinking or unevenness in an area can take a serious toll on infrastructure by sinking or cracking existing roads and bridges, which are expensive to rehabilitate. Another serious problem with land subsidence is that it makes saltwater intrusion more likely. As more water from the ocean or very deep underground saline water seeps into existing aquifers, that water becomes too saline to be viable for potable or agricultural uses. Thirdly, as that land subsides, the water-storage capacity under the surface shrinks too and the shrinkage can be permanent. This means that as aquifers get smaller, the groundwater capacity of the area in question permanently decreases.
Farmers are now resorting to drilling deeper and deeper to reach deeper layers of underground water since the outermost aquifers are running dry. Not only is this new practice expensive (prohibitively expensive for some), it also sends farmers into an “arms race” of sorts to get the water before someone else does—to the same detrimental effects mentioned above.
In California, water scarcity has contributed to contention between farmers for access to water ever since the state’s founding. Surface water is allocated to farmers according to water rights that date back to the stream of settlers that came in during the California gold rush in the second half of the 1800’s. Water rights work on a first-come, first-serve basis: the older your rights, the more priority you get over surface water (you can inherit or buy rights tied to a plot of land). This means that, even in “wet” years, farmers resort to groundwater to sustain their crops—especially if their rights to surface water are relatively new or “junior”. In that case, their access to surface water is more limited and very much so in times of drought.
However, farmers with junior water rights are not the only ones who are in trouble when the aquifers dry out. Land subsidence affects farmland no matter how senior the rights are. In fact, even with senior surface water rights, land subsidence affects how hard it is to get that water that you have rights to into your property. Usually gravity does the job, but if the land has sunk and is not level, pumps must be used to get water to where it needs to go. In addition, even farmers with the most senior rights usually get their allocations significantly cut during drought times, so they also rely on wells to compensate for those cuts.
In 2014 California joined the rest of the states in the arid and semi-arid Mid- and Southwest in passing legislation to regulate groundwater by enacting the Sustainable Groundwater Management Act. However, the legislation is fairly vague and its timeline is significantly drawn-out; it does not actually require agencies to meet a self-prescribed measure of sustainability until 2040. One detrimental aspect of the “arms race” of pumping water is that we might irreversibly affect the capacity of the land to store water in the future. Thus, we run the risk of compromising that potential by not taking more immediate action. In fact, there is no guarantee that by 2040 there will be any of our groundwater left.