So we all know that California is going through an intense drought. Yet, what may be surprising to learn is that the state is an agricultural powerhouse and provides the rest of the country with the majority of their fruits and a third of their vegetables. How is this possible? Well, the answer is simple: Groundwater.
Groundwater is defined as the water held underground in the soil or in pores and crevices in the rock. It is usually stored within permeable underground rocks known as aquifers, and in the case of California, 515 groundwater basins account for 38-46 percent of the total water used by the population. While these freshwater sources are invaluable in addressing our population’s needs, they are currently under threat of being depleted entirely.
Aquifers in the Central Valley, Colorado River Basin, and the Great Plains have undergone extreme degradation in recent years, because the amount of groundwater being withdrawn from them annually is not being replenished at the same rate. For example, NASA found that between 2004 and 2013, the Colorado River Basin lost 15.6 cubic miles of water, more than 75 percent of which was groundwater. In the Central Valley, it has been documented that wells must now be drilled twice as deep as in previous years (1000 feet) in order to strike water. Regarding the Ogallala aquifer, which underlies eight states in the Midwest, water levels in some areas have dropped up to 15 feet in the last ten years alone. Much of the depletion is attributed to the droughts that have been affecting the country in recent years. For example, as surface waters such as rivers and lakes are degraded, people have begun relying more and more on the previously untapped reserves of water underneath the surface to meet their growing needs. The question is, how have we been allocating these water sources and what are the consequences?
A recent study from 2012 determined that over half of nationwide groundwater depletion is from irrigation alone. When one considers the nature of groundwater replenishment, and that it occurs with the successful seepage of precipitation into the pores of the aquifer, it is clear that this is a problem. This is because California is currently experiencing a massive drought and the Midwest has been quite dry as well. For the millions of gallons that are drawn out of the aquifers in order to keep crop production high, water is not going back into them. The same study found that if this trend continues, 35% of the southern High Plains will be unsuitable for agriculture within 30 years. As serious as this example is, it does not represent just how bad this problem can become, and how ubiquitous it will be in different areas of our lives.
When an aquifer is depleted, it means that the water table is lower than it was originally, or then it would be if the aquifer was managed sustainably. This allows for land subsidence to occur. Subsidence is when land sinks, which happens above aquifers because the water table is no longer supporting the area. When the land sinks, it immediately removes the space between the water and itself, which effectively removes that area from the aquifer’s storage reserves. In simple terms, subsidence makes aquifers smaller, so that in future years, they will store less water than what was previously possible. In the context of the droughts that have been rolling across the country, increased dependence on aquifers for irrigation leads to a decreased ability to store water, and in the event of another drought, it will automatically be worse. This is because a reduced storage capacity means that even if people pump out the same amount of water as they have before, the water table will fall much more quickly during the next extremely dry weather event (less water to begin with).
As our dependence on aquifers increases, there is a direct, negative relationship to the quality of the water. Most of the aquifers contain a certain amount of saline groundwater. Usually a clear boundary exists between this saltwater and the freshwater, but as the freshwater is pumped to the surface and the water table is lowered, these disturbances can cause saltwater intrusion. These intrusions can completely contaminate the freshwater supply and cost millions in damages.
Another side to economic problems associated with aquifer degradation is that our overuse of this resource becomes very costly in the long run. As I mentioned above, in California for example, wells must now be drilled 1000 feet into the ground instead of the previous standard, which was 500 feet. Some estimates place this cost at upwards of $300,000 dollars per well. These wells may need to be redone in future years as well, as the water table dips below each benchmark. Eventually, they may simply run dry, and farmers, to mention just one of the groups impacted, will no longer be able to support their crops.
All in all, groundwater overuse and abuse is an issue that we cannot afford to ignore. It will affect our agriculture, personal water use, economic prospects, and environment, among other things. Considering its impact on groundwater reserves, we need to seriously evaluate the ways in which we support our agriculture and make changes. For example, drip irrigation is much more efficient than flooding fields but flooding fields is much less labor intensive. Water intensive crops are also grown in dry areas, usually because they are highly profitable. Water rights are also not clear in all states; someone may own the land, but cannot own the water. This allows people to shirk responsibility over sustainable water usage while also over allocating the amounts.
Policies will need to be enacted to change habits and practices such as those listed above, monitor our use of groundwater, and ensure that it is as efficient and sustainable as possible. Otherwise, we risk destroying one of the most fundamental systems on which our nation relies.