Could California have a lot more water supplies than anyone expected? It is an intriguing theory that caught some significant press attention last month, including an in-depth article in The Washington Post. Scientists at Stanford contend that California has vast amounts of water trapped deep underground at depths of 1,000 to 10,000 feet below parts of the Central Valley. Their calculations estimate that California has approximately 2,700 cubic kilometers of freshwater at these depths, which equates to about 2.22 billion acre-feet! (For conversion of cubic kilometers to acre-feet, each cubic kilometer of water is about 810,714 acre-feet.)
For parched California, this could be an interesting potential source of water if it were sustainably and economically recoverable. According to data from the most recent US Drought Monitor, the entire state of California is back under some form of drought. Extreme and exceptional drought still cover 42.8% of the land area. As we enter into the fifth year of drought, while some of the state’s reservoirs have recovered last winter, there is still much uncertainty about water supplies going forward. Water conveyance through the Delta remains challenging due to the Delta smelt and other endangered species. New regulations related to the implementation of the Sustainable Groundwater Management Act will add further uncertainty to many communities’ groundwater supplies. In this context of regulatory and water supply uncertainty, it is a welcome sight to find a new potential water supply. However, I believe that there are some practical, economic and regulatory hurdles that will make it unlikely that California will capitalize greatly on this water source. In this post, I will address some of the main reasons why this water source is an unrealistic source of significant supply. In my post next week, I will discuss what other more economical alternatives may be and where in the US they might be implemented.
A “new” source of supply in California
In drought-parched California, every drop of water counts. Increased demands for population growth, agriculture and environmental protection will ensure that water supplies in the future will remain tight. Truly finding new water supplies in the current environment in California could help to alleviate the strains on the Delta, the environment and existing water infrastructure. Needless to say, if this new water supply was substantial, it could be a game changer in California. At Stanford University’s Woods Institute for the Environment, researchers used data from 938 oil and gas pools and more than 35,000 oil and gas wells to estimate the amount of groundwater in 8 counties. (Data came from Los Angeles, Ventura, Santa Barbara, Kern, Fresno, Solano, Yolo and Colusa Counties.) The research concluded that the Central Valley’s groundwater reserves may contain three times the volume than previously estimated, or approximately 2.2 billion acre-feet of water supplies.
Why such a huge jump from the original estimates? The Stanford team found that the well data that the original estimates from the US Geological Survey relied upon were in some instances decades old and almost exclusively accounted for water within 1,000 feet of the ground surface. However, as the drought continues and many agricultural areas rely more on groundwater supplies, land owners and cities are tapping into water at depths greater than 1,000 feet. For example, in 2013, Central Valley cotton producer JG Boswell installed five wells each to a depth of 2,500 feet. These wells are as tall as two Empire State Buildings stacked on top of each other! Study co-author Robert Jackson at the School of Earth, Energy and Environmental Sciences said, “Water a thousand feet down used to be too expensive to use. Today it’s used widely.” The authors of the study determined that because of deep groundwater’s more widespread use, revised estimates of water supplies from this source should be considered. To put this newly estimated amount of water into context, the two largest surface water supply projects in California, the Central Valley Project and the State Water Project deliver a maximum of about 9 million acre-feet and 4.2 million acre feet respectively annually in a 100% allocation year. So if this deep groundwater supply theoretically could be tapped without harm, it could provide the equivalent of 168 years of full entitlement from both of these projects! But while it may be tempting to think that this newly estimated supply of groundwater can help to alleviate the water supply challenges in California, the reality is that much of this resource maybe challenging to tap for a variety of reasons.
The challenges of using this water supply
While it may be tempting for water officials to get excited about the potential discovery of billions of acre-feet of “new” water, there are some practical, economic and regulatory considerations that will make the widespread use of this water unlikely. These challenges may prevent this supply from seeing widespread use. First, pulling water from deep underground does not make economic sense in most instances. The drilling costs alone to install deep wells to reach these supplies can reach into the millions. In 2014, the City of Corcoran in the Central Valley had to spend $2.5 million in emergency funds to drill a 1,800 foot deep well, buy pumps and build extra pipelines after its municipal wells which at the time were between 400 and 1,000 feet deep began to fail. The well-drilling contract alone added up to $731,410. Once the well is in place, electricity costs will run higher to pull water from these depths, and those higher electricity costs will be paid over the entire useful life of the well. Further, water at these depths has varying levels of salinity, but portions of this supply is too salty to drink or use on crops as-is. If water districts were seriously interested in using this water source, they would have to invest in desalination systems to make the water usable, adding another layer of cost.
Second, the use of deep groundwater presents some serious sustainability challenges. Some basins that the Stanford study reviewed, particularly in Fresno and Kern Counties are on the State Department of Water Resources’ list of critically overdrafted groundwater basins. According to a 2015 Jet Propulsion Laboratory/NASA report, areas in the Central Valley including parts of the Stanford study area have experienced land subsidence at the rate of almost a foot a year during the drought. The subsidence could increase if we start extracting more water from these overdrafted basins.
Finally, regulatory hurdles would likely limit the widespread use of deep groundwater resources, particularly as it relates to the Sustainable Groundwater Management Act (SGMA). The SGMA legislation, passed in 2014 will create groundwater sustainability agencies to manage basins that the State Department of Water Resources deems either high or medium priority. Groundwater basins that are designated in critical overdraft will have to implement a groundwater sustainability plan (GSP) by January 31, 2020. All other medium and high priority basins will have to complete the sustainability plan by January 31, 2022. (see a full timeline of deadlines and implementation steps here) The state identified basins that need GSPs because their groundwater resources in most instances are not currently being managed sustainably. So it is likely, particularly in parts of the Central Valley, that groundwater pumping will decrease from current levels. The new regulatory framework implemented under SGMA likely will not allow widespread use of this resource particularly once groundwater sustainability plans are in place.
What to Make of the Study?
Study co-author Robert Jackson said, “For someone looking deep underground for water, it presents an opportunity and some risk. Nothing we found changes the observation that we have been pumping groundwater at rates that are completely unsustainable. We’re not advocating the use of this groundwater, but just identifying it.” This quote puts the findings and limitations of the study into good context. It is beneficial to have data about California’s aquifers, and the study certainly expanded our knowledge of the hydrology of the deeper parts of the Central Valley’s aquifers. However, I believe some of the media coverage on the topic was too quick to categorize this water as broadly usable. Also, with implementation of the SGMA, California’s groundwater regulations are slowly shifting towards greater sustainability, especially in areas that already have overdrafted aquifers. While there may be some instances where this water is usable, there are economic, practical and regulatory complications that will likely make this water unavailable in most instances.