Land subsidence is not a new topic of discussion in California. It has been a part of California’s agricultural history ever since farmers introduced large-scale wells to pump groundwater from the Central Valley’s aquifers. In a very interesting photo, USGS Scientist Dr. Joseph F. Poland stood next to a telephone pole near Mendota, CA in 1977 to show the effects of land subsidence on the valley floor. As you can see in the linked picture, he put signs on the telephone pole noting where the land would have been in 1925, 1955, and 1977. Dr. Poland’s analysis determined that the valley floor in that area fell approximately 8.93 meters (over 29 feet!) between 1925 and 1977 when he took that picture. Unfortunately, after a century of pumping in the Central Valley, little has yet changed to make the process more sustainable.
The unprecedented drought that California has experienced for almost five years has only increased the amount of groundwater pumping in the Central Valley. A recent NASA study confirmed what other scientific and anecdotal evidence pointed to – that groundwater pumping in some areas of the Central Valley since the start of the current drought caused some of the fastest recorded rates of land subsidence. In some areas of the Central Valley, the study identified areas where the land was sinking at a rate of 2 inches per month. Land subsidence presents some critical economic and sustainability challenges in both the short and long-term.
While at present little can be done to stop groundwater pumping in unadjudicated basins in California, the groundwater legislation passed last year aims to begin focusing on the over-pumping of groundwater in many areas across the state. State water officials have paid recent attention to the most critically overdrafted groundwater basins, releasing a draft report of the areas facing the worst records of groundwater depletion. The basins on this list will be the first areas mandated to implement a groundwater sustainability plan as part of the new groundwater legislation. But can these groundwater plans be implemented without causing major economic impacts to the communities in these areas? I will address this topic in this post.
California’s Most Critically Overdrafted Groundwater Basins
Last week, the State Department of Water Resources (DWR) issued a preliminary report of the most critically overdrafted groundwater basins across the state. (View the map of these basins here.) The report is part of the Department of Water Resources’ Bulletin 118, a comprehensive report of groundwater conditions throughout the state. DWR first published Bulletin 118 in 1980, and updated it again in 2003. Bulletin 118 provides a comprehensive report of approximately 515 basins and sub-basins across the state, providing information about basin geology, groundwater quantity and quality, and the current state of groundwater management practices within the basin. It also categorized the basins DWR considered in a critical state of overdraft. A basin in critical overdraft is defined as “when continuation of present water management practices would result in significant adverse overdraft-related environmental, social or economic impacts.” The areas that the state has identified as critically overdrafted face this dilemma as unprecedented drought conditions force water users to rely further on already stressed groundwater supplies.
Unsurprisingly, groundwater basins in the Central Valley stretching from Bakersfield to Stockton are considered in critical overdraft. Regular readers of the Hydrowonk Blog will also not be surprised to know that areas of San Luis Obispo (SLO) County are designated as in critical overdraft. Earlier this year, Rod Smith wrote a post about the water situation in SLO County, concluding that the significant increase in planted vineyard acreage in tandem with a worsening water supply only exacerbated the already tenuous water supply challenges in the area.
Other critically-designated areas may not immediately come to mind as places with severe groundwater challenges. The Pajaro and Soquel Valleys near Santa Cruz and Watsonville are on the list. Coastal agriculture in the area caused increased pressure on the groundwater supplies, and saltwater intrusion (caused when too much fresh groundwater near the ocean is pumped out and saltwater fills the void) became a problem in areas of the basin particularly along the coast. In 1984, a group of local stakeholders formed the Pajaro Valley Water Management Agency to address the issue of critical overdraft in the basin. The 2015 draft report however still identifies the basin as one in critical overdraft. In Southern California, basins around Oxnard, Santa Barbara, and the Borrego Valley in San Diego and Imperial Counties also made the critically overdrafted list.
Groundwater Pumping Causes Clear Challenges, but are there Clear Solutions?
While to the naked eye a drop of 2 inches on land in the Central Valley may be imperceptible, the negative effects of over-pumping of groundwater are much more visible. The sinking ground in the Central Valley is wreaking havoc on the surface water infrastructure that ironically was designed to help relieve the over-use of groundwater supplies. When the ground sinks as a result of over-pumping, roads, aqueducts, and other infrastructure that the communities in the area relies upon can buckle and crack. As subsidence increases in pace and severity, the negative effects continue to show up. For example, US News and World Report pointed to an area outside of Firebaugh (where President Obama visited in February, 2014 to discuss the drought) as a tell-tale example of land subsidence. The Russell Avenue Bridge over the Delta-Mendota Canal, a major aqueduct running through the Central Valley, has sunk to the point where the water in the canal is touching the bottom of the bridge. When the bridge was first built, workers were able to get a small boat under the bridge for inspections and repairs. Now because of land subsidence, the bridge will have to be raised to get the deck above the level of the water.
Water officials across the state have pointed out the need to act immediately on the over-pumping of groundwater. Lester Snow, the Executive Director of the California Water Foundation said, “As long as this [subsidence] continues, we risk further damage to roads, levees and buildings. There is no time to waste.” However, even the new groundwater law enacted last year will not attain immediate results. Basins in critical overdraft will have until 2020 to complete a groundwater sustainability plan; other lower priority basins that have to create a sustainability plan will have until 2022 to complete it. In the interim, legislation to increase groundwater conservation may be in the works.
When Governor Jerry Brown spoke on Meet the Press in late August, he implied that his administration would ramp up groundwater regulations beyond the legislation passed last year, but he gave few details on how this would be done. Governor Brown said, “California now has groundwater management for the first time in its entire history, so we are much more aggressive,” than in years past. “And we will be stepping it up year by year.” Will lawmakers in Sacramento introduce legislation to more aggressively control groundwater usage?
Despite the increased scrutiny on groundwater since the passage of last year’s legislation, the process will take many years to implement sustainability plans and many more years to see actual results from the plans. While the issue of groundwater over-pumping cannot be reversed in a day, our policymakers have to look to alternative ways to provide water supplies. Farmers rely on groundwater during the drought because there are limited surface water supplies. We can supplement our water supplies with further water storage projects and stormwater capture during times of plentiful rainfall. But at some point, during a drought, there will be less water supplies than what our farms and communities demand. At that point, the free market should sort out the highest and best use for these limited water resources.