Parts of California are Sinking a Foot a Year

Since the 1920s, excessive pumping of groundwater at thousands of wells in California’s San Joaquin Valley has caused land in sections of the valley to subside, or sink, by almost 30 feet. This subsidence is exacerbated during droughts, when farmers rely heavily on groundwater to sustain one of the most productive agricultural regions in the nation. Once the land subsides it's capacity to hold groundwater cannot be restored.

from Vasco et al

Subsidence induced by groundwater depletion is a grave problem in California’s Tulare Basin, and while certainly not surprise, scientists at NASA have been alarmed by how much faster the areas of the San Joaquin Valley are sinking during this extended drought period. NASA found that sections of the Tulare Basin are sinking at a rate of about a foot a year.

Subsidence can also cause structural damage to the infrastructure we build on top of the earth- like roads, bridges, and pipes.  Often, permanently losing storage space for water as the earth compacts. A group of scientists supported by their various organizations combined the data from two orbiting satellite-based systems to monitor the variations within the Tulare basin at various timescales.

Using the Sentinel-1 Interferometric Synthetic Aperture Radar (InSAR) observations, which provide estimates of the displacements of the Earth’s surface, and terrestrial water storage changes measured from NASA’s Gravity Recovery and Climate Experiment (GRACE) and GRACE Follow-on (FO) missions the scientists were able to model the groundwater changes.

 However,  changes in the gravity field sensed by GRACE and GRACE-FO can be traced to a variety of sources such as ground movement, soil moisture, water table variations, and snow cover. Thus, it was  diffcult, if not impossible, for the scientists to distinguish between water mass changes in the shallow unconfined aquifer and in the underlying confined aquifer using gravitational observations alone.

Corcoran clay separates the shallower unconfined aquifer from the confined aquifer below. Recharge occurs in the unconfined aquifer from snow, runoff, and precipitation. Groundwater storage in both the unconfined and confined aquifers is detected by the GRACE satellites. Compaction, believed to occur predominantly in the confined aquifer, causes the displacement of the Earth’s surface measured by Sentinel-1 Synthetic Aperture Radar (SAR) satellites.

Though much more work needs to be done, results suggest that available Sentinel and GRACE satellite data can indeed monitor hydrological variations over time. With future improvements in observations, and additional satellites planned for 2023, there should be even better monitoring of the changes in the Tulare basin in the future.

Read the article here if you are interested.

Vasco, Donald W., Kim, Kyra H., Farr, Tom G., Reager, J. T., Bekaert, David, Sangha, Simran S., Rutqvist, Jonny Beaudoing, Hiroko K., 2022/03/09: “Using Sentinel-1 and GRACE satellite data to monitor the hydrological variations within the Tulare Basin, California,” Scientific Reports, 3867 vol 12 issue 1.

Mandatory Water Conservation in California

For the first time in its history California has instituted mandatory water use restrictions. After three years of below-normal rainfall, California is currently facing its third most severe drought in recorded history; however, water usage in California is significantly higher than in previous droughts, the rainy season has finished, and the drought continues with no end in sight. Currently, all the water reservoirs in California are at less than half their capacity.

Last January Governor Jerry Brown declared a drought emergency and called for voluntarily water conservation, hoping to cut use in the urban and suburban water districts by 20%; unfortunately by May it was clear that voluntary measures had produced only a 5% savings. So, on Tuesday, the California State Water Resource Control Board approved an emergency regulation to force water agencies and urban state residents to increase their water conservation.

The new water conservation regulation primarily reduces outdoor urban water use. The regulation, adopted by the State Water Board, mandates minimum actions for water agencies and consumers to conserve water supplies both for this year and into 2015. Most Californians (like most residents of arid states) use more water outdoors than indoors, up to 50% of daily water use is estimated to be for lawns and outdoor landscaping.

Under the emergency regulation, all Californians will be required to stop: washing down driveways and sidewalks; watering of outdoor landscapes that cause excess runoff; using a hose to wash a motor vehicle, unless the hose is fitted with a shut-off nozzle, and using potable water in a fountain or decorative water feature, unless the water is recirculated. The regulation makes an exception for health and safety circumstances.

The larger water supplier’s agencies will be required to activate their Water Shortage Contingency Plan to a level where outdoor irrigation restrictions are mandatory and track progress towards their conservation goals. In smaller communities where no water shortage contingency plan exists, the regulation requires that water suppliers either limit outdoor irrigation to twice a week or implement other comparable conservation actions.

“We are facing the worst drought impact that we or our grandparents have ever seen,” said State Water Board Chairperson Felicia Marcus. “And, more important, we have no idea when it will end. This drought’s impacts are being felt by communities all over California. Fields are fallowed; communities are running out of water, fish and wildlife will be devastated. The least that urban Californians can do is to not waste water on outdoor uses. It is in their self-interest to conserve more, now, to avoid far more harsh restrictions, if the drought lasts into the future. These regulations are meant to spark awareness of the seriousness of the situation, and could be expanded if the drought wears on and people do not act.”

from UC Davis-dry irrigation systems

This past spring water allocations to farmers and ranchers were reduced based on priority of water rights. The University of California at Davis Center for Watershed Sciences study released Tuesday found that the current drought has resulted in the greatest water loss ever seen in California agriculture, with river water allocated for Central Valley farms reduced by roughly one-third. Irrigated agricultural consumes over 75% of the delivered water in California, which produces about half of U.S. grown fruits, nuts, and vegetables. As farmers have shifted to higher value horticultural and orchard crops, they have adopted more efficient irrigation technologies to stretch their water allocations, but have grown more dependent on groundwater to ensure the survival of orchards. Groundwater pumping is expected to replace a significant portion of the river water losses, with some areas more than doubling the amount of groundwater used from last year.

More than 80% of this groundwater pumping occurs in the San Joaquin Valley and Tulare Basin. California produces about half of U.S. grown fruits, nuts, and vegetables, much of it from the central valley of California where three crops a year can be grown and crop production is only limited by the amount of water delivered for irrigation, the groundwater is used to increase irrigation waters making up an estimated of 30% of water for irrigation in a “normal” year. The groundwater aquifer is predominately non-renewable.

So much water has been pumped that the land above the aquifer has subsided and can never recover. The water level in these aquifers has fallen hundreds of feet in the past few generations and according to the UC Davis report cannot be sustained. According to Jay Lund the director of the Center for Watershed Sciences to ensure that there is groundwater to carry the region thought future droughts we need to properly manage this resource. California is the only state without a framework for groundwater management.

from UC Davis- Orchards left to die

California Groundwater in 2011

In 1995, the Pacific Institute published a report that summarized the condition of the water supply in California stating that “California’s current water use is unsustainable. In many areas, ground water is being used at a rate that exceeds the rate of natural replenishment…” In their 2005 the Pacific Institute published another report. Pointing out that water demand and use continued to exceed sustainable supply. Mining of groundwater unconstrained by environmental or ecological limits will doom California.

In addition to NGOs the State of California has routinely prepared water scenarios and projections as part of long-term water planning. The California Water Plan, a regular analysis published by the California Department of Water Resources (DWR) is the major guide book for water planning within the state. The latest version of the Plan was released for public review in January 2009 and stated: “We must adapt and evolve California’s water systems more quickly and effectively to keep pace with ever changing conditions now and in the future. Population is growing while available water supplies are static and even decreasing.”

In August 2009 the Environmental Water Caucus published California Water Solutions Now under a grant from the Goldman Institute pulling together a unified view and list of recommendations from a diverse group of stakeholders. The report points out that California’s state water agencies cannot report on how much water is actually being used, where it is being used, where it is being diverted to, how much is being diverted, or how many diversions are illegal. Where it does have such data, the State Water Board estimates that the number of illegal diversions may be over 40 % of the number of active permits and licenses, which also fails to comply with the law in many cases.

No one has publically questioned the conclusions of these studies, yet life went on as before with unsustainable water use in the Central Valley where massive surface-water diversions cannot meet all the agricultural and urban water demand and the groundwater has continued to be used to meet the deficit. California lacks the political will to balance their water budget, and nature is an unforgiving banker. Whenever you pump water from a well it has to be balanced by a loss of water from storage in the groundwater aquifer. Groundwater is recharged from rain and sources of surface infiltration. If too much water is pumped, water tables can drop in unconfined aquifers, water pressure fall in confined aquifers, surface water and ecology could be impacted and in some locations with fine grained soils compaction and subsidence can take place. Some of the storage capacity of the groundwater basins has been permanently destroyed.

According to U.S. Department of Commerce, California’s GDP (gross domestic product) was slightly more than $1.8 trillion in 2007. GDP is the value of all goods and services produced in California. According to the U.S. Department of Agriculture, USDA, the total value of the agricultural output from the state’s farms and ranches was $36.6 billion in 2007, up from $31.8 billion the year before. This means that crop, meat and dairy sales account for about 2% of the state economy. However, when you count all the secondary economic impacts: wine making and sales, chesse making, olive oil production, juice making, food processing and packing this number grows to 7.9% of the California economy.In terms of national agricultural output, $36.6 billion in revenue represents 12.8% of the U.S. total. The state accounted for 17.6 % of crops, and 7 % of the U.S. revenue for livestock and livestock products. California produces about half of U.S. grown fruits, nuts, and vegetables. Several of these crops are currently produced only in California and California agriculture is entirely dependent on irrigation. Over 75% of all surface water is diverted to agriculture. California does not have adequate water to meet the demands of the agricultural sector. California feeds much of the nation.

The U.S. Geological Survey’s (USGS) Groundwater Resources Program is conducting large-scale multiyear regional studies of groundwater availability in the United States. The USGS has found that the volume of groundwater stored in the earth is decreasing in many regions of the United States especially California. The extent of groundwater level declines across the United States has not been monitored before now. Our demands on the groundwater have increased and our understanding of groundwater has improved. It is now very clear we are running a groundwater deficit.
http://pubs.usgs.gov/circ/1323/pdf/Circular1323_book_508.pdf

In general the Sacramento Valley receives more precipitation than the San Joaquin Valley, which includes the San Joaquin and Tulare Groundwater Basins, and despite the surface water diversions from the Sacramento Valley they are using less groundwater than the drier San Joaquin Valley and the groundwater level as reported by the USGS Central Valley Ground Waster Study has remained fairly stable in the past few decades, falling less than 10 million acre feet of groundwater storage near the end of drought periods and making up that loss and more after wet periods. The Tulare Groundwater Basin at the southern most portion of the San Joaquin Valley has seen a loss of 70 million acre feet of groundwater storage since 1962. Half of this loss, about 35 million acre feet has taken place since 1985.

In the early 1960s, groundwater pumping caused water levels to decline to historic lows on the west side of the San Joaquin Valley, which resulted in large amounts of surface subsidence. In the late 1960s, the surface-water delivery system began to route water from the wetter Sacramento Valley and Delta regions to the drier, more heavily pumped San Joaquin Valley. The surface-water delivery system was fully functional by the early 1970s, and there was some groundwater-level recovery in the northern and western parts of the San Joaquin Valley where subsidence was limited. The Tulare Groundwater Basin, the hottest and driest part of the Central Valley, has continued to have declines in groundwater levels and accompanying depletion of groundwater storage. The limits of the water not the Sacramento budget problems might be the limiting factor in California’s future.