This report - Land Subsidence from Groundwater Use in California - is hot off the press. It was prepared by the consulting firm of Luhdorff and Scalaminini Consulting Engineers with support from the California Water Foundation.
I have not read this report but the pedigree is superb. I know two of the contributing authors well - Vicki Kretsinger Grabert (especially well) and Michael Carpenter; both are top-drawer hydrogeologists. The advisory group is extraordinary - most are from the U.S. Geological Survey. I personally know or know the reputation of Don Helm, Stan Leake, Charles Heywood, Francis Riley, Michelle Sneed, Thomas Holzer, and Steven Ingebritsen - they are exceptional.
I just have to post the classic 1977 picture of Dr. Joe Poland in the San Joaquin Valley.
Download CA_Land_Subsidence_GW_Use_April2014
Executive Summary
California’s groundwater is a vital resource for the state that provides water supplies for urban and rural areas, supports a large agricultural economy, and benefits fish and wildlife habitats
and ecosystems. Groundwater meets about 40 percent of the state’s water demands in an average year (DWR, 2014). During droughts when surface supplies are limited, groundwater offers a critical buffer, providing a higher percent of the state’s water supply. In 2014, it is anticipated statewide groundwater use will be closer to 65 percent because of the critical nature of this year’s drought.
Historically, groundwater has been pumped as needed in many areas of the state, often with little regard for the deleterious effects of over pumping. Over pumping is not sustainable in the long- term and can lead to a number of adverse consequences, including water-quality degradation; increased energy costs for groundwater pumping; costs for well deepening or replacement; impacts to nearby rivers and streams; and land subsidence. This report highlights the current and historical impacts of land subsidence in California due to groundwater pumping and makes recommendations for monitoring and assessment.
This report confirms that land subsidence in California is not just a historical occurrence, but that it is an ongoing problem in many regions. The report presents key examples of significant historical subsidence and current active occurrences of subsidence, including the impacts and costs.
There is no comprehensive land subsidence monitoring program in California. The information in this report was compiled from individual regional or local studies, which usually were initiated after substantial subsidence impacts had occurred. The most comprehensive evaluation of land subsidence in California occurred between 1954 and 1970, to assist with the construction of the state and federal water projects. Funding for this program ended when groundwater levels recovered after completion of the state and federal water projects. The lack of comprehensive subsidence monitoring has had costly consequences for the state.
The California Water Foundation’s (CWF) vision is for California to meet its 21st century economic and ecological water needs sustainably. The CWF supports innovative projects and policies that address today’s water challenges, bringing together experts, stakeholders, and the public to achieve long-term, science-based solutions for the future
This report presents the following: · Subsidence processes especially as related to groundwater extraction
· Locations of areas subsiding as a result of groundwater extraction in California
San Joaquin Valley
o Subsidence from groundwater extraction in the San Joaquin Valley has been called the greatest human alteration of the Earth’s surface.
o By 1970, subsidence of more than 1 foot had affected 5,200 mi2—more than half of the valley — and in some areas it had reached 28 feet.
o Over the past decade, subsidence has been identified in two regions in the San Joaquin Valley, including 3.94 feet during a 31⁄2 year period near Corcoran, California.
o Subsidence has caused major impacts to infrastructure and physical features, including the San Joaquin River, Delta Mendota Canal, Friant-Kern Canal and San Luis Canal, as well as numerous privately owned canals and related infrastructure such as turnouts, bridges, pipelines, and storm sewers.
o These costs, add up to a total estimated cost of more than $1.3 billion during 1955-1972 (2013 dollars). Subsequent cost data are mostly unavailable.
Sacramento Valley
o Subsidence in the Sacramento Valley has resulted in wide scale destructive failure of steel groundwater well casings, making wells sometimes unusable.
o From the locations of damaged wells during a drought in 1976-1977, the subsidence appears to stretch from central Colusa County, through Yolo County, to Dixon in Solano County.
Antelope Valley
o Subsidence in Antelope Valley, east of Los Angeles, has been occurring for over 80 years. Increased pumping in the last 30 years due to population growth has accelerated the groundwater level declines to as much as 300 feet in some areas.
o Subsidence has adversely affected runways at Edwards Air Force Base and caused other negative consequences such as increased flooding and erosion; failed well casings; and damage to roads, homes, and other structures.
Coachella Valley
o Subsidence in Coachella Valley, in Riverside County, paused after importation of surface water began in 1949, but resumed in the 1970s as population and groundwater pumping increased.
o Earth fissures formed in 1948 and again recently. A subsidence study of a portion of the Coachella Branch of the All American Canal showed that the canal subsided as much as 1.35 feet from 1995 to 2010.
Enjoy!
“It is better to offer no excuse than a bad one.” — George Washington
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