Lahar Hazard Zones for Eruption-Generated Lahars in the Lassen Volcanic Center, California

U.S. Geological Survey (USGS) | September 25th, 2012

Lahars, Indonesian for volcanic mudflows or debris-flows, are a rapidly flowing mixture of rock debris and water that originates on the slopes of a volcano. Lahar generat

Lahars, Indonesian for volcanic mudflows or debris-flows, are a rapidly flowing mixture of rock debris and water that originates on the slopes of a volcano. Lahar generation requires an adequate source of water, abundant unconsolidated debris, steep slopes, significant relief, and a triggering mechanism (Vallance, 2000). Various triggering mechanisms include the rapid melting of snow and ice by pyroclastic flows, intense rainfall on loose volcanic rock deposits, a breakout of a lake dammed by volcanic deposits, and a debris avalanche.

Lake Lazarus: the strange rebirth of a Californian ecosystem

Nature Portfolio (Springer Nature) | November 12th, 2018

At the start of the twentieth century, Owens Lake in southern California was one of the largest inland bodies of water in the United States. By the mid-1920s, it was gone

At the start of the twentieth century, Owens Lake in southern California was one of the largest inland bodies of water in the United States. By the mid-1920s, it was gone, drained to provide water to a mushrooming Los Angeles. Over the past 30 years, the city has spent around US$2 billion to undo the damage. It has failed to restore the lake, but in The Spoils of Dust, Alexander Robinson describes how the effort has succeeded in another way: by creating a landscape no less valuable ecologically. By documenting the transitions the lake has undergone, he suggests a way forward for engineers, geologists, ecologists and landscape designers hoping to bring other environments back from the brink.

Lake Tahoe Nearshore Water Quality Protection Plan

California State Water Resources Control Board (SWRCB) | November 6th, 2014

In October 2013, the Desert Research Institute, UC Davis, and University of Nevada at Reno released the Lake Tahoe Nearshore Evaluation and Monitoring Framework Report (R

In October 2013, the Desert Research Institute, UC Davis, and University of Nevada at Reno released the Lake Tahoe Nearshore Evaluation and Monitoring Framework Report (Report) (NeST 2013). The Report presents a conceptual understanding of nearshore environment processes, assesses the heterogenic nature of the nearshore, highlights the lack of data available to characterize the environmental status of the Lake Tahoe nearshore, and emphasizes that current agency implementation efforts will benefit the nearshore environment. This Lake Tahoe Nearshore Water Quality Protection Plan (Plan) outlines the Lahontan Regional Water Quality Control Board’s (Regional Water Board) response to the changes in the Lake Tahoe nearshore environment as informed by the Report. Based on the Report findings and recommendations, the Regional Water Board will proceed with the following actions: (1) continue implementing programs that benefit nearshore environmental quality; (2) establish and implement an integrated nearshore monitoring plan to track change in the nearshore environment and track pollutant inputs to the nearshore; (3) evaluate localized “hotspots” where nearshore change has been documented and assess causes of observed degradation; (4) investigate climate change influence on nearshore water quality; and (5) assess the need for revised or new water quality standards to protect nearshore water quality. In establishing and maintaining nearshore water quality protection policies, the Water Board will continue to coordinate with other government agencies and the public. Because available resources are insufficient to fully implement all recommendations, a dedicated annual funding source must be found to adequately protect and enhance Lake Tahoe’s precious nearshore. The Plan elements and funding needs are presented in Attachment 1. The Plan also serves as response to a Legislative request in the 2012-2013 Budget Act specific to the Water Board’s approach to the nearshore.

Land subsidence along the California Aqueduct in west-central San Joaquin Valley, California, 2003–10

U.S. Geological Survey (USGS) | November 29th, 2018

Extensive groundwater withdrawal from the unconsolidated deposits in the San Joaquin Valley caused widespread aquifer-system compaction and resultant land subside

Extensive groundwater withdrawal from the unconsolidated deposits in the San Joaquin Valley caused widespread aquifer-system compaction and resultant land subsidence from 1926 to 1970—locally exceeding 8.5 meters. The importation of surface water beginning in the early 1950s through the Delta-Mendota Canal and in the early 1970s through the California Aqueduct resulted in decreased groundwater pumping, recovery of water levels, and a reduced rate of compaction in some areas of the San Joaquin Valley. However, drought conditions during 1976–77, 1987–92, and drought conditions and operational reductions in surface-water deliveries during 2007–10 decreased surface-water availability, causing pumping to increase, water levels to decline, and renewed compaction. Land subsidence from this compaction has reduced freeboard and flow capacity of the California Aqueduct, Delta-Mendota Canal, and other canals that deliver irrigation water and transport floodwater. The U.S. Geological Survey, in cooperation with the California Department of Water Resources, assessed more recent land subsidence near a 145-kilometer reach of the California Aqueduct in the west-central part of the San Joaquin Valley as part of an effort to minimize future subsidence-related damages to the California Aqueduct. The location, magnitude, and stress regime of land-surface deformation during 2003–10 were determined by using data and analyses associated with extensometers, Global Positioning System surveys, Interferometric Synthetic Aperture Radar, spirit-leveling surveys, and groundwater wells. Comparison of continuous Global Positioning System, shallow-extensometer, and groundwater-level data indicated that most of the compaction in this area took place beneath the Corcoran Clay, the primary regional confining unit. The integration of measurements strengthens confidence in individual measurement methods and provides the information at spatial and temporal scales that water managers need to design and implement groundwater sustainability plans in compliance with California’s Sustainable Groundwater Management Act. Measurements of land-surface deformation during 2003–10 indicated that the parts of the California Aqueduct closest to the Coast Ranges in the west-central part of the San Joaquin Valley were fairly stable or minimally subsiding on an annual basis; some areas show seasonal periods of subsidence and uplift that resulted in little or no longer-term elevation loss. Many groundwater levels in these areas did not reach historical lows during 2003–10, indicating that deformation nearest the Coast Ranges was likely primarily elastic. Land-surface deformation measurements indicated that some parts of the California Aqueduct that traverse farther from the Coast Ranges toward the valley center subsided. Some parts of the California Aqueduct subsided locally, but generally the California Aqueduct is within part of a 12,000-square-kilometer area affected by 25 millimeters or more of subsidence during 2008–10, with maxima in Madera County, south of the town of El Nido near the San Joaquin River and the Eastside Bypass (540 millimeters), and in Tulare County, west of the town of Pixley (345 millimeters). Interferometric Synthetic Aperture Radar-derived subsidence maps for various periods during 2003–10 show that the area of maximum active subsidence (that is, the largest rates of subsidence) shifted from its historical (1926–70) location southwest of the town of Mendota to these areas nearer the valley center. Calculations indicated that the subsidence rate doubled in 2008 in parts of the study area. Water levels declined during 2007–10 in many shallow and deep wells in the most rapidly subsiding areas, where water levels in many deep wells reached their historical lows, indicating that subsidence measured during this period was largely inelastic. Continued groundwater-level and land-subsidence monitoring in the San Joaquin Valley is important because (1) operational- and drought-related reductions in surface-water deliveries since 1976 have resulted in increased groundwater pumping and associated water-level declines and land subsidence, (2) land use and associated pumping continue to change throughout the valley, and (3) subsidence management is stipulated in the Sustainable Groundwater Management Act. The availability of surface water remains uncertain; even during record-setting precipitation years, such as 2010–11, water deliveries fell short of requests and groundwater pumping was required to meet the irrigation demand. In some areas, the infrastructure is not available to supply surface water, and groundwater is the only source of water. Because of the expected continued demand for water and the limitations and uncertainty of surface-water supplies, groundwater pumping and associated land subsidence remains a concern. Spatially detailed information on land subsidence is needed to minimize future subsidence-related damages to the California Aqueduct and other infrastructure in the San Joaquin Valley, as well as alterations to natural resources such as stream gradients, water depths, and water temperatures. The integration of data on land-surface elevation, subsurface deformation, and water levels—particularly continuous measurements—enables the analysis of aquifer-system response to groundwater pumping, which in turn, enables estimation of the preconsolidation head and calculation of aquifer-system storage properties. This information can be used to improve numerical model simulations of groundwater flow and aquifer-system compaction and allow for consideration of land subsidence in the evaluation of water resource management alternatives and compliance with the Sustainable Groundwater Management Act.

Land Subsidence along the Delta-Mendota Canal in the Northern Part of the San Joaquin Valley, California, 2003–10

U.S. Geological Survey (USGS) | November 19th, 2013

Extensive groundwater withdrawal from the unconsolidated deposits in the San Joaquin Valley caused widespread aquifer-system compaction and resultant land subsidence from

Extensive groundwater withdrawal from the unconsolidated deposits in the San Joaquin Valley caused widespread aquifer-system compaction and resultant land subsidence from 1926 to 1970—locally exceeding 8.5 meters. The importation of surface water beginning in the early 1950s through the Delta-Mendota Canal and in the early 1970s through the California Aqueduct resulted in decreased pumping, initiation of water-level recovery, and a reduced rate of compaction in some areas of the San Joaquin Valley. However, drought conditions during 1976–77 and 1987–92, and drought conditions and regulatory reductions in surface-water deliveries during 2007–10, decreased surface-water availability, causing pumping to increase, water levels to decline, and renewed compaction. Land subsidence from this compaction has reduced freeboard and flow capacity of the Delta-Mendota Canal, the California Aqueduct, and other canals that deliver irrigation water and transport floodwater. The U.S. Geological Survey, in cooperation with the U.S. Bureau of Reclamation and the San Luis and Delta-Mendota Water Authority, assessed land subsidence in the vicinity of the Delta-Mendota Canal as part of an effort to minimize future subsidence-related damages to the canal. The location, magnitude, and stress regime of land-surface deformation during 2003–10 were determined by using extensometer, Global Positioning System (GPS), Interferometric Synthetic Aperture Radar (InSAR), spirit leveling, and groundwater-level data. Comparison of continuous GPS, shallow extensometer, and groundwater-level data, combined with results from a one-dimensional model, indicated the vast majority of the compaction took place beneath the Corcoran Clay, the primary regional confining unit. Land-surface deformation measurements indicated that much of the northern portion of the Delta-Mendota Canal (Clifton Court Forebay to Check 14) was fairly stable or minimally subsiding on an annual basis; some areas showed seasonal periods of subsidence and of uplift that resulted in little or no longer-term elevation loss. Many groundwater levels in this northern area did not reach historical lows during 2003–10, indicating that deformation in this region was primarily elastic. Although the northern portion of the Delta-Mendota Canal was relatively stable, land-surface deformation measurements indicated the southern portion of the Delta-Mendota Canal (Checks 15–21) subsided as part of a large subsidence feature centered about 15 kilometers northeast of the Delta-Mendota Canal, south of the town of El Nido. Results of InSAR analysis indicated at least 540 millimeters of subsidence near the San Joaquin River and the Eastside Bypass during 2008–10, which is part of a 3,200 square-kilometer area—including the southern part of the Delta-Mendota Canal—affected by 20 millimeters or more of subsidence during the same period. Calculations indicated that the subsidence rate doubled in 2008 in some areas. The GPS surveys done in 2008 and 2010 confirmed the high subsidence rate measured by using InSAR for the same period. Water levels in many shallow and deep wells in this area declined during 2007–10; water levels in many deep wells reached historical lows, indicating that subsidence measured during this period was largely inelastic. InSAR-derived subsidence maps for various periods during 2003–10 showed that the area of maximum active subsidence (that is, the largest rates of subsidence) shifted from its historical (1926–70) location southwest of Mendota to south of El Nido. Continued groundwater-level and land-subsidence monitoring in the San Joaquin Valley is important because (1) regulatory- and drought-related reductions in surface-water deliveries since 1976 have resulted in increased groundwater pumping and associated land subsidence, and (2) land use and associated groundwater pumping continue to change throughout the valley. The availability of surface water remains uncertain; even during record-setting precipitation years, such as 2010–11, water deliveries have fallen short of requests and groundwater pumping was required to meet the irrigation demand. Due to the expected continued demand for irrigation supply water and the limitations and uncertainty of surface-water supplies, groundwater pumping and associated land subsidence is likely to continue in the future. Spatially detailed information on land subsidence is needed to facilitate minimization of future subsidence-related damages to the Delta-Mendota Canal and other infrastructure in the San Joaquin Valley. The integration of subsidence, deformation, and water-level measurements—particularly continuous measurements—enables the analysis of aquifer-system response to increased groundwater pumping, which in turn, enables identification of the preconsolidation head and calculation of aquifer-system storage properties. This information can be used to improve numerical model simulations of groundwater flow and aquifer-system compaction and allow for consideration of land subsidence in the evaluation of water-resource management alternatives.

Land Subsidence and Aquifer-System Compaction in the San Jacinto Valley, Riverside County, California

U.S. Geological Survey (USGS) | January 1st, 1976

Land subsidence caused by the East Mesa geothermal field, California, observed using SAR interferometry

American Geophysical Union (AGU) | April 15th, 1997

Interferometric combination of pairs of synthetic aperture radar (SAR) images acquired by the ERS-1 satellite maps the deformation field associated with the activity o

Interferometric combination of pairs of synthetic aperture radar (SAR) images acquired by the ERS-1 satellite maps the deformation field associated with the activity of the East Mesa geothermal plant, located in southern California. SAR interferometry is applied to this flat area without the need of a digital terrain model. Several combinations are used to ascertain the nature of the phenomenon. Short term interferograms reveal surface phase changes on agricultural fields similar to what had been observed previously with SEASAT radar data. Long term (2 years) interferograms allow the study of land subsidence and improve prior knowledge of the displacement field, and agree with existing, sparse levelling data. This example illustrates the power of the interferometric technique for deriving accurate industrial intelligence as well as its potential for legal action, in cases involving environmental damages. *Correction appended

Land Subsidence from Groundwater Use in California

California Water Foundation | April 5th, 2014

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

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. The purpose of this report is to summarize knowledge about the extent and costs of subsidence so that this information can be part of a larger discussion on sustainable groundwater management in California. This report confirms that land subsidence in California is not just an 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 1955 and 1970, to assist with the construction of the state and federal water projects. Funding for this program ended soon after completion of the state and federal water projects. The lack of comprehensive subsidence monitoring has had costly consequences for the state.

Land Subsidence from Groundwater Use in California (Summary Report)

California Water Foundation | April 5th, 2014

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

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. The purpose of this report is to summarize knowledge about the extent and costs of subsidence so that this information can be part of a larger discussion on sustainable groundwater management in California. This report confirms that land subsidence in California is not just an 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 1955 and 1970, to assist with the construction of the state and federal water projects. Funding for this program ended soon after completion of the state and federal water projects. The lack of comprehensive subsidence monitoring has had costly consequences for the state.

Land Subsidence in Santa Clara Valley, Alameda, San Mateo, and Santa Clara Counties California

U.S. Geological Survey (USGS) | January 31st, 1971