Tectonic setting of the San Diego formation aquifer,considered for conjunctive use storage

Keller, B.; Ward, Alex C.

doi:10.1016/s0895-9811(01)00052-9

Cited by 3 publications

(6 citation statements)

References 6 publications

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“…The onshore volume of the SDF is estimated to be between 341 and 532 million m 3 (City of San Diego 2016). The estimated offshore volume of groundwater nearly doubles the total volume of the SDF which is consistent with predictions by Keller and Ward (2001).…”

Section: Discussionsupporting

confidence: 86%

“…Conversely, the paleochannels marked WPC, which run parallel and west of Silver Stand section 1, also appear to have been incised into the SDF, but the resistive anomalies remain intact below these paleochannels. This preservation of fresh-to-slightly-saline pore fluids within the SDF, despite the presence of overlying Depositionally, the SDF is a mixture of shallow marine and nonmarine sediment (Keller and Ward 2001). As a result, the SDF contains multiple fining-upward sequences, sandy marls, conglomerates, and clayey layers (Ellis 1919) which is evident in the anisotropic ratios generated from the final resistivity models.…”

Section: Discussionmentioning

confidence: 95%

“…The combination of increasing water demand and diminishing sources of imported water suggests that groundwater extraction from the SDF may increase, in particular to supply municipal water to communities in southwestern San Diego area (San Diego County Water Authority 2021). Groundwater extracted from the SDF could originate from naturally recharged precipitation, or alternatively, from aquifer storage and recovery, a method that involves artificial recharge of the SDF with excess water during periods of low water use followed by extraction of this water during periods of high-water use (Keller and Ward 2001).…”

Section: Introductionmentioning

confidence: 99%

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Identification of fresh submarine groundwater off the coast of San Diego, USA, using electromagnetic methods

et al. 2022

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Climate change has a pronounced effect on water resources in many semiarid climates, causing populated areas such as San Diego County (USA), to become more vulnerable to water shortages in the coming decades. To prepare for decreased water supply, San Diego County is adopting policies to decrease water use and to develop additional local sources of water. One new local source of freshwater is produced by a desalination facility that purifies brackish groundwater from the coastal San Diego Formation. This formation has been studied extensively onshore, but little is known about the geology or groundwater quality offshore in the adjacent continental shelf. Because most groundwater systems are interconnected and complex, further analysis is needed to identify offshore geology, possible sequestration of freshwater in the shelf, and potential pathways for saltwater intrusion. This comprehensive understanding is important because seawater intrusion may limit use of the San Diego Formation and longevity of desalination facilities. Controlled-source electromagnetic methods are uniquely suited to detecting offshore groundwater as they are sensitive to changes in pore fluids such as the transition from fresh to brackish groundwater. This paper describes results from surface-towed electromagnetic surveys that mapped the pore-fluid salinity and possible fluid pathways in the continental shelf off the coast of San Diego. The results indicate a considerable volume of fresh-to-brackish groundwater sequestered in the shelf, both in continuous lenses and isolated pockets, that appear influenced by fault systems and shallow stratigraphy.

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Section: Discussionsupporting

confidence: 86%

Section: Discussionmentioning

confidence: 95%

Section: Introductionmentioning

confidence: 99%

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Identification of fresh submarine groundwater off the coast of San Diego, USA, using electromagnetic methods

et al. 2022

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“…The groundwater system consists of a shallow, unconfined aquifer and a deeper, regional confined aquifer (Anders et al, 2013). Both of these aquifers are composed of coastal sediments that progressively filled in the pull-apart basin formed by regional faulting (Keller and Ward, 2001) due to changes in sea-level and uplift over geological time (Hanson et al, 2009). Although the groundwater flow characteristics and pathways are under-constrained, the flow direction is generally westward, and recharge to the regional system is assumed to occur to the east of the wells sampled for this study near the transition from steep volcanic surficial geology to more permeable sediments (Flint et al, 2012;Seltzer et al, 2019b).…”

Section: Overview Of δ 40 Ar and Hydrogeology In San Diego Groundwater Systemmentioning

confidence: 99%

The triple argon isotope composition of groundwater on ten-thousand-year timescales

Seltzer

Krantz

et al. 2021

Chemical Geology

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This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing this version to give early visibility of the article. Please note that, during the production process, errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.

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“…On average, San Diego must import nearly 90% of its water from other areas, specifically northern California and the Colorado River (City of San Diego 2011). Much of the coastal San Diego area overlies a pullapart structural basin formed by strike-slip faulting, with normal faulting on the lateral margins (Keller and Ward 2001). The major rivers cut obliquely across these tectonically active features, creating narrow valleys that are successively eroded and refilled with sediment in response to uplift and sea-level changes (Hanson et al 2009).…”

Section: Hydrogeologic Settingmentioning

confidence: 99%

A Geochemical Approach to Determine Sources and Movement of Saline Groundwater in a Coastal Aquifer

et al. 2013

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Geochemical evaluation of the sources and movement of saline groundwater in coastal aquifers can aid in the initial mapping of the subsurface when geological information is unavailable. Chloride concentrations of groundwater in a coastal aquifer near San Diego, California, range from about 57 to 39,400 mg/L. On the basis of relative proportions of major-ions, the chemical composition is classified as Na-Ca-Cl-SO 4 , Na-Cl, or Na-Ca-Cl type water. δ 2 H and δ 18 O values range from −47.7‰ to −12.8‰ and from −7.0‰ to −1.2‰, respectively. The isotopically depleted groundwater occurs in the deeper part of the coastal aquifer, and the isotopically enriched groundwater occurs in zones of sea water intrusion. 87 Sr/ 86 Sr ratios range from about 0.7050 to 0.7090, and differ between shallower and deeper flow paths in the coastal aquifer.3 H and 14 C analyses indicate that most of the groundwater was recharged many thousands of years ago. The analysis of multiple chemical and isotopic tracers indicates that the sources and movement of saline groundwater in the San Diego coastal aquifer are dominated by: (1) recharge of local precipitation in relatively shallow parts of the flow system; (2) regional flow of recharge of higher-elevation precipitation along deep flow paths that freshen a previously saline aquifer; and (3) intrusion of sea water that entered the aquifer primarily during premodern times. Two northwest-to-southeast trending sections show the spatial distribution of the different geochemical groups and suggest the subsurface in the coastal aquifer can be separated into two predominant hydrostratigraphic layers.

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Tectonic setting of the San Diego formation aquifer,considered for conjunctive use storage

Cited by 3 publications

References 6 publications

Identification of fresh submarine groundwater off the coast of San Diego, USA, using electromagnetic methods

Identification of fresh submarine groundwater off the coast of San Diego, USA, using electromagnetic methods

The triple argon isotope composition of groundwater on ten-thousand-year timescales

A Geochemical Approach to Determine Sources and Movement of Saline Groundwater in a Coastal Aquifer

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