Geostatistical analysis of tritium, groundwater age and other noble gas derived parameters in California

Visser, A.; Moran, J. E.; Hillegonds, D. J.; Singleton, Michael; Kulongoski, Justin T.; Belitz, Kenneth; Esser, Bradley K.

doi:10.1016/j.watres.2016.01.004

Cited by 34 publications

(35 citation statements)

References 107 publications

(116 reference statements)

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“…In addition, managed aquifer recharge operations leave a distinguishable fingerprint in dissolved noble gas concentrations (Cey et al, ) with a larger excess air component. Groundwater recharge temperatures and excess air concentrations were derived from the dissolved concentrations of all atmospheric noble gases (He, Ne, Ar, Kr, and Xe) using the unfractionated air (UA) model (Visser et al, ). Excess air is expressed as ΔNe, defined as

ΔNe = ((), \frac{{Ne}_{sample}}{{Ne}_{equilibrium}} - 1) \times 100 %,

where Ne samples and Ne equilibrium are the concentrations of neon in the sample and in equilibrium with the atmosphere at the elevation and estimated recharge temperature, respectively.…”

Section: Study Area Methods Data and Analysismentioning

confidence: 99%

“…Samples were collected by LLNL or United States Geological Survey (USGS) staff and analysed for dissolved noble gas concentrations at LLNL (Ekwurzel, ; Visser et al, ). Noble gas derived parameters (excess air and recharge temperature) were based on the UA model (Visser et al, ). Samples were analysed for tritium at LLNL (Clarke, Jenkins, & Top, ; Surano et al, ) and the USGS (Thatcher, Janzer, & Edwards, ) and for stable isotopes by LLNL or the USGS (Kendall & Coplen, ).…”

Section: Study Area Methods Data and Analysismentioning

confidence: 99%

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Importance of river water recharge to the San Joaquin Valley groundwater system

Visser

Moran

Singleton

et al. 2018

Hydrological Processes

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Groundwater is not a sustainable resource, unless abstraction is balanced by recharge. Identifying the sources of recharge in a groundwater basin is critical for sustainable groundwater management. We studied the importance of river water recharge to groundwater in the south‐eastern San Joaquin Valley (24,000 km2, population 4 million). We combined dissolved noble gas concentrations, stable isotopes, tritium, and carbon‐14 analyses to analyse the sources, mechanisms, and timescales of groundwater recharge. Area‐representative groundwater sampling and numerical model input data enabled a stable isotope mass balance and quantitative estimates of river and local recharge. River recharge, identified by a lighter stable isotope signature, represents 47 ± 4% of modern groundwater in the San Joaquin Valley (recharged after 1950) but only 26 ± 4% of premodern groundwater (recharged before 1950). This implies that the importance of river water recharge in the San Joaquin valley has nearly doubled and is likely the result of a 40% increase in total recharge, caused by river water irrigation return flows and increased stream depletion and river recharge due to groundwater pumping. Compared with the large and long‐duration capacity for water storage in the subsurface, storage of water in rivers is limited in time and volume, as evidenced by cold river recharge temperatures resulting from fast infiltration and recharge. Groundwater banking of seasonal surface water flows and expansion of managed aquifer recharge practices therefore appear to be a natural and promising method for increasing the resilience of the San Joaquin Valley water supply system.

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ΔNe = ((), \frac{{Ne}_{sample}}{{Ne}_{equilibrium}} - 1) \times 100 %,

where Ne samples and Ne equilibrium are the concentrations of neon in the sample and in equilibrium with the atmosphere at the elevation and estimated recharge temperature, respectively.…”

Section: Study Area Methods Data and Analysismentioning

confidence: 99%

Section: Study Area Methods Data and Analysismentioning

confidence: 99%

Importance of river water recharge to the San Joaquin Valley groundwater system

Visser

Moran

Singleton

et al. 2018

Hydrological Processes

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“…This simplest excess air model was used in order to avoid bias in derived parameters resulting from the choice of the excess air model [23,25]. Data reduction followed the methods described in [27].…”

Section: Sample Collection and Data Reductionmentioning

confidence: 99%

“…Because of their conservative behavior in groundwater, the concentration of noble gases, especially the heavier gases whose solubilities have the strongest temperature dependency, can be used to deduce groundwater recharge temperature [28]. After measured noble gas concentrations are corrected for 'excess air' [26], recharge temperatures are typically calculated using an assumed pressure (often the atmospheric pressure at the elevation of the wellhead) and equilibrium solubility relationships [27]. However, because of the strong correlation between temperature and pressure in mountainous settings, calculated temperatures are non-unique and a range of plausible values, constrained by the physical conditions of the setting, must be considered [29][30][31].…”

Section: Sample Collection and Data Reductionmentioning

confidence: 99%

Tracers Reveal Recharge Elevations, Groundwater Flow Paths and Travel Times on Mount Shasta, California

Peters

Visser

Esser

et al. 2018

Water

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Mount Shasta (4322 m) is famous for its spring water. Water for municipal, domestic and industrial use is obtained from local springs and wells, fed by annual snow melt and sustained perennially by the groundwater flow system. We examined geochemical and isotopic tracers in samples from wells and springs on Mount Shasta, at the headwaters of the Sacramento River, in order to better understand the hydrologic system. The topographic relief in the study area imparts robust signatures of recharge elevation to both stable isotopes of the water molecule (δ 18 O and δD) and to dissolved noble gases, offering tools to identify recharge areas and delineate groundwater flow paths. Recharge elevations determined using stable isotopes and noble gas recharge temperatures are in close agreement and indicate that most snowmelt infiltrates at elevations between 2000 m and 2900 m, which coincides with areas of thin soils and barren land cover. Large springs in Mt Shasta City discharge at an elevation more than 1600 m lower. High elevation springs (>2000 m) yield very young water (<2 years) while lower elevation wells (1000-1500 m) produce water with a residence time ranging from 6 years to over 60 years, based on observed tritium activities. Upslope movement of the tree line in the identified recharge elevation range due to a warming climate is likely to decrease infiltration and recharge, which will decrease spring discharge and production at wells, albeit with a time lag dependent upon the length of groundwater flow paths.

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“…Geostatistical analysis of groundwater age tracers from wells sampled in the CV has estimated the depth to the top of well screens pumping pre-modern (age of 60 years of more) groundwater to be between 30 -120 m (Visser et al, 2016). According…”

mentioning

confidence: 99%

A Bayesian Approach to Infer Nitrogen Loading Rates from Crop and Landuse Types Surrounding Private Wells in the Central Valley, California

Ransom¹,

Bell²,

Barber³

et al. 2018

Preprint

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Abstract. This study is focused on nitrogen loading from a wide variety of crop and landuse types in the Central Valley, California, USA, an intensively farmed region with high agricultural crop diversity. Nitrogen loading rates for several crop types have been measured based on field scale experiments and recent research has calculated nitrogen loading rates for crops throughout the Central Valley based on a mass balance approach. However, research is lacking to infer nitrogen loading rates for the broad diversity of crop and landuse types directly from groundwater nitrate measurements. Relating groundwater ni-5 trate measurements to specific crops must account for the uncertainty about and multiplicity in contributing crops (and other landuses) to individual well measurements, and also for the variability of nitrogen loading within farms and from farm to farm for the same crop. In this study, we developed a Bayesian regression model that allowed us to estimate crop or other landusespecific groundwater nitrogen loading rate probability distributions for 15 crop and landuse groups based on a database of recent nitrate measurements from 2149 private wells in the Central Valley. The water & natural, rice, and alfalfa & pasture , respectively. In general, our probability based estimates compare favorably with previous direct measurements and with mass balance based estimates of nitrogen loading. Nitrogen mass balance based estimates are larger than our groundwater nitrate derived estimates for manured forage crops, nuts, cotton, tree fruit, and rice crops. These 15 discrepancies are thought to be due to groundwater age mixing, dilution from infiltrating river water, or denitrification between the time when nitrogen leaves the root zone (point of reference for mass balance derived loading) and the time and location of groundwater measurement.

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Geostatistical analysis of tritium, groundwater age and other noble gas derived parameters in California

Cited by 34 publications

References 107 publications

Importance of river water recharge to the San Joaquin Valley groundwater system

Importance of river water recharge to the San Joaquin Valley groundwater system

Tracers Reveal Recharge Elevations, Groundwater Flow Paths and Travel Times on Mount Shasta, California

A Bayesian Approach to Infer Nitrogen Loading Rates from Crop and Landuse Types Surrounding Private Wells in the Central Valley, California

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