Global aquifers dominated by fossil groundwaters but wells vulnerable to modern contamination

Jasechko, Scott; Perrone, Debra; Befus, K. M.; Cardenas, M. Bayani; Ferguson, Grant; Gleeson, Tom; Luijendijk, Elco; McDonnell, Jeffrey J.; Taylor, Richard G.; Wada, Yoshihide; Kirchner, James W.

doi:10.1038/ngeo2943

Cited by 270 publications

(213 citation statements)

References 39 publications

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“…Fossil (Pleistocene) groundwater has mostly recharged as local precipitation because flow paths from the foothills to the discharge areas near the valley centre are naturally longer (Izbicki, Radyk, & Michel, ). Mixtures of modern and fossil groundwater, representing 28% of all samples, are vulnerable to modern contamination (Jasechko et al, ), but recharge rates and sustainability are difficult to determine. The age ranges found in groundwater—decades to millennia (Jasechko et al, )—reflect the large capacity of subsurface storage to buffer interannual variability and drought.…”

Section: Discussionmentioning

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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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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Section: Discussionmentioning

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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“…Our study, in addition to others (Gardner et al, ; Harrington et al, ; Hogan et al, ; Smerdon et al, ), provides evidence that deeply sourced, “fossil” groundwater and shallow, “young” groundwater can each have a large impacts on river water chemistry. Fossil groundwater—groundwater stored for more than 12,000 years—has been identified in over one hundred aquifer systems around the globe (Jasechko, ) and likely comprises more than half of all groundwater stored in the upper 1 km of the crust (Jasechko et al, ). However, evidence for fossil groundwater discharges to rivers, while available, is less widespread than their detection in deep wells.…”

Section: Discussionmentioning

confidence: 99%

Formation waters discharge to rivers near oil sands projects

Ellis

Jasechko

2018

Hydrological Processes

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Groundwater discharges in the western Canadian oil sands region impact river water quality. Mapping groundwater discharges to rivers in the oil sands region is important to target water quality monitoring efforts and to ensure injected wastewater and steam remain sequestered rather than eventually resurfacing. Saline springs composed of Pleistocene‐aged glacial meltwater exist in the region, but their spatial distribution has not been mapped comprehensively. Here we show that formation waters discharge into 3 major rivers as they flow through the Athabasca Oil Sands Region adjacent to many active oil sands projects. These discharges increase river chloride concentrations from river headwaters to downstream reaches by factors of ~23 in the Christina River, ~4 in the Clearwater River, and ~5 in the Athabasca River. Our survey provides further evidence for the substantial impact of formation water discharges on river water quality, even though they comprise less than ~2% of total streamflow. Geochemical evidence supporting formation water discharges as the leading control on river salinity include increases in river chloride concentrations, Na/(Na + Ca) ratios, Cl/(Cl + SO4) ratios and decreases in 87Sr/86Sr ratios; each mixing trend is consistent with saline groundwater discharges sourced from Cretaceous or Devonian aquifers. These regional subsurface‐to‐surface connections signify that injected wastewater or steam may potentially resurface in the future, emphasizing the critical importance of mapping groundwater flow paths to understand present‐day streamflow quality and to predict the potential for injected fluids to resurface.

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“…During a press conference at the European Geosciences Union (EGU) General Assembly 2017, Professor James Kirchner (ETH Zurich) reported on a recent paper that he co-authored (Jasechko et al, 2017). This paper stated that fossil groundwater can contain a small fraction of water less than 50 years old, as evidenced by detectable levels of tritium remaining from nuclear bomb testing in the 1950s.…”

Section: Groundwater Example: Journalists Can Distort Results By Takimentioning

confidence: 99%

HESS Opinions: Science in today's media landscape – challenges and lessons from hydrologists and journalists

Lutz¹,

Popp²,

Emmerik³

et al. 2018

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Abstract. Media such as television, newspapers and social media play a key role in the communication between scientists and the general public. Communicating your science via the media can be positive and rewarding by providing the inherent joy of sharing your knowledge with a broader audience, promoting science as a fundamental part of culture and society, impacting decision and policy makers, and giving you a greater recognition by institutions, colleagues and funders.However, the interaction between scientists and journalists is not always straightforward. For instance, scientists may not 30 always be able to translate their work into a compelling story, and journalists may sometimes misinterpret scientific output.In this paper, we present insights from hydrologists and journalists discussing the advantages and benefits as well as the potential pitfalls and aftermath of science-media interaction. As we perceive interacting with the media as a rewarding and essential part of our work, we aim to encourage scientists to participate in the diverse and evolving media landscape. With this paper, we call on the scientific community to support scientists who actively contribute to a fruitful science-media 35 relationship.Hydrol. Earth Syst. Sci. Discuss., https://doi

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Global aquifers dominated by fossil groundwaters but wells vulnerable to modern contamination

Cited by 270 publications

References 39 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

Formation waters discharge to rivers near oil sands projects

HESS Opinions: Science in today's media landscape – challenges and lessons from hydrologists and journalists

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