WaterUnderground

Water Underground

Baseflow, groundwater pumping, and river regulation in the Wisconsin Central Sands

Baseflow, groundwater pumping, and river regulation in the Wisconsin Central Sands

By Sam Zipper, postdoctoral fellow at Madison and author of tacosmog.com

We often think of groundwater as a nonrenewable reservoir, deep underground, and with good reason – less than ~6% of groundwater globally entered the ground within the past 50 years. However, where a river or stream intersects the water table, water is able to move from the aquifer to the stream (or vice versa). This supply of shallow groundwater to streams is called ‘baseflow’, and is an important supply of water for many streams worldwide, especially during dry seasons or periods of drought. Below, we can see that baseflow makes up more than 50% of total streamflow over most of the world:

global_baseflow

Global estimates of baseflow index – the proportion of streamflow that comes from groundwater or other slowly varying sources, like upstream lakes and wetlands.

The ability of groundwater to contribute to streamflow depends on the water level of the aquifer in the area surrounding the stream. Therefore, human actions that lower groundwater levels (such as pumping for urban or agricultural use) can impair the ability of an aquifer to supply water to streams during dry periods, with potentially devastating consequences for streamflow.

One example close to my home is the Central Sands region of Wisconsin, which is a large region found (not surprisingly) in the center of the state with particularly sandy soils. The sandy soils are perfect for growing potatoes, and the Central Sands is primarily an agricultural region; however, because water drains quickly from sandy soils, irrigation has become an increasingly important part of the landscape:

centralsands

In addition to agriculture, however, the Central Sands region is home to many rivers, lakes, and streams. Recently, one river in particular has become a microcosm of the debate surrounding the impacts and trade-offs of agricultural water use: the Little Plover River. While only 6 miles long, the Little Plover is a prized brook trout fishery and important ecosystem within the region. According to American Rivers, which listed the Little Plover as one of America’s 10 most endangered rivers in 2013, streamflow in the Little Plover has been decreasing since the 1970s and flows today are roughly half of the historical normal. The situation in the Little Plover came to a head in 2005, when several stretches of the Little Plover dried up, with predictably negative consequences for the fish.

Over the past decade, the Little Plover has been mired in legal controversy. In 2009, the Wisconsin Department of Natural Resources established what they call a “Public Rights Flow”, or a required amount of streamflow that the public is entitled to flow through the river. The advocacy leading to the establishment of this Public Rights Flow was primarily by conservation groups like the River Alliance and Trout Unlimited, with the goal of protecting fish and the rest of the stream ecosystems. In order to set the threshold, the Wisconsin Department of Natural Resources first established a baseline level as the 7-day average low flow with a 10% probability of occurring in a given year, and then adjusted this value upwards based on estimates of the flow necessary for to provide fish habitat and recruit trout. Despite the positive step of establishing a Public Rights Flow, measurements during the 2012 drought were consistently below the thresholds set by the Department of Natural Resources, and the Little Plover even dropped below the thresholds in 2013 and 2014, both of which were relatively wet years for Wisconsin.

plover

The Little Plover in 1997 and the first time in ran dry in 2005 (Friends of the Little Plover)

The current debate surrounding the Little Plover hinges on whether the Department of Natural Resources is legally allowed to consider cumulative impacts when permitting new high capacity wells in the region. Previously, the Department of Natural Resources was not considering cumulative impacts, which means that for every well application, they are only allowed to think about that well in isolation – and the effects of a single well are typically small enough that the Department of Natural Resources does not have sufficient grounds to deny a permit. However, the relatively small impacts of many individual wells can add up to cause a big overall effects on local groundwater resources. This changed in 2014, when a judge ruled that the Department of Natural Resources should be considering cumulative impacts. The effects of this ruling remain to be seen, but it improves the DNR’s ability to manage groundwater and surface water resources while considering the interactions between the two.

Thus, the Little Plover River provides a powerful example of a case where a little bit of groundwater drawdown can lead to big environmental, political, and economic issues. Currently, hydrogeologists at the Wisconsin Geological Natural History Survey and USGS Wisconsin Water Science Center are working on developing a groundwater flow model of the region to help understand the impacts of groundwater withdrawals on the aquifer, and what that means for local surface water features like streams and lakes. Because the waters of the Central Sands are valued for many different uses, including farming, urban supply, and outdoor recreation, the team building this model has been working closely with different groups of users to determine the priorities and needs of the various water users the region, and make sure that their scientific tool they develop is both useful to and trusted by the decision-makers in the region. As the future of the Little Plover and other rivers unfold under increasing human pressures and climate change, it is critical that water scientists work together with the public to conduct fair and unbiased science that provides timely and useful information for the decision-making process.

Tracking the Fallout and Fate of Fukushima Iodine-129 in Rain and Groundwater

Tracking the Fallout and Fate of Fukushima Iodine-129 in Rain and Groundwater

This post is written by Matt Herod, and reposted here with permission…

A recently published paper (by myself and colleagues from uOttawa and Environment Canada) investigates the environmental fate of the long lived radioisotope of iodine, 129I, which was released by the Fukushima-Daichii Nuclear Accident (FDNA). Within 6 days of the FDNA 129I concentrations in Vancouver precipitation increased 5-15 times above pre-Fukushima concentrations and then rapidly returned to background. The concentrations of 129I reached were never remotely close to being dangerous, however they were sufficient to distinguish the impact of the FDNA on the region.

Subsequent sampling of groundwater revealed slight increases in 129I concentration that were coincident with the expected recharge times. This suggests that a small fraction of the FDNA-derived 129I may have been transported into local groundwater after infiltrating through soils.

Iodine129_Precip_Sample_BC_JP

What is iodine-129 and where does it come from?

Iodine-129 is the longest lived isotope of iodine with a half-life of 15.7 million years. It is radioactive and occurs everywhere throughout the environment. It is produced in three ways. The first two are natural and the third is by the nuclear industry.

The natural production of 129I occurs in the atmosphere and in soil/rocks. The atmospheric production happens when a cosmic ray proton hits a xenon-129 nucleus and removes a neutron, replacing it and creating an iodine-129 nucleus. The production in soil and rocks happens when a uranium-238 nucleus spontaneously fissions and one of the halves it releases has a mass of 129 ala, iodine-129.

The anthropogenic production occurs because when uranium fissions in a nuclear reactor sometimes one of the parts is 129I. This anthropogenic production is by far the largest source in the environment as substantial amounts have been released by nuclear fuel reprocessing. This 129I that has been released can trace a host of environmental processes and inform us about what happens to 129I or the much more dangerous, 131I. The current levels of 129I are much too low to pose a health threat to humans or the environment, but do allow 129I to be used as an environmental tracer.

129I from Fukushima is present in Vancouver, B.C. rain

The purpose of this research was to discover the fate of 129I in the released by Fukushima, which although a small amount, was isolated in time and space. We measured the 129I deposition in rain and its subsequent movement though soils and see if it reached groundwater. The results tell us about the impact of Fukushima, how 129I moves, where it is attenuated, and how quickly contaminants in this aquifer move from the ground surface to the water table. This knowledge can then be applied to understand 129I behavior in other settings such as nuclear waste repositories and watersheds or it can be used to learn about the behavior of other types of contaminant in this aquifer and how vulnerable it is to contamination.

The results in rain show an increase in 129I concentrations of up to 220 million atoms/L*. This increase was seen ~6-10 days after the emission from Fukushima began and are 5-15 times higher than rain samples collected before Fukushima. Following this increase 129I concentrations returned to background with a few weeks. This agrees with other studies monitoring the fallout of Fukushima derived radioisotopes [Wetherbee et al., 2012]. Furthermore, atmospheric back trajectory modelling shows trajectories for air parcels arriving in Vancouver from over the Pacific ocean and Japan.

Figure2_129IPrecip

We also calculated the mass flux of 129I from Fukushima. That is the actual quantity of 129I that was deposited on the region in grams, or in this case in atoms/m2. This was calculated by simply multiplying the concentration of 129I in rain by the amount of rain that fell. We found that only about 15% of the annual 129I deposition in the Vancouver region could be directly linked to Fukushima affected rain events. The total mass deposited by Fukushima was ~0.0000000000002 (2 x 10^-13) grams. This is a negligibly small quantity with respect to radioactive risk.

Despite the fact that the deposition of 129I from Fukushima was infinitesimally small it was still measurable. Therefore, the question became where did it go and can we learn about local groundwater resources using 129I as a tracer?

129I variation in groundwater may be due to Fukushima

The results in groundwater show very small 129I concentration increases. Two different wells were sampled. The first had a recharge time, which is the time it takes for water to move from the water table to the well screen, where it is sampled, of 0.9 years and the second had a recharge time of 1.2 years [Wassenaar et al., 2006]. The exact time it takes for water and dissolved contaminants to travel through the unsaturated zone was unknown. However, the sediments of this aquifer are very coarse and are known for their ability to rapidly transport contaminants, such as nitrate [Chesnaux and Allen, 2007]. Therefore, if we were going to see 129I from Fukushima this was an ideal location.

The increases in groundwater 129I concentrations were seen in two different wells (ABB03 and PB20) located close to one another. The two wells also had slightly different recharge times. The first was 0.9 years and the second was 1.2 years. The 129I anomaly in the first well occurred at 0.9 years and in the second well at 1.2 years. These 129I anomalies, which occurred exactly when the recharge age predicted they would, suggests that some of the 129I deposited by Fukushima was reaching the wells and causing these increases.

Gwater_129Iconc

In order to verify if it was possible for 129I to travel from the ground surface to the water table in the time required to produce the variations observed we modelled its transport time and attenuation through the unsaturated zone.

The time it took for 129I to reach the water table in the model was then added to the previously dated recharge time to get an estimate for how long it might take 129I from Fukushima to reach the wells we sampled. The results show that it is indeed possible for 129I deposited in rain to infiltrate through the unsaturated zone and reach the wells in time for us to detect it. However, this rapid transport assumes that certain flow paths exist to rapidly conduct 129I due to the heterogeneous lithology of the unsaturated zone. There is evidence of such flow paths [McArthur et al., 2010].

To summarize,

 

  • Within a week of the FDNPP accident elevated 129I concentrations were observed in precipitation. This agrees very well with work on other radionuclides in air filters and rain.
  • 129I concentrations in rain returned to background within a few weeks. However, discrete pulses of elevated 129I occurred for another several months.
  • Elevated 129I concentrations were measured in two wells and corresponded with the expected recharge times indicating that 129I from Fukushima can be traced into groundwater.
  • Vadose zone modeling has shown that 129I can be rapidly transported to the water table and reach the well screen in accordance with groundwater ages.
  • We propose 129I transport is enhanced by preferential dispersion of 129I that exists due to the heterogeneous nature of the vadose zone.
  • This results in variability in groundwater 129I concentrations that preserve the variability in the input of 129I via washout with some dampening of the signal due to attenuation and dilution.

 

 

Fukushima Model

 

Thanks for reading, if you have any questions or concerns please leave a comment or send me an email to discuss further!

*Note: 100 million atoms/L of 129I is equivalent to an activity of 0.00000014 (1.4 x 10^-7) Bq/L. These quantities are extremely low level and only the most sensitive analytical methods in the world can detect them. This amount of radioactivity is several orders of magnitude lower than the natural background radiation produced by naturally occurring radionuclides in soil and the atmosphere. For more on naturally occurring radioactivity see here. Even a clean rainfall has about 1 Bq/L of tritium (radioactive hydrogen), which remains from atmospheric weapons testing in the 1960’s

Access the full paper here: http://onlinelibrary.wiley.com/doi/10.1002/2015WR017325/abstract

References

Chesnaux, R., and D. M. Allen (2007), Simulating Nitrate Leaching Profiles in a Highly Permeable Vadose Zone, Environ. Model. Assess., 13(4), 527–539, doi:10.1007/s10666-007-9116-4.

McArthur, S. A. Q., D. M. Allen, and R. D. Luzitano (2010), Resolving scales of aquifer heterogeneity using ground penetrating radar and borehole geophysical logging, Environ. Earth Sci., 63(3), 581–593, doi:10.1007/s12665-010-0726-9.

Wassenaar, L. I., M. J. Hendry, and N. Harrington (2006), Decadal geochemical and isotopic trends for nitrate in a transboundary aquifer and implications for agricultural beneficial management practices., Environ. Sci. Technol., 40(15), 4626–32.

Wetherbee, G. A., D. A. Gay, T. M. Debey, C. M. B. Lehmann, and M. A. Nilles (2012), Wet Deposition of Fission-Product Isotopes to North America from the Fukushima Dai-ichi Incident, March 2011, Environ. Sci. Technol., 46(5), 2574–2582.

Nature Geoscience digging into water underground this month!

Nature Geoscience digging into water underground this month!

Nature Geoscience is digging hard into water underground – the February issue is part of a special focus on groundwater. The cover this month is a gorgeous (groundwater-filled?) waterfall by Glen Jasechko, Scott’s brother.  The groundwater focus includes:

As part of the focus the journal made our paper on modern groundwater free to registered users for a month – so go download it an check out this and the other papers too!

Fantasy Bottled Water Brands of Tomorrow: Ogallala Water

Fantasy Bottled Water Brands of Tomorrow: Ogallala Water

We are peering into the not-so-distant future to imagine what the brand geniuses of the future will be serving up for discerning water consumers!

The Brand: Ogallala
Source: Great Plains
Why? Deep down, you know you love it.

Promotional Copy:

Ogallala Water: GET PUMPED.

Swill waters run deep so we go deep, deep, deep into the Great Plains water table to pipe this ancient, undisturbed water to your table. No raunchy reuse here. Ogallala Water is guaranteed free of questionable recharge sources and serves up 30% less* in every freshly-pumped bottle.

*50% less in some areas. Supplies are limited.

Parody Ogallala Bottled Water

Consume less fantasy and more facts at:

Reposted with permission from thristyinsuburbia.com.

How easily does our understanding of ‘CRUSTAL PERMEABILITY’ flow ? A new Geofluids special edition…

How easily does our understanding of ‘CRUSTAL PERMEABILITY’ flow ? A new Geofluids special edition…

Permeability is a crazy parameter: heterogeneous on many spatial scales, highly variable over up to 20 orders of magnitude, and transient on many temporal scales. Yet, for better or for worse it is essential to our understanding of numerous earth processes, as well as how human impact and interact with the earth.

I have had the honor of guest editing a special issue  of Geofluids called ‘Crustal Permeability” with Steve Ingebritsen of the USGS.  It is a burly, 400-pages which encompasses papers on both static and transient permeability as well as papers from a wide variety of locations, lithologies and time scales. We hope you will take a look at it

Permeability1

http://engineeringlectures.com/permeability-2/permeability-4

A new data portal for permeability!

A new data portal for permeability!

Permeability data is tucked many dusty corners of the web and in even dustier reports, books and thesis. The purpose of the Crustal Permeability Data Portal is to ‘unearth’ (pun intended!) permeability data by providing links to online, peer-reviewed permeability data that is open to anyone around the world.

This data portal colldata portalates links to other data sources rather than hosting data and is a community-based effort that grew out of a compilation of papers on Crustal Permeability (Geofluids special edition and forthcoming Wiley book).

A related community-based effort is the Digital Crust which a 4D data system of spatially-located data. The Crustal Permeability Data Portal is different from the Digital Crust since it will not host data and data does not have to be spatially located.

Why should I contribute data?

  • data availability is crucial to the core scientific principle of reproducibility
  • sharing is easy and feels good
  • some journals (e.g. Nature) and most scientific funding agencies (NSF, NSERC, NERC etc.) encourage or require data management and sharing

What are the data requirements?

  • Peer-reviewed, that is published in a peer-reviewed journal, book or report
  • Permeability or other related fluid flow and transport parameters such as porosity, storage etc.
  • Hosted on a publicly available on an online data repository such as figshare or institutional webpages such as the USGS

It’s simple: All you need to do is upload your data and fill out this form.

When it snows, it pours (into aquifers)! Recharge seasonality around the world…

When it snows, it pours (into aquifers)! Recharge seasonality around the world…

Written by Scott Jasechko
University of Calgary
isohydro.ca
twitter.com/sjasechko


Groundwater is renewed by rain and melted snow that moves under the ground, a process called groundwater recharge. The percentages of summer versus winter precipitation that make it under the ground are expected to be different for a number of reasons including larger plant water use during the summer, and larger areas of frozen ground during the winter.
seasonal_recharge-01
Our recent research shows that winter precipitation is more likely to move under the ground than summer rain in many areas, including grasslands in Canada and the USA, deserts in Australia and Mexico, and valleys in China and Europe [Jasechko et al., 2014].

But most groundwater is managed over many years, not single seasons [Gleeson et al., 2010]. So who cares if recharge is biased to winter precipitation?

That groundwater recharge is biased to the wintertime matters because of ongoing and anticipated climate change. The warming world is changing how much precipitation falls during the winter and how much falls during the summer [Vera et al., 2006]. One implication of our work is that changes to winter precipitation are likely to have a disproportionately large impact on groundwater recharge compared to similar changes to summer rain.

Winter snow packs are declining in many cold areas [Hernández-Henríquez et al., 2015]. The impacts that declining snow packs and other changes brought on by global warming will have on groundwater recharge, remain unclear.


Most (70%) of this post is in plain language according to up-goer 5. Scott commented that he is much better at drawing snowflakes than he has ever been before thanks to https://www.youtube.com/watch?v=m9Ge-M5ljSI

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