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Squeezed by gravity: how tides affect the groundwater under our feet

Squeezed by gravity: how tides affect the groundwater under our feet

Post from the Conversation, by Gabriel C Rau, Ian Acworth, Landon J.S. Halloran, Mark O Cuthbert

When returning from a swim in the ocean, sometimes it seems as though your towel has moved. Of course, it’s just that the water line has shifted.

The natural rise and fall of the ocean at the beach is an excellent demonstration of gravitational forces exerted by the Sun and the Moon. Although the tidal force is small, it is strong enough to pull regularly on the ocean, making an enormous volume of water rise and fall.

What you might not know is that tidal forces from the Sun and Moon also influence the air we breathe and the solid ground we stand on. These effects are referred to as atmospheric and Earth tides.

While we don’t tend to notice Earth and atmospheric tides, they do affect both the land and the world’s largest freshwater resource located underneath our feet: groundwater. This occupies the pores that exist in geological materials such as sand or soil, much like water in a kitchen sponge.

We have developed a method that incorporates tidal influences to monitor our precious groundwater resources without the need for pumping, drilling or coring.

Water beneath our feet

It has been estimated that groundwater makes up 99% of the usable freshwater on Earth. If all of Earth’s groundwater were extracted and pooled across the world’s land surface, it would be enough to create a lake 180 metres deep.

While this sounds like a lot of water, it is important to remember that not all groundwater is available for use. In fact, groundwater is currently mined on a global scale, especially in drier parts of the world, where groundwater underpins human activities during times of drought.

Groundwater extraction can lead to a downward shift in the land surface level (known as “subsidence”), particularly if groundwater is removed from underground zones that contain soft clays. This is a significant global problem, especially in coastal areas, due to urbanisation and associated water demand.

Alternatively, a long wet period with excess rainfall can cause the groundwater to rise up and cause flooding.

Effect of tides on groundwater

Deeper groundwater buried underneath layers of different types of sediments is under great pressure (in groundwater terminology this is called “confined”). The gravity change from Earth tides squeezes the sediment, and therefore changes the pressure of the water in the pores.

The atmospheric tides add to the weight that is sitting on top of the groundwater and cause a change in stress that results in a downward squeezing.

Groundwater at that depth responds to these stress changes, which can be measured as tiny water level fluctuations inside a groundwater borehole.

We have developed a new approach that exploits these tidal influences to calculate important subsurface properties. For example, this can predict how the pressure is lowered when groundwater is pumped, and by how much the land surface would sink as a result of shrinking subsurface material (just like squeezing a kitchen sponge).

The method basically allows accurate calculation of the compressible subsurface properties from the groundwater response to Earth and atmospheric tides.

This development is significant because it will allow analyses of a subsurface water reservoir (called an aquifer) without human-induced stresses such as pumping or taking physical samples of the material through drilling or coring in addition to constructing a borehole.

All that’s needed for this analysis is a roughly 16-day period of continuous measurements of groundwater levels and atmospheric pressure at hourly intervals.

Groundwater levels are routinely recorded as part of water monitoring programs around the world and in Australia, as funded by the Federal Government groundwater NCRIS scheme. Atmospheric pressure is a standard parameter measured by weather stations, such as operated by the Bureau of Meteorology.

The effects of tidal forces on groundwater might be less apparent to us than their effects on the ocean, but they’re just as important. Our new method of understanding the influence of tides on groundwater significantly reduces the effort to predict the response to groundwater pumping and the potential for land subsidence.

This technique can make passive use of existing boreholes and could be applied to the global archive of groundwater levels to inform more sustainable groundwater resource development in the future.

Groundwater Speed Dating! Can you find a match?

Groundwater Speed Dating! Can you find a match?

Post by Matt Herod

Welcome to the first edition of groundwater speed dating. In today’s post I introduce you to a motley crew of isotopes and chemicals that hydrogeologists and geochemists use to date the age of groundwater. After meeting all of the contestants it will be up to you to pick your favourite and perhaps propose a second date. On your groundwater samples that is.

Starting to find some answers on water chemistry of baseflow samples from the Yukon. The first step in groundwater dating…picnic style. (Photo: Matt Herod)

Before I introduce you to our contestants I should briefly make it clear why groundwater dating is important. Understanding how old groundwater is may be one of the most, if not the most important aspect of protecting groundwater as a resource and preventing depletion of groundwater reserves from overpumping. For example, pumping an aquifer with a groundwater age of 10 years can be done semi-sustainably as any water extracted will take ~10 years to replace. However, pumping water with an age of 100,000 years is exploiting a nearly non-renewable resource. There may be lots of it, but the aquifer could take a long time to recover. Think of it like this: the water being pumped has to come from somewhere. Pumping could draw more water into the aquifer from recharge (not always an option) to replace what is lost, the water pumped could be from groundwater already stored in the aquifer, or it could be groundwater that was leaving the aquifer via discharge into a river or lake that is now diverted to your well.

Another great reason to know the groundwater age is to assess the vulnerability of an aquifer to contamination. If groundwater is young it is likely that the host aquifer is more vulnerable to contamination. Furthermore, knowing the age of groundwater throughout an aquifer will also allow a hydrogeologist to assess how quickly contamination will spread and if it can be contained. There are other reasons that it is beneficial to know the age of groundwater and if you’re interested I refer you to some of the references below.

I should also mention that the clock on a groundwater age starts once it becomes groundwater. That means that once my rain drop infiltrates into the ground and reaches the water table. The time it takes for the water to infiltrate through the soil layer is not included in the date which can add several months. Therefore, when I say groundwater is one year old, this means that it was likely rain from last year that has now reached the well, but it may be slightly older when you factor in the vadose zone travel time.

Are you ready to meet your speed dating contestants!? Pick the one that you’d like to date (the best isotope for your particular groundwater sample).

Note: You’ll see reference to cosmic rays a lot below. For reference see this primer in a previous blog post.

Name: Carbon-14
Nickname: 14C, The Cool One
Personality: Bada^s, Awesome
Half-life: 5730 years
Groundwater age range: 100 -100,000 years
A little about me:
14C, nicknamed radiocarbon, is the isotope that everyone wants to meet. Used by hydrogeologists in a vast range of dating applications for almost any organic material (organic = has carbon in it) it can also be used to date groundwater. 14C is produced by cosmic ray interactions with nitrogen in the atmosphere. 14C was also produced in significant quantities by atomic weapons testing and created a “bomb pulse” like our contestant tritium below which is also used to date groundwater. The great thing about radiocarbon is that since we know exactly how much is produced we can always estimate an age. However, dater beware. The age obtained from 14C and many other groundwater dating tools is the apparent age, which means it is inexact and vulnerable to aggregation errors when mixing young and old water mix, and requires the dater to consider other sources of inorganic carbon that contain no 14C such as ancient limestone. There are ways to correct for these issues, but great care must be taken so don’t be deterred from choosing 14C…maybe a bit of that coolness will rub off on you!? (Of course, as hydrogeologists we don’t need any extra coolness).

Name: Krypton 85 and Krypton 81
Nickname: 85Kr and 81Kr, The Twins
Personality: Different, One short tempered, the other slow to anger
Half-life: 81Kr: 10.75 years, 85Kr: 230,000
Groundwater age range: 10 – 100 and 10,000 -1,000,000 years (using different Kr isotopes)
A little about me:
These two twins could not be more different. Both are isotopes of krypton but with hugely different applications. You won’t see them in Twins magazine (twinsmagazine.com). The source of 85Kr is low level emissions from the nuclear industry, mainly fuel reprocessing. It has a short half-life meaning it can only be detected in groundwater a few decades old.

On the opposite end of the spectrum 81Kr is used for dating extremely ancient groundwater and is a relatively new dating tool for hydrologists. See me previous post on atom trap trace analysis for the details on this method that has made 81Kr dating possible. 81Kr is produced by cosmic ray interactions with gases in the atmosphere that become incorporated into rain that can recharge groundwater. 81Kr is the newest tool in the isotope hydrologists kit and has been used to date waters over 100,000 years old! It isn’t often you see twins so different than this pair. Nevertheless, they may be worth a longer look in your future?

Name: Tritium
Nickname: 3H, The Friendly One
Personality: Popular, Nice
Half-life: 12.3 years
Groundwater age range: 10-100 years
A little about me:
Tritium is the popular isotope in groundwater dating. Of all the isotopes in this competition, 3H is picked more often than the rest combined. Tritium has a short half life making it an ideal tracer and dating tool of young groundwater. Before the 1950’s all tritium in groundwater was natural and produced by cosmic ray interactions in the atmosphere. However, following the atomic weapons testing in the 1950’s and 60’s the tritium concentration in the atmosphere, rain and groundwater increased drastically. This made it possible to date groundwater using what hydrogeologists know as the “bomb peak”. This method has been enhanced using the decay product of tritium, 3He, as well to overcome the loss of tritium by decay over the time since weapon’s testing ended. While 3H may become less useful in the northern hemisphere as the bomb peak decays, the natural variability of 3H production in the southern hemisphere with fewer anthropogenic sources suggests 3H may become ever more useful! http://www.hydrol-earth-syst-sci-discuss.net/hess-2016-532/. Don’t be deterred by it’s popularity and the crowds, tritium is the real deal!

Name: Chlorine-36
Nickname: 36Cl, The Hard to Get
Personality: Evasive, Sends Mixed Signals
Half-life: 301,000 years
Groundwater age range: 10,000 – 1,000,000
A little about me:
36Cl is produced in the atmosphere by cosmic rays and has been used widely for dating ancient groundwater that is tens to hundreds of thousand years old. However, chlorine-36, while popular, is also “high-maintenance”: 36Cl requires more than just a run of the mill accelerator mass spectrometer (AMS) to measure. Indeed, in order to measure 36Cl on an AMS it needs to have the ability to remove the isobar sulphur-36 that interferes with the measurement of the much rarer (and thus sought-after by hydrogeologists) atoms of 36Cl in a sample. Only the highest energy AMS instruments or those with special capabilities, such as an isobar separator, can perform the measurement of 36Cl accurately. Nevertheless, sometimes it is worth putting in the extra effort for the reward. Will you?

Name: Uranium 234-238 Disequilibrium
Nickname: U-Disequilibrium (234U/238U), The Complicated One
Personality: Confusing, Game Player
Half-life: N/A
Groundwater age range:
A little about me:
You don’t come across U-disequilibrium dating that often, but when you do have a beer. U-disequilibrium is a bit mind-bending and requires a very thorough understanding the of the nuclear and geochemical processes at work in your sample location. Basically, it works because as 238U decays in rocks it shoots out alpha radiation, aka. 4He nuclei, at high energies. These bullets of helium break the crystal lattice of the minerals around the 238U atom allowing groundwater the get in. The groundwater then preferentially dissolves some of the 238U grand-daughter, 234U. This means there is more 234U than 238U dissolved in the water (by activity). The (activity) ratio of 234U/238U is greater than one and is predictable over time if you know the geochemical and hydrogeological characteristics of the system. This means you can correlate the ratio you measure to an age. This is an oversimplification of the method, but at it’s core that’s how it works. If you’re persistent, and work hard to understand U-disequilibrium the date is worth it. Will you put in the hard work?

Name: Iodine-129
Nickname: 129I, The Forgotten One
Personality: Quiet, Interesting
Half-life: 15,700,000 years
Groundwater age range: < 80,000,000 years
A little about me:
My personal fave but so forgotten it didn’t merit the figure above! See my PhD thesis for why. The short of it is that I think 129I has a wide variety of applications but we don’t yet fully understand its transport in groundwater and thus applying it is difficult. Therefore, people often overlook 129I for groundwater dating. It is similar to 36Cl in that it requires an AMS to measure, and they are both halogens. 129I has a very long half life and it is interesting because it is produced in three ways: cosmic rays, 238U fission in rocks, and nuclear fuel reprocessing. This makes it a tracer of modern groundwater and allows it to constrain the age of water that is less than 80 million years old as well! If you’re willing to take a chance and explore, perhaps 129I could be the one for you!?

Pick the isotope you’d like to date and leave a comment below!

Feature image from warsaw social.

Monitoring groundwater drought without measuring it

Monitoring groundwater drought without measuring it

Post by Anne van Loon, University of Birmingham

You might remember that the summer of 2015 was extremely dry in large parts of Europe (Figure 1), leading to crop losses, wildfires, drinking water supply deficiencies, and reductions in energy production and navigation (Van Lanen et al., 2016), whether you experienced it yourself or read about it in the newspapers. Based on incomplete information the European Environment Agency already estimates the total economic losses of the event at more than 2 billion Euros (http://www.eea.europa.eu/data-and-maps/indicators/direct-losses-from-weather-disasters-3/assessment).

Figure 1: Media coverage of the 2015 drought in Europe (source: The Guardian)

Seventy-five percent of EU inhabitants depend on groundwater for their water supply, which makes groundwater management extremely important. To manage groundwater effectively during drought periods like 2015, data about groundwater levels are needed in (near-) real time. However, observations of groundwater levels are rarely available in real time, even in Europe, one of the most densely monitored areas of the world.

In a just published paper, we therefore tested two methods to estimate groundwater drought in near-real time (Van Loon et al., 2017). The first method is based on satellite data from the GRACE satellites (Gravity Recovery and Climate Experiment, grace.jpl.nasa.gov), a cool new pair of satellites that measure the Earth’s gravitational field to estimate changes in the amount of water on Earth. Previous research had suggested that the Total Water Storage (TWS) anomalies derived from GRACE could represent hydrological drought (e.g. Thomas et al., 2014). With models the TWS anomalies can be decomposed into their compartments, including groundwater storage. The second method uses a statistical relationship between rainfall and historic groundwater levels, which depends on aquifer properties and has previously been used to study past drought events (e.g. Bloomfield and Marchant, 2013).

To test both methods we looked at the benchmark 2003 drought for two regions in southern Germany and eastern Netherlands. First, we used observed groundwater level data from 2040 monitoring wells to calculate the Standardized Groundwater Index (SGI), which ranges from 0 (abnormally dry) to 1 (abnormally wet) (Figure 2a). Interestingly, the SGI reveals the patchiness of the 2003 groundwater drought caused by differences in aquifer characteristics. Quickly responding aquifer systems experienced drought in response to low rainfall in previous months and slowly responding aquifer systems experienced wetness in response to high rainfall in the preceding year (you might be aware of the 2002 summer floods in the same region). GRACE TWS showed dry anomalies in Germany and (to a lesser extent) in the Netherlands (Figure 2b), but the coarse resolution of GRACE prevents it from picking up the high spatial variability in groundwater levels we saw in the observations (Figure 2a). The groundwater storage derived from GRACE TWS by subtracting surface and soil storage gave abnormally wet conditions in most parts of the study regions (Figure 2c), with drier than normal values only in the eastern part of Germany which in the observations was mostly wetter than normal (Figure 2a). Finally, we calculated a form of the SGI based on the response of groundwater to precipitation (Figure 2d). The spatial pattern of this precipitation-based SGI closely resembles the observed SGI (Figure 2a), although it slightly overestimates the severity of the groundwater drought in Germany.

Figure 2: The 2003 groundwater drought in southern Germany and eastern Netherlands, derived from a) observed groundwater levels (standardised groundwater index, SGI), b) GRACE Total Water Storage (anomalies with regard to the long-term average), c) groundwater anomalies based on GRACE and model outputs (anomalies with regard to the long-term average), and d) observed precipitation and the relationship between precipitation and groundwater levels based on historic data (standardised groundwater index, SGI). Adapted from Van Loon et al. (2017).

We then used the precipitation-based SGI to estimate the 2015 groundwater drought in the same regions (Figure 3). This showed a completely different picture than the 2003 drought. Almost the whole region of southern Germany experienced an extreme drought, whereas the Netherlands was quite wet in August 2015. No patchiness in groundwater levels was observed in 2015, because both short- and long-term rainfall were below average. This means that the 2015 drought was more severe in terms of water resources for drinking water and irrigation because all groundwater wells had low levels, compared to about two thirds in 2003.

Figure 3: The 2015 groundwater drought in southern Germany and eastern Netherlands, derived from observed precipitation and the relationship between precipitation and groundwater levels based on historic data (standardised groundwater index, SGI). Adapted from Van Loon et al. (2017).

Based on our analysis, we think that using readily available rainfall data and the historic relationship between rainfall and groundwater is a cunning way to monitor groundwater drought at a high enough resolution for water management. However, this technique still has more uncertainties than using real-time groundwater observations directly. To prevent issues with drinking water supply for the EU’s 380 million people that depend on groundwater, there is a clear need to measure groundwater levels and make them freely available in real-time.

The scientific paper on which this blog is based can be found here (http://www.hydrol-earth-syst-sci.net/21/1947/2017/).

References

Bloomfield, J. P. and Marchant, B. P. (2013) Analysis of groundwater drought building on the standardised precipitation index approach, Hydrology and Earth System Sciences, 17, 4769–4787, doi: 10.5194/hess-17-4769-2013.

Thomas, A. C., Reager, J. T., Famiglietti, J. S., and Rodell, M. (2014) A GRACE-based water storage deficit approach for hydrological drought characterization, Geophysical Research Letters, 41, 1537–1545, doi: 10.1002/2014GL059323.

Van Lanen, H. A. et al (2016) Hydrology needed to manage droughts: the 2015 European case. Hydrological Processes, 30: 3097–3104. doi: 10.1002/hyp.10838.

Van Loon, A. F., Kumar, R., and Mishra, V. (2017) Testing the use of standardised indices and GRACE satellite data to estimate the European 2015 groundwater drought in near-real time, Hydrology and Earth System Sciences, 21, 1–25, doi: 10.5194/hess-21-1-2017.

 

Global fossil groundwater resources—the grandkids like hanging out with the grandparents!!!

Global fossil groundwater resources—the grandkids like hanging out with the grandparents!!!

Post by Scott Jasechko, University of Calgary

Groundwater is the world’s largest family of fresh and unfrozen water, and its members range from young to old. There are toddler groundwaters recharged more recently than the year ~1960. Our earlier research showed that these modern groundwaters make up only a small share of global groundwater stocks (Ref. 1 and Water Canada).

But what of ancient ‘fossil’ groundwater—defined as groundwater that first moved under the ground more than 12,000 years ago, before the current “Holocene” time period began?

Many studies have discovered fossil groundwaters (Refs. 2-7). These ancient groundwaters may have first become isolated under the ground during one of the ice ages (~12,000 to 2.6 million years ago), or when dinosaurs wandered the planet (230 to 65 million years ago), or even before complex multicellular life evolved (e.g., more than 1 billion years ago).

Our research shows that fossil groundwaters are widespread, based on a compilation of groundwater radiocarbon, which is common in young groundwaters but less common in fossil groundwaters.

Our recent work (Ref. 8) has two main findings:

First, we show that fossil groundwater likely makes up most of the fresh and unfrozen water on planet Earth. Fossil groundwater is common at depths deeper than ~250 meters below the ground. Our finding highlights that most aquifers take a long time to be flushed, implying that most groundwater is not rejuvenated at time scales that are consistent with water management timeframes (~decades).

Second, we show that many deep well waters that are dominated by fossil groundwater also contain some modern groundwater. That is, fossil well waters are often mixed up with recent rain and snowmelt. Because some human activities pollute recent rain and snowmelt, our finding implies that deep wells are not immune to the impacts of modern-day land uses on water quality.

Back to our family analogy – our two main findings are: (i) ‘groundwater grandparents’ (i.e., fossil water) make up most of the global groundwater family (lots of grandparents, only a few grandchildren), however, (ii) groundwater youngsters (less than ~50 years in their age), are often found to hang out at deep depths with groundwater grandparents. Once in a while, youngsters may carry the consequences of bad modern habits (i.e. contamination) down to the deep depths where the groundwater grandparents live, sullying deep groundwaters once considered immune to modern contamination.

 

Fossil groundwater discharges to the surface near the Clearwater River of northeast Alberta (56.735°N 110.471°W; video of the spring https://vimeo.com/211124266)

References

1) Gleeson T, Befus K, Jasechko S, Luijendijk E, Cardenas MB (2016) The global volume and distribution of modern groundwater. Nature Geoscience, 9, 161-168. http://www.nature.com/ngeo/journal/v9/n2/full/ngeo2590.html
2) Thatcher L, Rubin M, Brown GF (1961) Dating desert groundwater. Science 134, 105-106. http://science.sciencemag.org/content/134/3472/105
3) Edmunds WM, Wright EP (1979) Groundwater recharge and palaeoclimate in the Sirte and Kufra basins, Libya. Journal of Hydrology 40, 215-241. www.sciencedirect.com/science/article/pii/0022169479900325
4) Phillips FM, Peeters LA, Tansey MK, Davis SN (1986). Paleoclimatic inferences from an isotopic investigation of groundwater in the central San Juan Basin, New Mexico. Quaternary Research 26, 179-193. http://www.sciencedirect.com/science/article/pii/0033589486901031
5) Remenda VH, Cherry JA, Edwards TWD (1994). Isotopic composition of old ground water from Lake Agassiz: implications for late Pleistocene climate. Science, 266, 1975-1978. science.sciencemag.org/content/266/5193/1975
6) Sturchio NC et al. (2004) One million year old groundwater in the Sahara revealed by krypton-81 and chlorine-36. Geophysical Research Letters 31, L05503. onlinelibrary.wiley.com/doi/10.1029/2003GL019234/full
7) Holland G, Sherwood Lollar B, Li L, Lacrampe-Couloume G, Slater GF, Ballentine CJ (2013) Deep fracture fluids isolated in the crust since the Precambrian era. Nature 497, 357-360. http://www.nature.com/nature/journal/v497/n7449/full/nature12127.html
8) Jasechko S, Perrone D, Befus KM, Cardenas MB, Ferguson G, Gleeson T, Luijenjijk E, McDonnell JJ, Taylor RG, Wada Y, Kirchner JW (2017) Global aquifers dominated by fossil groundwaters but wells vulnerable to modern contamination. Nature Geoscience doi:10.1038/ngeo2943.

Musical groundwater?

Musical groundwater?

Post by Kevin Befus, University of Wyoming

I don’t mean to get your hopes up, but keep them up there. I’m not talking about recording the sonorific excitement that is groundwater flow. And, I’m not talking about the squeak of a pump handle, the gurgling of a spring, the grumble of a generator, or the roar of a drill rig. Rather, I want to share with you some songs that reference groundwater in one capacity or another, though references to specific capacity have yet to be found. Groundwater might not be photogenic …more discussion to follow, but is it musical?

For the last couple of years, I have been amassing a playlist of songs that reference water (well, ever since I discovered how perfect “Once in a Lifetime” by the Talking Heads was for motivating me during graduate school…in my opinion, there is no better song to listen to before hitting submit on that manuscript or grant for good scientific mojo). Sifting through a couple hundred songs that sometimes only marginally use water to metaphorize the human condition, I have honed the list to an ordered version of what I consider “The best/only groundwater songs”:

1) Once in a lifetime – Talking Heads
See previous post for a thorough run down

2) Water of Love – Dire Straits
A yearning for water/love, deep underground and hard to find. Let’s hope for some recharge to elevate the water table and maybe even support the river’s running free.

3) Cold Water – Old Time Relijun
Warning, this song is different, but it is about groundwater and wonderfully so. “Cold water going down…through the roots, through the mud, through the rocks, through the ground, through the sand, through the Earth and all the land”. Talk about groundwater flow and potential recharge! It’s also cold, fitting the gross expectation that groundwater near recharge areas is cooler (in regional flow systems at least) than further along the flow system.

4) I am a River – Foo Fighters
They find a groundwater system that thinks it is a river beneath a subway floor…a classic case of mistaken identity.

5) Hallelujah Band – Eilen Jewell
“I climbed down underground
to listen for a new sound
found a river underneath our feet
dark and silent, deep”

Sounds like a quiet unconfined karst groundwater system to me.

6) You Don’t Miss Your Water – Otis Redding

7) Cool Water – Sons of the Pioneers (later sung by Johnny Cash, Joni Mitchell, and others)

8) Water in a Well – Sturgill Simpson

9) Water – Jack Garratt

10) Our Lady of the Well – Jackson Browne

11) Crow Jane – Skip James (also Derek Trucks Band)

12) Well Run Dry – Phat Phunktion

My musical explorations have taught me love is like water. Groundwater? Maybe, depends on its amount, depth, and quality. Wells can be the source of good and bad waters, and we can have some say on whether it’s one or the other. These songs and others (that don’t reference groundwater specifically) bemoan or extol love/water, which comes or goes and can be so uncontrollable.

Groundwater can also be a source of contemplation. Water underground is often interpreted as “silent” (in both “Hallelujah Band” and “Once in a Lifetime”), but springs are allowed to burble and gurgle. So long as we have saturated conditions in a simple single-porosity system, I would bet the groundwater flow is generally difficult to hear. But remember, groundwater is under pressure (atmospheric, hydrostatic, or otherwise) and “wants” to break free (Queen references…couldn’t help myself), especially when in confined aquifers.

There is at least one more way groundwater systems can invoke contemplation. Back before powered pumps, drawing water from a well took time, and that time could be used to think through the triumphs and trials of life. Maybe that’s one reason why groundwater hydrologists are often excited to get into the field.

Quick aside, San Diego has recently started a music festival called GROUNDWATER, where modern house music is the theme. I have not yet sifted through their performers’ lyrics in search of water references, but I would gladly take your help. Words may be in low concentrations.

Join my musical adventures in groundwater and share your finds with us in the comments below!

For your hydrogeological musical pleasure:

feature image: IAH Netherlands Chapter

Of Karst! – short episodes about karst

Of Karst! – short episodes about karst

Episode 1 – A different introduction to karst

by Andreas Hartmann Lecturer in Hydrology at the University of Freiburg

Usually, textbooks or lectures start with the theoretical background and basic knowledge of the topic they try to cover. Writing my first contribution to the Water Underground blog I want to take advantage of this less formal environment. I will introduce karst as I and many others around the world see it. As the most beautiful environment to explore and study.

Some of you may not be familiar with the term karst, its geomorphology or hydrological consequences. But I am almost certain that most of you have seen the landforms in the four pictures below.

Tower karst (1st photo) is typical of tropical regions. The picture below is taken close to Guilin, Southwest China, and I am sure many of you remember James Bond “The Man with the Golden Gun” and the beautiful tower karst islands at which parts of movie takes place (episode 3 will be a special feature about karst in the movies). Tower karst reaches heights up to 300m and often referred to by its Chinese name Fenglin or Fengcong karst, when occurring in a large number.

The 2nd photo shows the opposite landform: a huge hole in the forest ground. This is not a crater but a very big collapse sinkhole at Vermillion Creek, Northwest territories, Canada. It has an ellipse shape (60m x 120m) and 40 m below the surface, it has a lake whose depth has not yet been determined. You may not have previously heard the term sinkhole. But on the news one day you will hear stories of holes suddenly swallowing cars or entire houses in Florida or Mexico. If not due to mining, those were most probably collapses that occurred due to karstification.

Figure 1: (1) amazing tower karst Li River, Gulin, China (duskyswondersite.com), (2) collapse sinkhole , Vermillion Creek, Northwest territories, Canada (pinterest.com), (3) Kalisuci Cave at Jogjakarta, Indonesia (ourtheholiday.blogspot.com), (4) spring of the Loue River, France (wikiwand.com)

The most popular features of karst are caves, some of them as large as entire buildings. The 3rd photo shows how it may look inside a karstic cave (Kalisuci Cave at Jogjakarta, Indonesia). Note that there are plenty of stalactites and that there is a lot of water that will eventually find its way back to the surface discharging a karstic spring.

The 4th photo shows the spring of the Loue River, France, which is one of the largest springs in Europe. The volumes of water coming out easily compare to the discharge of medium size rivers. If you ever saw a spring that big it must have been a karst spring!

In the Of Karst! series, I will take you on a journey through more of these amazing characteristics of karst. I will show how its evolution over time can produce the landforms shown here. I will show how karstification affects the resulting movement of water on the surface, in caves systems and in karstic rock. And I will explain why karst is so relevant for our societies. In episode 2 (late June 2017) I will speak of how karst evolves. Episode 3 (early October 2017) will a special feature about karst in James Bond other famous movies.

Andreas Hartmann is a lecturer in Hydrology at the University of Freiburg. His primary field of interest is karst hydrology and hydrological modelling. Find out more at his personal webpage www.subsurface-heterogeneity.com

What is the volume (in kegs) of groundwater is stored on earth?

What is the volume (in kegs) of groundwater is stored on earth?

Last week I gave a ‘blue drinks’  presentation for a networking evening for the Victoria chapter of the Canadian Water Resources Association entitled “How much groundwater is on earth?” based on our paper from Nature Geoscience last year. Since the night was hosted at Philips Brewery, an awesome local brewery (who makes Blue Buck, the perfect blue drink, and lots of other great beer), I decided to calculate how many kegs of groundwater we have on earth or said another way “what is the volume (in kegs) of groundwater is stored on earth?

So this blog post is a skill-testing question for all the nerds out there – answer below in the comments knowing:
a keg is 58.7 liters = 5.87e-11 km3 so there are 1.7 e+10 kegs in a km3.

Hint it is more than 1.7 e+10 kegs…. and one person during the evening got it almost correct.

Research mini-conference in fourth year groundwater class

Research mini-conference in fourth year groundwater class

Fourth year and graduate students led a fun mini-conference during class in Groundwater Hydrology (CIVE 445, Civil Engineering at University of Victoria) yesterday. Local consulting and government hydrogeologists joined, making the students both nervous and excited to be presenting to professionals with up to forty years of groundwater experience. The presentations were the culmination of a term-long independent group research project – they also write a research paper (which is peer-reviewed by their classmates). And the mini-conference culminated in beers at the grad club, unfortunately drinking beer brewed with surface water.

It seemed like a win-win-win for everyone. The students loved meeting and presenting to, and being grilled by, the people who had mapped the aquifer they were modeling or asked if their model is based on any real data. The practitioners loved seeing the new ideas and enthusiasm of the students. And I loved seeing the interaction and learning.

For any prof reading this, here is a description of the Group Research Project and the conference poster:

 

 

 

 

 

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