water cycle

Good groundwater management makes for good neighbors

Good groundwater management makes for good neighbors

Post by Samuel Zipper, postdoctoral fellow at both McGill University and the University of Victoria, in Canada. You can follow Sam on Twitter at @ZipperSam.


Dedicated Water Underground readers know that this blog is not just about water science, but also some of the more cultural impacts of groundwater. Keeping in that tradition, today’s post begins with a joke*:

Knock, knock!

Who’s there?

Your neighbor

Your neighbor who?

Your neighbor’s groundwater, here to provide water for your plants!

Figure 1. Typical reaction to joke written by the author.


Perhaps this joke needs a little explanation. As we’ve covered before, groundwater is important not just as a supply of water for humans, rivers, and lakes, but also because it can increase the water available to plants, making ecosystems more drought resistant and productive. However, we also know that groundwater moves from place to place beneath the surface. This means that human actions which affect groundwater in one location, like increasing the amount of paved surface, might have an unexpected impact on ecosystems in nearby areas which depend on that groundwater.

Imagine, for example, two neighboring farmers. Farmer A decides retire and sells his land to a developer to put in a new, concrete-rich shopping center. Farmer B continues farming her land next door. How will the changes next door affect the groundwater beneath Farmer B’s land, and will this help or hurt crop production on her farm?

In a new study, my colleagues and I explored these questions using a series of computer simulations. We converted different percentages of a watershed from corn to concrete to see what would happen. Our results showed that the response of crops to urbanization depended on where the land use change occurred.

Figure 2. Conceptual diagram showing how urbanization might impact crop yield elsewhere in a watershed. From Zipper et al. (2017).

In upland areas where the water table was deep, replacing crops with concrete caused a reduction in groundwater recharge, lowering the water table everywhere in the watershed – not just beneath the places where urbanization occurred. This meant that places where the ecosystems used to be reliant on groundwater could no longer tap into this resources, making them more vulnerable to drought. However, places where the water table used to be too shallow saw boosts in productivity, as the lower water table was closer to the optimum water table depth.

In contrast, urbanization happening in lowland areas had a much more localized effect, with changes to the water table and yield occurring primarily only in the location where land use changed, because the changes in groundwater recharge were accounted for by increased inflows from the stream into the groundwater system.

So, what does this mean for the neighboring farmers we met earlier?

For Farmer A, it means the neighborly thing to do is work with the developers to minimize the effects of the land use change on groundwater recharge. This can include green infrastructure practices such as rain gardens or permeable pavement to try and mimic predevelopment groundwater recharge.

For Farmer B, the impacts depend on the groundwater depth beneath her farm. If the groundwater beneath her farm is shallow enough that her crops tap into that water supply, she should expect changes in the productivity of her crops, especially during dry periods, and plan accordingly.

*Joke written by scientist, rather than actual comedian.


For More Information:

Zipper SC, ME Soylu, CJ Kucharik, SP Loheide II. Indirect groundwater-mediated effects of urbanization on agroecosystem productivity: Introducing MODFLOW-AgroIBIS (MAGI), a complete critical zone model. Ecological Modelling, 359: 201-219. DOI: 10.1016/j.ecolmodel.2017.06.002



Sam Zipper is an ecohydrologist. His main research focuses broadly on interactions between vegetation and the water cycle, with a particular interest in unintended or indirect impacts of land use change on ecosystems resulting from altered surface and subsurface hydrological flowpaths. You can find out more about Sam by going to his webpage at: samzipper.weebly.com.

Groundwater & Education – Part One

Groundwater & Education – Part One

Post by Viviana Re, postdoctoral researcher at the University of  Pavia (Università di Pavia), in Italy. You can follow Viviana on Twitter at @biralnas.

Part one of a two part series on groundwater and education by Viviana.


Education /ɛdjʊˈkeɪʃ(ə)n
The process of receiving or giving systematic instruction, especially at a school or university.

  • from Latin educatio(n-), from the verb educare
  • Educare is a combination of the words e (out) and ducare (lead, drawing), or drawing out.

Based on this definition, I should change the title of this post to: Drawing out groundwater (from the well). This is actually the main occupation of groundwater scientists, isn’t it? Not only are we always withdrawing groundwater from a well or a borehole while sampling, but we also often have to “draw it out” when dealing with managers and policy makers, as sometimes they seem to forget about this hidden (but very important) component of the water cycle. Therefore, we are quite used to these forms of “drawing out” – but what about education? Are we really that effective in “drawing out” groundwater in explaining its peculiarities, issues, and connections within the whole water cycle and, more generally, with the environment?

Indeed, the effort of shedding light on something that is not so visible nor easily studied has the side effect of forcing us to focus solely on it, with a resulting tendency of developing sectorial approaches to water management.

In the preface of a UNESCO Technical paper, I found the following excerpt: “Water resources schemes are now increasingly considered as integrated systems and consequently, civil engineers, geologists, agricultural engineers and hydraulic engineers engaged in planning and design no longer work in isolation”. The document is dated 1974 but, still in 2017, we are somehow struggling to fitting groundwater into Integrated Water Resources Management (IWRM) and to connecting mental and structural “silos”. Quoting Daly (2017), the latter is particularly relevant (especially when education is at stake): if on the one hand, specialization can be the driver for a sound knowledge; on the other hand, this can encourage people to get stuck in their own individual disciplines (or said in other words, their “silos”). Indeed, “silos” exist in their structures, but can also exist as a state of mind that can go hand in hand with tunnel vision (Tett, 2015).

Therefore, in my opinion, the new generation of groundwater scientists (and teachers) should have a new mission: to work (and therefore, to teach) coherently with the integrated and complex nature of the water cycle. In fact, the role of hydrogeologists and groundwater scientists in times of increasing freshwater demand, exacerbated by population growth and climate change effects, requires a serious shift towards a more holistic approach targeting sound groundwater assessment and long-term management.

Arguably, if we are still discussing possible ways of practically implementing this integration, we should definitely start asking ourselves if the the “business as usual” way of working and teaching is effective.  If it is not, we must begin investigating how we can go beyond classical approaches to draw groundwater out of the well.

Playing with kids while sampling … can we call it capacity building?!


To be continued …

[Read More]

Are we in the age of postmodern groundwater?

Are we in the age of postmodern groundwater?

My humanities colleagues and friends are always talking about postmodernism or pomo for short (see this funny satire). I’ve been thinking a lot lately about ‘modern groundwater’ (stay tuned for a cool paper), so I started wondering if there is ‘postmodern groundwater’.

Modern groundwater is groundwater recharged since the huge spike it tritium in the early 1960’s due to above ground thermonuclear testing. But tritium has a short half-life, so atmospheric tritium concentrations have largely decayed back to pre-bomb spike concentrations (see graph below). So does this mean that we are in the age of postmodern groundwater or pomo gw?


Tritium concentrations in precipitation through time (from USGS)

Googling ‘postmodern groundwater’ comes up with nothing, so maybe I’m on to something new. The only thing online that is close seems to be Michael Campana’s more political and very interesting ‘Postmodern water cycle” shown here:

pomo_water cycle

The Postmodern Water Cycle by Kate Ely, Umatilla Basin hydrologist extraordinaire for the Confederated Tribes of the Umatilla Indian Reservation, as posted on waterwired.


One in four of world’s big cities water-stressed

One in four of world’s big cities water-stressed

From the McGill Newsroom

As more people move to urban areas, cities around the world are experiencing increased water stress and looking for additional water supplies to support their continued grow.

The first global database of urban water sources and stress, published online this week in Global Environmental Change, estimates that cities move 504 billion litres of water a distance of 27,000 kilometers every day. Laid end to end, all those canals and pipes would stretch halfway around the world. While large cities occupy only 1% of the Earth’s land surface, their source watersheds cover 41% of that surface, so the raw water quality of large cities depends on the land use in this much larger area.

An international team of researchers from nine institutions, including McGill University in Montreal, surveyed and mapped the water sources of more than 500 cities, providing the first global look at the water infrastructure that serves the world’s large cities. The study was led by Rob McDonald, senior scientist with the Nature Conservancy in Arlington, Va.

Prof. Bernhard Lehner and PhD student Günther Grill of McGill’s Department of Geography contributed a detailed global map of rivers, lakes and watersheds to help map the water sources of each city, while Prof. Tom Gleeson of McGill’s Department of Civil Engineering conducted analysis for groundwater sources.

The research team used computer models to estimate the water use based on population and types of industry for each city, and defined water-stressed cities as those using at least 40% of the water they have available. Previous estimates of urban water stress were based only on the watershed in which each city was located, but many cities draw heavily on watersheds well beyond their boundaries. In fact, the 20 largest inter-basin transfers in 2010 totaled over 42 billion liters of water per day, enough water to fill 16,800 Olympic-size pools.

There is good news in the findings: Many cities are not as water-stressed as previously thought. Earlier estimates put approximately 40% of cities into the water-stressed category. This analysis has the number at 25%.

The study finds that the 10 largest cities under water stress are Tokyo, Delhi, Mexico City, Shanghai, Beijing, Kolkata, Karachi, Los Angeles, Rio de Janeiro and Moscow. (Neither of the two Canadian cities analyzed — Toronto and Montreal — was water-stressed, according to the definition used in the study.)

The study also makes clear the extent to which financial resources and water resources are intertwined. It is possible for a city to build itself out of water scarcity — either by piping in water from greater and greater distances or by investing in technologies such as desalinization — but many of the fastest growing cities are also economically stressed and will find it difficult to deliver adequate water to residents without international aid and investment.

“Cities, like deep rooted plants, can reach a quite a long distance to acquire the water they need,” says McDonald. “However, the poorest cities find themselves in a real race to build water infrastructure to keep up with the demands of their rapidly growing citizenry.”

The study also reveals that:

  • Four in five (78%) urbanites in large cities, some 1.21 billion people, primarily depend on surface water sources. The remainder depend on groundwater (20%) or, rarely, desalination (2%).
  • The urban water infrastructure of large cities cumulatively supplies 668 billion liters daily. Of this, 504 billion liters daily comes from surface sources, and that water is conveyed over a total distance of 27,000 km.
  • Land use in upstream contributing areas affects the raw water quality and quantity of surface water sources.
  • An estimated one-quarter of large cities in water stress contain $4.8 trillion of economic activity, or 22% of all global economic activity in large cities. This large amount of economic activity in large cities with insecure sources of water emphasizes the importance of sustainable management of these sources, not just for the viability of individual cities but for the global economy.

The research was supported by a grant from the Gordon and Betty Moore Foundation.


“Water on an urban planet: urbanization and the reach of urban water infrastructure,” Robert. I. McDonald, et al, Global Environmental Change, published online June 2, 2014. http://dx.doi.org/10.1016/j.gloenvcha.2014.04.022

Groundwater extraction can move mountains

Groundwater extraction can move mountains

Contributed by Pascal Audet (webpage or email)


Historic 1977 photo of Dr. Joseph Poland, USGS, considered the pioneer of scientific subsidence studies. Dates on telephone pole indicate previous land elevations in an area SW of Mendota. Photo credit: U.S. Geological Survey

Next time you eat food grown in the San Joaquin Valley of California, think about this: the water used for growing them probably came from under ground. Farmers do not really have a choice because the amount of water from rain and snow can’t keep up with the needs for growing food. Every year more water is drawn out of the ground for irrigation. Because of this, the floor of the San Joaquin Valley goes down as the sediments compact once the water is out (see picture on right).

In the latest work from our team, we find a surprising side effect of groundwater pumping: the mountains surrounding the valley (the Sierra Nevada and California Coast Ranges) are moving up a few millimeters each year, as shown by a large number of GPS instruments. This may seem very small to humans, but for hard rocks it is quite fast. We find that this uplift can be explained by the loss of water out of the ground, as shown by gravity data from the GRACE satellite. The water lost through irrigation lowers the weight on the Earth’s crust, which responds by bouncing back up like a spring.

One interesting implication of this study is the impact on earthquakes on the San Andreas Fault. Uplift of the crust (and mountains) decreases the grip on the fault, making it easier to slip and cause small earthquakes during busier times of groundwater pumping. Perhaps more important, our study shows that humans can really move mountains through industrial agriculture. In California, this effect may get worse because more droughts, earlier snowmelt and different rainfall patterns are expected due to climate change.

This article is the second in a series of plain language summaries on Water Underground (link to first). The 5upgoer word processor showed that ~80% of the words in this post are in the 1000 most common words in the English language. For recent news coverage of this article check out this.

Best groundwater song ever? “Once in a Lifetime” by the Talking Heads?

Best groundwater song ever? “Once in a Lifetime” by the Talking Heads?

Kevin Befus
Contributed by Kevin Befus, University of Austin – Texas

If there has ever been a song for hydrogeologists, “Once in a Lifetime” by the Talking Heads is the best. Here’s why I have taken this song on as my hydrogeologic theme song.

But first, here is a link to the music video, in all of its early 1980’s glory:

Music is great because the listener can interpret the music and lyrics with their biases. My bias in this song is not about the drudgery of life (1) . It is about water which is everywhere in this song, and maybe that means we humans see water as mundane, everywhere and maybe a bit menacing. I fully encourage you to evaluate your life through this song, but let’s get on to the hydrogeology!

Where does this song get the hydrogeology right? I was surprised.
“Water flowing underground” – groundwater moves and is not still (but can be super slow), except maybe in stagnation points that may also be dynamic (2).

“same as it ever was” – groundwater responds over long time scales, but may not always be in the same place (3) . Even still, water is eventually renewed and continues on its many paths through the water cycle, same as it ever was.

“Into the blue again” – back to the ocean, with an average retreat of 4000 yrs (4) ; shout out to the submarine groundwater discharge community (5)!

“After the money’s gone” – water can be something we retreat to as a source of comfort or leisure, but here’s an idea: what do we do with water problems when the money is gone? How do economics affect water resources? Do we turn off the pumps and let water flow to the blue again, L.A. (6)?

“Water dissolving and water removing” – shout out to hydrogeochemists and transport modelers (7) ; yes, you, Chebotarev (8)!

“There is water at the bottom of the ocean…remove the water from the bottom of the ocean” – there sure is, and more than we thought (9)! Maybe a water resource that will be tapped more and more.

“Under the rocks and stones” – well, there is water under rocks and stones, but also inside, brushing but sadly missing porosity and saturation. This doesn’t mean I don’t like this lyric.

“Silent water” – if there is any water on Earth that is silent (and that is unlikely, depending on the definition of what sound is), groundwater would be a good place to imagine a silent water droplet.

The underlying theme of passing time is what really gets me. Once in a lifetime, this water is flowing underground. What a great way to introduce the timescales of groundwater flow! Or, even begin a lesson on groundwater, ranging from basics to interactions at the coast or human impacts? How precious is this water if it can only be replenished once in a lifetime?

May we someday not have to say to ourselves, “my god, what have we done?”

1. http://www.allmusic.com/song/once-in-a-lifetime-mt0011967560
2. Gomez, J. D., and J. L. Wilson (2013), Age distributions and dynamically changing hydrologic systems: Exploring topography-driven flow, Water Resour. Res., 49(3), 1503-1522.
3. Gleeson, T., Y. Wada, M. F. Bierkens, and L. P. van Beek (2012), Water balance of global aquifers revealed by groundwater footprint, Nature, 488(7410), 197-200, doi: 10.1038/nature11295.
4. https://www.e-education.psu.edu/earth540/content/c3_p7.html
5. Burnett, W. C., H. Bokuniewicz, M. Huettel, W. S. Moore, and M. Taniguchi (2003), Groundwater and pore water inputs to the coastal zone, Biogeochemistry, 66(1-2), 3-33, doi: 10.1023/B:BIOG.0000006066.21240.53.
6. http://www.wrd.org/engineering/seawater-intrusion-los-angeles.php
7. http://ponce.sdsu.edu/the_salinity_of_groundwaters.html
8. Chebotarev, I. I. 1955. Metamorphism of natural waters in the crust of weathering. Geochimica et Cosmochimica Acta, Vol. 8, 22-48, 137-170, 198-212
9. Post, V. E. A., J. Groen, H. Kooi, M. Person, S. Ge, and W. M. Edmunds (2013), Offshore fresh groundwater reserves as a global phenomenon, Nature, 504(7478), 71-78, doi: 10.1038/nature12858.


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