Water Underground

A Tanzanian groundwater safari through the last 2 million years

A Tanzanian groundwater safari through the last 2 million years

Post by Mark Cuthbert, Research Fellow and Lecturer at Cardiff University, in the United Kingdom, and by Gail Ashley, Distinguished Professor at Rutgers University, in the United States.


During the dry season, Lake Masek in Northern Tanzania (see map) is a lovely place to be if you’re a hippo or a flamingo, but for humans it’s an inhospitable environment. We were on ‘safari’ (a scientific one of course, but the wildlife was a massive bonus! Photo 1-left) to try and better understand the distribution of freshwater in this dryland landscape.

Map: Locations on our groundwater safari in Northern Tanzania.

Watching our backs in case of predators, we ventured out of the safety of our Land Rover for Gail to sample the lake water, as salt blew in drifts around us off the desiccated edges of the lake bed (Photo 1-right). It was very salty and not potable for humans. All the streambeds that run into the lake were dry and yet our Masai guide told us that nearby we could find freshwater all year round.

Photo 1: (L) The amazing wildlife in the Ngorongoro Crater & (R) Saline-alkaline Lake Masek.

Intrigued, we set off around the edge of the lake and as we came over the crest of a small ridge were met with the most remarkable site – 1000s of cattle and goats queuing up for water from pools on the edge of the dry river valley just downstream of the lake. We waited for the queues of animals to die down and asked permission from the local guardians of the water source to investigate (Photo 2). The pools turned out to be fed from groundwater flowing out of rocks at the side of the valley. In contrast to the salty water from the adjacent lake, these springs were fresh and potable. We think the water is very old having originally fell as rain on the flanks of the ancient Ngorongoro Highlands (see map) before flowing slowly under gravity through layers of volcanic rocks 10’s of km to the springs. Because there’s so much groundwater stored in these rocks, and because they are not very permeable, the water seeps out quite slowly. So the springs keep running all through even the longest droughts and are vital water supplies for local people.

Photo 2: Asking permission to sample at Eremet springs

We travelled east along the same dry river valley in which we’d encountered the springs. Here the river, which only flows during the wet season, has cut itself into a steep ravine called Olduvai Gorge. We walked down the side of the gorge travelling back in time ~2 million years, the rocks and sediments around us telling a well-documented story of how the environment has changed over that time. Many exciting fossil discoveries have also been made in the gorge including some of our oldest human ancestors (Photo 3-left). For us one of the most interesting discoveries was geological evidence of ancient springs (Photo 3-right) found in the same layers as fossil human ancestors and stone tools which Gail has documented going all the way back to nearly 2 million years ago (read more here). There are clues from the surrounding sediments that there was a lake nearby but it was salty and alkaline, and we think the springs would have kept flowing for 100s or even 1000’s of years during persistently drier periods experienced in the past (read more here).

The springs that were flowing in the Olduvai area 2 million years ago, just like the springs on the margins of present day Lake Masek, would have been the only freshwater for miles around and vital for sustaining life during dry periods. Since there are hundreds of freshwater springs dotted around present day drylands in the East African rift system, we can hypothesise that during dry periods in the past, similar locations would have acted as ‘hydro-refugia’ – places where animals could find the necessary freshwater for survival in an otherwise dry landscape. In dry periods there would be lots of competition for these resources and populations would have become isolated from each other for quite long periods. During wetter periods springs would have enabled our ancestors and other species to move long distances across the East African landscape and beyond, acting like stepping stones connecting river corridors and lakes and enabling populations of different species to encounter one another (read more here). Groundwater was likely therefore an important control on the movement and evolution of humans in this environment.

Photo 3: (L) Paranthropus boisei (‘Zinj’) hominin skull found at Olduvia gorge (Photo Credit: Tim White PhD, Human Evolution Research Center, University of California, Berkeley) & (R) Mark Cuthbert next to a tufa (calcium carbonate) deposit thought to be evidence of groundwater discharging near the site that the Zinj fossil was found.

Groundwater is often ‘out of sight and out of mind’. Our safari gave us a glimpse into its importance in sustaining life in a dryland environment not just in the present day, but also for our ancestors going back at least 2 million years through some climatically turbulent periods. The challenge going forward is how that groundwater resource can be protected to make sure it’s there when it’s needed in the face of an uncertain climatic future.

Acknowledgements: it has been a massive privilege to be able to explore this landscape and ponder how freshwater has shaped life here over millions of years. Particular thanks to our guides Joseph Masoy and Simon Matero, logistical support from Charles Musiba (LOGIFS – Laetoli-Olduvai Gorge International Field Camp) and TOPPP (The Olduvai Paleoanthropological and Paleoecological Project), our hosts at the Ngorongoro Conservation Area Authority, and all our collaborators on the papers cited.


Mark Cuthbert is a Research Fellow and Lecturer in the
School of Earth and Ocean Sciences, at Cardiff University in the United Kingdom. Mark’s work currently focuses on coupled hydrological-climate process dynamics in order: to understand & quantify groundwater sustainability; to improve interpretations of terrestrial paleoclimate proxy archives; to understand Quaternary paleoenvironments & how they influenced our evolution as a species. Read more on Mark by clicking on the links below.

TwitterResearch website




Gail M. Ashley is a Distinguished Professor and Undergraduate Program Director of Quaternary Studies Program at Rutgers University, in the United States. Gail studies modern physical processes and deposits of glacial, fluvial, lacustrine, arid landscapes, and use this information to interpret paleoenvironments. Read more about Gail by going to her research website.

Want to contribute to IAHS’ discussion about 23 unsolved problems in hydrology?

Want to contribute to IAHS’ discussion about 23 unsolved problems in hydrology?

Inspired by the famous list of unsolved math problems (hence the header image), the International Association of Hydrological Sciences has an interesting challenge for us all: define 23 unsolved problems in hydrology:

The International Commission on Groundwater is going to submit a few problems via the LinkedIn forum. A few of us at Water Underground are going to put our thinking caps on and submit a problem or two. If you would like to be part of the discussion very early in 2018, get in touch with Tom Gleeson.

On the social responsibility of water scientists

On the social responsibility of water scientists

Post by Viviana Re, a post-doctoral research fellow at the Department of Earth and Environmental Sciences of the University of Pavia, in Italy.


Should we feel a moral obligation to engage, if our work has real implications on society?

As an environmental scientist, with a PhD in Analysis and Governance of Sustainable development, I grew up “multidisciplinary-minded’ and the three-pillars of sustainability soon become my bread and butter.

However, as I progressively specialized in hydrogeology I had to confront myself with a new world, more technical, definitely interesting, but perhaps a bit suspicious with social sciences (at least some years ago), and where “no quantitative data” was often considered as a synonym of “no substance”.

When, back in 2013, I first presented the concept of socio-hydrogeology at an international congress on hydrogeology I divided this world in two. Some people definitely loved this new approach and found a lot of similarities with their work and research interests. Others, more skeptical, asked me if I decided to quit SCIENCE and dedicate myself to politics instead.

Besides the fact that I generally prefer to be pleased than criticized, I admit I am sincerely grateful to all those who shared with me their perplexities as they made me realize that:

  • I should improve my communication skills;
  • I shouldn’t take anything for granted – multidisciplinary and integrations are the roots of my research but this may not be the case for everyone;
  • I should better engage in promoting the incorporation of the social dimension into hydrogeological sciences and in fostering the connection between science and society.

These things follow from my belief that, as scientists, we should all have a key role in ensuring that the results of our hard work are really used to foster the long-term protection of groundwater resources worldwide.

This is part of our social responsibility, right?

As Stephanie J. Bird says in her paper Socially Responsible Science Is More than “Good Science

“[…] as members of society, scientists have a responsibility to participate in discussions and decisions regarding the appropriate use of science in addressing societal issues and concerns, and to bring their specialized knowledge and expertise to activities and discussions that promote the education of students and fellow citizens, thereby enhancing and facilitating informed decision making and democracy.”

Therefore, as groundwater scientists, part of our responsibility is to commit to share the results of our investigations outside the academic sphere and to find the most appropriate way to engage with civil society. This can be done in several ways, like through public speaking, social networks, media release and active involvement with local communities relying upon the water resources we are studying.

Academics-ivory-tower (Frits Ahlefeldt)

But, is this enough? Is outreach sufficient to ensure that we effectively bridge the famous gap between science and society?


What if we also engage to live more sustainably and to help driving the changes we aim to inspire with our research?

As scientists, every time we write about our work and research results, we almost always find ourselves discussing water distribution on Earth, the global water crisis and the need for sustainable water resources management. We often tell people the importance of saving water, recycling and reducing pollution, and certainly we aim to use the best available scientific tools for providing this information. But then, in our minds, it should also lead us to question whether we, the scientists, actually live sustainably and act responsibly.

Are we really acting to ensure safe water resources, for future generations? We know our food and good consumptions depend on energy and water, but still the global water demand is rising. Still, is there something we can do to diminish our water and ecological footprint? Is there something that we can do to bring the scientific knowledge in our everyday life? What if we would better engage to inspire people, our friends and local communities, and become true advocates of (ground)water protection and management?

We’ve decided to take action on these issues through Responsible Water Scientist, a project launched almost a year ago my myself and my friend and colleague Raquel Sousa. Responsible Water Scientist, is a space where we aim to encourage a broader discussion on the little changes in the daily routine that can make scientists real advocates of groundwater conservation for a more sustainable world. These changes can involve our dietary choices, shopping attitudes and consumption patterns, but are all closely related to our water footprint and the future of global water resources.

Bulk shopping saves plastic packaging and reduces our carbon and water footprint.

Drinking tap water (if safe and available) and bringing our own water bottle will significantly reduce the amount of plastic bottles produced per year.


Shopping bulk, reducing our meat consumption or engaging for a zero waste lifestyle may seem really challenging at first, but the effort is really worth it, indeed, every drop matters! Don’t you agree?

Find out more on Responsible Water Scientists here, and join our community on social networks by sharing your ideas and experience! All comments and inputs are more than welcome!

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Presenting Responsible Water Scientist with a keynote lecture at the 44th congress of the International Association of hydrogeologists (Croatia, September 2017).


Viviana Re is a post doctoral research fellow at the Department of Earth and Environmental Sciences of the University of Pavia (Italy). Her research interests are: isotope hydrogeology, groundwater quality monitoring and assessment, groundwater for international development. She is currently working on the development and promotion of a new approach, called socio-hydrogeology, targeted to the effective incorporation of the social dimension into hydrogeochemical investigations.

TwitterPersonal website

An alternate career path for Groundwater Science-Engineering PhDs

An alternate career path for Groundwater Science-Engineering PhDs

Post by Jim Roy, Research Scientist at Environment and Climate Change Canada.


A recent editorial in Nature highlighted the relative scarcity of academic positions available to graduating PhD students (Many junior scientists need to take a hard look at their job prospects; 25 October, 2017). It notes that “it has been evident for years that international science is training many more PhD students than the academic system can support”. Firm figures aren’t available, but the article suggests maybe < 5 % will land a full-time academic job. That number may be somewhat higher for Groundwater-related disciplines, but the point remains that many should “make plans for a life outside academic science.”

However, it’s not all doom and gloom; indeed the article goes on to state that “it is good for PhD students and postdocs to pursue careers outside academia. Many will find similar challenges and rewards in industry.” There are a lot of options for Groundwater PhDs in industry and the plethora of supporting consulting firms: in mining, oil and gas, tunnel and dam engineering, municipal water supply, and contaminated site remediation, to list a few. However, there is an additional career path to consider, especially if you want to continue doing research – the government scientist, like me.

According to Wikipedea: A government scientist is a “scientist employed by a country’s government, either in a research-driven job (for example J. Robert Oppenheimer on the Manhattan Project), or for another role that requires scientific training and methods.” I’ll be focusing on those that do research (encompassing science and engineering), at least for much of their work.  And in this blog, I’ll be comparing their job duties and conditions to that of the professor, the research job with which the majority of students and post-docs are most familiar and traditionally aiming for.  It’s what I thought I would be too, coming out of grad school. Now it’s been 10 years since I took up my position as a Research Scientist focusing on groundwater contamination/quality with Environment Canada (now Environment and Climate Change Canada) – enough time to have experienced the ups and downs of the Canadian economy and the changing of the governing party, with repercussions of both for federal science priorities and budgets. The discussion below is based largely on my own experience, with insight gleaned from talking with colleagues in other government agenciesa over the years. It’s also highly generalized; the exact situations will vary by country, agency, and even by individual scientist, and may change over time. But hopefully it’s good enough for a light-hearted introduction to this alternate career area.

So here goes – my Top 10 list of how a government scientist job is different than academia:

  1. Freedom

                All scientists want to do work that is meaningful, but not all scientists get to choose on what topic that work will focus. In general, government scientists undertake research on issues of government priority that will advise on federal policy, regulations, and management activities, or that will provide service to important national industries or the public. So their work should have a meaningful impact on their country, if not more broadly; they just don’t get to decide on the priority topics (with exceptions for certain agencies or programs). However, often these priority topics are general enough that there is some range of projects that can fit within them, giving the scientist some flexibility on their research focus. Also, by advising their management and government representatives of important topics, government scientists may influence the direction of government priorities. Also, a government scientist may be afforded some leeway to work on additional topics outside these priority areas with a small fraction of their time. Government research usually targets short- to intermediate-term achievements, as fits the common government election cycle. However, some priority topics may last for decades – see North American Great Lakes eutrophication and algal blooms – waxing and waning in importance with the severity of the problem (costs!) in relation to the other pressures on the government (the economy!). For those who choose this career path – beware, though, when government priorities change, your research area may have to change too.

                For academics, their options are typically much broader, encompassing everything between applied research with immediate implications to research so basic that nobody can predict what may eventually come of it. The caveat to this is that an academic’s research topic often has to be deemed important enough and applied enough for “someone” to fund it. Industry funding is usually quite applied. But even government funding agencies, which are usually the primary support for more basic academic research, are increasingly imposing greater direction over the acceptable topics of proposed research. So perhaps this extra freedom isn’t so vast in practice.

  1. Trading places?

                Many government scientists are appointed to one or more adjunct professor positions at universities where their academic collaborators reside. These could be at nearby universities or those across the globe, and these locations may change over a career. It isn’t a paid position, but allows for closer research ties, including the (co-)supervision of undergraduate and graduate students, which benefits both the university and the government agency. Such positions may also afford access to laboratory space on campus or to additional research funding (held at the university, but directed by the adjunct professor).

                I haven’t heard of a case of the opposite arrangement – adjunct government scientist – but it might exist. Academics may pop in and be given some office space and support during a sabbatical while collaborating with a government scientist, but they’re really just temporary squatters.  If anyone out there knows of such a situation, feel free to post below.

  1. No teaching ( 🙂 or  🙁 )

                An obvious difference, this can be viewed as good or bad news depending on how much you like it.  I enjoyed teaching while I was a grad student. Many scientists give guest lectures or even short-courses at local universities. I taught an entire hydrogeology course for a university colleague during his sabbatical – so this can be an option for some in government who have an interest. Not having required teaching does provide greater flexibility in scheduling your work (especially field trips) and leaves more time for research and/or other important activities, like playing hockey or “family life”.

  1. Professors have grad students; government scientists have technicians

                The model for academic research is based on students and post-docs (a team of them often) carrying out the primary duties of research under the supervision of their professor. Certainly there are exceptions where the professor carries out their own study, but generally they lack the time for this. However, professors may have technicians too. It’s common for some to hire current or past students as technicians for a few years after they graduate, while (senior) professors may have dedicated technicians.

                In contrast, the model for government scientists is to have one or more dedicated and highly-experienced technicians available to assist in their research. Separate analytical laboratory or field teams may also be available. Although, with tightening budgets this technical support seems to be dwindling. It’s also fairly common for post-doctoral fellows to be hired by government agencies to work with their scientists – I’ve worked closely with 2 post-docs over my 10 years at Environment and Climate Change Canada. And what’s more, through adjunct professor positions or just collaborations, government scientists may also work with and (co-)supervise students from a partner university, just not to the same extent as for the academics.

                Thus, there can be a fair bit of overlap between these two models, especially when collaborations extend between academics and government researchers; and this integration, I think, makes for better science all around.

  1. Both are sought out by regulators and policy-makers

                Government scientists might have the inside track to the ear of policy-makers, but advice from academics is often gathered via workshops and contracts for reviews and reports as well.  Sadly, in large departments especially, some bureaucrats may not realize they have internal expertise in an area like hydrogeology. Which leads us to the next point…

  1. Governments typically do a poorer job of selling/showcasing their scientists

                Academics have much more freedom to showcase themselves and their work to the public, the science community, and business/industry. This can be through personalized research web pages, starting a blog (like this one!), and greater freedom to speak to the media (depending on the presiding-government’s rules for their scientists).  They also tend to attend more scientific conferences, where they and their students can advertise their scientific wares to a range of audiences.

  1. No consulting on the side

                Not all professors consult, but many do, which can provide a boost in income and lead to funding or in-kind support opportunities for their research or to job opportunities for their students. I haven’t heard of any government agencies that allow their scientists to consult as a side profession. In part, they want all your time devoted to your job working for them; but it also runs into “conflict-of-interest” concerns.  Now that doesn’t mean you can’t have a side-job (e.g., selling pottery, repairing dishwashers, stand-up comedy, teaching Yoga), but it can’t relate to your science profession.

  1. Border-crossing restrictions

                Working on national (or state/provincial) priority research commonly means government scientists work predominantly on sites in their own country (region), unless inter-jurisdictional agreements are made to combine or share research expertise. In contrast, academics are able and encouraged to work at international sites, which can expand the range of research topics and potentially funding sources available to them.

  1. Less competition for funding (except when the coffers are bare)

                Much of my funding is internal, requiring much shorter (i.e., less onerous) proposals than is typical for my academic colleagues seeking funding through centralized national funding agencies (e.g., NSERC in Canada) or from industry partners. My proposals may still go through a competitive process, though, sometimes with external reviews.  How substantive this internal funding is compared to academic funding will depend on the agency, how science is viewed by the current government, the state of the economy, and the importance of the topic. When internal research budgets are tight, there may not be sufficient funding to go around, especially for those not working directly on key priorities. Of note, some government agencies allow their scientists who have adjunct status at a university to apply for the same set of grants as academics. Whether such proposals are frowned upon or judged differently by funding agencies is up for debate.

  1. Joy in their work

                Frustrations with too-much time devoted to administrative tasks and seeking funding are prevalent in both government and academic research areas. But still, the opportunity to do research on interesting, challenging, and important topics at the edge of our current scientific understanding brings enjoyment / fulfillment to both government scientists and academics. We all feel that slight quickening of the pulse when “the data is in” and we learn if the expected outcomes were realized or (better yet) something different (new!) might be going on.  It’s why we do what we do. In hydrogeology, there remains much to explore, especially at the inter-disciplinary mixing zones around the edges of our specialty. And we’ll need new concepts, new methods, and new connections to move our understanding forward. Scientists from academia and government and industry and other groups can all contribute to this quest. For graduating PhDs, hopefully this leaves you with multiple career path options for joining in the fun.

a In Canada, besides Environment and Climate Change Canada there are also PhD-holders doing groundwater-related research in Natural Resources Canada, Agriculture and Agri-Food Canada, and the National Research Council. In the U.S., much great groundwater research is carried out by the U.S. Geological Survey, with research also carried out by other federal and state agencies. Many other countries have similar geological or environmental departments or agencies with PhDs doing some or much research.  You can look these up on the web, though often government scientist pages aren’t nearly as good as those for academia.


Jim Roy is a Research Scientist at Environment and Climate Change Canada. His current research focuses on: groundwater contaminant impacts on surface waters and aquatic ecosystems, groundwater contributions of phosphorus to surface waters, potential leakage of Alberta oil sands tailings ponds to the Athabasca River, and groundwater and gas systems. Find out more about Jim by clicking on the links below.

Twitter Page | Research Profile

AGU fall meeting New Orleans – what we’re most looking forward, to reduce your FOMO!

AGU fall meeting New Orleans – what we’re most looking forward, to reduce your FOMO!

Two words: French Quarter. OK, well beyond that quite a few things…

On Sunday the fun kicks off with the Hubbert Quorum (link) – a nice and informal meeting with lots of interaction.

On Monday is Advances in Hydrologic Science by Early Career Scientists: A Discussion of the Publishing Process (TH13A; link)

On Tuesday is Mars Underground: Subsurface Waters, Diagenesis, Hydrothermal/Metamorphic Processes, and Their Importance for Planetary Evolution (P24B; link).

On Tuesday night is a memorial jam for Mark Pagani with our very own Mark Cuthbert in the band:

On Wednesday is Hydrology eLightning Session: Tropical Drought, Floodplains, and Ecological Sustainability (H34D; link) and
Fluid Migration Through Subduction Zones (T33F; link):

Thursday is busy:
The MacGyver Session: The Place for Novel, Exciting, Self-Made, Hacked, or Improved Sensors, Data Acquisition, and Data Transmission Solutions to Understand the Geosphere (H41J; link)
Hydrology, Society, and Environmental Change: Coupled Human-Water Dynamics Across Scales (H43R; link)
Novel Insights into Organic Matter Sources, Pathways, and Fate in Groundwater and Surface Waters (B41K; link)

On Friday is Balancing the Water Budget: A Physical Basis for Quantifying Water Fluxes Using Data and Models (H51N; link) and Regional Groundwater Quality, Availability, and Sustainability: Advances, Methods, and Approaches for a Complex, Changing World (H53O; link)

P.S. the AGU Ecohydrology technical committee compiled a list of relevant sessions (link).post: http://www.aguecohydrology.org/agu-sessions.html

P.P.S. If you can’t make AGU, the virtual meeting AGU On-Demand live stream and later YouTube archiving of selected sessions is great (link), especially check out the Monday 10:20-12:20 Union session on “Creating Inclusive and Diverse Field and Lab Environments Within the Geosciences” (link).

P.P.P.S. FOMO is fear of missin out!

Listed compiled by Tom Gleeson from suggestions by Anne Jefferson, Grant Ferguson, Elco Luijendijk, Sam Zipper, Andy Baker, Mark Cuthbert.

Hydraulic fracturing close to groundwater wells

Hydraulic fracturing close to groundwater wells

Post by Scott Jasechko, Assistant Professor of Water Resources with the Bren School of Environmental Science & Management, at the University of California, Santa Barbara, and by Debra Perrone, non-resident Fellow at Water in the West and an Assistant Professor, also at the University of California, Santa Barbara, in the United States.


In December, 2016, the Environmental Protection Agency finalized a report [Ref. 1] on hydraulic fracturing and drinking water resources that, among other conclusions, states:

(a) Quote from [Ref. 1]: “scientific evidence that hydraulic fracturing activities can impact drinking water resources under some circumstances”

(b) Quote from [Ref. 1]: “When hydraulically fractured oil and gas production wells are located near or within drinking water resources, there is a greater potential for activities in the hydraulic fracturing water cycle to impact those resources.”

Tens-of-millions of Americans rely on groundwater stored in aquifers for drinking water. Because it is possible that hydraulic fracturing activities can impact water resources (i.e., quote (a) above), and because groundwaters located close to hydraulic fracturing activities are more likely to be impacted than those farther away should a contamination event occur (i.e., quote (b) above), it is important to assess how many domestic groundwater wells are located close to hydraulically fractured wells.

In a recent study [Ref. 2], we assessed how close domestic groundwater wells are to hydraulically fractured wells, and to oil and gas wells (some hydraulically fractured, some not). Due to consistencies limitations in both oil and gas and groundwater well datasets, we limited our analysis to groundwater wells constructed between 2000-2014, hydraulically fractured wells likely stimulated during the year 2014, and oil and gas wells producing in 2014.

Our study has two main findings.

First, we found that most (>50 %) recorded domestic groundwater wells constructed between 2000 and 2014 exist within 2 km of at least one hydraulically fractured well in 11 US counties (Fig. 1). Further, about half of all recorded hydraulically fractured wells that were stimulated during 2014 are located within 2-3 km of at least one domestic groundwater well. We suggest these regions where groundwater wells are frequently located near hydraulically fractured wells might be suitable areas to focus limited resources for further water quality monitoring.

Figure 1. The percentage of domestic groundwater wells that were constructed between 2000 and 2014 that have a recorded location that lies within a 2 km radius of the recorded location of at least one hydraulically fractured well that was stimulated during the year 2014.

Second, we assessed the proximity of oil and gas wells being produced in 2014 – some hydraulically fractured but others not – and groundwater wells. We found that many domestic groundwater wells are located nearby (<1-2 km) at least one oil and gas well, and, that actively-producing oil and gas wells are frequently located nearby at least one domestic groundwater well (Figure 2). Many of the potential contamination mechanisms associated with the construction, stimulation and use of hydraulically fractured wells are also associated with conventional oil and gas wells, including potential for spills on the land surface and well integrity failures [Ref. 3]. Therefore, assessing potential water quality impacts resulting from activities associated with oil and gas production derived from both hydraulically fractured wells and from conventional oil and gas wells is important.

Figure 2. The upper panel shows the distance between recorded oil and gas wells producing in 2014, and recorded domestic groundwater wells constructed between 2000 and 2014. The lower panel shows the distance between recorded domestic groundwater wells constructed between 2000 and 2014 and the nearest recorded oil and gas wells producing in 2014 (see Ref. [2] and references therein for data sources).

We conclude that (i) publicly-available groundwater well construction data are critical for managing groundwater resources and completing water quality risk assessments (see Ref. 4 for data quality information), and emphasize that not all states currently provide access to digitized groundwater well construction records (e.g., Figure 2), (ii) hotspots exist where activities related to oil and gas production occur nearby domestic groundwater wells, and these regions may be targeted for further groundwater quality monitoring, and (iii) assessing how frequently activities in the hydraulic fracturing water cycle impact groundwater quality may be vital to securing high quality water pumped from many domestic water wells where oil and gas production is common.

Figure 3. Hydraulically fractured well situated close to an irrigation system in California’s San Joaquin Valley.



[Ref. 1] U.S EPA. Hydraulic Fracturing for Oil and Gas: Impacts from the Hydraulic Fracturing Water Cycle on Drinking Water Resources in the United States (Final Report). U.S. Environmental Protection Agency, Washington, DC, EPA/600/R-16/236F, 2016. Accessed from https://www.epa.gov/hfstudy November 15, 2017.

[Ref. 2] Jasechko S., Perrone D. (2017). Hydraulic fracturing near domestic groundwater wells. Proceedings of the National Academy of Sciences.

[Ref. 3] Vengosh A., Jackson R. B., Warner N., Darrah T. H., Kondash A. (2014). A critical review of the risks to water resources from unconventional shale gas development and hydraulic fracturing in the United States. Environmental Science & Technology 48, 8334-8348.

[Ref. 4] Perrone D., Jasechko S. (2017). Dry groundwater wells in the western United States. Environmental Research Letters 12, 104002.


Scott Jasechko’s research focuses on fresh water resources, and uses large datasets to understand how rain and snow transform into river water and groundwater resources.

Find out more about Scott’s research at : http://www.isohydro.ca.




Debra Perrone  is interested in the multifaceted interrelationship between water, energy, and food resources. Her research explores how the interactions among these resources affect decisions and tradeoffs involved in water resource management.

Find out more about Debra’s research at: http://debraperrone.weebly.com/.

Bedrock: A hydrogeologist’s devotional

Bedrock: A hydrogeologist’s devotional

Post by Kevin Befus, Assistant Professor at the College of Engineering and Applied Science at the University of Wyoming, in the United States.


I want to share a book with you that has encouraged me through initial academic mires (I was only in graduate school for 7 years…) and inspired me to expand my perception and appreciation of the natural world.

The book is Bedrock: Writers on the Wonders of Geology [Savoy et al., 2006]. It is a carefully curated collection of snippets and excerpts from international literary sources describing geologic processes and outcomes. Most of the writings come from the 20th century with several exceptions extending not quite as far back as the Pleistocene. Each chapter, or collection of writings, is oriented around a theme in the earth sciences, one of which is “Rivers to the Sea”…the creative views of hydrologic, mainly riverine, processes chapter. While the excerpts are the main event in each chapter, a quick introduction to each selection is given within the broader geologic context along with some reasoning in why each was chosen.

Bedrock is not a book about hydrogeology, and it really doesn’t directly talk about water underground. BUT, Earth is explored in the excerpts, and developing connections between groundwater and other geologic processes is our job, not the literary masters who “contributed” tidbits to the book. As you should have expected, John McPhee shows up a number of times, but not too much. Many of the early geologists (e.g., G.K. Gilbert, James Hutton, and John Wesley Powell) and environmentalists (e.g., Rachel Carson and John Muir) also share their reflections of geologic forces on nature.

As someone who reads blogs about groundwater, remember to extend the literary reflections to include how the topics interact with groundwater systems. For example, the cover image evokes excitement (or consternation) from a groundwater hydrologist, as it shows the coastline of Nullarbor Plain in southern Australia, home to the “world’s largest limestone karst area” (http://www.australiangeographic.com.au/travel/destinations/2016/04/hidden-nullarbor).

My suggestion for reading this book is to take it slow: one excerpt in the morning to kick-start the day, remembering why it is you do what you do. Be inspired, awed, and reminded of how geological processes have shaped our world over billions of years. Or, read an entry when the day has taken a turn to the slow or chaotic. Like any good devotional, Bedrock has great re-readability and also points you towards the original documents for more in-depth explorations of literary (hydro)geology.

Happy reading!

Savoy, L. E., E. M. Moores, and J. E. Moores (2006), Bedrock: Writers on the Wonders of Geology, Trinity University Press, San Antonio, TX.




Kevin Befus leads the groundwater hydrology group in the Civil and Architectural Engineering Department at the University of Wyoming. With his research group, he studies how groundwater systems respond to hydrologic conditions over glacial timescales and in mountainous and coastal environments.  You can follow along with Kevin’s research through any of the links below:

Twitter | Research Group Page | UW Faculty Page








Feature photo image source: 

Community advice to young hydrologists, Part 1

Community advice to young hydrologists, Part 1

We at Water Underground loved reading Young Hydrologic Society’s post titled “Community advice to young hydrologists” – an advice column written by a network of established scientists in the field. We appreciated the column so much, in fact, that we have decided to re-blog the post to you (with YHS’s consent, of course). We’ve split up their post by question, and have added in hyperlinks to all contributors and related material (as has always been our inclination). Happy reading!


Question: What book or paper has been most influential to your career and why?

Groundwater by Freeze and Cherry – this textbook, now out of print, was a critical reference as I began my graduate training in hydrogeology and I still refer to it today.

Jean Bahr (University of Wisconsin)








I can think of no single one.  However, papers that were a combination of field observations and clever analyses leading to new insights always are intriguing.  Papers which I find of little value are those that propose a new modeling approach with little to no field verification, or which use existing models to reach some conclusion.  For example, we seem to be seeing a proliferation of papers using complex models to highlight some “new” effect of climate change on the hydrologic cycle, with no grounding in hindcasts. (See this, also) The musings of Keith Beven always have been insightful, including his Advice to a Young Hydrologist.

Jerad Bales (CUAHSI)



I can’t identify single “most influential” books or papers – I learned early to read as widely as possible, and not just within narrow/specific research problems of direct interest. I have been inspired by a range of articles – including books on philosophy, history of physics, etc. – which broadened my approach and ways of looking at a given problem. Indeed, some of my most influential work developed from studying methods and approaches in statistical physics and physical chemistry.

Brian Berkowitz (Weizmann Institute of Science)



The most important influence was a person – Mike Kirkby and particularly the undergraduate course on quantitative hydrology he taught at the University of Bristol when I was taking my degree there (later, I would do a post-doc with him at Leeds that resulted in the development of Topmodel). That gave me a lot of reading to do – but it was probably not the hydrological reading that had most influence, but rather the papers on theoretical geomorphology starting with Horton BGSA 1945, then picked up by Kirkby, Frank Ahnert and others in the late 1960s. I struggled to understand them (at the time I wanted to be a geomorphologist but I have never quite finished getting the water part right) but they left me the idea that it was possible to theorize about environmental processes and systems in approximate but useful ways.

During my PhD the most influential paper was undoubtedly Freeze and Harlan JH 1968, and the papers about the field site I was applying my model to by Darrell Weyman (HSB 1970, IAHS 1973). If I had talked to him a little more (he was doing his PhD at Bristol while I was an undergraduate) or read those papers more carefully, then I might have been more realistic in my PhD modelling.

The most important book at that time was Zienkowicz, Finite Element Modelling (that was the technique I was trying to master). Hillslope Hydrology edited by Kirkby was also important but came later.

Keith Beven (Lancaster University)


Paper: Scale of Fluctuation of rainfall models by I. Rodriquez-Iturbe. It formed the basis for my MSc research that I did during 11 months in Davis California (As a Dutch Student from Wageningen). It was extremely difficult stuff, but I kept on it and it understanding gave me the stamina to really dig into a subject. It was the basis for my first paper entitled “Analytically derived runoff models based on rainfall point processes” in WRR. To obtain better background I also read in depth the influential.

Book: Random Functions and Hydrology by R. Bras and I. Rodriquez-Iturbe.

Marc Bierkens (Utrecht University)




Dooge’ 1986 Looking for hydrologic laws in WRR. This paper gives a broad perspective on science, including scales.

Günter Blöschl (TU Vienna)









Konrad and Booth (2005), Hydrologic changes in urban streams and their ecological significance, American Fisheries Society Symposium, 47:157-177.  This paper is a bit outside my area of expertise, but I think the linkage they make between physically measurable streamflow changes and stream ecology represents a fundamental shift in thinking from engineering hydrology to more of an eco-hydrology perspective.  They illustrated that we need to go beyond analyzing just changes in peak flow or low flows (or fixed percentiles), to look at more derived metrics that better capture hydrologic regime change.

Laura Bowling (Purdue University)




That is a very hard question. As a Geography undergraduate student, I had to write a particular essay on the “all models are wrong” theme and this involved critiquing two papers which completely changed my worldview about models and modelling: Konikow and Bredehoeft’s 1992 ‘Ground-water models cannot be validated’ Advances in Water Resources 15(1):75-83.  and Beven’s 1989 ‘Changing ideas in hydrology – the case of physically-based models’ Journal of Hydrology.

But in the last year, I would say it has been Lab Girl by Hope Jahren (2016) who is a gifted and talented scientist and writer and has the knack of intertwining the natural world with tales of remaining brave in your career. I wish I’d had the opportunity to read it earlier in my career.

Hannah Cloke (University of Reading)


Ecological and General Systems – H.T. Odum. This book explores general systems theory in the context of ecosystem behaviors. It is holistic, comprehensive, and full of important insights about the structure and dynamics of systems.

Matthew Cohen (University of Florida)





It is a novel by Milan Kundera: “Slowness”. My natural tendency is to rush up, be as fast as possible, quickly fix things… Yet, speed often leads to miserable outcomes. Many lines of Kundera’s book are still in my mind, and they work as a continuous reminder for me that only slowness allows thoughtful consideration, serious reflection, and appreciation of reality. Realizing this has strongly influenced my academic career as it made me focus on the quality (and not the quantity) of my work.

Giuliano Di Baldassarre (Uppsala University)



Several hydrogeology-related texts were very helpful for me.  These include some of Mary Hill’s papers, John Doherty’s PEST manual (as much for the philosophy as the instruction), some of Jasper Vrugt’s early papers, and work by both Wolfgang Novak and Steve Gorelick on measurement design. The real recommendation would be to find authors that you enjoy and read as much of their work as possible – in this category, I would add Shlomo Neuman, Randy Hunt, Hoshin Gupta, Dani Or, Keith Beven and Graham Fogg. I am sure that I am forgetting more than I have listed. I think it is equally important to read broadly. Rather than provide a list, I’ll encourage you to look at my recent paper in Ground Water (Sept 2016) for some suggestions!

Ty Ferré (The University of Arizona)




Book:  Groundwater Hydrology by David Keith Todd, 1st edition, 1959. As a 3rd-year undergraduate in hydrology at the University of New Hampshire in 1973, this book (and course by Francis Hall) kindled my interest in groundwater and completely changed my career path, which previously was essentially an aimless sleepwalk through my major in mathematics.

Paper/report:  Kaiser, W. R., Johnston, J. E., and Bach, W. N.. 1978, Sand-body geometry and the occurrence of lignite in the Eocene of Texas: The University of Texas at Austin, Bureau of Economic Geology Geological Circular 78-4, 19 p.  This paper demonstrated in stunning detail how modern borehole geophysical data together with understanding of the geologic genesis of sedimentary deposits could be used to create unprecedented subsurface maps of aquifer/aquitard system heterogeneity and structure. This led me down the long path of better integrating groundwater hydrology and geologic depositional systems.

Graham Fogg (UC Davis)


My interests have been in predictive hydrometeorology. The following were influential books at the start of my carrier in the late 70s and early 80s: Dynamic Hydrology by Eagleson; by Wallace and Hobbs; Applied Optimal Estimation by Gelb (ed).  These represented the fields of hydrology, meteorology, and estimation theory with applications to prediction, and were the necessary pillars to build predictive hydrometeorology.

Konstantine Georgakakos (Hydrologic Research Center in San Diego)






Haitjema and Mitchell-Bruker (2005) which taught me to think of groundwater as a process that interacts with topography, climate and geology in complex but predictable ways.

Tom Gleeson (University of Victoria)









The paper that has been most influential to my career is most certainly  “Johnston, P. R., and D. H. Pilgrim (1976), Parameter optimization for  watershed models, Water Resources Research, 12(3), 477–486. I read this paper during my graduate work in the early 1980’s and was intrigued by their report that “A true optimum set of (parameter) values was not found in over 2 years of full-time work concentrated on one watershed, although many apparent optimum sets were readily obtained.”

On the one hand this paper clearly identified an important problem that needed to be addressed. On the other (as I often remark during talks on the subject), I think it was remarkable as an example of a paper reporting the apparent “failure” of the researchers to achieve their goals … how often do we see people reporting their failures in the literature these days :-). More of this kind of work – reporting a scientific study and accurately reporting both successes and failures … but especially failures … is critically important to the progress of science, so that people can both contribute to solutions and also avoid unsuccessful forays down paths already tried.

In any case, the paper clearly pointed me towards an important problem that led to me adopting a path of research over the past decades, which led to the development of the SCE and SCEM  optimization algorithms (and indeed a whole field of optimization developments), studies into impacts of model structural deficiencies, multi-criteria methods for parameter estimation, the diagnostic model identification approach, and more recently the Information Theoretic approach.

The 1990 paper by Michael Celia et al on the numerical solution of Richards equation, recommended to me by Philip Binning at the beginning of my Honours Project at Newcastle Uni. This paper made a big impression on me because it provided a very clear exposition of how to solve a challenging modelling problem – and played a bigly role in getting me interested in research.

Dmitri Kavetski (University of Adelaide)


The Ecological Studies Series, published by Springer, was the most influential in my career because several books published in the Series (e.g., Forest Hydrology and Ecology at Coweeta edited by Swank and Crossley and Analysis of Biogeochemical Cycling Processes in Walker Branch Watershed edited by Johnson and Van Hook) sparked my interest in forest hydrology and biogeochemistry. In tandem with the superb mentorship of Prof. Stanley Herwitz (Clark University), I decided to embark upon a career as a forest hydrologist as a sophomore in college. I never looked back.

Delphis Levia (University of Delaware)





The papers of the series “Plants in water-controlled ecosystems” (2001, Advances in Water Resources 24), by Laio, Porporato, Ridolfi, and Rodriguez-Iturbe have been among the first and most influential I have read. Their clean, analytical approach to the complex interactions among vegetation, soil, and climate remains deeply inspiring. As an example of inter-disciplinary work (actually outside hydrology), I would like to mention the book by Sterner and Elser (2002) “Ecological stoichiometry. The biology of elements from molecules to the biosphere” (Princeton University Press) – a great example of how integrating knowledge from various sources around a common theme can yield deeper understanding and perhaps even lay the foundation of a new discipline.

Stefano Manzoni (Stockholm University)



The Hewlett and Hibbert 1967 conference paper “Factors affecting the response of small watersheds to precipitation…” is perhaps the best paper ever written in hydrology. For a full homage, please look here. The paper is field-based, theory focused and a blend of bottom-up and top-down research, before that was even ‘a thing’. It inspired me in my graduate research in the 1980s; I continued to read it and ponder it in my first years as a professor, as I strived to follow in Hewlett’s footsteps. He was my mentor even though he retired before I could ever meet him.

Jeff McDonnell (U Saskatchewan)




 In general, the books that have been most influential to me refer to sister disciplines. The reason is that I found illuminating to study methods and models used in statistics and economics for the purpose of applying them to hydrology for the first time. Thus, the most influential book to me has been “Statistics for long-memory processes”, by Jan Beran. The very reason is that I found there a detailed explanation of models that were useful to get to target with my Ph.D. thesis. 

Alberto Montanari (University of Bologna)



Chamberlin TC. 1890. The method of multiple working hypotheses. Science 15: 92-96 (reprinted in Science 148: 754–759 [1965]). I read this paper as part of a second-year course in Archaeology, which I took as an elective in my undergraduate program. Although the writing style is somewhat archaic, this article introduced me to the value of hypothesis-based thinking in science and the need to avoid favouring a pet hypothesis or model. It is instructive also to read the many follow-up essays to gain a broader perspective on hypothesis-based research and, more broadly, the “scientific method.”

Dan Moore (University of British Columbia)





I think I was more influenced by my peers, colleagues, mentors, supervisors and friends as I learn better through discussions and challenges. One of the more memorable papers is one of Manning (Manning, R. (1891). “On the flow of water in open channels and pipes,” Transactions ofthe Institution of Civil engineers of Ireland.) and it’s associated history. In this paper he actually suggested a far more ‘complex’ formulation than the formula which is today widely known as the Manning equation – history has it that it was never adopted widely as well as many subsequent more more sophisticated formulations. Science doesn’t work linear and we are sometimes less rational or objective (if the latter is actually possible) than we believe.

Florian Pappenberger (ECMWF)


“Show me a person who has read a thousand books and I’ll show you my best friend; show me a person who has read but one and I will show you my worst enemy.” I have been influenced by many and I can’t say one is *the* most influential or important alone.  At the moment, I am reflecting on (McCuen RH. 1989. Hydrologic Analysis and Design. Prentice Hall: Englewood Cliffs.) As far as being a hydrology textbook it is not particular special, but it is written extremely clearly with a lot of good step-by-step workflows.  Most importantly, the book integrates throughout its whole development the concept of analysis versus synthesis, and this has been central to how I approach my research.  We do both analysis and synthesis.

Gregory Pasternack (UC Davis)


This is very difficult to say. I must admit that my academic work started from engineering practice and I only started reading the international literature very late in my career. But a book that has been very influential to me was the book by Fischer et al. (1979) “Mixing in inland and coastal waters”. Fischer soon died in an accident after this book was published. The book introduced me to the fundamentals of mixing processes in estuaries, on which I had done substantial field research and had developed my own practical engineering method, which I still use, but which lacked a fundamental theoretical basis. I am still working on finding this fundamental basis, and Fischer’s book put me on that track.

Hubert Savenije (TU Delft)


It would be tough to answer what’s been the most influential to my career as a whole, but I could answer what was the most influential to my early career, and that was Menke’s Geophysical Data Analysis: Discrete Inverse Theory.  I labored through that book for years during my PhD. My copy has dog-eared pages and writing throughout as I tried to figure out inversion methods.  Finally getting my head around the mathematics of inversion really opened up some doors for me early on.  Davis’ Tools For Teaching also really helped me think about how to be as effective a teacher as I could be.

Kamini Singha (Colorado School of Mines)



Books are hardly ever influential once you are actually ‘in’ research. Early on, look for the best review articles in your field. They will ‘set the scene’ for you.

Keith Smettem (The University of Western Australia)






Opportunities in the hydrologic sciences”, National Academy Press. This landmark book which defined hydrology as a science appeared right at the start of my PhD. It provided a nice framework for my own research and that of my fellow PhD students in those days.

Remko Uijlenhoet (Wageningen University)





It is difficult to select one single work from the literature that has been influential over my entire career in groundwater flow and transport modeling.  But, there is one book that I used as a grad student that I still refer to today.  It is “Conduction of Heat in Solids” by Carslaw and Jaeger.  The book is a treatise on analytical solutions to diffusion equations.  The lesson for me is that knowledge from other disciplines (in this case thermal engineering) can be applied to problems in hydrology.  Another lesson is that we can learn a lot and gain important insights through wise approximations that have analytical solutions.

Al Valocchi (University of Illinois at Urbana-Champaign)


Abramowitz & Stegun: Math is something you look up, not something you try to memorize.

Nick van de Giesen (TU Delft)






In hydrology, some of the most influential books for me have been Handbook of Hydrology (edited by David Maidment) and Principles of Environmental Physics (Monteith & Unsworth). These two books are so rich in physics, empirical equations, recipes, and references. Of course the times have changed and nowadays you can google almost anything, but some of the chapters in these books are so well written that I still regularly use them. They also have the benefit that they summarise areas of research where things haven’t actually changed too much since the 80ies – the physics we use haven’t become that much more sophisticated, and sometimes in fact less so; whereas the field measurements on which a lot of the empirical rules and equations are based generally also haven’t been added much to since.

Outside hydrology, some books that have made me think differently about the field and my research include

Emergence: The Connected Lives of Ants, Brains, Cities, and Software (Johnson) – one of the first popular science books I read that made me think different (about ecohydrology)

The Sceptical Environmentalist (Lomborg) – I didn’t accept his reasoning but it was seductive and it forces you to really pick apart the logical and rhetorical flaws he uses.

Thinking, fast and slow (Kahneman) – which really made me realise the questionable quality of my analytical rigour and decisions in general (also those of anyone else, though!).

Albert van Dijk (Australian National University)


Physical Hydrology by Dingman and Elements of Physical Hydrology are both great textbooks. Why: just lots of “basics” well explained, emphasizing the need to understand PROCESSES.

Doerthe Tetzlaff (University of Aberdeen)



House at Pooh Corner, specifically, Chapter VI. In which Pooh invents a new game and Eeyore joins in.  The first paragraph is an awesome description of a classic watershed and affirms my theory that hydrology is truly everywhere… even on Mars.  Indeed, the search for “life” has largely been a search for “water.”

Todd Walter (Cornell University)





Comparative hydrology, edited by Malin Falkenmark and Tom Chapman (1989). This book is one of the first to examine global hydrology phenomena. It asserts that a comprehensive and systematic description of hydrological processes is (i) possible (ii) not too complicated. Until then I’d thought the task was impossible, so I found the approach inspirational for my research.

Ross Woods (University of Bristol)

Of Karst! – short episodes about karst

Of Karst! – short episodes about karst

Post by Andreas Hartmann Assistant Professor in Hydrological Modeling and Water Resources at the University of Freiburg.


Episode 3 – Learning about karst by … KARST IN THE MOVIES!

Before writing about karst hydrology in “Of Karst! Episode 4”, I have been urged to present some more visual information on karst landforms. Of Karst! Episode 1 focused on the abundance of hilarious karst landforms in nature. This episode focusses more on the appearance of karst features in famous movies and TV programs that may be familiar to some of us, although we may not have watched them through the eyes of a karst fanatic at the time.

In the next episode, we follow the path of the water from the karstic surface with karstic towers and dolines, through caves and conduits, to spectacular karst springs where waters emerge to the surface.

Movie makers have their reasons to pick spectacular landscapes for their stories and, Of Karst!, those landscapes are crowded with karst features. Let’s begin with James Bond. Created in the 70s, “The Man with the Golden Gun” finds a spectacular showdown just in front of a lovely tower karst at the Khao Phing Kan island in Thailand. Tower karst is a karst landform that is, characterized by residual hills of limestone rising from a flat plain or the ocean.

Figure 1: Bonds‘ duel with villain Scaramanga in front of a tower karst rock (Khao Phing Kan, Thailand; http://www.criminalelement.com, http://www.marinaaonang.com)

Similar landforms were chosen as scenery for a recent remake of the King Kong saga. Fighting with intruders and evil monsters from the deep subsurface (karst caves?), Kong had the pleasure living on the beautiful Cat Ba Island in Northern Vietnam, whose characteristic landscape evolved due to the strong dissolution of limestone.

Figure 2: Silhouette of Kong between the Tower Karst mountains of Cat Ba Island located at Ha Long Bay, Vietnam (https://c1-zingpopculture.eb-cdn.com.au, http://www.baolau.com).

The opposite landform to tower karst landforms are karstic dolines, which occur commonly as funnel shaped depressions on the surface, also formed by carbonate rock dissolution. These depressions do not only funnel the water downwards to the subsurface, but also create favorable conditions for the installation of (very) large radio telescopes. The largest of those was built a couple of years ago in China but a similarly impressive one can be found in Puerto Rico, where James Bond had to deal with his evil competitor Trevelyan in “Goldeneye”.

Figure 3: Bond fighting with evil Trevelyan in Goldeneye high above the Arecibo Observatory in Puerto Rico that was built just in the middle of a karst doline (https://i.pinimg.com, http://www.si-puertorico.com).

Underneath the tower karst and dolines, karst dissolution creates wide networks of karstic caves and conduits. With increasing dissolution of the carbonate rock, these features may also emerge at the surface, which was probably the case for the Azure Window at Malta. This karst landform was chosen as the background of a conversation of the famous Khaleesi and her spouse Drogo in “Game of Thrones”. Unfortunately, this amazing land form is not available for further movies as it was recently destroyed by a storm.

Figure 4: Khaleesi speaking to her beloved Drogo in Game of Thrones in front of the Azure Window in Malta (http://nypost.com).

Deeper in the subsurface, the famous Devetàshka cave in Bulgaria set the stage for a dramatic showdown in “The Expendables 2”, when Stalone’s plane crashed through the cave entrance that used to be the exit of groundwater flows emanating from karst. Imagine the tremendous amounts of water filling the karst system over thousands of years that are capable of forming a cave that can (almost) host an entire airplane!

Figure 5: Stalone’s plane crashing into the Devetàshka karstic cave in Bulgaria in The Expendables 2 (www.huffpost.com, www.wikipedia.org).

Due to the formation of dolines, caves and channels, karst springs are usually quite large in terms of their discharge. They also provide amazing sets for fantasy movies. Even though the springs of the St. Beatus Caves in Switzerland only inspired Tolkien for the scenery of the Rivendell, the town of the elves, their similarity is obvious.

Figure 6: Elves’ town Rivendell in Lord of the Rings, whose scenery was inspired by the karst spring of the St Beatus caves in Switzerland (http://www-images.theonering.org, http://tilomitra.com).

This movie-based tour through karst systems may have given you an impression how rainfall becomes discharge in karst systems. Of Karst!, Episode 4, will combine this impression with the hydrological, and more scientific point of view. It will speak to the complexity of these specific surface and subsurface land forms, and elaborate on why exploring and understanding these processes is worthwhile.



Andreas Hartmann is an Assistant Professor in Hydrological Modeling and Water Resources 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

Where does the water in streams come from when it rains?

Where does the water in streams come from when it rains?

Post by Anne Jefferson, associate professor in the Department of Geology at Kent State University, in the United States.


The title of this blog post might seem like a question with an obvious answer, or even a silly question to pose on a blog devoted to groundwater, but if you don’t see the connection between streamflow and underground water, you need to keep reading.

Water in streams during storms does come from the sky, but often it’s not the water droplets falling in a particular rain storm that are going rushing down the stream during that storm. Very little precipitation falls directly on the stream channel, because streams occupy very little of the landscape. So most water in a stream has to travel over or under the ground to get there. Traveling from some random point in a catchment to a stream takes time, and there are usually other water molecules between the freshly fallen raindrop and the channel.

Water molecules that can’t infiltrate into the ground become surface runoff. Surface runoff tends to reach the stream channel fairly quickly, because the water molecules encounter much less flow resistance than water moving through soil or bedrock and because all of the other water molecules between them and the stream are also on the same downhill express lane to the stream. So a water molecule that becomes surface runoff can reach a stream minutes to hours after the raindrop first hit the land surface.

On the other hand, raindrops that infiltrate into the ground take a much more leisurely approach to reaching the stream. Underground, flow resistance is really high, relative to what surface runoff encounters, because the water molecules have to squeeze through tiny and tortuous open spaces between soil particles, roots, and rock. They may even be trapped by capillary forces or stick to mineral or organic surfaces. Plus, underground, there are lots of other water droplets also slowly making their way to the stream. Being a water molecule that goes underground to reach a stream is not so much taking an express lane, as joining the back of a barely moving traffic jam that stretches as far as the eye can see. In the minutes, hours, and days during which a stream runs high following a rainstorm, that poor underground water molecule may only have moved a few meters to a few hundred meters toward the channel. Indeed, its main function in joining the back of the traffic jam was to give a pressure wave nudge to the water molecules closer to the channel, urge them to get a move on, and increase the rate they discharge into the stream.

With those general concepts in mind, let’s turn our attention to humid, forested landscapes. Most rain will infiltrate into the soil, disappear underground, and join the back of the traffic jam. As a consequence, when we look at the water rushing along in a stream channel, during or shortly after a storm, mostly we are not seeing water that fell from the sky in the storm. We’re seeing the ghosts of storms past. Catchment hydrologists call this “old” water. To put some numbers on it, 60-80% of the volume of streamflow during and immediately following a storm is typically old water. Even at the peak of the streamflow, ~50% of the water in the stream is old water.

The Cuyahoga River in Kent, Ohio under low flow conditions, October 2017.

The Cuyahoga River in Kent, Ohio, at high flow, March 2014.

How did hydrologists figure out that the water in streams during storms is old water (at least in forested landscapes)? It would be virtually impossible to go out to a catchment and measure the water flowing across all possible surface runoff, soil water, and groundwater paths.

Wouldn’t it be convenient if there was some way to label the water molecules as new or old and then just count the ratio of new to old water molecules in the stream at a given time? Fortunately for hydrology, variations in the isotopes of hydrogen and oxygen in the water molecules provide just such a tracer. Beginning in the late 1960s, hydrologists realized that they could use the storm-to-storm differences in the isotopic ratios of rainfall to identify water that came from the most recent storm versus water that didn’t. Thus the technique of isotope hydrograph separation was born. The popularity of the method grew rapidly, hydrologists began to try it out in catchments all over the world. This led to more recent work carefully laying out the assumptions and limitations associated with the technique and developing ever more sophisticated methods of analysis. Even more important than the method itself was that hydrologists, confronted with the reality that most of the water in the stream during a storm was old, had to then come up with mechanistic explanations for how that was possible. I don’t think it’s hyperbolic to say that isotope hydrograph separation really helped revolutionize the field of catchment hydrology.

When I teach hydrology, I teach students that in our forested corners of Ohio the water in the stream during storms is old and I explain the mechanisms. But I also think it’s important for them to understand the technique that helped generate those insights, and so I make sure to teach them about isotope hydrograph separation. With the support of an NSF grant, I developed a teaching module that gives students a chance to work with real data and do their own hydrograph separation. My hope is that the exercise will give them a deeper appreciation of the technique, the assumptions and uncertainties it contains, and the insights it is able to provide. This teaching module is available on the SERC website for anyone to use in classes or just for fun. There are data to download, step-by-step directions, and links to related readings. If this post has spurred your interest in streamflow generation or isotope hydrograph separation, I encourage you to check it out. Other good places to learn more about applications of isotopes in hydrology at the SAHRA website or in this book chapter by Kevin McGuire and Jeff McDonnell.

Kent State students measuring discharge in the stream where we conducted the hydrograph separation.


Anne Jefferson is an associate professor in the Department of Geography at Kent State University. Anne‘s research focuses on watershed hydrology, groundwater-surface water interactions, and landscape evolution in human-altered and volcanic landscapes. Current projects of her’s focus on green infrastructure, stormwater management, and stream restoration. Keep up to date with Anne by clicking on any of the links below:

Research profile | Twitter | Personal Website