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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!

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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)

 

 

 

 

 

 

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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)

 

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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)

 

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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)

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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)

 

 

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

Günter Blöschl (TU Vienna)

 

 

 

 

 

 

 

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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)

 

 

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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)

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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)

 

 

 

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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)

 

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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)

 

 

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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)

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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)

 

 

 

 

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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)

 

 

 

 

 

 

 

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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)

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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)

 

 

 

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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)

 

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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)

 

 

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 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)

 

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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)

 

 

 

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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)

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“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)

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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)

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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)

 

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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)

 

 

 

 

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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)

 

 

 

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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)

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

Nick van de Giesen (TU Delft)

 

 

 

 

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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)

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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)

 

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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)

 

 

 

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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)

Groundwater organic matter: carbon source or sink?

Groundwater organic matter: carbon source or sink?

Post by Andy Baker, Professor researching groundwater, caves, past climate, organic carbon and more at the University of New South Wales, in Australia.

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We know a lot about the carbon cycle, right? Increased carbon dioxide emissions since the Industrial Revolution have perturbed the carbon cycle. This has led to rising atmospheric carbon dioxide levels and climate change.

Not all this extra carbon accumulates in the atmosphere as carbon dioxide. Carbon sequestration is also occurring, for example in the oceans and terrestrial biosphere. All the carbon fluxes and stores on the planet must balance. In recent years there has been a hunt within the terrestrial system to quantify some missing carbon, such as the particulate organic carbon in river systems and dissolved organic carbon in glaciers.

So, what about groundwater? Could this be a previously unrecognised source or sink of carbon? We already know that the global volume of groundwater of 1.05 x 1019 litres is the world’s biggest source of freshwater. But groundwater natural organic carbon concentrations are low: typically, 1 part per million (ppm). This means that the global groundwater organic carbon store is just 10.5 x1015 g. For comparison, rivers are estimated to sequester this amount in just four years. Basically, there’s no significant store of organic carbon in groundwater.

But hold, on, this raises another puzzle, which is: where has all the organic carbon gone? Groundwater is recharged from rivers and from rainfall. Rivers have much more dissolved organic carbon than the 1 ppm found in groundwater. And the recharge from rainfall passes through the soil. And soil leachates also have much higher dissolved organic carbon concentrations than groundwater. So, despite the high concentrations of organic matter in the soil and rivers, most of this organic matter is ‘lost’ before reaching the groundwater. Is it biologically processed (and therefore a potential source of carbon dioxide)? Or is it sorbed to mineral surfaces (and therefore a potential sink of carbon)?  Most likely, both processes occur in competition.

Groundwater organic matter: a carbon source or sink? We don’t know. But a few groups are working on the puzzle. For example, our group at UNSW Sydney is collecting groundwater samples and measuring organic carbon sorption to minerals, and microbial use. In the USA, groundwater data has been mined to understand the rate of loss of organic carbon in groundwater. This December, river and groundwater experts come together at the AGU Fall Meeting to share our understanding. Not least because surface and groundwater are interconnected systems.

Collecting groundwater samples to understand whether organic matter is a carbon source or sink. Long field days at the UNSW Wellington Research Station mean the final sample is often collected at dusk.

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Andy Baker is the Director of Research and UNSW’s School of Biological, Earth and Environmental Sciences. His research interests include hydrology, hydrogeology, cave and karst research, paleoclimatology, and isotope and organic and inorganic geochemistry. You can find out more information about Andy at any of the links below:

Research profile | Twitter | Facebook

Western water wells are going dry

Western water wells are going dry

Post by Scott Jasechko, Assistant Professor of Water Resources at the University of Calgary, in Canada, and by Debra PerronePostdoctoral Research Scholar at Stanford University, in the United States of America.

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Wells are excavated structures, dug, drilled or driven into the ground to access groundwater for drinking, cleaning, irrigating, and cooling. We recently mapped groundwater wells across the 17 western states [1], where half of US groundwater pumping takes place. The western states contain aquifers key to United States food production, including the Central Valley of California and the central High Plains.

Millions of water wells exist in the western US, alone. About three-quarters of these wells have been constructed to supply water for household uses. Nearly one-quarter are used to irrigate crops or support livestock. A smaller fraction (<5 %) supports industry [1].

Western US water well depths vary widely (Fig. 1). The great majority (90%) of western US well depths range between 12m and 186m. The median western US well depth is 55m. Wells with depths exceeding 200m tap deep aquifers bearing fresh groundwater, such as the basal formations in the Denver Basin aquifer system, and the deeper alluvium in the California Central Valley. Shallow wells are common along perennial rivers, such as the Yellowstone, Platte, and Willamette Rivers.

Fig. 1. Western USA wells depths. Each point represents the location of a domestic, industrial or agricultural well. Blue colors indicate well depths of less than the median (55m), and red-black colors indicate well depths exceeding the median.

The wide variability of well depths across the west (Fig. 1) emphasizes the value of incorporating well depth data when assessing the likelihood that a groundwater well may go dry.

We know wells are going dry in the western US: journalists have identified numerous communities whose well-water supplies have been impacted by declining water tables [2-4]. While several studies have assessed adverse impacts of groundwater storage declines—such as streamflow depletion [5], coastal aquifer salinization [6], eustatic sea level rise [7], land subsidence [8]—few studies address the question: where have wells have gone dry?

Here we put forth a first estimate of the number of western US wells that have dried up (Fig. 2). We compared well depths to nearby well water level measurements made in recent years (2013-2015). We define wells that have likely gone dry as those with depths shallower than nearby measured well water levels (i.e., our estimate of the depth to groundwater).

Fig. 2. Schematic of a well that has gone dry (left) and a well with a bottom beneath the water table (blue) that may still produce groundwater (right). Even wells with submerged bottoms may be impacted by declines in groundwater storage because (i) pumps are situated above the well bottom, (ii) pumping induces a localized drawdown of the water table in unconfined portions of aquifer systems, (iii) well yields may decline if the hydrostatic pressure above the well base declines.

We estimate that between 0.5% and 6 % of western US wells have gone dry [1]. Dry wells are common in some areas where groundwater storage has declined, such as the California Central Valley [9] and parts of the central and southern High Plains aquifer [10,11]. We also identify lesser-studied regions where dry wells are abundant, such as regions surrounding the towns of Moriarty and Portales in central and eastern New Mexico.

Dry wells threaten the convenience of western US drinking water supplies and irrigated agriculture. Our findings emphasize that dry wells constitute yet another adverse impact of groundwater storage losses, in addition to streamflow depletion [5], seawater intrusion [6], sea level rise [7], and land subsidence [8].

Some wells are more resilient to drying (i.e., deeper) and others more vulnerable (i.e., shallower). We show that typical agricultural wells are deeper than typical domestic water wells in California’s Central Valley and Kansas’ west-central High Plains [1]. Our finding implies that reductions to groundwater storage will disproportionately dry domestic water wells compared to agricultural water wells, because domestic wells tend to be shallower in these areas. However, in other areas, such as the Denver Basin, typical domestic wells are deeper than typical agricultural wells. This comparison of different groundwater users’ well depths may help to identify water wells most vulnerable to groundwater depletion, should it occur.

So, what option does one have when a well goes dry?

Groundwater users whose wells have gone dry may consider a number of potential, short-term remedies, some of which may include (i) drilling a new well or deepening an existing well, (ii) connecting to alternative water sources (e.g., water conveyed by centralized infrastructure; water flowing in nearby streams), or (iii) receiving water delivered by truck.

Drilling new wells, deepening existing wells or connecting to alternate water supplies is often costly or unavailable, raising issues of inequality [12]. Receiving water deliveries via truck [13] is but a stopgap, one that may exist in parts of the western United States but not elsewhere, especially if high-use activities (e.g., irrigated agriculture) are intended [14]. In places where water table declines are caused primarily by unsustainable groundwater use, a long-term solution to drying wells may be managing groundwater to stabilize storage or create storage surpluses.

Realizing such sustainable groundwater futures where wells are drying up is a critical challenge. Doing so will be key to meeting household water needs and conserving irrigated agriculture practices for future generations [15]. We conclude that groundwater wells are going dry, highlighting that declining groundwater resources are impacting the usefulness of existing groundwater infrastructure (i.e., wells). The drying of groundwater wells could be considered more frequently when measuring the impacts of groundwater storage declines.

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Scott Jasechko is an assistant professor of water resources at the University of Calgary. In November 2017, Scott joins the faculty of the Bren School of Environmental Science & Management at the University of California, Santa Barbara.

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

 

 

 

Debra Perrone is a postdoctoral research scholar at Stanford University with a duel appointment in the Department of Civil and Environmental Engineering and the Woods Institute for the Environment. In November 2017, Debra will join the Environmental Studies Program at the University of California, Santa Barbara as an assistant professor.

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

 

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References

[1] Perrone D and Jasechko S 2017 Dry groundwater wells in the western United States. Environmental Research Letters 12, 104002 doi: 10.1088/1748-9326/aa8ac0. http://iopscience.iop.org/article/10.1088/1748-9326/aa8ac0

[2] James I, Elfers S, Reilly S et al 2015 The global crisis of vanishing groundwaters. in: USA Today https://www.usatoday.com/pages/interactives/groundwater/

[3] Walton B 2015 In California’s Central Valley, Dry wells multiply in the summer heat. in: Circle of Blue http://www.circleofblue.org/2015/world/in-californias-central-valley-dry-wells-multiply-in-the-summer-heat/

[4] Fleck J 2013 When the well runs dry. in: Albuquerque Journal https://www.abqjournal.com/216274/when-the-well-runs-dry.html

[5] Barlow P M and Leake S A 2012 Streamflow depletion by wells—understanding and managing the effects of groundwater pumping on streamflow. US Geological Survey Circular 1376 (Reston, VA: United States Geological Survey)

[6] Barlow P M, Reichard E G 2010 Saltwater intrusion in coastal regions of North America. Hydrogeol. J. 18 247-260.

[7] Konikow L F 2011 Contribution of global groundwater depletion since 1900 to sea-level rise. Geophys. Res. Lett. 38 L17401

[8] Galloway D, Jones D R and Ingebritsen S E 1999 Land subsidence in the United States. US Geological Survey Circular 1182 (Reston, VA: United States Geological Survey)

[9] Famiglietti J S, Lo M, Ho S L, Bethune J, Anderson K J, Syed T H, Swenson S C, Linage C R D and Rodell M 2011 Satellites measure recent rates of groundwater depletion in California’s Central Valley. Geophys. Res. Lett. 38 L03403

[10] McGuire V L 2014 Water-level Changes and Change in Water in Storage in the High Plains Aquifer, Predevelopment to 2013 and 2011–13  (Reston, VA: United States Geological Survey)

[11] Scanlon B R, Faunt C C, Longuevergne L, Reedy R C, Alley W M, Mcguire V L and McMahon P B 2012 Groundwater depletion and sustainability of irrigation in the US High Plains and Central Valley. Proc. Natl Acad. Sci. 109 9320–5

[12] Famiglietti J S 2014 The global groundwater crisis. Nature Climate Change 4 945-948.

[13] The Times Editorial Board 2016 When it comes to water, do not keep on trucking. in: LA Times http://www.latimes.com/opinion/editorials/la-ed-water-hauling-20160729-snap-story.html

[14] James I 2015 Dry springs and dead orchards. in: Desert Sun http://www.desertsun.com/story/news/environment/2015/12/10/morocco-groundwater-depletion-africa/76788024/

[15] Bedford L 2017 Irrigation, innovation saving water in Kansas. in: agriculture.com http://www.agriculture.com/machinery/irrigation-equipment/irrigation-innovation-saving-water-in-kansas

Everything is connected

Everything is connected

Post by Anne Van Loon, Lecturer in Physical Geography (Water sciences) at the University of Birmingham, in the United Kingdom.

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In recent years the human dimension of hydrology has become increasingly important. Major flood and drought events have shown how strongly water and society are intertwined (see here and here). The hydro(geo)logical research community is increasingly including this human dimension, for example within the IAHS Panta Rhei decade (link), which focuses on the interface between environment and society and aims to “make predictions of water resources dynamics to support sustainable societal development”. Previous Water Underground blog posts have shown the importance of this topic and highlighted opportunities and methodologies for scientists to engage with socio-hydro(geo)logy and humanitarian projects. Viviana Re, for example, introduces the term socio-hydrogeology and promotes sustainable groundwater management in alliance with groundwater users (link). And Margaret Shanafield argues that humanitarian groundwater projects are “an opportunity for scientists to have an impact on the world by contributing to the collective understanding of water resources and hydrologic systems” (link).

In our interdisciplinary project CreativeDrought (link), which uses local knowledge and natural and social science methods to increase local preparedness for uncertain future drought, we are applying these ideas and we realise how important different types of connections are in our two-way learning process. We just completed our second fieldwork phase of the project that consisted of workshops in which groups of people from a rural community in South Africa experimented with potential future drought scenarios and created stories about how they would be impacted by the drought and what they could do to prepare for and adapt to it. Our scientific team consisted of hydrologists and social scientists from local and UK-based institutes and the groups in the community who participated were the village leaders, livestock farmers, irrigation farmers, young mothers, and elderly people.

Young women collecting water from communal standpipe (photo: Sally Rangecroft).

Both the scientific team and the community groups were interested to learn from each other’s knowledge and experience (or just curious, see photo below of our Zimbabwean colleague Eugine measuring irrigation canal discharge with an apple). During the time we spent in the community (four weeks in March/April and two weeks in July) we both learned about important connections. As hydrologists and hydrogeologists we know that different parts of the hydrological system are connected and that these connections are extremely important if you want to understand, predict, and manage the system. Knowledge about the connection between groundwater and surface water is what we as hydrologists could bring to the community. The community was getting their water from different sources: drinking water from a groundwater well, irrigation water from a reservoir that releases water into the river, and water for bathing, washing, brick making, and cleaning cars from the river. By showing how a drought would affect each of these water supplies and discussing amongst groups that would be affected differently by a drought, they learned about the connection between the water bodies and how abstraction in one would affect the other.

Researchers measuring discharge with help of schoolchildren and collecting stories about previous droughts and floods (photos: Anne Van Loon and Sally Rangecroft).

We scientists also learned some important connections from the community. For example, our project focuses on drought but when we asked the community to tell us about droughts they had experienced in the past, many also told us about flood events. For the community, both are water-related extreme events that often even impact them similarly, with crop loss, drinking water problems, diseases, etc. Even though floods and droughts are governed by different processes (floods by fast, mostly near-surface pathways and droughts by slower, sub-surface storage related pathways) and different tools and indices are used to characterise both extremes, people at local scale have to deal with both floods and droughts when the hydrological system goes from one into the other or when both occur simultaneously in different parts of the hydrological system. We realised that our academic world is so fragmented that we often forget about connecting floods and droughts in our scientific work. Furthermore, we forget that we may affect one hydrological extreme when trying to manage our resources for the opposite hydrological extreme.

The most important, but unintended connections we discovered, however, were the connections between people. During our stays in South Africa, we connected as hydrologists and social scientists and between the UK-based and local researchers, learning to communicate across different disciplines, languages and audiences. The project also helped the community rediscover some connections between generations (young mothers and elderly ladies) and between different sectors (livestock farmers and irrigation farmers). And finally, we as a scientific team connected with the community. As a token for our newly established connection, the children’s dance group performed traditional dances during our final visit with the chief and the village leaders (see below), only bestowed on very special guests. That is the best confirmation we could get that personal connections are important and that our water management and our science depend on them!

Everyone connected: researchers, village leaders, dancers (photo: Khathutshelo Muthala).

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Anne Van Loon is a catchment hydrologist and hydrogeologist working on drought. She studies the relationship between climate, landscape/ geology, and hydrological extremes and its variation around the world. She is especially interested in the influence of storage in groundwater, human activities, and cold conditions (snow and glaciers) on the development of drought.

Bio taken from Anne’s University of Birmingham page.

Is highway de-icing ‘a-salting’ our aquifers?

Is highway de-icing ‘a-salting’ our aquifers?

Post by Mark Cuthbert, Cardiff University, and Michael Rivett, GroundH20 plus Ltd; University of Strathclyde.

If you live in a cold climate, have you ever wondered where all the de-icing salt (or ‘grit’ as we call it in the UK) that gets spread on the roads in winter time ends up, aside from that accumulating salty grime that coats your car? As you might expect, most of the salt gets washed off the highways as the salt has the desired effect of melting the ice, or carried away by rain. This salty ‘runoff’ ends up in streams nearby via pipes which drain the highway. However, that is not the end of the story…

We studied a major highway intersection on the edge of UK’s second largest city, Birmingham (more than a million people), to see how much of the salt spread on the highway ends up in groundwater. Our interest stems from concerns of the national regulator to understand not only how much salt ends up in streams, but also the potential long-term build-up of salt in underlying groundwater resources that are pumped for public and private water supply. Although the origin of salt in streams and lakes is relatively well studied, the pathways by which salt moves from highways to groundwater are poorly understood and quantified.

The various ways salt could be getting in to the groundwater are shown in Figure 1 and a bit of detective work was required to find out what was going on.

Figure 1*

This involved dressing in silly (and warm) clothes, and pulling our equipment around on a sledge, which was a lot of fun (see photos below).

The authors, Mark (left) and Mike (right), enjoying some urban winter fieldwork.

Our main field activities were fortuitously timed to include the severe winters of 2009-10 and 2012-13. We collected information about the amount of salt spread on the roads and measured the salt concentrations in the local streams, as well as in the shallow and deep groundwater wells in the area around the highway network.

7 km of motorway drained to the studied stream. Over the winter of 2012-13 we estimated that around 510 tonnes of de-icing salt was applied to the highway and major road network across the catchment. Most of that washed off the road via drains when it next rained or as the snow and ice melted, and ended up in the stream which flows under the highways. Some of it ended up on the roadside verges – this was not quantified, but would likewise eventually leach into the underlying groundwater over time.

We estimated about 12% of the de-icing salt, that’s around 63 tonnes over the 2012-13 winter, leaked through the bottom of the stream channel into the groundwater in the sandstone aquifer beneath, and may pose a risk to groundwater supplies in the area (see “9” in Figure 1, and results in Figure 2). While increases in groundwater chloride concentrations observed to date have been modest, and fortunately remain far below the drinking water standards, the steady year-upon-year build-up of salt in groundwater remains a concern. This is especially the case as the UK’s de-icing salt applications reached record levels in the recent severe winters and add to a potential de-icing salt legacy in our aquifers that has accumulated now over some 50 plus years.

Figure 2*

So how concerned should we be that so much salt is flowing down these streams and into the groundwater around our highways? There isn’t yet a simple answer to that but, with a global trend towards increasing urbanisation, this is an important area of ongoing and future research.

 

Further details of our published research to date on the Birmingham case study may be found at:

Rivett, M.O.,  Cuthbert, M.O., Gamble R., Connon, L.E., Pearson, A., Shepley, M.G., Davis, J., 2016. Highway deicing salt dynamic runoff to surface water and subsequent infiltration to groundwater during severe UK winters.  Science of the Total Environment 565, 324-338. http://dx.doi.org/10.1016/j.scitotenv.2016.04.095 (*figures reproduced with permission) [Read More]

How did our planet get its water?

How did our planet get its water?

Post by WaterUnderground contributors Elco Luijendijk and Stefan Peters from  the University of Göttingen, in Germany.

After my first ever scientific presentation, someone in the audience asked a question that caught me off guard: “Where does the groundwater come from?”.  “Ehm, from rainfall”, I answered. The answer seemed obvious at the time. However, we did not realize at the time that this is actually a profound question in hydrogeology, and one that is rarely addressed in hydrology textbooks and courses: “How did our planet get its water?”. To find out how far science has come to answering this question I (EL) joined up with a geochemist and meteorite expert (SP) to write this blog post.

We are lucky to live on a planet of which ~71% of the surface is covered with water, located mostly in rivers, lakes, glaciers and oceans at the surface and as groundwater in the shallow subsurface. Liquid water sustains life on our planet and seems to play a critical role in plate tectonics. And incidentally, it also to gives hydrogeologists something to study. Liquid water is so important in sustaining life, that the search for life on other planets in our solar system or beyond always focuses first on finding planets with liquid water.

Not only do we have abundant liquid water, we seem to have just the right amount. Compared to our direct planetary neighbors, Mars and Venus, we are extremely lucky. On the surface of Mars, at present, water mainly occurs as ice, whereas tiny amounts of water vapor are present in the Martian atmosphere. Venus also has minute amounts of water vapor in the atmosphere, but its blazingly hot surface is entirely devoid of water. In contrast to Mars and Venus, some objects in the solar system that are further away actually have too much water. Take for instance Enceladus, a moon of the planet Saturn, at which an icy crust overlies a 10 km deep water ocean. The amount of water on Enceladus is so large that it causes a wobble in the rotation of this moon, which is one of the reasons why this large volume of water was discovered in the first place. Clearly Enceladus is great for ice-skating, but probably not for sustaining land-based life similar to humans.

Figure 1: From left to right, Venus, Earth and Mars. Which one would you like to live on? Source: ESA (link) .

So how did we on Earth get so lucky?

It turns out that this depends on which scientist you ask. There are two theories:
Theory 1: The major building blocks of the Earth contained water from the start. This water then accumulated at the surface of our planet (by “degassing” from the mantle) and formed the oceans and the hydrosphere.
Theory 2: The major building blocks of the Earth were bone dry, and most of the water was delivered by comets and water-rich asteroids some time after most of our planet’s mass had formed by accretion.
So far, scientists do not have reasons to discard either of these theories, but there are two important arguments in favor of water being delivered after most of the planet had already formed:

Earth formed in a hot region of the solar system from which molecules with “low” condensation temperatures such as water had largely been removed before planetary accretion started (Albarède, 2009). Secondly, the ratio of heavy to light water in Earth’s oceans is similar to that of water in some comets and asteroids (Hartogh et al., 2011). Although you may not have noticed this when you last opened your water tap, a very small fraction (0.016 %) of the water on our planet is heavy, because it contains an extra neutron. The similarity in heavy water composition between asteroids and comets and Earth’s oceans does not prove that water on Earth was delivered by comets, but it certainly is consistent with this scenario. To make matters more complicated, however, the recent European space agency mission Rosetta to the water-rich comet 67P/Churyumov–Gerasimenko found that it has a very different ratio of heavy to light water than our oceans, which certainly complicates the debate.

Figure 2 Comet 67P/Churyumov-Gerasimenko losing water (and dust) as it gets closer to the sun. Source: ESA

Interestingly, neither theory can directly explain why our direct planetary neighbors, Mars and Venus, are so dry compared to Earth. So is it possible that these planets once were similar to Earth, and contained more water in their early days than that they do now?

Due to the high surface temperatures at Venus, any liquid water near the surface would immediately evaporate and diffuse into the atmosphere of the planet as a gas. We know that due to the lack of a protective magnetic field on Venus, solar winds continuously erode the atmosphere of the planet. If Venus had abundant water in the past, such erosion by solar winds would therefore have effectively stripped water from the planet’s atmosphere. Similar to Venus, Mars also does not have a protective magnetic field, but the temperatures and pressures at the Martian surface are significantly lower than at Venus’ surface, allowing water to be present at the surface as ice. In fact, Mars may have had a denser atmosphere in the past that allowed liquid water to be present at the surface. Nowadays, erosional features such as channels are the dry witnesses that water indeed once occurred as a liquid on the surface of the planet.

Figure 3. Dry channels (in inverted relief) in the Eberswalde delta on Mars as seen by NASA’s Mars Global Surveyor (link)

As a summary, we have an idea on why our planet was lucky enough to keep large amounts of water compared to Venus and Mars. However, do we know how our planet got its water in the first place? Unfortunately we are still not sure. There is hope though: we keep getting closer to the answer thanks to recent research on the composition of water on our planet and comets and asteroids in the solar system. So stay tuned, there’s a good chance that science will be able to answer this question in the coming years…

References
Hartogh, P. et al. (2011), Ocean-like water in the Jupiter-family comet 103P/Hartley 2, Nature, 478(7368), 218–220.
Albarède, F. (2009). Volatile accretion history of the terrestrial planets and dynamic implications. Nature, 461(7268), 1227-1233.

Limits to global groundwater use

Limits to global groundwater use

Post by WaterUnderground contributor Inge de Graaf. Inge is a postdoc fellow at Colorado School of Mines, in the USA.

Groundwater is the world’s most important source of freshwater. It supplies 2 billion people with drinking water and is used for irrigation of the largest share of the world’s food supply.

However, in many regions around the world, groundwater reserves are depleting as the resource is being pumped faster than it is being renewed by rain infiltrating through the soil. Additionally, in many cases, we are still clueless about how long we can keep drawing down these water reserves before groundwater depletion will have devastating impacts on environmental and socio-economic systems. Indeed, these devastating effects are already being observed.

The most direct effect of groundwater depletion is the decline in groundwater levels. As a direct impact, groundwater-pumping cost will increase, so too will the cost of well replacement and the cost of deepening wells. One of the indirect consequences of declining water levels is land subsidence, which is the gradual sinking of the surface. In many coastal and delta cities, increased flooding results in damages totaling billions of dollars per year. Next to this, declining groundwater levels lead to a decrease in groundwater discharge to rivers, wetlands, and lakes, resulting in rivers running dry, wetlands that are no longer sustained, and groundwater-dependent ecosystems that are harmed.

Over the past decades, global groundwater demands have more than doubled. These demands will continue to increase due to population growth and climate change.

The increase in demands and the aforementioned negative effects of groundwater depletion raise the urgent question: at what time in future are the limits to global groundwater use reached? This is when and where groundwater levels drop to a level where groundwater becomes unattainable for abstraction, or that groundwater baseflows no longer sustain river discharges.

In my PhD research, I predicted where and when we will reach these limits of groundwater consumption worldwide. I defended my dissertation last year April at Utrecht University, in the Netherlands.

Where and when are the limits reached?

Results show that many large aquifer systems are already highly depleted, especially for intensively irrigated areas in dryer regions of the world, like India, Pakistan, Mid West USA, and Mexico (see Figure 1). New areas experiencing groundwater depletion will develop in the near future, such as Eastern Europe and Africa. Future predictions show that some areas, like the Central Valley, and the High Plains Aquifer, partly recover when more recharge will becomes available. Notwithstanding, environmental groundwater demands will increase as to buffer more irregular streamflow occurrences due to climate change.

Figure 1: Estimated groundwater depletion (1960-2010) in [m], masked for aquifer areas, and zooms for hotspot regions, which are the intensively irrigated regions of the world.

In 2010, about 20% if the world population lived in groundwater depleted regions, where groundwater dropped below the economical exploitable limit. As a rule of thumb: the economic limit is reached when groundwater becomes unattainable for a local farmer, which is approximately when the water level drops to 100 m below the surface. In 2050, 26% to 36% of the world’s population will live in areas where the economic exploitable limit is reached (see Figure 2). Evidently, this persistence and increasing level of groundwater stress will impair local development and generate tension within the global socio-economic system.

Figure 2: First time that groundwater falls below the 100m limit.

 

Global-scale simulations

To answer my main question, I studied the effects of groundwater abstractions on river low flows and groundwater levels worldwide, as well as which trends in river low flow frequency and groundwater level change can be attributed to groundwater abstractions.

I used a newly developed physically based surface water-groundwater model to simulate i.a. river flows, lateral groundwater flow, and groundwater-surface water interactions at a high resolution (approx. 10×10 km) at the global scale. Total water demands were estimated and account for agricultural, industrial, and domestic demands. I simulated groundwater and surface water abstractions based on the availability of the resource, making the estimate reliable for future projections under climate change and for data-poor regions where we do not know how much groundwater or surface water is abstracted. Next, I developed a global-scale groundwater model. I estimated alluvial aquifer thickness worldwide, as no data at the global scale is available (see Figure 3). Aquifer thickness is one of the parameters you need to estimate groundwater flow and storage.

Figure 3: Estimated alluvial aquifer thickness. White areas are mountain regions, where no aquifers are simulated.

Simulations were done for the recent past and near future (1960-2050) and the results include maps and trends of groundwater heads, groundwater fluctuations, and river discharges.

In conclusion, most of our water reserves are hidden underground and most of our groundwater abstractions rates exceed groundwater renewing rates, leading to depletion. The growing demand and the expected climate change bring our groundwater reserves under mounting pressure. More than two-thirds of all abstracted groundwater is used for food production. Every year the world’s population is growing by 83 million people.

Improving our knowledge about how much water we can use in the near future while avoiding negative environmental and socio-economic impacts is therefore extremely important. A study like this contributes to the knowledge gap and can help guide towards sustainable water use worldwide to overcome potential political water conflicts and reduce potential socio-economic friction, as well as to secure future food production.

Want to read more? Check out the recent AGU press release or if you have more time… read my papers on dynamic water allocation (click here), development of a global groundwater model (click here, or here), or read my PhD thesis (here).

 

Author Inge de Graaf receiving her PhD degree from her advisor, professor Marc Bierkens (at Utrecht University, Netherlands). Note Tom Gleeson’s bald head in the lower left…

FloPy: A Python interface for MODFLOW that kicks tail!

FloPy: A Python interface for MODFLOW that kicks tail!

Authored by: Kevin Befus – Assistant professor, Department of Civil and Architectural Engineering at the University of Wyoming


Groundwater modeling is getting better. Models are becoming more sophisticated with simpler interfaces to add, extract, and process the data. So, at first appearances, the U.S. Geological Survey’s (USGS) recent release of a Python module named FloPy for preparing, running, and managing MODFLOW groundwater models seems to be a step backwards.

Oh, but it isn’t.

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First, a couple disclaimers. Yes, at the time of writing this I work for the USGS and use this new Python module for my research. Did I have to use FloPy? No. Am I glad I did? YES! Before using FloPy, I dabbled in the various non-commercial MODFLOW interfaces but got bogged down on how many drop down menus, pop-up menus, wizards, and separate plotting programs with their own menus were needed to make a meaningful groundwater model on top of a new lexicon of variable names (IUPWCB must mean “internally unknown parameter with concentrated bacon”, right?).

FloPy made its official debut in February 2016 with a Groundwater methods report 1. Bakker et al. do an excellent job telling us why we should use FloPy. I’ll leave that to you and tell you what I think.

Here’s what is great about FloPy:

  1. FloPy is 100% MODFLOW. No tweaks to anything. You choose the executable file you want it to use or compile it yourself, and you’re off!
  2. You have the near-infinite data management, manipulation, and plotting capabilities of Python at your fingertips. Python has a lot of packages. It can be overwhelming. You can rely commercial packages like ESRI’s arcpy if you want, but there’s a list of free libraries that give you even more freedom to get the input data just right. Since I mentioned freedom, here’s the list of free libraries I find useful but it is in no way an endorsement nor exhaustive: scipy, numpy, gdal, osgeo, fiona, shapely, cartopy, pyshp, pandas, matplotlib, and let’s not forget…flopy!
  3. It’s easy to duplicate and alter an existing model. Once you have your script perfect for running a particular groundwater model, you can take pieces of it to make a slightly altered version, or you can pop it in a loop that runs through your uncertain inputs for sensitivity testing. Change your grid with the flip of a variable, and make sure that mesh converges!
  4. Loading other MODFLOW models works great. Say you want to run someone else’s model with slightly different recharge, but their recharge is variable in space. Since FloPy incorporates numpy’s grid/matrix handling capabilities, you can change individual entries with row-column selections or change the whole recharge grid by multiplying it by either a single number or say a random matrix with a normal distribution and some added noise. If you just want to use their recharge data to run your own model, you can save the position coordinates (they have hopefully provided you with their coordinate system and model transformations) and recharge arrays to your very favorite format (csv, nc, mat, tif) and load it later as a matrix to add to your model, all in a single Python script.
  5. Building off of the ability to load or create MODFLOW models, FloPy has functions for plotting 2D map or cross-section views of the model discretization, boundary conditions, and results. Shapefiles can be included in these plots if they are in the same coordinate system as the model or extracted from the model (ever want a polygon feature of every model cell with attributes for every property of that cell?). I do my own shapefile manipulations in Python, but FloPy has some great plotting tools built in.
  6. You already have the data in Python. See what adding a low permeability layer does to spring discharge. Then, with the model made, you have to make sense of it. Maybe develop some interesting spatial or time series analyses. Enter Python. Plotting with matplotlib also makes beautiful, journal article-worthy figures…with enough sweat and tears from your end (not as many as you may think). Yes, this is a repeat of 2), but, seriously, it’s in PYTHON!
  7. FloPy is totally free. Python is free. Tons of science-oriented libraries in Python are free.

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Here’s a flashy example.  It is straightforward and only takes one script to create a SEAWAT model from scratch and plot the 2D steady state salinity distribution and flow vectors for a simple Henry 2 problem based on a slightly edited FloPy example script.  There are more than a dozen example scripts available on the FloPy site as well as a very cool capture ratio script provided in the methods report 1.

For the groundwater educators out there, a FloPy groundwater model script can be paired with homework questions that get students testing how changing hydraulic conductivity in certain parts of the model changes the water table configuration. Or maybe a new well needs to be drilled on a plot of land near a spring… The scenarios are endless. Students can develop a fundamental understanding of groundwater flow while getting experience with both groundwater modeling and computer programming. Win, win, and win.

Essentially all of the standard MODFLOW packages are operational in FloPy, and there are varying levels of support for some of the specialized MODFLOW compilations and processing tools (e.g., MODFLOW-USG, MODFLOW-NWT, MT3DMS, SEAWAT, PEST, and MODPATH). PEST and MODPATH are currently not executable with FloPy, but these features will probably be added in a future release (I have made my own klugy modules for running ZoneBudget and MODPATH that interface reasonably well with the rest of FloPy).

Get on your way and give FloPy a try today!


Links

The Python package is available online at https://github.com/modflowpy/flopy.

The documentation is available online at http://modflowpy.github.io/flopydoc/index.html.

The USGS FloPy page is http://water.usgs.gov/ogw/flopy/.


References

Bakker, M., V. Post, C. D. Langevin, J. D. Hughes, J. T. White, J. J. Starn, and M. N. Fienen (2016), Scripting MODFLOW Model Development Using Python and FloPy, Groundwater, doi:10.1111/gwat.12413.

Henry, H.R., 1964. Effects of dispersion on salt encroachment in coastal aquifers. In: Cooper, H.H. (Ed.), Sea Water in Coastal Aquifers: U.S. Geological Survey Water- Supply Paper 1613-C p. C71–C84.


About the author:

Kevin Befus is a groundwater hydrologist with geology and geophysics experience — examining geological, biological, and chemical processes, especially considering their connections to water across scales.

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What caves can teach us about climate, past and present

What caves can teach us about climate, past and present

Authored by:

Gabriel C Rau, Associate Lecturer in Groundwater Hydrology at UNSW, Australia

Andy Baker, Director of the Connected Waters Initiative Research Centre at UNSW, Australia

Mark Cuthbert, Research Fellow in Hydrogeology at the University of Birmingham, UK

Martin Sogaard Andersen, Senior Lecturer at UNSW, Australia


Have you ever enjoyed the cool refuge that an underground cave offers from a hot summer’s day? Or perhaps you have experienced the soothing warmth when entering a cave during winter?

When descending into a cave, you may not only enjoy the calm climate, you may also admire the beauty of cave deposits such as stalagmites, stalactites and flowstones, known by cave researchers as speleothems.

Perhaps you already know that they grow very slowly from minerals in the water that drips off or over them. This water originates from rain at the surface that has travelled through soil and limestone above, and seeped into the ground and ended up in the cave.

As speleothems grow, they lock into their minerals the chemical signatures of the environmental and climatic conditions of the time the rainwater fell at the surface. So, as a stalagmite grows, the surface climate signature is continuously trapped in the newly created layers.

Some very old stalagmites hold climatic signatures of the very distant past, in some cases up to millions of years. They contain an archive of the past climate as long as their age, often predating global weather station records.

Installation of high-resolution temperature sensors inside the cave.

Above and below

But if a cave remains cool during summer and warm during winter, how is its climate related to that of the surface? And how does this affect the chemical signature recorded by speleothems?

To understand the relationship between surface and cave climate, our research group, Connected Waters Initiative Research Centre at UNSW Australia, conducted multiple field experiments at the Wellington Caves Reserve in New South Wales.

During the experiments, the surface and the cave climates were measured in detail. For example, highly accurate temperature sensors were used to measure the water temperature at the surface, and at the point where water droplets hit the cave floor forming stalagmites.

The research team initiated controlled dripping in the cave by irrigating the surface above the cave with water that was cooled to freezing point to simulate rainfall.

The cold water allowed us to determine whether the drip water in the cave is affected by the conditions at the surface or those along its pathways through the ground.

We also added a natural chemical to the irrigation water, which allowed us to distinguish whether the water in the cave originated from the irrigation or whether it was water already present in the subsurface.

Our results revealed a complex but systematic relationship between the surface and the cave climate. For example, surface temperature changes are significantly reduced and delayed with depth.

Our research illustrates how to decipher the surface temperature from that in the cave. Understanding this is necessary to correctly decoding past surface temperature records from their signatures preserved in stalagmites.

Keeping it cool

We also discovered that air moving in and out of the cave can cool cave deposits by evaporating water flowing on the cave deposits. This cooling can significantly influence the chemical signature trapped in the cave deposit and create “false” signals that are not representative of the surface climate.

In other words, it will make the surface climate “look” cooler than it actually was, if not accounted for. While this is more likely to occur in caves that are located in dry environments, it may also have to be considered for stalagmites in caves that were exposed to drier climates in the distant past.

Temperature loggers installed on stalactites to measure the drip water temperature.

Our new knowledge can also help scientists select the best location and type of stalagmite for the reconstruction of past climatic or environmental conditions.

This new discovery is significant because it can improve the accuracy of past climate signals from cave deposits. It may also help us understand previously unexplained artefacts in existing past climate records. By improving our understanding of the past climate we can better understand future climate variations.

Protecting springs from groundwater extraction: is a ‘drawdown trigger’ a sensible strategy?

Protecting springs from groundwater extraction: is a ‘drawdown trigger’ a sensible strategy?

By Matthew Currell – Senior Lecturer at RMIT University

Springs, some of which have been flowing for hundreds of thousands of years, have been disappearing in Australia due to human water use over the past century. Following a hotly contested court case, Australia’s Environment Minister imposed a 20cm ‘drawdown limit’ at a set of springs, to protect them from a proposed coal mine. However, this ignores a fundamental principle of hydrogeology, known as ‘capture of discharge’ and as a result, the springs may still be under threat.

Why are springs important?

Springs are a groundwater system’s gift to the surface.  They provide a constant source of water to the landscape throughout the year, and many have been doing so for millenia. This is why they are often of great importance to indigenous people and why they play an important part in the history of human settlements. Springs also provide valuable ecological refuges in dry landscapes and are often home to endemic species. However, springs are vulnerable to the effects of groundwater extraction.

The disappearing springs of the Great Artesian Basin

Recently, a group of Australian ecologists and hydrogeologists published a study of ‘lost springs’ that have disappeared from the Australian landscape since European settlers began drilling for water and minerals in the Great Artesian Basin (GAB) – the world’s largest artesian aquifer system (the term ‘artesian’ means that when a wellbore intersects one of the aquifers, groundwater flows freely to the surface, often gushing meters up into the air). Groundwater in the Great Artesian Basin travels many hundreds of kilometres across the Australian continent, before surfacing as clusters of springs, which provide life in otherwise dry landscapes (Figure 1). Research by colleagues of mine estimates that some of these springs have been discharging water (at variable rates) for hundreds of thousands of years.  This is based on dating the minerals that have been continuously precipitating at the spring outlets over geologic time. The drilling of wells in the Great Artesian Basin began in the late 1800s and was encouraged by governments, as a way to ‘open up the landscape’ for further white settlement into the country’s harsh, arid interior. Many of these artesian bores were allowed to flow freely for decades (some are still uncapped), leading to major declines in groundwater pressures throughout the Great Artesian Basin. Sadly, this has also caused many springs to disappear.

Great_Artesian_Basin

Figure 1 – Map of Australia’s Great Artesian Basin, which covers four states, showing the major areas of groundwater recharge and discharge, where springs emerge at the surface.  Source: ABC Science: http://www.abc.net.au/science/articles/2012/04/04/3470245.htm

Recent threats to springs from mining

More recently, another human activity threatens springs – mining. In particular, parts of Australia have recently experienced a boom in coal seam gas and large coal mining proposals. Large volumes of groundwater must be pumped from the aquifers above and adjacent to the coal and gas deposits to allow them to be mined. Extracting groundwater for mining means that some water that could otherwise reach the surface at springs is re-directed towards the gas wells or mine pits.  Figure 2 shows a map of oil and gas exploration and production permits that currently cover the Great Artesian Basin. Many of these are yet to be developed but would involve significant groundwater extraction.

Great_Artesian_Basin2

Figure 2 – Map of the Great Artesian Basin showing active oil and gas leases. From: SoilFutures Consulting, (2015): Great Artesian Basin Recharge systems and extent of petroleum and gas leases (2nd ed)

Recently, a major international company has also proposed the largest coal mine in Australia’s history – the Carmichael Coal Mine & Rail Project. Within 10 kilometres of the proposed mine site is a group of Great Artesian Basin springs – the Doongmabulla Springs. These springs are an ecological refuge, providing an oasis of green in an otherwise dry landscape (as can be seen in drone footage here: https://www.youtube.com/watch?v=RglMko3GwQA). The springs are of high cultural and ecological significance to the local Indigenous Wangan and Jagalingou people, and for this reason (among others) these people are strongly opposed to the mine.

Colleagues of mine recently participated in a hotly contested court case, arguing over whether or not the Carmichael Mine poses a threat to the survival of the Doongmabulla Springs – recognised by the Land Court judge as having ‘exceptional ecological significance’. The argument centred on whether or not the springs are fed by water from the same group of aquifers that will be excavated and de-watered by mining, or shallower aquifers. Ultimately, the Court decided that the mine was unlikely to pose an imminent threat to the springs, and upheld the environmental authority that was earlier granted by the Australian Government. This was in spite of testimony of some expert hydrogeologists that the most likely explanation for the springs is a fault that brings deep groundwater to the surface (more about the case and the mine can be read here).

Protection of Great Artesian Basin Springs

In Australia, the native flora and fauna supported by Great Artesian Basin springs are protected under the country’s highest piece of environmental legislation – the Environment Protection and Biodiversity Conservation Act (1999). This recognises the extraordinary level of endemism in these spring systems – many support species that are found in a single spring pool or group of springs, and nowhere else on earth. If a mining project is located in an aquifer that supports ‘GAB Springs’, the Act specifies that the Environment Minister must impose conditions to protect the springs’ water source. The mining company must then develop a monitoring and management plan, and a set of contingency measures to ensure impacts can be minimised.

In order to protect the Doongmabulla Springs from potential impacts of the Carmichael mine, the Environment Minister chose to apply a drawdown limit or ‘trigger’ level of no more than 20cm, stating:

“I took a precautionary approach by imposing a drawdown limit of 20 cm at the Doongmabulla Springs Complex (condition 3d), to ensure that there are no unacceptable impacts to the springs”

Problems with a drawdown ‘trigger’ to protect springs

Limiting drawdown to 20cm at a spring may sound like a strict criterion to ensure minimal impact from groundwater extraction (as this is a relatively small change in the water level). However, the approach has a number of pitfalls, as I recently outlined in a technical commentary in an article for the journal Groundwater.

The drawdown ‘trigger’, applied at the springs themselves, ignores one of the fundamental principles of hydrogeology, which is that groundwater extraction affects aquifers in two major ways; firstly through depletion of water in storage, and secondly through capture of discharge. All groundwater and surface water systems are subject to a ‘water budget’, whereby an increase in extraction at one point leads to a corresponding decrease in water stored or water available somewhere else. It has long been recognised that when groundwater extraction begins, there is generally a period in which storage depletion – shown by declining groundwater levels in the aquifer near the extraction point – is the dominant effect. However, in the long-term, extraction is balanced mostly by a decrease in the discharge reaching the surface. It is the ‘capture of discharge’ which is the most important effect to consider when protecting springs from pumping – as spring water is entirely composed of groundwater discharge. Unfortunately, this ‘capture’ is not well predicted by monitoring the amount of drawdown, particularly at the point of discharge itself.

As Figure 3 below demonstrates, it is quite possible for a spring (or a gaining stream) to experience minimal drawdown, but for the flow of water from the aquifer to the surface to decrease or even cease entirely. For this reason, by the time 20cm of drawdown has been noticed at the Doongmabulla Springs – which are located about 8 kilometres from the mine site – it is likely that the flow directions and water budget will have been fundamentally changed, and possible that the springs may ultimately cease to flow, as has occurred in many other parts of the Great Artesian Basin.

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Figure 3 – Example of how groundwater levels change during groundwater extraction.  Drawdown may be small at a spring or stream until it is too late (fr: Currell, 2016).

Alternative approaches to management and protection of springs

It can be argued that the setting of a drawdown ‘trigger’ at a spring or stream is a classic case of ‘reactive’ environmental management, whereby management action is taken only in response to an impact when or after it takes place. Because of the relatively high level of uncertainty in most hydrogeological systems, the time-lags that occur between an activity such as pumping and the hydrological response, and the difficulty in directly observing groundwater behaviour, a pro-active approach to monitoring and managing impacts from mining and other activities is needed. As I argue in the technical commentary, a far more effective approach to springs protection would include a program to understand the source aquifer for the springs, an assessment of the water budget before and after the mining development (through modelling), and a monitoring program that maps out water level patterns and flow directions in the aquifer(s) regularly through time and also monitors flow rates at the springs. These activities should be undertaken up-front during the environmental impact assessment. If ‘trigger’ levels are to be used as an effective management tool,  these should be set as specified water levels at a series of points set back some distance from the springs, to identify negative effects before they reach the springs.

While this may sound onerous for the mining company, the importance of the springs to the indigenous people and ecological environment means that it is worth making the effort to use the best hydrogeological science possible to protect them.

Bonus Figures
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Artesian well in the Great Artesian Basin providing a constant flow of hot water. (Source: Wikipedia commons)

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Evidence of springs that have gone dry, from sites in Australia’s great Artesian Basin.  From: Fensham, R. et al., 2015 In search of lost springs: a protocol for locating active and inactive springs. Groundwater Volume 54, Issue 3, pagese 374-383, 5 October 2015 DOI: 10.1111/gwat12375 (link)