Megawatersheds: New or Déjà Vu?

Fellow waterblogger and economist extraordinaire David Zetland posted an item on 4 April 2009 on Robert Bisson's megawatershed concept, which Bisson and his firm, EarthWater Global (now known as Earth Water Technologies) have employed to find groundwater supplies across the globe.

David asked me if I had any comments and I did, which he kindly included in the post. I did not comment on Bisson's technology and success, but rather with the statement from his Wikipedia entry (presumably written by Bisson):

Coined by groundwater pioneer Robert A. Bisson, the term "Megawatershed" describes deep-seated subsurface aquifer systems that may consist of gravel, fracture-hosted bedrock, and/or sedimentary structures, which are integrated in terms of recharge, storage, transmissivity, and containment. They may not coincide with surface topographic divides and may receive recharge from parts of several surface drainage basins including massive amounts of mountain block recharge. "Megawatershed" is a conceptual model, or paradigm, that describes this new class of groundwater domain [emboldening mine].

My concern is the statement that "'megawatershed" is a "new class of groundwater domain." It's not, nor was it first described c. 1987, as is stated later on:

Equally important, the perfecting of computer-based geographic information systems (GIS) allowed skilled explorationists to combine and analyze many different types of data quickly and accurately, leading to major discoveries of oil, gas, minerals and, more recently, to breakthroughs in the understanding the nature and extent of groundwater resources, including the discovery of complex aquifer systems coined "megawatersheds" by the explorers who first documented the phenomenon, circa 1987, in the Great Rift systems of East Africa, where mountain block recharge from mountains and highlands in Ethiopia, Sudan, Kenya, and Chad remains largely untapped.

Bisson and his colleagues may have coined the term "megawatershed" (though I have heard the term applied to very large surface watersheds), but what they are really discussing are large-scale regional groundwater flow systems, which have been known (at least in North America) for over 100 years. So although their exploration approaches may be novel and successful, the concept of 'megawatershed', as used by Bisson, is just déjà vu.

One item before starting: if you look at the figure below (from the Aguanomics post), you'll note the piezometric surface (Q: Which horizon in the aquifer does this PS represent?). The PS is tunnel-shaped in the center of the megawatershed. If that's the case, the water should be moving downward, not upward as indicated. So it's a recharge area, not a discharge area. Unless of course, successively deeper PSs are also tunnel-shaped, but progressively higher in elevation than the PS shown. For a region to be a discharge area as shown (upward groundwater flow), the hydraulic head must decrease as you approach the land surface (or increase with depth). That is not what is indicated.

If the piezometric surface shown is supposed to be the water table, then the central region is a recharge area, not a discharge area as indicated.

Someone needs to rethink this diagram. A simple solution: just leave out the "tunnel" and the business about "ground water mounding." But that won't address the problem of the groundwater flow along the fault plane and the groundwater flowing down from the mountains. Can't have two flow lines intersecting!

So here we go.

Each figure below represents a two-dimensional (vertical cross section) groundwater flow system, from land surface (top) to the base of the system. Turquoise lines are flow lines and gray lines are equipotentials - lines of equal hydraulic head. The figures do not reproduce very well.

Below is Figure 7.6 taken from G. Hornberger et al., 1998, Elements of Physical Hydrology, The Johns Hopkins University Press (JHUP). The figure itself is based on one in J. Toth, 1963. A theoretical analysis of groundwater flow in small drainage basins. J. Geophysical Res. 68: 4795-4812. The word 'small' is somewhat of a misnomer, since the diagrams are plotted using dimensionless scales (ratios); the figures can represent very large (100s or more kilometers in lateral extent) or very small (few kms).

Note that (b) shows local (L), intermediate (I) and regionalR) groundwater flow systems, and that more than one surface watershed is spanned by the I and R systems. So this qualifies as a "'megawatershed."

Here's another one from Toth (1963):

Keep in mind that Toth used analytical mathematics to develop these flow nets. Numerical methods were used by R. Allan Freeze and Paul Witherspoon, and these methods formed the basis of Freeze's PhD dissertation at UC-Berkeley in the late 1960s. He used these numerical models to explain some of the features he observed in the Prairie Provinces of Canada. Here is Figure 7.8 from Hornberger et al.  (1998):

Again, because the distances are expressed as ratios these systems can be as large or as small as you wish.

A classic paper by Burke Maxey [Maxey, George B., 1968. Hydrogeology of desert basins. Ground Water 6: 10-22] describes, among other things, the regional groundwater flow systems of the Great Basin, citing the aforementioned works plus Hubbert's classic work on groundwater flow [Hubbert, M.K., 1940.  The theory of ground-water motion. J. Geol. 48(8): 785-944]. Other works from the 1940s,1050s, and 1960s are cited by Maxey, a lot of them by Tom Eakin of the USGS.

To their credit, Bisson et al. do cite the 1991 work of Tom Burbey and Dave Prudic (USGS Prof. Paper 1409-D) on Great Basin regional flow systems.

A good, brief, overall reference to which I can direct you is: Fetter, C.W., 2001. Applied Hydrogeology, 4/e. Prentice Hall, 598p. His Chapter 7 on "Regional Ground-Water Flow" is a great summary of the work done, starting with N.H. Darton's classic works in the 1890s and early 1900s on the (regional) Dakota aquifer. Chapter 8, "Geology of Ground-Water Occurrence" is also worth perusing. Note that Figure 8.6 is a much better representation of Bisson's "megawatershed" than his own diagram above.

You can also check out R.A. Freeze and J.A. Cherry, 1979. Groundwater. Prentice Hall, 604p. It's dated but still a great resource; see Chapters 6 and 11.

In fact, any good introductory hydrogeology textbook generally has a chapter on regional groundwater flow.

And pumping from 'megawatersheds' is not necessarily sustainable, nor is the water 'new water'. Each case must be evaluated on its own merits.

Bisson's "megawatershed" or "regional groundwater flow system" - take your pick, but they are both the same. The former may be a new(?) term, but the latter's been around quite some time, and they are both the same thing.  I'll go with the latter.

And give credit where credit is due.

All done now.

Note: read Michael Wallace's comment to David Zetland's post.

"I can foretell the way of celestial bodies, but can say nothing of the movement of a small drop of water." -- Galileo (from Bisson et al., 1995)

Comments

[Michael]

Hi, Joe.

You can find some information here (I just Googled them):

http://bloom.bg/2fIOAAl

My criticism of them stemmed from their claim that their conceptual model - the 'megawatershed' - was something new. It wasn't.

I don't think they were con artists.

[Joe]

Just what has happened to Earthwater Global llc? I had a lot of faith and hope in them. Does it mean they were American hyper conmen?
Jk

[José Rosas]

PLEASE... I need somebody's help!
I need to contact EarthWater Global's people, mainly Robert Bisson, Thomas O'Mara or Jay Lehr, because phone numbers in NY do not answer and there are no shown email addresses.
Any info will be greatly appreciated. Please respond to [email protected]

[Water Witch]

Prior to "Plate Tectonics" being coined, the phenomenon was well known as continental drift and other such terms. The unification of these theories into one scientifically defendable theory/concept has proven to be wildly useful and widely accepted by the scientific community at large over the past 50 years. Therefore I say why all the Megawatershed bad press, give credit where credit is due to Bisson and Lehr for bringing together accepted and modern scientific concepts into one unifying concept/model with a clear descriptive name.

[Michael]

Dear Jay,

Thanks for your comment. Good to hear from you. You missed a great UA H&WR Third Ephemeral Reunion on 19 April.

I think you should indicate that you are a co-author of both 'Modern Groundwater Exploration' and 'The Encyclopedia of Water'.

I repeat your third paragraph:

'A Megawatershed, as defined, is comprised of 3 fundamental components: highland precipitation with associated infiltration into bedrock supporting active and continuous recharge; fracture-controlled bedrock throughflow; and outflow.'

Sounds suspiciously like a regional groundwater flow system. I can think of flow systems in the Great Basin that fit this description, and here in Oregon we have one on the eastern flank of the Cascades. Both were known as such before you and Bisson came along with the 'Megawatershed' concept. And as we both know, there are other examples, too.

Your contribution is that you would brand them as 'Megawatersheds' and claim that they are a 'new class of groundwater domain'. Not so - give credit where credit is due.

Bisson may have developed a scheme to exploit these systems for water supply, but they are not a new concept.

I would note that Bisson's Wikipedia article says that these systems can be developed in "gravel, fracture-hosted bedrock, and/or sedimentary structures."

Finally, you should see Michael Wallace's (a fellow UA hydrologist) recent comment on the Aguanomics blog:

http://aguanomics.com/2009/04/megawatersheds.html

Apparently you folks can't distinguish compressional from extensional tectonics.

By the way, I recommend:

Bethke, Craig M. and Marshak, Stephen. (1990) Brine migrations across North America-the plate tectonics of groundwater. Annu. Rev. Earth Planet. Sci., 18, p. 287-315.

It has a strong economic geology orientation, but it's a great paper. I don't think they mention the term 'Megawatersheds' at all.

[Jay Lehr]

Dear Michael,

I feel it necessary to respond to your recent blog posting on Megawatersheds in order to correct some fundamental misunderstandings you appear to have over the paradigm.

Megawatersheds, as defined in Modern Groundwater Exploration (2004) and in The Encyclopedia of Water (2005), are indeed a new class of groundwater domain. The entire premise of the Megawatershed Paradigm is essentially the unification of solid earth geological concepts. Each of the component concepts is widely accepted by the Earth Science community as real and valid (such as Plate Tectonics and mountain precipitation estimates). It is the bringing together of these solid earth processes within a framework of hydrology that makes the Megawatershed unique.

A Megawatershed, as defined, is comprised of 3 fundamental components: highland precipitation with associated infiltration into bedrock supporting active and continuous recharge; fracture-controlled bedrock throughflow; and outflow.

The defense of the Megawatershed Paradigm lies in modern Earth Sciences. Modern satellite-derived precipitation estimates in inaccessible highland regions indicate orders of magnitude more precipitation than previously believed; this water is not included in the presently accepted world water balance, but should be. In addition, advances in bedrock hydroseismicity demonstrate deep infiltration of this mountain precipitation into and through mountain blocks. This phenomenon of long-distance lateral percolation of fluids along regional faults systems commonly underlying sedimentary basins is further evidenced by modern advances in fracture and fault mechanics. In order to round out the system and support the sustainability of these Megawatershed systems groundwater discharge has been found (and is being quantified in much higher levels than previously thought) in regions such as playa lakes, salt basins and deep offshore discharge sites.

Therefore, as you can clearly see, by definition, resources developed from a Megawatershed are sustainable. We agree the component attributes of the Megawatershed are not new, however the unification of them in a single model is. Furthermore it is clear that Megawatersheds are complex earth process systems distinct from traditional regional groundwater systems in sediment environments.

Finally I am encouraged that you recognize the novelty of our approach to groundwater exploration. Our adaptation 35 years ago of modern geologically theory together with state of the art oil, gas and mineral exploration techniques enhanced with satellite data and advanced GIS capabilities do indeed represent the first fully integrated and predictably successful exploration capability for deep groundwater resources. We show in our successes and publications that this approach enables EarthWater Global to move beyond local groundwater exploration to understand the regional extent of these Megawatershed systems and provide solutions for persons in need of water. At EarthWater Global we believe now is the time for the field of groundwater hydrology to take the leap forward and join us in the continental-scale understanding of groundwater systems which will lead to the discovery of vast quantities of water in Megawatersheds all around the world.

Jay
J.H. Lehr, Ph.D. Chief Scientist, EarthWater Global LLC

[Account Deleted]

Wow. Groundwater hydrologist extraordinaire in action!

[Joe Becker]

Certainly nothing new here except the word "megawatershed" and perhaps even that isn't new. Further, the use of that term to describe ground-water systems will be confusing to non-technical people, as watershed is commonly referred to as a surface-water feature. Use of the term just seems like hype to me.