[00:00:22] Bridget Scanlon: I am pleased to welcome Randy Hanson to the Water Resources Podcast. Randy is currently President of One-Water Hydrologic and he founded this company and prior to that, Randy worked at the US Geological Survey for 38 years developing hydrologic models and water supply analysis of regional watersheds nationally and internationally. So thank you so much Randy for joining me today.
[00:00:54] Randall Hanson: Well, thanks so much for having me and hopefully we can cover a few interesting things today.
[00:01:00] Bridget Scanlon: Right, right. So when we chatted it before, we thought we would start with the Rio Conchos. And because there's a lot of interest in the Mexico-US Treaty and delivery of water and things like that, and Randy has done quite a bit of work on the Rio Conchos, which is a tributary of the Rio Grande. About 75,000 square kilometers. So, and then Randy will also talk a little bit about his methodologies and, he was a big contributor to MODFLOW and developing the One-Water Hydrologic Flow Model (OWHM), focusing on conjunctive use of surface water and groundwater and hope we will learn more about that and if we have time, then we can talk a little bit about it, the Colorado, but Randy is based in San Diego, so, he knows a lot about the California water issues. And I see a lot of parallels with the Rio Conchos, many of the issues that you have in the Central Valley. So I think we'll have some overlap there also, Randy. So maybe we can start with the Rio Conchos analysis and one of your papers titled, "Capturing Wetness for Sustainability from Climate Variability and Change in the Rio Conchos, Chihuahua, Mexico." So mostly these days people often talk about drought and drought impacts on water resources, but here you are focusing on trying to capture the water from wet periods and managing that. And of course Mexico not meeting, their treaty, the deliveries, they're required for treaty with the US.
Maybe you can describe that a little bit, also, Randy.
[00:02:32] Randall Hanson: Be happy to. What we ended up doing with my colleagues in particular, Dr. Marussia Renteria via Lobos at the Autonomous University of Chihuahua. We decided that we would try to take a look at really what's going on in the Rio Conchos. And it turns out based on input I've had from other hydrologists in the area that even though the treaty was developed, there really wasn't any follow up or sub substantial information that looked at analyzing what the cycles of drought and whether any of these extreme events that have been occurring for decades were ever being accounted for in any way. What's ironic is that there's actually two treaties. So there's the treaty of 1906 and that governs the delivery of water by the United States to the Acequia Madre, diversion near Juarez, and that was done before there were reservoirs, before Elephant Butte or any of the other reservoirs were built and what not. So, ironically, way back then, they had the foresight to include climate and drought conditions as modifications to potential modifications to deliveries.
When the 1944 treaty came along this was not done. And what we really feel is, is needs to be adjusted in the treaty, is the of length of these treaty delivery periods. So the Rio Conchos is six tributaries in that watershed that deliver water from Mexico to the Rio Grande and the Lower Rio Grande below the national Park the Big Bend Park.
And so really what they have is a, as a five year period, but it's a sliding scale five year period, which I would respectfully suggest is unfair because the minute they have an extreme event, or anything like that, they reset that five year period. And so you end up with a delivery and that would've been good for the entire five years, and now suddenly you're on the hook for a whole new delivery.
And what we discovered in our climate analysis is that the real period is more like eight years of drought. And that actually dry periods for the last few centuries based on tree rings have been anywhere from 12 to 43 years in length. And anything more than a decade is a mega drought a decade or more.
And so, this is part of what's been going on there for a very long time, and the treaty really ought to reflect those conditions in our second paper, if I may say that. One of the other things that we've discovered is that there are these extreme wet events and the Francisco Madero Reservoir, which is a small pass-through reservoir on the San Pedro River, which is a tributary to the Rio Conchos has overflowed 26 times since it was built in the 1950s. And when you look at that aspect of it what you end up seeing is that most of those are related to extreme events.
And these extreme events include the enormous number of East Pacific hurricanes and tropical storms we're already up to, we've already had four. There's been none in the Atlantic, and we've already, this year alone, we've already had four tropical storms slash hurricanes in East Pacific. So we're up to number four. And so we are off and running. And it's increased in the East Pacific from about a dozen to more than 20 a year. So the sea surface temperatures are becoming warmer and more variable. The convergence zone is moving latitudinally up and down a lot more and so on.
So anyhow, these things are creating these extreme events and capturing some of that water, which is way more than, and in many cases more, way more than a hundred percent of the treaty delivery requirement is really important. And I have other colleagues such as Dr. Laura Norman, who's at the USGS in Tucson, who's been studying this throughout Arizona.
She's also involved with some joint projects. Now they're looking at trying to capture some of this on some large ranches just outside of La Paz in Baja Sur, Mexico. So again the cyclones that are coming through the hurricanes and they're trying to capture some of that water in some way or another.
So anyway, so it, a lot of people are doing it. We're doing it in the Central Valley. As you well know. It's become formal through laws and permitting in the Central Valley. So they're protecting wetland areas, so you can't just divert the water anywhere.
So anyway, so there's a lot of people that are trying to do this, and it's not just in the US and it's encouraging to see the people are seeing that's gotta be a part of conjunctive use and sustainability.
[00:07:09] Bridget Scanlon: Right, right. So, so the treaty, the 1944 Mexico-US Waters Treaty it requires a transfer of 400 million cubic meters of water, which is about, I mean, a million cubic meter is about an acre foot of water. But then there's this five year period, so there are some constraints on that.
And as you said, they reset the clock which doesn't seem fair, I agree. So you have been focusing on,, that one paper was very comprehensive, describing a lot of the changes that have occurred in the basin. So the Rio Concho is the major source of water that Mexico delivers the water to the US right?
The Rio Concho. And so in the Rio Concho then there have been land use changes and expansion of agriculture and then changes in the type of land use to more perennial crops, which we've seen in California too. Probably pecan orchards and things like that, and then also population growth.
So all of these things increasing water demand in the basin and hardening that water demand, which is difficult to deal with when you have a drought and because you can't just simply fallow the land and not grow the perennial crop. So, these are the same issues that you've been dealing with in the Central Valley.
[00:08:32] Randall Hanson: They are, and the big difference is whether there will be limits on land use development either in the Central Valley, there's some claims that maybe on the order of more than 800,000 acres of Central Valley has to be retired to bring it back into sustainability in some sense, so, we'll see how that goes or whether they can capture more water and offset some of the, that demand.
But land use and climate are the two big drivers of demand. And that's what we're seeing not only in Mexico but in the Central Valley and a lot of other places as well.
[00:09:09] Bridget Scanlon: Right. In some of the plots that you had in that paper, you show the increased economic value of those so the economic value of these perennial like pecans and almonds in California and these sort of things are much higher than traditional annual crops.
So, so economics is the driver there for those sorts of land use change.
[00:09:30] Randall Hanson: Yep. And they had record in the Bravo Basin, that part of the Lower Rio Grande in New Mexico. They, during the last, this last large drought, they had record yields of pecans in those areas. So they really are still able to sustain their profitability even through these intermediate sized droughts which is a challenge because of how they are sustaining that at the same time as is sustaining the resources and replenishing them.
[00:09:59] Bridget Scanlon: And I think in California, the Center Valley, Jay Lund and others have written reports and papers saying the economic impacts of drought have not been as great as they expected or anticipated because I guess the water was moving up to the higher value users and there were the water markets and some of those irrigation districts like Arvin Edison and others.
And so, then those high-end users then could pay more for the water and maintain their perennial trees and stuff.
[00:10:28] Randall Hanson: Right. And we've seen this in other places, unfortunately. And, if I may, probably the bad example is Chile. And where they went to a complete free market on water. And the mining companies and the larger agricultural entities bought up a lot of the water rights, and it really became an issue.
So there has to be some combination of a market and governance that kind of constrains things and assures some element of sustainability and not just continued growth a continued unbridled growth model, so to speak. And what we're seeing in the Central Valley, unfortunately, is that people are drilling wells deeper and deeper.
And that's triggering a lot of the secondary bad effects that are outlined. The six deadly sins, as I call them in SGMA, and that includes things like land subsidence and increased salinity and so on.
[00:11:19] Bridget Scanlon: Right, right. And SGMA is the Sustainable Groundwater Management Act that was initiated in 2014 during your extreme drought. And in the Conchos Valley studies. Then you put a lot of emphasis on climate teleconnections and these drivers of wet and dry periods and inter-annual variability.
And I think in one of the reports, the papers that I was looking at you mentioned over a 70 year period there were about almost 60 months of very wet extreme wet conditions. And then about 80 months of extreme dry, or, high based on SPI data. So maybe you can describe that variability then.
And then you mentioned that the reservoir was overtopped about 26 times since it was built. And if we can capture more of this flood water then we could try to move towards more sustainable management.
[00:12:15] Randall Hanson: That, that's really the key and the fact that we know that these cycles really affect water management at a variety of different scales. And we actually kind of encapsulated that really you end up with climate cycles that are affecting annual operations. But then you also have climate cycles that are decadal and inter-annual with the decadal, and that's operations development. Then there's multi-decadal and there's multi century, and we know that a lot of times developing projects, whether it's building a reservoir or a canal system or whatever, that a lot of times these things take a decade to occur. So we really have to be looking at multiple time periods to try to get a handle on how to not only change governance, but also to enhance the funding of these projects and to develop these projects . And so that's a common driver. And that's what we're also doing that in the Central Valley.
I'm involved with Central Valley Salts. And we're looking at salinity and nutrient management there. And these things are going to take decades to get over. So you have to keep the climate context that these cycles are occurring in these different cycles. And whether it be the megadroughts and a lot of this is even down in the Rio Conchos is being driven, believe it or not, by the Pacific Decadal Oscillation, which is the temperature differences in the Northern Pacific that drive the winter storms. And even though most of the rainfall in the Rio Conchos is during the summer monsoon, it's still affected greatly by the Pacific Decadal Oscillation, which is about 11 to 30 year cycles or several modes in the PDO. But that's a biggie.
[00:13:54] Bridget Scanlon: Right, right. And many people are familiar with El Nino Southern Oscillation, ENSO cycles and that's maybe three to seven years and El Nino and La NIna conditions and if we expect it to be wet or dry in either of those. And so the Rio Conchos I guess, you mentioned maybe La Nina wet conditions associated with La Nina in the Rio Conchos, and then you have this longer term cycle the Pacific Decadal Oscillation and then the conditions, whether it's positive or negative impacting, a longer-term impact. And what's really nice about your analysis is the extremely long timescale that you developed from the tree ring data. I mean, that is amazing. And so you were, maybe you can describe a little bit how you linked the tree rings to El Nino conditions and then we're able to extend that back in time for a millennium almost, I think.
Yeah.
[00:14:47] Randall Hanson: We did several things. One thing to note is that of the 20 of these overflows, these reservoir overflows were more than a hundred percent of the five-year treaty delivery. Eight occurred during La Nina, six in neutral conditions, and 11 during El Nino conditions. So we. We acknowledge that El Nino and ENSO is important, but it's maybe not one of the major drivers in these areas.
So then we brought in the tree rings. It was really the folks at the Earth Lab at Lamont Doherty had these Tree rings and they weren't in the tree ring catalog. I was able to contact them. They shared those with us. And one was for a Casas Grande, which went back over 1200 years which is really amazing.
And the Casas Grandes civilization is an amazing piece of of indigenous history because they were one of the only pre-Columbian civilizations that had a water well. And so they were there for quite a while. We tried to relate that in that sense. So we, for the tree rings, what we did is we did the same thing that we do with other climate time series, we turned them into a cumulative departure and that allows us to look at basically the first derivative of change. And then we do a frequency analysis of the residuals. We de-trend that with a fourth order polynomial, typically for long time periods. And then look at the residuals, what we're doing with the detrendings, we're taking out partial, larger cycles, and so we're just down to what's left in from those larger cycles. And then, and so we did that for the tree rings as well as all the other hydrologic time series. And then we also then tried to reconstruct historical ENSO events by looking at the categories of the ENSO event versus the width of tree rings.
And we extrapolated that back through the 1200 years of the Casas Grande tree rings to look at the occurrence of ENSO. But what was also equally important, we were also able to discover a group at the University of Utah, and I love to bring in other people's work because that's what really brings a lot of this together.
And they discovered a cave full of rabbit bones just south of Tijuana. And they analyzed these rabbit bones and then correlated it with some lake sediments in Ecuador and they had discovered that, in fact, there were no El Ninos there was no ENSO for over 5,000 years coming out of the last Ice Age.
And so it's something that a lot of people like to think that it's something that's regular, it's not. It has other cycles in it. And it was non-existent for a very long time. So we see all these different elements of cycles that are occurring at decadal up to a century and millennial timescales.
[00:17:32] Bridget Scanlon: And that's amazing. And it's great because, I mean, the more data you can bring to bear on a problem you increase your confidence in what you're thinking, the conceptual understanding of what's going on in the system. So, so that's wonderful. So basically you're saying that there were no ENSO cycles for 5,000 years.
So, the last glacial was like about 10,000 years ago. So, from 10,000 to 5,000 years no evidence of ENSO cycles during that time. And then you mentioned Pacific Decadal Oscillation, which is a longer timescale, multidecadal. And so, do you have more wet events? During a negative phase or a positive phase of the Pacific Decadal Oscillation.
[00:18:15] Randall Hanson: The positive PDO is cooler, wetter. The negative is drier warmer. And the thing that really creates these extreme events is when these various cycles, whether it be ENSO, PDO and the big driver of drought in North America is the AMO, the Atlantic Multi-decadal Oscillation.
And so when these are coming in and out of phase with each other, that's when you get these really extreme events that they could contribute to the being more of these extreme events and then combined with what's going on in the East Pacific, in the ENSO 3-4 region. But yeah, so that, that's really what we see and we see that a lot of those climate indices. We actually analyze all those climate indices, which no one else had done that I was aware of, and found that there's all these other cycles that are multi-decadal cycles that occur in all of them. So they're all variable and some of them are dancing together and some of them, sometimes they're together and sometimes they're not.
[00:19:10] Bridget Scanlon: Right. And one of the things in, when you looked at the longer timescale, then I think you related some of those, that variability changes in solar cycle so maybe you can describe that a little bit today, Randy.
[00:19:22] Randall Hanson: Well, it was again bringing collaborators together. So I had these tree ring indices and the cumulative departure from Casas Grandes and I shared it with Dr. Chris Iso, who's now retired at the University of Arizona. And he writes me back and he goes, "My God, Randy, that's the millennial solar oscillation, which is 1,470 years."
And he had already done a bunch of work looking at carbon 14 of tree rings. And so we brought him in on our analysis. And in our, and it's in our first paper. And he was able to show quite a bit of correlation with the carbon 14 data that he had meticulously analyzed from tree rings from North America. And I had other people say, we're one of the first people to analyze and see this anywhere outside of ice cores. They see it in ice cores. But so, yeah. So this millennial solar oscillation is a big deal. And it was really thanks to the collaboration with Chris, that allowed us to bring in this additional element of what's going on.
A lot of the climate people will say it's not important because it's not enough of an oscillation to perturbation, but when you look at things like tree rings that show these oscillations over these multi century periods, I would probably beg to differ.
[00:20:40] Bridget Scanlon: And so you had tree rings then from Casas Grande in the Conchos. Are there other tree rings in Mexico, in that region, or was that the only
[00:20:51] Randall Hanson: We looked at three different ones. That and each, the others had long periods, but not quite as long as the Casas Grande.
[00:20:59] Bridget Scanlon: And were they consistent? Was there good consistency?
[00:21:03] Randall Hanson: They were, there are some minor modifications and a lot of that probably is micro climates and rain shadows from some of the large mountain ranges there . So everything, but it also is very coincident with the work that was done at the University of Arizona Tree Ring Lab.
And they looked at Bristol Cone Pine and Ponderosa Pine in Arizona. And they saw very similar cycles in their work. And that was another thing that we collaborated with them as well.
[00:21:30] Bridget Scanlon: And so what actual trees were you looking at Casas, Grandes, or in these other what type of trees were they?
[00:21:38] Randall Hanson: They're largely pine trees. And they, and when they do a tree ring index, my understanding is it's a set of trees. It's not just one tree. And so they're reconstructing from a group of trees that live in a certain area, whatnot. But a lot of these trees can live pretty long.
[00:21:53] Bridget Scanlon: Right, right. Well, that's wonderful to have this long term context, because a lot of hydrologists these days, it seemed like they focus a lot on remote sensing data, satellite data. So, so 20 years is when the world 20 years ago is when the world started, you know?
[00:22:08] Randall Hanson: Right.
[00:22:09] Bridget Scanlon: And so, really important to have longer term context to understand systems.
And then as you mentioned earlier on, hurricanes and tropical storms from the Pacific and the Atlantic can also play an important role in these wet periods. And now when you mentioned hurricanes from the East Pacific is that are they related at all to the atmospheric rivers that Mike Dettinger talks about.
[00:22:33] Randall Hanson: They're actually not. But what, if you look at the recent studies that Marty Ralph, and Mike Dettinger and others have been doing what we're, what they're suggesting in their studies is that there will probably be more of those and that they'll have a broader swath of latitude that they occur.
So we've actually, more recently, if you've even had a few way down here. So, I mean, they can hit anywhere from North Alaska all the way down to Northern Baja at this point. And they're, based on Mike's one of Mike's more recent papers he did suggest that this was going to be more of a player in all of this.
But it just a matter of how, it used to be called the Pineapple Express and it was really the jet stream kind of extreme coming off the Hawaii high. In many ways, but that's it's moved around quite a bit more. And there's a more of these. So the, the simple answer is yes, I think they'll play into this, but that's occurring above the convergence zone, which is really where the hurricanes and tropical storms are occurring.
That convergence zone is moving north now. It was way down near Costa Rica a few months ago, and now it's almost back up where it typically is this time of year around Acapulco. So it's, it moves back and forth,
[00:23:49] Bridget Scanlon: Right, and you mentioned that the rain from these events is more in the winter, but most of the rain in the Rio Conchos is summer monsoon just like Arizona in those places. So, we talk a lot about the river flow and the reservoirs.
You have three reservoirs I think in the Rio Conchos and, how they function. But then there's also the groundwater. When we talk about one water, what you are referring to, I guess, is conjunctive management of surface water and groundwater. So, groundwater is a very important and transboundary aquifers play a critical role in the water resources management. So maybe you can describe a little bit about the relative importance of surface water and groundwater. Are the people irrigating mostly with surface water, do they shift to groundwater during drought or what happens?
[00:24:42] Randall Hanson: It is. And even in the Rio Conchos, during, I think it was the drought of 94, they drilled hundreds of wells. And so this can happen very quickly. And people are, they don't get the monsoons, they don't get the surface water that they need. There was also some conflicts with the farmers because the government wasn't releasing water from some of the reservoirs during one of the dry periods.
So, there, there definitely been some issues in the Rio Conchos. This is obviously the whole unfortunate issue that triggered the Supreme Court lawsuit over the Rio Grande and in the Macia Basin in New Mexico and Texas that additional pumpage and more groundwater pumpage was starting to interfere with the deliveries under the operating agreement between the various irrigation districts there.
And that caused conflict, legal conflict, which is still yet not resolved. But, so this is a really common thing, and we're seeing that. We just saw that in the Central Valley, people are drilling wells left and right during these drought periods.
So they're trying to compensate for the lack of surface water by extracting more and more groundwater. The problem is that a lot of that groundwater is anywhere from thousands to tens of thousands of year olds. So they're really mining old groundwater and causing these secondary bad effects like land subsidence as well.
So we're just seeing that in a variety of places and it's certainly an issue. We'll, we will see what happens there. There are definitely some changes in governance that have to occur in Mexico as well as in the United States to make that more feasible in many ways. So we'll see,
we'll see if people are able to do that.
[00:26:26] Bridget Scanlon: I mean, in one way it is helpful to use both surface water and groundwater. And in the Central Valley, during wet periods you get those deliveries from the north to the Central Valley. And so they irrigate mostly with surface water and then during a drought those deliveries are shut off.
You've got the Delta Smelt endangered species and so then they turn to groundwater. So it seesaws between about 70% surface water, I think during wet periods to 70% groundwater. But if they didn't use the surface water during the wet periods, you'd be in a lot worse trouble. And of course, they built all those aqueducts in the fifties, sixties, to bring the water from the humid region in the north to the south. So, and everywhere. We are seeing this, I think Cape Town, during the drought in the city, they were all drilling wells. Sao Paulo during drought, they all drilling wells. So I mean, it's there, it's ubiquitous and and so it's the go-to if you don't have the surface water, but the problem is it's not really monitored or managed or things like that.
So it's a bit if it was managed better, then maybe we could use it as a resource more effectively or have it more sustainable.
[00:27:36] Randall Hanson: And combined with maybe, if possible, limiting the amount of expansion of land use because that's the other driver. It's not just drought it's the expansion of agriculture into areas that may or may not really be warranted in some sense. But that's a governance issue. That's, part of the resource management.
[00:27:56] Bridget Scanlon: Right, right. And of course, a lot of these regions, they want that economic development and tax base, everything. And so there are a lot of conflicting things going on. It's difficult to constrain. So Randy, you have made huge contributions to MODFLOW, which is like, the most widely used groundwater model.
Now, maybe we shouldn't be calling it groundwater because you've got the One Water version. So maybe you can describe a little bit how that has evolved. You were involved in developing the farm packages and all of that and then the conjunctive use would be great to hear how that came to pass and how it evolved over time.
[00:28:40] Randall Hanson: It all started at the University of Arizona. And one of Tom Maddock’s students Wolfgang Schmidt was finishing his PhD dissertation there, and they were applying it to the lower Rio Grande and Macia Basin in New Mexico. And I, as an alumni of U of A as well, I was back there and interacting with Tom Maddock and Wolfgang.
And they were showing me what they were doing. I said, "Oh my God." This is what we need for theCentral Valley. And the key was initially was that what we were trying to do is to create a more integrated hydrologic model so it wasn't just groundwater and maybe some minor interaction with surface water flows, but now we wanted to actually build a supply and demand framework where the various components of the model could talk to each other and say, "Hey, I need this amount of water over here," or " I don't have enough water," so I'm going to have to deficit irrigate, or a variety of other, reactions or, or behaviors where they were coupled together. So we're looking at land use, including land use through the farm process, which is what Wolfgang developed for his PhD dissertation back in 2004.
And then finally adding in climate, which came in with that. And then as we got into the whole Rio Grande issues and trying to help them evaluate the Bureau of Reclamation did an environmental impact statement to show that their operations were feasible into the future.
And Ian Ferguson is the technical services group in Denver helped develop reservoir operations. So now we have reservoir operations. So we're coupling all these different things together into what we now call One Water version of MODFLOW. And it really allows us to look at drain return flows and a variety of other things.
And they all talk to each other and in a supply and demand context. So that's what we think is meaningful about it. There are a few other codes that kind of do similar stuff, but uh, we would argue that ours is probably one of the more complete ones. And it was rated by the World Bank as one of the best conjunctive use simulators as well.
[00:30:54] Bridget Scanlon: Right. And plus it's developed through the government. And so it's available to anybody,
[00:30:58] Randall Hanson: Free, yes.
[00:30:59] Bridget Scanlon: yes. Right. I mean, you may have to pay for a user interface or whatever, but essentially, I mean, when you compare some what they charge for using some models, it's really nice to have a free product that anybody can use and it's great then that you include the linkages and feedbacks between these different because sometimes somebody will ask me to write something about groundwater and I say, I can't write about groundwater without considering surface water.
[00:31:25] Randall Hanson: Yep.
[00:31:25] Bridget Scanlon: And so, I think we've moved beyond these silos of groundwater. So we, I mean, we've regulated them separately for a long time. We're still in many places. We still are. But we need to acknowledge that they're connected and understand how they're connected and those dynamics. And so do you feel like when people use One Water then that they develop a lot deeper insights into how the system works.
[00:31:51] Randall Hanson: Well, not only better insights into how it works, but also it gives them the ability to try out different mitigation or adaptation strategies. So if they're over exploiting a resource, what, what can they do to compensate for that whether it be, reduced land use or additional replenishment and or a variety of other activities.
And that's really what I think has been really helpful in many of the applications of one water in various places. And it's being used in California a lot. We have it being used in a lot of other parts of the world. It really does allow people to say, well, okay, this is going to be over exploitation.
What can we do to compensate for that? And what other, how can we get other forms of that, of water that, that maybe weren't captured or weren't being used or reused, and see how they can reduce the inequity between supply and demand.
[00:32:47] Bridget Scanlon: Right, right, and another tool that you developed a while back was the hydro climate toolkit. And I guess that is to help people understand how to analyze these Climate Indices and teleconnections and things like that. So, that's very valuable also. So if you are running MODFLOW then and considering these climate drivers and stuff, then you get a feel for the inter-annual to decadal variability.
And oftentimes, when, I mean, I think it's just the psychology of it. When you're in a drought, you think you're never going to get out of it, and when you're in a wet period, you think you're never going to get into a drought. But it's understanding that it's managing these extremes is really the challenge.
[00:33:30] Randall Hanson: Yep. And being able to have a simulator that can allow you to have those components and those components are talking to each other is really essential in being able to look at what the transition is from one setting, too much to too little. And we don't ever have average conditions in California.
It's either one or the other, and it's so, so that, that's becomes even more critical in that context.
[00:33:55] Bridget Scanlon: And I think, maybe, and you talk about different adaptation strategies. I mean, in the past you, when you had annual crops, you, if you were in a drought, you could fallow and you could see that, and you would see that. I guess with the farm package that people, there would be a lot of fallowing going on, and you could see it from the satellite data.
But then when you harden that demand with orchards and nut trees and things like that, then that option goes away. And then, so this conjunctive management is really important and I mean when you have a wet period, then I mean, you mentioned those reservoirs in Rio Conchos over topping.
If you could capture that water then and get it into the aquifer so it's there for the next drought or it could replenish some depletion that you had. And we, it seems like we have plenty of depleted aquifers. I mean, Lenny Konikow estimated there was about a thousand cubic kilometers of storage space created by groundwater depletion in the US.
So that's a big reservoir that is there. And I guess you are doing that in California with flood managed aquifer recharge and ag managed aquifer recharge and all of these different things, so I think that's great.
[00:35:12] Randall Hanson: It's a start. And we'll see how it shakes out. It, there's a lot of devils in the details. Replenishing waters that are of the different chemistry can be challenging. It. And we, we saw that, and it the classic example of that is, is what happened in Tucson, Arizona. They were pumping too much in the, down in the southern part of the basin.
I did the modeling for that as well. And I can tell you that then they went to some wells in the northern part of the basin, and this woman had bequeathed her land on the tank of Verde Wash as a wildlife refuge. All the mesquite. And, but those that pumping started to kill all the mesquite and the habitat for these birds,and so they had to stop that. And then they brought in the central Arizona project water, but it had a different chemistry and then their ozonation dropped the pH. Anyway, make a short story long. They started delivering water that was chemically incompatible and it ruined people's houses and their dishwashers and it was a big issue.
So you have to be careful and there's a lot of different facets to, to replacement sources and replenishment and how you do these things. So I think that's what we're. We're going to see more and more of and we've seen that for years. I know you probably know that, but when people have multi aquifer wells that are screened over different aquifers of the upper ones are oxidized and calcium carbonate waters and the lower ones might be reduced waters and it causes a lot of well screen encrustation. So there's a lot of secondary effects to these situations where they're trying to, create other sources and then blend the sources together.
[00:36:51] Bridget Scanlon: Yeah I think in Tucson there were a lot of people walking around with pink shirts for a while because of the iron.
[00:36:57] Randall Hanson: Yeah.
[00:36:59] Bridget Scanlon: But I mean, so, I, we were doing an analysis and you saw that for the Colorado and in Arizona. And then some folks saying that the mantra is pump and replenish there.
So they keep pumping the groundwater and then now they recharge the aquifers with the Central Arizona project water through these spreading basins and also with the surface water irrigation when they switched from groundwater to surface water irrigation. I mean, everybody, sometimes I think people are naive and they just, think well managed aquifer recharge, intentional, but then they don't consider if they're irrigating with surface water versus groundwater. I mean, if you're irrigating with surface water, it's could be similar to managed aquifer recharge if it's not very efficient. But they bring it, make a big deal about intentional. But I mean, the aquifer doesn't know whether you are intending it or not. It just happens.
[00:37:52] Randall Hanson: Right. Well, and that, that was the big discovery when we did the original Central Valley hydrologic model . And even with the more recent version is that really inefficient irrigation. There's some people in, European scientific communities that think, oh no, this all has to be dreadfully efficient.
And actually the inefficiency is wonderful. And inefficient irrigation is one of the biggest elements of recharge in the Central Valley as an example of that. So I've always been an advocate that some of that's probably okay.
[00:38:23] Bridget Scanlon: Right. Well, I mean your colleague Claudia Faunt she said inefficient surface water irrigation and extremely efficient drip when you're using groundwater. And the Murray Darling Basin when they spend so much billion, six or $7 billion on precision ag, lining canals and everything, and then didn't take into account the fact that they were losing that recharge, is impacting surface water. So it's all connected. And so that's what I love about your work is one water and bringing MODFLOW forward and considering conjunctive management of surface water and groundwater and, we were doing, I mean, Helen Dahlke at UC Davis did a study many years ago on how much extreme flows could, the high magnitude flows, could they capture in California. Four recharge greater than 90th percentile. And we did a similar analysis in Texas in some years. It was equivalent to the water use in the state, if you could capture it, but the challenge is capturing it. So I think, we are becoming much more aware of these things and I think different types of recharge projects will help to manage that.
[00:39:31] Randall Hanson: Well, and that's something that, that my colleagues like Laura Norman at the USGS has looked at quite a bit, and some of this stuff is pretty low tech. It's installing, Gabions. and things like that in stream channels rubber dams, other things like that, that can be, temporary redirection of water and that that's being done in, in a variety of locations.
And so there's a lot of creative, some of it's high tech and some of it's low tech, but you, and it also helps with sediment erosion too, things like Gabions. So you can do a lot of different things that to help redirect those extreme events and get some of that water infiltrating into adjacent floodplain areas that are also permeable and connected.
[00:40:10] Bridget Scanlon: Right, right. And I think even some studies in Kenya, sand dams and stuff like that, and the big problem with the, these increasing extremes is that you get a lot of erosion and sediment movement and stuff like that. So, having these things in place will help with the recharging aquifers and taking advantage of that extreme flows. And another thing that I liked about your analysis that you get to the basics, which is like, what can we do? Reduce demand, increase supplies, store, transport, all of these fundamental things. And then you can test a lot of these then with your modeling analysis to see how best to adapt.
[00:40:50] Randall Hanson: That's the key. And you have some ideas. We can try it out and what we typically try to do with these models is that we. which everyone does, you calibrate it on the historical period, but that really allows you to develop skill with the model so that when you do these projections, either, whether they're climate projections or adaptation mitigation scenarios or whatever, that you have some skill how things are being behaved.
And the ability to estimate pumpage, which is what we do with the farm process for agriculture, is really very useful because we can then have an idea of what demand might look like and how it might change under different scenarios of the future.
[00:41:31] Bridget Scanlon: Right, right. So that's essential then if you're going to try to adapt. And so, since you've worked in a lot in California, in many places, of course in the southwest, but also in Mexico, do you see that then the Rio Conchos then that they may be able to use more managed aquifer recharge or maybe more surface water irrigation during these, where to take advantage of those high flows when they over top. And what do you think is the predictive skill for estimating when you might get those reservoirs over topping, considering the climate indices.
[00:42:03] Randall Hanson: That's a great question and I've had many. A water district, say, Hey if we knew a year in advance what's coming, we would, they'd let out water earlier. They would create more storage space. And in some places I was working in Taiwan and they have several reservoirs there, and they actually dredged them constantly, 24 7.
They're constantly dredging because the cyclones come through and create so much sediment inflow as well as water that they are constantly having to adapt to these extreme conditions. So it, there, there's been some amazing examples of this in different places. But the idea of, being able to, have some kind of prediction, whether it's through the frequency analysis and we show that in the second paper that, even a year or two into the future, it looks like we can show that. And actually, Mike Dettinger and I showed that way back when on our Ventura stuff back in 2004. So we were already looking at that possibility.
So you can get a little bit a headstart on some of this as to what, just based on the historical cycles. They're not a hundred percent reliable, but they would give you a good indicator so that's something that we've advocated for a long time.
[00:43:12] Bridget Scanlon: And I guess, the Corps of Engineers is moving in that direction with their forecast informed reservoir operations. Where you do have good forecast skills, then they can change the management. Rules for the reservoirs, which were developed maybe decades ago under a different climate cycle or whatever, so it's nice to see these people adapting to these things and trying to manage the water resources to move towards more sustainable management. And one of the things we say, reduce demand, increase supplies, and you said land use, maybe a cap on agricultural expansion.
But you also mentioned there were some breweries that looking for permits in Mexico. And Conagua denied.
[00:43:50] Randall Hanson: They did in Mexicali, yes. And they do consume quite a bit of water. But that's just another, another example of non-agricultural water uses, whether it's the maquiladoras breweries. In Central Valley, we have we have meat processing, poultry and vineyard processing of waters that all are creating these additional consumptions of water and additional waste streams that have to be dealt with .
So that, that's been a big issue in many settings. It's, it is not just agriculture.
[00:44:19] Bridget Scanlon: Right. And one of the terms that you mentioned when we chatted recently was Wild Water. And I had never heard that term and so I think it's really cool. So this is water that runs off before it reaches the stream, before it becomes a water of the US?
[00:44:34] Randall Hanson: Well, before it becomes what is sometimes called Project Water. And so when you have the bureau of reclamation in particular, it would be the Central Valley Northern part of the Central Valley or the Colorado or the Rio Grande they have reservoirs and those are being operated by the Bureau of Reclamation.
And so any water that's coming out of those is part of agreements of distribution. And there may be also water rights embedded in those . And so that's project water, but water that's coming in during these extreme events, off the peripheral watersheds before it hits the main river.
It's not Project Water, and so it's been termed wild water.
[00:45:15] Bridget Scanlon: Right, right. So if we could improve our management of wild water, then I think that would help us become more sustainable.
[00:45:23] Randall Hanson: And people are looking at ways of capturing that, so that's a common thing.
[00:45:28] Bridget Scanlon: Right. Well thank you so much, Randy. Our guest today is Randy Hanson. He's president of One Water Hydrologic and previously worked at the US Geological Survey. I really appreciate your time and we will provide highlights of this discussion and links to various papers and reports and modeling tools and things like that, that listeners can evaluate after they listen to the podcast.
[00:45:51] Randall Hanson: Thank you so much. And just one last plug look for my new book with Richard Evans from Jacobs in Melbourne, Australia. We're the co-authors of the new John Cherry book on conjunctive water management, and that should be coming out in the next month or so. And it has model exercises in it as well.
So, hopefully that'll be of interest to many practitioners.
[00:46:11] Bridget Scanlon: Well, that's wonderful. I commend you for the taking the time to do that. I can barely manage to do a tweet, not to mind a book, but thank you so much, Randy.
[00:46:22] Randall Hanson: All right. Thank you so much, Bridget for having me and look forward to seeing more of your podcasts.
[00:46:28] Bridget Scanlon: Thanks.
