Come Rain or Shine

Santa Cruz River Lives Again

November 04, 2020 USDA Southwest Climate Hub & DOI Southwest Climate Adaptation Science Center Season 1 Episode 6
Come Rain or Shine
Santa Cruz River Lives Again
Show Notes Transcript

Urban expansion and mismanagement of the Santa Cruz River in southern Arizona had led to a dry river bed for much of the year. Using effluent (treated wastewater), the City of Tucson Water Department brought perennial flow back to a portion of the river, just South of downtown Tucson. The returned water recharges groundwater to the local aquifer, while restoring vegetation and wildlife to this stretch of the river. James McAdam from Tucson Water, and Michael Bogan and Drew Eppehimer from the University of Arizona, describe the Santa Cruz River Project (, including its benefits to the ecosystem and local community, as well as challenges they experienced along the way. Episode photo by Michael Bogan.

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Santa Cruz River Lives Again

Emile Elias: [00:00:00] Welcome to come rain or shine podcast of the USDA Southwest Climate Hub 

Sarah LeRoy: [00:00:06] and the department of Interior Southwest Climate Adaptation Science Center or Southwest CASC. I'm Sarah Leroy science communications coordinator for the Southwest CASC 

Emile Elias: [00:00:17] and I'm Emile Elias, director of the USDA Southwest Climate Hub.

Here, we highlight stories to share the most recent advances in climate science, weather and climate adaptation and innovative practices to support resilient landscapes and communities. 

Sarah LeRoy: [00:00:34] We believe that sharing some of the most forward thinking and creative climate science and adaptation will strengthen our collective ability to respond to even the most challenging impacts of climate change in one of the hottest and driest regions of the world.

Many rivers in the Southwest US used to flow year round in portions. But with groundwater pumping and diversions now only flow for parts of the year. The Santa Cruz river in Southern Arizona is one such river where urban expansion and mismanagement of the river had led to a dry river bed for much of the year. Using effluent or treated wastewater, the city of Tucson Water Department brought perennial flow back to a portion of the river, just South of downtown Tucson. Known as the Santa Cruz heritage project, the water recharges groundwater to the local aquifer while restoring vegetation and wildlife to this stretch of the river and providing many other benefits. Today, we're talking with a representative from Tucson Water and two researchers from the University of Arizona about the benefits of this project, and if it could be used as a model for other rivers in the Southwest.

From Tucson Water we welcome James McAdam, superintendent of public information and conservation. And from the university of Arizona, we have Michael Bogan assistant professor in the School of Natural Resources and the Environment and Drew Eppehimer, a PhD candidate in the arid lands resource sciences interdisciplinary graduate program, and also a graduate fellow with the Southwest CASC.

Welcome everyone. First we'd like to hear from James on how this project came about, what prompted Tucson water to use effluent in this stretch of the river. And could you please describe the project a little further? 

James McAdam: [00:02:41] Sure. Thank you for having me. Let's see. So the Santa Cruz river through downtown, you know, dried up in the early middle part of the last century.

And I'd say probably ever since then people have dreamt about bringing water back to this area that is the birthplace of Tucson. There's, you know, right along the banks of the Santa Cruz river right in this area is where there's the, my understanding is the oldest evidence of irrigated agriculture in North America.

Some of the longest continuous inhabitation or habitation. Anyway, it's a really important part of the community and to have a dry river in it that used to flow is kind of heartbreaking. So I've been at the city of Tucson, uh, for seven years. And I can tell you in the first, three four years, I heard three or four different schemes about ways to re-wet the Santa Cruz river for different reasons they just didn't happen.

Um, so. In 2016 or 2017, our director Tim Thomure, started. He was a new director at that time. And Tim brought with him a, an approach to water management that is known as One Water, and that relates to the idea that all sources of water have value. Storm water, recycled water, ground water, surface water, and that they should be managed accordingly.

And so he helped the utility shift its focus, in just what we're providing through the meter to customers, to managing water as a, as a resource holistically. And really Tim just made us a priority. He said, You know what let's do it. And he challenged staff to make it happen. And so it took about two years and by it, I mean discharging our recycled water through our refrain system into the Santa Cruz river to re-wet it through downtown.

And so about a two year process, and what we did is we used our existing reclaimed water system, which is our purple pipes. Our treated effluent. So, Pima County treats effluent, treats waste water to a very high standard. And then we do a little bit of additional treatment to it. And then we send it through pipes all through throughout town, which go to schools and golf courses and other large irrigators.

And we use that recycled water for that purpose. And a use had kind of leveled out on that over the past decade or so. And so we had available water and we have actually needed additional places to store it in the aquifer. And so, two year process of planning, permitting, construction. There wasn't a whole lot of construction because we use the existing reclaims system but then a lot of outreach and communication with the neighborhoods and the city and the County and the state agencies, just about everybody. We had our, so on June 24th of 2019, we first began discharging recycled water into the Santa Cruz river.

And it's about can go up to 1,950 gallons per minute. Which generates about at that level of generates two to three miles of surface smarter flow downstream, which is going North. And you know, we, we had our, we chose June 24th of 2019 because it's El dia San Juan, which is a Catholic Saint who is, there's a traditional festival here in Tucson that is for that Saint and relating to that Saint because he's a patron Saint of water in the Sonoran desert, he's known as the patron Saint of the monsoons. And so we thought that was a great day to do that. And we partnered with the existing DOD San Juan festival committee to sponsor that and put those celebrations together.

So that's how it all started. And that's the bones of it. Oh, excuse me. I should add one thing. Really, the main purpose of the project is to recharge reclaimed water into the aquifer. And that is the primary purpose of the project from Tucson Water's perspective. Of course it has many other benefits, including rewetting the river.

Growing vegetation, supporting wildlife, improves the look and feel down there, and that has impacts for recreation and economic development. And yes, so that's it. 

Emile Elias: [00:08:25] Excellent. Thanks James, for that history, from the perspective of Tucson Water, and now turn to Michael and ask you what role the University of Arizona plays in the project.

Michael Bogan: [00:08:37] Yes, thank you for having us. This is a really exciting opportunity for us as ecological researchers from the university. As James mentioned, from Tuscon Water's perspective, the goal is to put water in the aquifer, but there are these ecological benefits that come along with it. That really provided us with a unique opportunity to study the ecological rebirth of the river. So although the primary purpose is aquifer recharge and ground groundwater recharge, you know, as James mentioned, there's all these side benefits that come along with it, this is really important because as you mentioned at the top, a lot of rivers in the Southwest dried, and I think even understated the issue or, you know, in reality, more than 90% of river miles in Arizona have dried up in the last 150 years, you know, vast stretches of the Santa Cruz, the Gila of Salt in the San Pedro. And so this is a really great opportunity to put water back into systems that we dried up. Because we've dried up so many rivers, there's a lot of critically endangered species, including almost all of our native fish species.

And then a lot of animals that rely on river corridors, things like yellow billed cuckoos and other migratory birds. So it's a really cool opportunity. And it's in our own town, which is also meaningful. And to me, it represents a little bit of a course correction. You know, we had alluded to, we have a very deep history of human history on the river, the Tohono O’odham and their Hohokam ancestors sustainable use the water resources for millennia, you know, going back 4,000 years.

And it only took the colonial period a few decades to mess that up and make the river disappear. So this, this is really an opportunity to put water back into the new business. And then we, as ecologists can study, you know, which species return, which species are coming back and making use of this new habitat.

And especially after it had been dry for so many decades, will they come back quickly? Some take longer. Those are all ecological questions that are interesting and exciting for us to address. Um, and thanks to that public outreach that James mentioned of Tucson Water, you know, we knew the exact day that the project was going to start, knew when the water is going to be turned on.

And so we could look at this as, as a ecological experiment, you know, with a start date, this is the day we're going to start making our observations. Um, so basically a really large scale experiment that we couldn't do on our own because we don't have, you know, as researcher of U of A,  water that we could just pour into a river bed, 24 hours a day.

So we're studying a lot of, you know, both large and small critters that are using this new water resource downtown things from showy dragonflies and toads that you can hear calling along the river at night downtown, to tiny little aquatic insect larvae things like mayflies and caddisflies that you really need a microscope to see well, but that are moving in and living in the river bed and then providing food for things like birds and other species like. So, so far what we're seeing in the river downtown, probably not a big surprises, things that are really good at getting there on their own things that can fly, like dragonflies can fly pretty long distances, toads can hop over dry land and get back into the river.

Because it is, it's isolated from existing breaches of the river. Now we're making these initial observations and then thinking about what species we might be able to help  get back to the river. You know, things like, like fish that can't walk, fly and get back there on their own. Um, so we're, we're, we're wanting to know how much benefit ecological benefit we're getting from the river.

But the hard part is, is that there's not really any historical information about what the ecology of the river was before we dried it up. So it's not like other studies where you can say, okay, before you did this, these species were here. And then after you did this, these species were here. In this case, we don't have a reference.

You don't have a reference river as a point to, to see when the heritage project becomes a full success. And so what we're doing as a reference point for comparing our observations in the heritage project is looking at some of these reaches of the Santa Cruz that are also dependent on affluent. But that have been slowing for a lot longer period of time.

And so the treatment plants in North Tucson, the Agua Nueva and the Tres Rios student plants, have been letting water out in the riverbed there for decades now. And so, um, that's really the focus of a lot of through my graduate students research has been. What's going on, ecologically in these existing reaches. And how long will it take the heritage project to get as diverse as the observations that he's making from, from the existing reaches?

Emile Elias: [00:13:51] Excellent. Thanks, Michael. It's really an interesting opportunity to study this human influenced ecosystem as water is being put back into the river. And so now I want to turn to Drew. You just mentioned your graduate students, and so Drew your research, your research focuses on documenting the conservation value and effluent dependent reaches of the river.

And can you describe to us what your research has shown so far? What you've learned. 

Drew Eppehimer: [00:14:20] Yes, of course. So my stream ecology research has focused on established effluent sections of the river that Michael mentioned previously. And so these have been flowing for decades and more recently, since 2013, they've been really putting out high quality water into the river.

So thanks to these great treatment plant upgrades that happened here in Tucson. And so these established sections of the river can then serve as reference sites as it was mentioned before. So this will show the future potential of this new heritage project, what it can become in the future in terms of ecological benefit.

And so in this older established section of the river, which is just downstream from the new heritage project so far, we've found a really impressive diversity of aquatic invertebrates. So aquatic invertebrates are those things like aquatic insects, as well as other things like small crustaceans that live in these rivers and streams here.

And so to date, we've identified over 150 different types of invertebrates that are living in this effluent in the river. And so what's really cool is that it also includes pollution, sensitive species like mayflies and caddisflies. Which we often find in very high abundance and beginning in the end of 2017, the Sonoran Institute, as well as myself, we went out and we were able to document that the Gila topminnow, an endangered fish species is in fact, living in these effluent stretches of the Santa Cruz river, near Tucson. And so this all kind of illustrates that these effluent flows provide not just habitat, but also relatively healthy habitats. Um, that I think it's going to become increasingly important for biodiversity and conservation.

As our natural surface water resources continued to become more scarce. 

Emile Elias: [00:16:18] I have a follow up question for you on that. That's really interesting. And it makes me wonder if that means that the water is of a sufficient quality to allow these sensitive species to come back. And so it's kind of a benefit of this extra treatment that's being done by Tucson Water to allow these sensitive species?

Drew Eppehimer: [00:16:41] Presence or absence of water is crucial. But depending on how diverse and robust community riparian and aquatic community that you want to support that, then question comes down to the quality of the water, which in artificial managed systems like this, that relates back to the treatment standards at the wastewater treatment plants. So the water reclamation facilities that are discharging the effluent, and so that, that will vary across, you know, different plants in different regions, in different countries, which have different standards.

So really there's a lot of site specific content that goes into these river systems that are supported by treated waste water.

Sarah LeRoy: [00:17:23] Thanks Drew. So we've talked a lot about all of the, you know, the myriad of benefits from this. Right. But I wonder if there were any challenges in implementing this project. Um, so James, you might start with you on this one being from Tucson Water. 

James McAdam: [00:17:41] Sure. Well, first of all, for us as Tucson Water, this is completely novel.

We've been, we've had our reclaimed water system for decades. We're one of the first utilities to begin to use recycled water for irrigation. So that's not new, but discharging it into the environment is totally new and all of a sudden being responsible for a river downtown. Which is not only has as all these species, you know, depending on it, but there's a multi-use, you know, bike and pedestrian path on either side that is quite popular.

And I think it's actually a lot more popular now that there's water flowing in the middle of it. There's been some challenges in terms of culturally as a utility, a water utility. Helping everybody come up to speed on kind of the sensitivity of a project. For instance, we had an issue kind of early on where we had to turn off the water because we ran out of chemicals.

We ran out of sodium bisulfite that we use to de-chlorinate. And so it was a short turn off, but the kind of thing where. We're starting actually, we're getting calls today from the media because we've turned off that we've turned the water down quite a bit, which speaks to I'd say one of the bigger challenges for the area of the aquifer that we are in downtown has all kinds of contamination in it.

There's old landfills. There's you know, just all kinds of industrial and commercial contamination in the aquifer, and right downstream of where we're discharging water. There's an old landfill at the base of Sentinel Peak. And we have a, we have a number of state permits, but one of them is a state water quality permit that.

Essentially says the water level. So as we're discharging water into the, into the aquifer, the aquifer level is rising. And once it gets to a certain height that water could begin to come in contact with these old contents of this landfill, the landfill is really old. They're not lined, like a modern landfill would have some kind of liner to it.

Our washes, you know, the Santa Cruz, the Santana, the Rito are literally lined with dozens of these old landfills. Dig out the sand for, you know, making bricks or whatever and dump in your trash. And so anybody who works along these channels knows about them. Right now, we are, uh, have had to turn the water, the flow of the water down, um, in order to manage the level of the aquifer.

So it doesn't rise too high, so that we'd be violating our permit. So right now, today, I want to say we're at 800 gallons per minute. Previously we had found a level of about a thousand gallons per minute, which is about half of our permitted volume that was keeping the aquifer level. That is a challenge, not so much to the recharge component of it, but certainly to the idea of maintaining a, you know, a healthy living ecosystem, and a recreational asset. 

Sarah LeRoy: [00:21:14] Thanks! Michael, Drew, do you have anything to add to what James said? 

Michael Bogan: [00:21:20] Yeah, I'll follow up on that. You know, I think from an ecological perspective, the changing water levels and outages, when you have to turn the water off are definitely a challenge.

You know, if you're a fish, you can't just wait. Uh, you know, a few days until the water comes back. So, so it's a challenge from an ecological perspective. Um, but I also think it's offered a really interesting opportunity for, um, people like me and Drew, researchers to have a lot more communication with, uh, natural resource managers, like do some water.

At that early stage, when James was talking about when they had the turn on the water or turn off the water, they had their dechlorination supplies. You know, I was in contact with hydrologists, with folks from Tucson Water through that period. And they let me know, you know, this is what was going on. This is how long it might last.

And so we were able to adjust our ecological studies with that. And then later on, once that problem was solved, there were still other issues often related to the aquifer water levels that James mentioned where Tucson Water would consider or turned down dramatically. And it might have a very specific impact on some aspect of the ecology.

And I was able to observe that and then call up, do Tucson Water and say, Hey, you know, would it be okay if we do just turn up the water just a tiny bit more? Cause it's just a little bit of water would make a huge difference to the ecology, you know, and they were able to do that within five or 10 minutes. Um, so there's really interesting opportunities for collaboration between academic researchers and natural resource managers in this kind of situation.

And I think, you know, those, those collaborations and those conversations are in, in and of themselves a challenge. Um, because it's, it's not something that we're used to doing necessarily, and it's not something that we do well and there's also layers of bureaucracy to deal with. Um, just to give you an example, there are, James mentioned their state water permits, which is through the Arizona Department of Water Resources.

And when we want to do anything with the ecology, let's say, for example, try to introduce topminnow into the heritage reach. Which would be a great ecological benefit we have to us, you know, the researchers have to be part of that conversation, the City, Tucson Water as part of that kind of conservation.

The County, Pima County owns the river bed. And so they're a part of that conversation. The state Arizona Game and Fish Department manages the actual populations of fish. So they're a part of it. And then the Federal Fish and Wildlife service is actually in charge of the endangered status of the species.

So you've got to get all of those people together in a room and agree on a plan to do something like get topminnow back into the river downtown after a hundred year absence. So that's, that's a challenge, but it's also a great opportunity to force conversations and encourage collaboration when often we're off in our own silos and separate.

Emile Elias: [00:24:29] Thanks, Michael. And thanks for sharing this example of the flagship successful collaborative project. It's really impressive that you were able to get so many agencies coordinating and working together. And the organization that I work for, the Southwest Climate Hub covers New Mexico, Arizona, Nevada, and Utah.

So big footprint and really dry, arid lands. And so I'm curious. If you see this project as a potential model for other ephemeral rivers. So I'm curious if you see this project as a potential model for other ephemeral rivers in the Southwest, or do you know of other cities doing something similar?

Drew Eppehimer: [00:25:13] So. The practice of discharging treated waste water into rivers and streams as being common for generations, right? And initially, at least that was because of these rivers and streams, whether they have water in them or not, are a great conveyance mechanism to get rid of this effluent. Um, and in arid climates, especially like you were mentioning. So these effluent discharge flows that have gone into rivers and streams that don't have much surface water to begin with.

They have unintentionally or accidentally created or recreated or augmenting aquatic habitat. And so that is initially started in this kind of accidental unintentional way, but it hasn't been until relatively recently that perceptions about effluents have started to change. And so we've gone from thinking of it as more of a waste to now more of a resource.

And so today's becoming more common uh, for utilities for counties and cities to think of and manage effluents as it benefits to the environment. And so in that sense, the Heritage project is a great example because it not only combines recharge for the aquifer, but also with other benefits, like ecological health and supporting biodiversity, as well as recreational environmental education opportunities for the public.

Although not completely analogous to the specific heritage project in Tucson. There are a couple of examples of other cities in the state of Arizona that are doing similar things. So utilizing effluent for environmental or recreational purposes. So near Phoenix at the confluence of the Salt and Gila rivers, which would be dry without these large inputs of treated effluent is treated wastewater from a treatment plant near Phoenix.

And so these large volumes of effluent are now supporting river flow there in the Tres Rio's wetlands and the Base and Meridian wildlife area. And so this restoration and flood control project was completed pretty recently. So in 2010, and then also in that same year in 2010 in Northern Arizona, there was an agreement between the city of Flagstaff and the Arizona Game and Fish commission.

And so this agreement then guarantees minimum environmental flows of effluent into the Rio de Flags, a small stream flowing through downtown Flagstaff specifically so that it could support riparian habitat for birds and wildlife.

Michael Bogan: [00:27:49] As Drew mentioned, the effluent dominated systems or effluent dependent systems, which would otherwise be dry are actually really common across the Southwest. There's good examples. Like you mentioned in Arizona, but all across Southern California and New Mexico places like the Los Angeles river, the Santa Ana River, Las Vegas wash, these are all systems that are effluent dependent and would be otherwise dry.

But again, this is all kind of, these are accidental ecosystems. Cause there wasn't necessarily any thought or planning to it. It was just who said, put the water in to get rid of it, or maybe there is some thought to recharge the aquifer. So I think that the unique part about, um, uh, the heritage project is that as ecologists we're here from day one, so we can actually monitor what is the exact benefit.

You know, how long does it take for different benefits to appear? You know, whereas these other rivers often started slowing, you know, as far back as the fifties or in the seventies. And they, they were not, they were basically viewed as ecologically worthless and some people weren't studying what the benefits are.

Whereas with planning, things like the heritage project, we can be there from day one. And I also think, even though, as James mentioned earlier, the primary purpose still of heritage is groundwater recharge, um, Tucson Water acted differently in that they reached out a lot more to the community ahead of time than a normal groundwater resource project would do.

So I think the Heritage project really provides a model for how you can do recharge and do it in a better way than we've done it in the past where we're studying the ecological benefits, we're engaging the community and what these projects look like, what the community wants to see in the river bed.

Considering those cultural needs, the benefits to water resources and also the ecological benefits. We've often, again, kept those in separate silos, but with a project like the heritage project, they really all belong together and we all should be having conversations together.

Sarah LeRoy: [00:29:56] Well thanks everybody, this has been a great conversation. We're about out of time, I just to open it up and see if you know, anybody had some last comments they'd like to make before we sign off.

James McAdam: [00:30:10] So, you mentioned briefly one of the cool things that happened alongside the launch of the Santa Cruz River Heritage project was a change in state legislation in Arizona that previously prior to 2019, If you took reclaimed or recycled water and you constructed a basin somewhere and use that patient to recharge the reclaimed water.

You would get 95 or a hundred percent credit for that water for storing it in the aquifer. But if you took that same water and put it into a wash, like the Santa Cruz river, you would get 50% credit, and they called that the cut to the aquifer. And there's a number of reasons for that, but the negotiations over the management of the Colorado river, that drought contingency plan, that Arizona was part of the negotiations for in 2019.

Again, our director, Tim Thomure was a part of party to those negotiations and was able, with a coalition of other stakeholders to get that rule changed as a part of those negotiations. There's a lot of sort of horse trading associated with getting this drought contingency plan on the Colorado river and, uh, Tucson Water in the city of Tucson through Tim actually got to play a really, really exciting and pivotal role.

 Essentially providing a backstop for some farmers in Pinal County who are going to be seeing decreases in Colorado river water. There was sort of a horse trade that we could introduce this, a change to the recharge credit system. So now the water that we are discharging in the Santa Cruz river, we're getting 95% credit for that due to this change in state law. Interestingly that this change in law actually solved a really big issue, that the Bureau of Reclamation had, who is in charge of a large amount of reclaimed water or versus, excuse me, recycled water that is discharged further downstream and that they hold in trust for the native American tribes.

They have the same issue. And so they just, what, we have, what this rule has essentially done, now we have an incentive to keep water in the river rather than pulling it out and putting it in constructed recharge, etcetera.

Michael Bogan: [00:33:01] I just wanted to add briefly, something that I neglected earlier that is definitely relevant to what James just mentioned with the Colorado river and getting legislative changes that benefit projects like the heritage project. And that's, you know, the role of NGOs and non governmental organizations and kind of bridging the divides between these different stakeholders and these different manage resource managers and researchers, and locally here in Tucson, we've got the Sonoran Institute who's been playing that role for quite a while and helping to bridge the research world and the management world.

And then helping to push politically through their networks for things like changes in the groundwater recharge law. So that's, that's a really important player in, in local communities and I think they'll only be more important as we try to export this model to other places, and change groundwater recharge laws in other places that will, will have the same benefits that we're seeing here on the Santa Cruz.

Emile Elias: [00:34:03] Thank you so much. Thanks James and Michael and Drew for taking the time to speak with us about both the legislative and ecological impacts of this novel collaborative project, the Santa Cruz River Heritage project. So thanks for your time and speaking with Sarah and I.

Michael Bogan: [00:34:24] Thank you.

Emile Elias: [00:34:24] Thanks for listening to Come Rain or Shine, podcast of the USDA Southwest Climate Hub 

Sarah LeRoy: [00:34:33] and the DOI Southwest Climate Adaptation Science Center. If you liked this podcast, don't forget to subscribe, like, or follow for more great episodes. If you want more information, have any questions for the speakers or would like to offer feedback, please visit or

Emile Elias: [00:35:07] Our sincere thanks to USDA Agricultural Research Service, the Sustainable Southwest Beef Project and the US Geological Survey for supporting this podcast.