Episode 21: Watering Urban Green Spaces
“My vote is for the trees, because trees could live and beautifully perform functions to cool urban heat islands, sequester carbon dioxide, provide shade and can do so for up to 150 years”
Janet Hartin & Amir Haghverdi
A conversation with Janet Hartin (University of California Cooperative Extension Area Environmental Horticultural Advisor and Director for San Bernadino & Los Angeles Counties) and Dr. Amir Haghverdi (Assistant Cooperative Extension Professor of Water Management at University of California, Riverside) about watering turf grass, trees, and other urban vegetation as well as drought strategies. Released May 21, 2020.
guests on the show
Janet Hartin
As an environmental horticulture advisor for landscape ornamentals in Los Angeles and San Bernardino counties, Hartin does research and extension in the area of sustainable landscaping. She focuses on water conservation; water quality protection; green waste use; and low-maintenance pest resistant landscapes. Hartin regularly partners with a wide array of public and private landscapers, irrigation industry personnel, arborists, water district personnel, and others employed in the green industry and associated fields. In addition to her research and extension roles, Hartin serves in several statewide UC ANR leadership positions such as associate editor for environmental horticulture, statewide co-leader of the UC ANR environmental horticulture team, appointed member of the statewide UC ANR water strategic initiative team, and appointed member of the statewide Master Gardener advisory committee. Learn more here and follow her on Twitter @J_Hartin.
Amir Haghverdi
Dr. Amir Haghverdi is an Assistant Professor of Irrigation and Water Management in Cooperative Extension in the Environmental Sciences Department at the University of California Riverside. He develops practical recommendations and and tools for sustainable urban and agricultural water resources management. The Haghverdi Lab uses field research trials, laboratory analyses, and computer modeling to improve irrigation water management and precision agriculture. Dr. Haghverdi also applies remote sensing, GIS (geographic information systems) and GPS (global positioning system) technologies, machine learning, and wireless sensors for water management. He received his Ph.D. in Biosystems Engineering from the University of Tennessee-Knoxville and recently received a Universities Council on Water Resources (UCOWR) Early Career Award for Applied Research. Learn more here and follow him on Twitter @UCRWater.
TRANSCRIPT
Mallika Nocco
Thank you for joining us on Water Talk. In today's episode we are talking with Janet Hartin and Dr. Amir Haghverdi. Janet is an area environmental horticulture advisor and the county co-director of cooperative extension for San Bernardino County. She specializes in soil plant water relations in the urban landscape with a strong focus on trees. Amir is an assistant Cooperative Extension professor of water management at UC Riverside. He also specializes in soil plant water relations, and precision irrigation in urban landscapes. HE also has a strong focus on turf grass and ground covers.
One of the things that I would like everyone to think about right now with this episode is just the spectrum, right? We talked about actually some pretty polarizing issues, turf grass can be a polarizing issue to talk about, native species and the language around them. And the idea of native species and non native species, this can also be a polarizing topic. But here in this episode, we really try to present a balanced and also la spectrum of choices for everyone who's thinking about managing water and managing plants in these urban landscapes during a dry year. Sam, Faith, do you have any thoughts?
Faith Kearns
I think it's a really timely topic. Obviously, people are looking for really pragmatic advice about how to cope with a year where we're going to be needing to conserve water, and what that means for the landscapes that we're all pretty intimately involved with, meaning our yards, city parks, and things like that. And one of the things I really appreciate is that, particularly the work that Janet's been doing recently around how we can continue to have urban trees into the future, both thinking about how climate change is affecting urban trees, but also how when we stop watering, it can affect trees, which are actually really important for keeping temperatures down and also keeping water in the landscape.
Sam Sandoval
I think this is perfectly a follow up episode from Erik Porse in a previous episode related with urban water management. They bring on these numbers related with how much water is used in the outdoors of our houses on the landscape. And how important it is to keep an eye. Similarly please, just be aware of specific actions to reduce that and appreciate that they are not even in one or the other camps related with turf grass or native versus non native plants. It's mostly these kind of gray areas that I think you will find how to adjust now that we're in a drought.
Mallika Nocco
The other thing that I think about is, you know, we talk a lot about a changing climate, and how urban heat islands might be exacerbated as the climate continues to change. And there's a lot of work that's been done on how trees and urban canopies can provide these cooling services and really help to mitigate some of these heat island effects. And one thing to think about in a dry year, especially, is that these trees, in order to provide us the services, they need water.
So without further ado, let's get ready to hear some deep insights from Janet and Amir. So my first question is for you: Can you tell us a little bit just about urban landscapes by the numbers in California? Why is it important for us to be thinking about city landscapes and lawns in terms of their water consumption?
Amir Haghverdi
Thank you. This is actually a great question. And with a good way to start, before I answer your question, I would like to actually tell you that my work is mainly in Southern California, my research, and then inland Southern California. So, some of the numbers and the information that we'll be talking about during this podcast are mainly from the research that we're doing in this region and with California being such a diverse state, the numbers may actually vary based on each region in Northern California and Southern California. But back to your question, roughly I would say around 50% of the water that we are using in urban settings goes towards urban irrigation in residential areas. And that number actually could be much higher in summer months when the crop water need is actually at its highest level.
I was reading some numbers, actually one reference suggests as high as 90%, which is really high. And we could tell that it's the major consumer of water resources in urban settings in US West in general. And what makes things complicated actually draws attention to urban water management and urban irrigation is the fact that US West is generally arid and subject to droughts, some of the largest cities in the nation are actually located in this region. So what happens is that we are seeing these spikes in population. So you're expecting, especially in Southern California, most of the population is located in So Cal, so the demand is high for indoor water use. And then you're seeing these droughts and climate change also, is making things more complicated. And that is why it's really important to think about improving irrigation efficiency and then basically conserving water and having it as a strategy now and in the future water conservation as a way of life in California.
Mallika Nocco
Wow, that 90% in the peak time period of the water going to landscapes that floors me. What a statistic. So when I think about just this landscape, and also what these plants in the urban areas, and specifically in Southern California, and what they are providing to the landscape, I was wondering, Janet, if you could tell me a little bit more just about the role of these plants, and also just the importance of ornamental plants specifically?
Janet Hartin
So, growing food is of course of critical importance, and we really need to allocate adequate amounts of water for that purpose. We have food deserts, where people don't have access to fresh fruits and vegetables. But with that said, ornamental plants do play an important role. They cool urban heat islands; they can reduce temperatures by 10 to 15 degrees in our hot urban city climates. Typically in a city, urban heat islands are hotter areas than in the surrounding area due to asphalt surfaces, and in general, the built environment. So well placed trees can decrease temperatures in these urban heat islands by 10 to 15%, with the greatest gains in the inland and desert areas of the state. So, I think that when we're thinking about climate change, the one aspect that brings us I think all to the same table is looking at the impression and urban area of it being a lifeline and bringing people together, that the more dark asphalt can actually be just the opposite response and bring people apart. So, bringing people together in a city, planting more trees and having more greenery not only produces more oxygen, but it helps to bring people in neighborhoods together.
Mallika Nocco
Yeah, that's a really interesting tension. Because I always think about it like, oh, we want to reduce, and we want to conserve water. But if we're getting this benefit, it makes sense that you'd want to know well, how much is too much? Or how much are we paying for the cooling? And then conversely, how much cooling are we losing if we get rid of the water that's cooling us? That's super interesting. And it actually kind of brings me to the next topic or question I wanted to talk about, which is turf grass.
I would say that turf grass is a very controversial and I think it can even become like an emotional topic for people. I know people who just hate turf grass and that makes them angry when they see it. And I know for other people, the turf grass that they're managing is just their pride and joy. So, I feel like it's very emotional. And because they're all these strong opinions, it seems like there's almost a dichotomy between this 100% old school lawn turf grass look, or like a xeriscape, planted with very low water using native plants. And I guess I'm curious if there's a middle ground or is there a continuum? Or what would this middle ground look like? And I know, Amir, you do a lot of work with water use and turf, and I have heard that it drinks a lot of water. And I'm curious kind of what your thoughts are on this topic?
Amir Haghverdi
That's a really good question. So, as you mentioned, my research group has been working on turfgrass irrigation management for a number of years now. And to be more precise, you're working on autonomous irrigation, management of turf and all other landscape species. So, I believe personally, that turf is necessary even in arid regions, but not that much for residential areas. But I agree turf has a relatively high-water requirement. One thing that people need to keep in mind is that for turf and for other landscape species that are irrigated, we have different cultivars, for example, whatever we have warm season turf, cool season turf, etc that tend to use less water. And also, we can, as a management strategy, you can actually stress your landscape, and it degrades the quality a little bit, but you save water, so we call it deficit irrigation. Through the studies that we did, we realized that you can actually bring down the water application and still have an acceptable quality for residential areas if some people want to.
I would like to point out that there are basically two components in this concept of irrigation and conserving water. One component is what type of landscapes we have and how much water they need, there is another component that is as important or even maybe more important in practice, and that's the irrigation efficiency, how you do the actual irrigation application and how much of the water is being wasted? Just my anecdotal observation, what I see from my research and then read in the scientific literature is that more than half the applied water for landscape irrigation could be wasted due to our irrigation efficient irrigation, broken or poorly maintained irrigation systems. So that's an easy fix relatively. So, it's important for people to understand that even if you switch to landscape, the species that need less water, if you do a poor job in terms of scheduling irrigation and maintaining the irrigation system, then you still have that big waste of water that you can fix if you follow scientific recommendations for irrigation.
Mallika Nocco
That's kind of wild. I mean, it's analogous to food waste in a way just thinking about all of this water that's being wasted because of the inefficiency of the system. I guess the follow up that I have is what are some resources out there for people to do a better job, I think about just the average person that might be irrigating plants at home. And I wonder if they are over irrigating or not being optimal about the timing? How would they know that? And what could they do to fix it? Like, where would they go?
Janet Hartin
This is my favorite topic. So, one thing that comes to mind is it you don't need to rip out a perfectly good landscape to save water. That takes a lot of time, and it can be really expensive. My recommendation based on research is to start simple, like watering less in the fall and winter than in the summer. About 85% of an average plant’s water use occurs in June, July, and August. And we're down to about 15% of that need going into the fall. Also watch for water running off the surface of the soil, like Amir mentioned, if necessary. And also I wanted to mention a study that Loren Oki, Dave Fujino, Karrie Reid, Darren Haver, and the late Chuck Ingels and me conducted over a multi-year period, it was funded by the California Department of Water Resources basically to determine how much water can actually be saved in our landscapes, which in this case were commercial parks, school grounds, churches.
Where the water loss typically occurs, we found out that just keeping irrigation systems in good repair and applying the right amount of water at the right time actually saved more water than plant selection. So, the good news is again that you don't have to start all over. One of the most efficient watering methods has always been found just to be the good old fashioned watering hose. You can watch where the water's going, you can move it out as the trees increase their secondary growth and get broader. You want to water outward from the trunk to the drip line rather than in the trunk area itself. And the other thing is to make sure that you prioritize watering your trees over annuals and other plants. If push comes to shove, and we're either in another drought and water is limited, or if there's imposed water restrictions through the government in which we really have to pick and choose what plants that we want to maintain.
So, my vote is for the trees, because trees that could live and beautifully perform their functions to cool urban heat islands and sequester carbon dioxide and provide shade can do so for up to 120, sometimes 150 years, if well selected and cared for. But in a typical city scape they last 15 or 20 years. So, let's think about trees and what we all can do to help them to prosper. And I have a couple of resources to add to what Amir suggested. If you've heard of the Master Gardener program, there are volunteers that are stationed throughout the state and they address home gardening and landscaping inquiries and even during COVID many of them are available via helplines, and sometimes by phone. So, to find your local program, the fastest way is just I think to Google Master Gardener along with the name of your county. The other searchable online indices are locals which I think we'll get back to later. And a couple other plant selection databases that are really fun to look at and compare your needs and space to drought tolerant plants that are suggested for your area.
Mallika Nocco
Thanks Janet. So, everyone who's may be listening on Spotify or iTunes or some of these other podcasting platforms. One follow-up that I have, and I just want to make sure I'm understanding this, is the idea that the climate is changing. And some of these native species, they may not be suited for the climates to come. And even the climate that we're in.
Janet Hartin
That is a very fair and accurate assessment Mallika. Some nativea simply don't perform well in urban heat islands such as asphalt coated parking lots, and some introduced plants actually perform better under those conditions. And they actually take less maintenance than the natives due to their inherent qualities that were selected for, such as pest resistance. So, we also have to think about some of the natives like Joshua Tree, my favorite Yucca, where I live out in Coachella Valley, and I live not too far from Joshua Tree National Park. And the sad reality is that the Joshua trees are only living when the seeds are actually viable five to 600 feet above the parent plant. So, the seeds around the parent plan at the lower elevations have a horrible a really low survival rate. So, the Joshua trees, that used to perform really, really well in Joshua Tree National Park at their native elevation are now requiring a higher elevation to continue to perform the functions and the beauty that they used to.
Mallika Nocco
That's really interesting to hear just the changes. And I'm sure that will probably resonate with a lot of the listeners out there. I want to think about the future in this sense, because I know that when it comes to plants, there's a lot of folks who are interested in technological solutions. And I think about it on the agricultural end. I do research with drones and think about smart sensors. And Amir, you're thinking about that in this urban context for irrigation management, you do a lot of work with smart sensors and technology. And I pictured this fully automated landscape. And it seems like there might be some misinformation out there about just how to implement some of these sensors and different tools and how much water they might save. And I was just wondering, what are some of the most important ways or what are some of the best ways to try to implement and incorporate these new technological solutions into urban landscapes to save water?
Amir Haghverdi
That's my favorite topic. It gives me hope and energy to keep working on this line of research. So I always think that we are promoting, we have the autonomous cars and why don't we have autonomous systems to manage the water resources and irrigation is part of it. When I dream about future, I see smart cities that basically are embedded with robust autonomous systems, data driven artificial intelligence-based models. And then, as you mentioned, drones collecting data and then we convert data to useful information and manage our precious water resources. So, part of that is happening right now when we talk about cutting edge research projects.
But if I want to talk about the practical aspects, and specifically about irrigation in residential areas, there are a few types of smart systems that they would like to talk about. We have been working extensively on implementation of these type of technologie, to basically manage irrigation in urban settings and also in agricultural fields. And you know that my background is in agriculture, I've been working on agricultural water management and still I work on agricultural products, but also enjoy working on urban landscape irrigation in Southern California. So in urban settings and new residential areas, you have these smart irrigation controllers. Basically, they are timers crossed with a brain and that brain is basically a sensing system that either works based on soil moisture sensing, or based on sensing weather parameters, or to be more precise evapotranspiration, which is combined crop or landscape use and evaporation from the soil. So all these products are out there. They have been out there for a number of years.
And then if you look at the scientific literature, most of the work has been done in humid regions in Florida and North Carolina, I see that big numbers 40 to 80% water saving has been reported, especially because they get a lot of rain and they just avoid unnecessary irrigation when it's raining. In California, the story is a little bit different, the work that we do research wise, we try to develop water conservation strategies again autonomously. How can we use these products, can we rely on them? And we evaluate in terms of algorithms behind the scenes because most of them blackbox, you don't know what the algorithm is behind the scenes, so we evaluate them in terms of reliability and ease of use. One thing I can say for sure is that even with this smart controllers, set it and forget, it wouldn't work. I mean, it never does. So you need to do a good job in terms of programming these systems properly and again, maintaining the irrigation system.
Well, another thing that I would like to mention is that not all of the products that are out there are really smart in terms of being science based. And it's really important for people to look at the scientific literature, we have a publication out for smart evapotranspiration or weather based controllers, that again is for free, people can look at it. And one more thing I would like to mention is we have the smart controllers that basically regulate irrigation applications. They work pretty good, there is water saving associated with them if they programmed correctly. I realize that some people are concerned about the price tag. So there are rebate programs, at least in Southern California, that pays most if not the entire cost of the product, there's a significant portion of that. So you get the product for free. Installation is easy.
And then there are other products that you can use on top of the smart controllers that to me can save a lot of water, no need to even know how to program them, for example, rain shut off devices. And in California, there are actually regulations that you're not supposed to irrigat, when it's raining. And you shouldn't irrigate, I think, four or eight hours afterwards, at least. So range of devices are another useful products that when it's raining, they shut off the irrigation system. So if rainfall is happening overnight, you don't see it, if you go to sleep, if you're at work, you cannot turn off your irrigation system, it automatically shuts off the system and they suspend the water if they are paired with smart controllers for, again, 48 hours or some of them users can actually define that period. Really important for people to start using the technologies that are out there.
Mallika Nocco
Thank you so much, Amir. That was pretty interesting. And once again, I feel like the theme of this is that doing a good job with the scheduling, it's boring, but it's what's gonna save water seems like that is kind of one of the takeaways today, I want to talk a little bit about one of these rebate programs I've been hearing about and it's got an awesome kind of nickname. It's called Cash for Grass. And I was wondering, what is it and how does it work? And is there anything that people need to be considering if they decide to participate in Cash for Grass?
Janet Hartin
Yeah, when we're talking about cash for grass, I guess, definitions are kind of important here. I don't want to disappoint anybody. We're not talking about pot or marijuana. We're talking about turf. So it's that four letter word again, turf or lawn, remember that if you're done with your lawn, if you don't have kids, or dogs, and you don't want to maintain an irrigation system that's sprinkler base that is high maintenance, then you might want to take advantage of these programs. So basically, water districts are offering rebate checks, sometimes even irrigation controllers, I've seen valves and I've seen other equipment offered in exchange for lawn removal. Sometimes it's $1,000 or even more. It tends to go up later in the season when money's left that needs to be spent per household, it might be $1 a square foot up to a maximum. So I think while the basis for these programs are certainly solid, especially when you're going to swap out a thirsty full season grass, you need to remember that whatever that that sprinkler system was irrigating besides the grass needs to be taken care of.
So the case and point is: don't forget your trees. If the trees in the same landscape have been receiving most of their water from the sprinkler system that watered the lawn that you're removing, remember to continue to water your trees. Back to the hose, a hose works great, just remember to water where the majority of the roots are, which is in that drip point of the tree away from the trunk. And think twice about buying into the cash for grass program offered in the heat of the summer. Because even drought resistant plants need regular watering until their root zones expand. So they're very small, they're going to be restricted pretty much to the area in which they were in the routing zone in their pot. And they're going to need for the most part very frequent watering. So if you can only water because of some kind of regulation twice a week, it's really a horrible time, even for drought tolerant natives, to be putting anything in the ground in July or August because they really need watering probably every day for the first few weeks until they start to establish a deeper and wider root system.
Mallika Nocco
I think hopefully will help some folks out and save some trees. You know, one of the questions that we really like to ask our guests and actually one of the questions that I always love the answer to this question because I never really know what I'm going to hear is just what do you want all of us to know about your work? And how can we support the work that you're doing?
Janet Hartin
That's a great question. And so many things come to mind. But I would have to say that from a social justice point of view, that any way that we can come together to help ensure that our trees are in a position where in the future, they can be at the desired 25% tree canopy in all neighborhoods, rather than in just the more wealthy neighborhoods in which they tend to have a higher canopies, because trees really are a lifeline trees and other plants provide all the oxygen that is the reason that we're here. So if we can do one thing together, I think it's not only taking care of trees on our property, but engaging ourselves with civic tree planting and maintenance programs.
Sometimes we plant a lot of trees, and then we forget about their care and their watering. So get engaged locally, and look into the neighborhoods in which the tree canopies may really be hurting, and engage families, youth, contact Master Gardeners of California, and sometimes AmeriCorps is involved with us. But I guess that I'm thinking of retiring in three years, and anything that comes to mind would have to be in that realm. I'd love to see California in a better place for my children's children than it is right now.
Amir Haghverdi
I would like to use this opportunity to promote the UC Cooperative Extension System. So UC is a public land grant university, which means that we take outreach very seriously, just like the Research and Education mission of university, I'm talking about scientists who dedicate their life to advance science and generate reliable science based information, not days or weeks or years to advance the research. But the actual impact happens when people will start using the information widely. Specifically, when we talk about water conservation, this outreach arm is designed to help people to help citizens to translate science based information and disseminate that to the general public. So I think we all have an obligation to make the best use of available water in California and conserve limited water resources, especially in Southern California.
Mallika Nocco
I love those answers. Those are both really good to know and good to think about. So yeah, thank you so much. And at this point, I'm going to open it up to Faith to see if she has anything she wants to ask the two of you. She's been listening intently.
Faith Kearns
Yeah, so one of the things that occurred to me and listening to was that we've talked a lot about in this podcast and just in general the idea of an irrigation paradox in agriculture, where you can focus on water use efficiency, but end up not necessarily overall conserving water, because the conserved water might just go to growing more crops. And so it occurred to me to ask if that same sort of paradox happens in an urban setting, does irrigation efficiency lead to water conservation in urban landscapes in a way it may not in agricultural landscapes?
Janet Hartin
That's a great and fairly complex question. And there's been some research on that by our UC and our colleagues. And there's differences in the findings so far, and I'm certainly not the economic expert. But when we're looking at water use in our urban areas, one of the criticisms is, why should I conserve water in my backyard when they're building a new development across the street of 525 track homes? So what's the use? I've heard that and then I've heard well, even though 50 to 60%, of urban water is directed toward landscape irrigation, when you're looking at the whole water use from a statewide perspective, it's 6 to 8%. And so there you go, just turn off all the water and we'd save a whopping 6% of the state water.
So there's a lot of different philosophies that I would just say that I think it's something that we need to really, really be having conversations about. We need to look at the resources that we have, we need to look at short and longer range goals. And where do we want to be in 10, 20, 30, or 40 years, not only at the state level, but at the municipal level when it comes to urban landscapes? And how do we start planning today for tomorrow taking all of these very, very valid considerations into focus?