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🔬 "Watering Urban Green Spaces"

Water Talk

Photo by Nerea Martí Sesarino / Unsplash

Hosts: Drs. Mallika Nocco, Faith Kearns & Sam Sandoval
Guests: Janet Hartin | Environmental Horticulture Advisor & County Co-Director | University of California &
Dr. Amir Haghverdi | Assistant Cooperative Extension Professor of Water Management | University of California
Category: 🔬 Research

Podcast’s Essential Bites:

[4:27] AH: “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 requirement is […] at its highest level. So I was reading some numbers [that] suggest as high as 90%. […] It's the major consumer of water resources in urban settings in [the] US West in general. And what makes things complicated and actually draws attention to urban water management and urban irrigation is the fact that [the] US West […] is generally arid and subject to droughts. Some of the largest cities in the nation are actually located in this region. […] And that is why it's really important to think about improving irrigation efficiency and then basically conserving water and have it as a strategy now and in the future water conservation as a way of life in California.”

[6:25] JH: “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. Typical in a city, urban heat islands are hotter areas 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, then one aspect that brings us […] 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 and the more reradiated, he can actually be just the opposite response and bring people apart.”

[10:05] AH: “There are basically two components […] of irrigation and conserving water. One component is […] what type of landscape 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 do you do the actual irrigation application and how much of the water is being wasted? Just my anecdotal observation and what I see from my research […] is that more than half the applied water for landscape irrigation could be wasted due to our […] 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 species that need less water, if you do a poor job in terms of scheduling irrigation and maintaining irrigation systems, then you still have that big waste of water that you can fix if you follow scientific recommendations for irrigation.”

[11:41] JH: “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 and 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, cycle water […] if necessary.”

[12:40] JH: “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. […] 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.”

[13:16] JH: “The other thing is to make sure that you prioritize watering your trees over […] other plants. […] 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 cityscape they last 15 or 20 years. So let's think about trees and what we all can do to help them to prosper.”

[18:26] AH: “[For] irrigation in residential areas, there are a few types of smart systems. […] In urban settings and new residential areas, you have these smart irrigation controllers [that] are timers that process 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. […] Most of the work has been done in humid regions in Florida and North Carolina. […] 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.”

Rating: 💧💧💧

🎙️ Full Episode: Apple | Spotify
🕰️ 31 min | 🗓️ 05/21/2021
✅ Time saved: 29 min

Additional Links:
Master Gardener Program

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