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FAQ: UC Davis campus landscape irrigation during drought

As you are aware, California is experiencing its fourth year of drought. As a result, people are very conscious of watering practices, both at their own homes and public facilities such as the UC Davis campus. While every unit on campus is working to conserve water, the information in this article addresses how the UC Davis Arboretum and Public Garden is working to conserve water in its landscapes throughout campus as well as in the Arboretum.

Q:  How are you committed to saving and reducing water?

A:  Per the Governor’s mandate, the entire UC Davis campus has a 25% water savings mandate over 2013 water use numbers. To date the Arboretum and Public Garden has already achieved a 30% water reduction and we are on target to exceed this goal in 2015.  We are also actively working on converting turf areas into very-low water use landscapes that include Arboretum All-Stars, California natives, and other region-appropriate plants. We have cut back on irrigation schedules and run times across campus, we are using the minimum amount of water necessary to keep the campus tree canopy alive, and we are letting some of our turf areas go dormant.

The key component in our ability to reduce irrigation so quickly without the loss of our campus landscape has been our investment in a centralized “smart” irrigation system. Over ten years ago we started converting our manual system to one that automatically alters water use based on weather data, soil, and plant type. This change has allowed us to reduce our water use despite the addition of new landscapes and growth on campus.

LEARN MORE: How low can they go?

Q:  Where, what, and when do you water?

A:  The campus waters all of its landscaping, but not all landscaping is watered equally. Areas that get little public use, such as turf next to a building, is watered only enough to keep it alive and to prevent erosion. Areas like the Quad, or other high-use areas, such as sports and intramural fields receive more water. By being smart about our water use, we can still recognize significant water savings while maintaining places the public and student body can use for recreation.

Watering typically takes place between midnight and 6 a.m. However, there are places where you might see irrigation during the day. On grass areas, this could be during system testing or to prepare a sports field before a game.

Q:  Why do I see some areas along the Arboretum being watered during the day? Why is there overspray in these areas?

A:  On some areas of the campus, but primarily within the Arboretum’s scientific collections and demonstration gardens, the irrigation system is old, or does not exist. These areas require hand-watering with hoses and/or portable sprinklers. Because these systems require people to manually start, stop and move them, you will see them being used during the day. This type of irrigation is not as efficient, which is why you see overspray onto paths—wind can also create overspray.  Installing new irrigation systems from scratch is very expensive, and will need to be phased in over many years. However, in order to be immediately responsive to the drought conditions, the university is investing in temporary irrigation systems within the Arboretum. These temporary systems will be set up over the summer of 2015 and allow for automated, more precise nighttime watering to reduce overspray and water use. As permanent systems are funded and installed, the temporary systems will be removed.

Q:  Where are you cutting back?

A:  We are cutting back in almost all areas with the exception of heavily used fields for sports programs and event spaces, such as the Quad.

Q:  What water savings have you achieved to date?

In 2014 the Arboretum and Public Garden reduced its water use by over 100 million gallons and is on track to exceed that again in 2015. This represents a 30% savings in water use over our 2013 numbers.

Q:  Why do I see irrigation in construction areas on what look like weeds?

A:  Some areas of construction are mandated by the State to have vegetative cover of a certain percentage to mitigate potential soil erosion. Irrigation in these areas is required to meet this goal even if the vegetation is weedy; areas like these will not be watered during the summer.

Q:  Why do I see some areas around trees that look like they are soaked or muddy?

A:  The best way to irrigate trees during drought is to apply water less frequently, but more deeply. In other words, the frequency of watering is reduced, but when watering does occur, it will be for longer. This method soaks the root zone to allow the water to penetrate deeper into the soil; here, a smaller amount water is lost to evaporation so it stays available to the tree for longer. Overall, less water is used, but the area around the trees can look soaked or muddy for a period of time.

Q:  Why are there green bags around some trees?

A:  In areas where we have younger trees in turf areas, slow-release watering bags allow for a targeted application of water on the new trees while the surrounding turf areas go dormant or partially dormant due to reductions in water application. These bags allow the trees to survive and become established with less total water to the site. These types of bags are used in dry environments without tree-specific irrigation systems, and are very efficient users of water. Each of the 240 bags the campus is currently using is estimated to save 1000 gallons of water annually.

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Q:  Why is there water in the Arboretum waterway?  With the drought, can we afford to have water there?  Shouldn’t it be dry?

A:  During the winter months, stormwater flows into the waterway.  In the summer months, all the water in the Arboretum waterway is campus recycled wastewater.  Rather than discharging the treated wastewater directly into Putah Creek, it first flows through the Arboretum waterway, then goes to the creek.  This use of the recycled water provides habitat for the fish, otters, turtles, and birds that live along the waterway, keeps the riparian plants healthy, and creates a park-like atmosphere along the Arboretum.

Q:  Couldn’t you irrigate with the recycled water?

A: Some landscaped areas in south campus do use recycled water for irrigation. This kind of water only works on landscapes with plants that can tolerate the high salt levels found in recycled water.  If it were used on existing campus landscapes, it could kill our trees and plants over time.  While the salt levels won’t harm the wildlife or plants along the creek banks, if it were used outside of this area, the wetting and drying cycles involved with regular irrigation would cause the salts to concentrate in the soil over time.

Q: How can I help?

A:  If you see broken irrigation heads or lines, or irrigation running that doesn’t seem to fit the above-referenced exceptions, please call the campus work order desk at (530) 752-1655.

Please know we not only have an active conservation plan, but a reason behind each irrigation choice we make. With your help and an eye on maximum water savings, we are confident that our water saving landscape planning and practices can become a model for other universities and cities throughout the state.

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