Trees play a key role in water conservation

Trees in the landscapeTrees play a valuable role in water conservation by intercepting and storing water. They stabilize soil with their extensive root systems, reducing soil erosion and runoff and thus improving water quality. Wooded areas conserve and naturally filter water, recharging the ground water supply and preventing the transport of sediments and chemicals into streams.

To illustrate, in Boise, the 23,000-plus publicly managed street trees intercept 19 million gallons of storm water annually, a service worth more than $96,000 to the city. Consider that same service being carried out by thousands of privately owned landscape trees throughout the city of Boise, and you can appreciate the magnitude of the service trees provide in a single community.

Shade provided by trees also helps reduce temperatures during our hot summers. As Susan Bell, UI Extension Horticulturalist in Ada County notes, “One healthy tree is equivalent to a 10-room air conditioner”.

Although trees are critical to water conservation, keeping trees healthy in southern Idaho can be a challenge.

Even with sufficient irrigation water, the desert climates of southwestern Idaho are less than ideal for tree survival and health. The combination of hot summer temperature and low relative humidity produces conditions of constant stress, especially if the trees are marginally adapted. If water becomes less available in the future, with concurrent limitations on irrigation, many of the tree species commonly planted in the region will not survive. Therefore, it’s important to carefully select trees for new plantings that have the best opportunity to thrive despite our dry conditions.

A new UI Extension publication, “Trees for Southwestern Idaho Landscapes: Selection and Proper Irrigation” (Bulletin 884) provides guidance on choosing tree species adapted for the region and on how to irrigate efficiently. Efficient irrigation not only conserves our precious water resources, but reduces your water bill. The new publication is available free at