So here we are again, starting the summer with low water levels in reservoirs, increased potential for wildland fires, and water use restrictions. In this third consecutive year of drought in California, and in light of increased residential water use through this spring, Governor Newsom has directed urban water suppliers to expand their efforts to limit water use. He also has called on all Californians to “understand and track the amount of water they use and measure their progress toward their conservation goals.”
The East Bay is served by several water agencies, each of which has a water shortage contingency plan that outlines actions to take during different stages of drought. Based on those contingency plans, East Bay water agencies have implemented voluntary or mandatory residential water use reductions that currently range from 8 to 15 percent depending on the agency, most with surcharges or penalties for excess use.
For residential water customers with gardens, the greatest water use is outdoors. So how can you keep your garden alive, healthy, and fire resilient while meeting water use restrictions? Here are some suggestions gathered from a number of sources, including East Bay Municipal Utility District, Contra Costa Water District, CNPS, UC Cooperative Extension, UC Division of Agriculture and Natural Resources, Oakland Firesafe Council, Tree of Life and other native plant nurseries, our Bay Leaf article on fire-resilient landscaping by Jane Francis, and more.
Know how much water you use
This sounds pretty basic, but it can be helpful. Your monthly water bill provides information about how much water you use, but it’s not very immediate. Some water agencies allow you to track your water use by setting up an online account. If you don’t mind handling your household water meter’s heavy concrete lid, you can also read your own meter to learn about your water use in real time. Most East Bay water agencies provide information on their websites about how to access and read your meter.
Tweak your irrigation system before you tweak your plants
Irrigation system leaks are common and costly in terms of water waste. It only takes a little time to run a check on your system and identify problems like a leaking valve or line, a misaligned spray head, a sprinkler blocked by vegetation, or a geyser from a missing emitter. CCWD offers a DIY Irrigation System Check and EBMUD offers a WaterSmart Home Survey Kit.
If you’re watering areas of your garden with fan-spray sprinkler heads, which are subject to evaporation and apply water much faster than the soil can absorb it, consider replacing them with multi-stream rotary heads. At just one-quarter of the application rate of spray heads, rotary heads need longer watering times, but the water goes where it’s supposed to.
During our dry season, plants’ water needs change based on temperature and day length. Adjust your irrigation schedule to match those seasonal changes: as the days get shorter in late summer and plants need less water, reduce the number of watering days but keep the length of time for each irrigation station the same. Do the opposite with longer days and warmer temperatures in early- to mid-summer.
Water your plants according to their needs
Many of our local drought-adapted natives, as well as natives from other summer-dry regions of California, go dormant in late summer and prefer to be left in that state until the weather cools and the rains begin. Excess water during the dormant period may make these plants more susceptible to pathogens. Know what your plants need and water accordingly.
Also pay attention to signs of stress from underwatering in shrubs or trees if you’re watering them less than they’re used to. Leaf wilting that doesn’t reverse by morning, sunburn, and twig and leaf drop are some of the signs that a plant is experiencing water stress.
Water at the coolest time of day
The best time of day to water is when it’s cool and evaporation is low. Early morning between midnight and 6 a.m. is ideal: temperatures are lower, the soil is cooler, and the air is more likely to be still, which means more irrigation water will be absorbed by plants instead of evaporating. If a heat event is predicted, try to water in advance of the heat rather than when it’s already hot.
Water less frequently but more deeply
Native plants with extensive, deep root systems will be better able to survive during times of water restriction. You can encourage plants’ roots to grow deeper by the way you water them, and in the process you will be losing less water to runoff and evaporation.
Although there are differing opinions about the schedule for deep watering, everyone agrees that deep watering is indeed the best way to get plants through a drought. The main idea is to water less frequently but more deeply by applying water more slowly. Plant roots will grow deeper as they follow water that penetrates deeper into the soil.
Deep watering works best with drip irrigation, soaker hoses, or other methods that apply water more directly to the soil. Run the water long enough to wet the soil to a depth of 12-18 inches, the root zone of many woody plants. You can determine how deeply your irrigation water penetrates by watering for a set amount of time (for example, 10 minutes) and then very gently digging into the soil in a small spot to check how far down the soil is wet. Based on what you find, you can adjust the watering time to assure that the root zone gets wet to its full depth.
Some sources suggest that the best way to assure deep water penetration without runoff is to water for five or ten minutes two or three times in one morning with an hour between each run. For irrigation systems with spray heads, this is probably the only way to apply water slowly enough to avoid runoff. Others say it is best to apply water all in one period of time but slowly enough that it doesn’t puddle or run off. This method is probably better suited to drip systems, soaker hoses, and similar slow application methods. If you’re watering with a hose, you can deliver water more slowly and deeply by turning the water pressure down by half and watering for twice as long.
Once you have begun watering deeply, reduce your water use by slowly increasing the number of days between waterings. Start by waiting an extra day or two and watch how your plants respond. If you need to conserve further, slowly add more days between irrigating, watching your plants and your water meter.
If you have to choose, save the big woody plants
If drought restrictions only allow enough water to irrigate part of your garden, spend that water on established woody plants that need summer irrigation (not native oaks!) rather than on annuals and short-lived perennials. If the annuals and perennials succumb, you can grow them again relatively quickly. Keeping trees and shrubs sufficiently watered increases their resistance to pests and diseases as well as their fire resilience, and it also preserves their habitat value.
If you have a lawn, consider sacrificing it to save your trees and shrubs while you’re conserving water. You can sheet mulch it and replace it with drought tolerant, pollinator-friendly natives during the rainy season.
Plant at the right time
Avoid introducing new plants into your garden during a drought; even drought-tolerant plants need frequent irrigation for the first year or two to become established. If our rainfall situation improves, plant in the fall when the soil and air are cooler and the rains have begun.
Avoid heavy pruning
Pruning stimulates new growth, which makes a plant thirstier, so in a drought only prune trees and shrubs to remove dead or damaged branches.
Like pruning, fertilizing stimulates new growth, which means the plant will need additional water.
Mulch or don’t mulch
Mulch is like a layer of insulation on the soil, holding in moisture and thereby reducing the amount of supplemental water plants may need. However, some kinds of mulch can be fire hazards when they are dry. Tests of different types of organic mulch materials ranging from shredded bark to wood chips to shredded rubber have demonstrated that they are all combustible and can spread fire to structures like fences and buildings. Inorganic mulches like stones or gravel are fire resistant, but in large amounts they absorb heat and increase the temperature in the immediate area, thereby increasing drought stress on nearby plants.
Consider some longer-term adaptations to drought
There are a number of ways to conserve water in your garden that involve greater investments of time and/or money. These include upgrading your irrigation system and introducing alternative sources of water by:
- redesigning your irrigation system to replace spray heads with high-efficiency rotating nozzles that reduce runoff by applying water much more slowly
- replacing a spray system with a more efficient drip system
- installing a “smart” irrigation controller with sensors that automatically adjust irrigation timing based on temperature, precipitation, soil moisture, humidity, etc.
- setting up a “laundry-to landscape” greywater system to provide laundry wastewater for part of your garden
- constructing a rainwater harvesting system to capture and store roof runoff for later use in watering your garden
- and when the timing is right, replacing plants that require more water with drought-tolerant natives adapted to your local soil and climate—that is, locally native plants like those offered at our chapter’s Native Here Nursery.
Before making big changes, check with your local water agency to learn whether it offers rebates for lawn removal or other upgrades that improve water use efficiency.
With luck, we will have more rain and a deeper Sierra snowpack this coming winter. But if we don’t, remember that your garden will need thoughtful watering during a dry rainy season too.
— Sue Rosenthal, Bay Leaf editor, CNPS East Bay Chapter