Susan Handjian is a garden educator in the San Francisco Bay Area. She was a contributing editor of Plants and Landscapes for Summer-Dry Climates.
By: Susan Handjian , 5:21 PM GMT on June 11, 2012
It was during my years as a water conservation professional that I began to connect the dots between water use and environmental health.
At first I was pretty naïve, thinking I’d talk to my customers about choosing more appropriate plants and using less water in their gardens and that would be that. It didn’t take long to realize that plants and water are intimately connected to the health of waterways, groundwater, and watersheds all over the planet.
Water is not just what you use in your own home and garden. It’s connected to every cloud, drop of rain, and expanse of snow, in a never-ending cycle of change.
As water morphs through its many manifestations in the hydrologic cycle, it often carries with it what is added along its journey. Here’s where the gardener’s role in the protection of a clean water supply becomes vital. When you pass through a neighborhood and see water from sprinklers running off sidewalks and driveways you are witnessing what's called non-point source pollution. This means that instead of pollution coming from a single, identifiable factory or processing plant, it’s coming from the aggregate of home landscapes, draining into local watersheds.
How can that be? A little water running off the pavement causes pollution? Alas, it does, and taken together it has a significant impact on the health of the world water supply.
One problem is the way in which we care for our lawns, the number one landscape material in the US. In 2005, there were 46.5 million acres of lawn in the United States, an area equaling the states of Delaware, Rhode Island and Pennsylvania combined. A 1,000 square foot lawn may use anywhere from 10,000 to 40,000 gallons of water during a typical summer.
Whether we do the work ourselves or have someone do it for us, the typical lawn receives several applications of high-nitrogen fertilizer annually. That fertilizer may contain herbicides and fungicides.
And don’t forget the small amounts of soil that naturally slough off from the planted landscape as sediment. Add liberal amounts of water from irrigation runoff and you end up with a chemical soup coursing across impermeable sidewalks and driveways into gutters and down into storm drains. Here it disappears from sight but not from the environment. It will end up in groundwater and in waterways nearby and thousands of miles away as water continues on its endless cycle.
Here are some things we gardeners can do to break the cycle of overwatering and the resulting unwitting contributions to pollution:
There’s an old saying that if the only time you walk on your lawn is when you mow it, it’s time to rethink its place in your landscape. The American love affair with lawn goes back centuries and is deeply ingrained, but in our drought-prone modern age, the time has definitely come to adjust our thinking about having lawns and especially about the way we care for them.
Avoid runoff by keeping lawns off sloped areas. Two-to three-foot buffers of tough, low-growing ground covers can be installed in areas where planted areas meet sidewalk and driveway. Any overspray from lawn is absorbed by the ground cover before it reaches the pavement.
Irrigate in the early morning hours to avoid evaporation caused by solar radiation. It is also generally less windy in the morning.
Another useful technique is to use “repeat cycling” on your irrigation controller. In other words, if you regularly irrigate for 15 minutes and see that water runs off after six, set your run times to three five-minute spurts with 30 minutes in between to allow time for water to penetrate.
Take advantage of the latest technology developed to deal with runoff problems. New high efficiency nozzles called stream sprays effectively reduce or even eliminate runoff.
If you have large areas of lawn, investing in a weather-based irrigation controller that establishes a base schedule will help to ensure that the lawn is watered in short segments only when it needs it.
Keeping the height of the lawn taller, 1 ½ to 2 inches, during the warmest months of the year reduces the need for water because the blades of grass shade the ground.
Also, resist the urge to fertilize, especially with high-nitrogen blends. More nitrogen leads to rapid growth and requires more mowing and more water. Instead, try raking a fine layer of compost into the turf at the beginning of the rainy season. This will gradually condition the soil and provide necessary nutrients for a healthy lawn.
Where possible, favor drip or other low-volume irrigation over spray. Drip is measured in gallons per hour as opposed to gallons per minute and does away with overspray. It still has the potential for runoff, but that is usually remedied quickly. Water is applied slowly and close to the ground. Drip irrigation technology comes to us from some of the driest places on earth, such as Israel and Australia, and has improved considerably since the clumsy systems of just 10 to 15 years ago.
Remember, efficient irrigation doesn’t have to be a fancy automatic set-up. There are soaker hoses made of recycled tires that do a good job of getting water directly into the soil.
Some say that hand watering is the most efficient way to irrigate. It does allow you to see how much water each plant is getting and also gives you a chance to observe plants up close to see any problems that might not be obvious from a distance. I water by hand, and find that I count on that quiet time of contemplation and appreciation of the garden.
Mulching is one of the most powerful tools you can use to cut water use in your garden. By applying a three-inch layer of chopped or shredded bark, compost, or leaves you are creating a physical barrier between the soil and the sun. In arid and semi-arid parts of the American West, this simple act can reduce the temperature of the soil by as much as 70%. This means that the soil retains moisture far longer and the need for irrigation is dramatically reduced.
But that’s not all – with mulch, seeds of water-robbing weeds have difficulty germinating, and if they do the weeds will be much easier to pull. If you place several layers of newspaper under that mulch you are sheet mulching, a technique that can beat weeds back over time.
Your valuable drip irrigation components are very vulnerable to the deleterious effects of solar radiation, and mulch protects them and extends their lives. It doesn’t hurt that mulch also covers up unsightly tangles of tubing.
Something miraculous takes place at the junction between mulch and soil. As the mulch decomposes, it feeds the beneficial organisms living underground, increasing the amount of water-retaining organic material in the soil.
As if the above weren’t enough, mulch finishes off the garden, giving it a unified and polished look.
One caveat about mulch: If you are trying to attract ground-nesting native bees, leave at least some areas in the garden bare so these invaluable insects have space to raise their young.
Graywater and Rainwater Harvesting
Water recycling and rainwater harvesting have become increasingly popular ways to save water. Graywater from showers and the rinse cycle of washing machines can be diverted to the garden, and thousands of gallons of rainwater coursing off rooftops can be saved in storage for future use.
Over the past 20 years or so there has been a growing awareness of the connection between miles of impermeable surfaces and urban runoff with its potential for pollution. Cities such as Atlanta, Georgia, Chicago, Illinois, and Sacramento promote the use of permeable, sometimes called pervious, concrete surfaces to reduce runoff and break the cycle of pollution.
For the gardener, this means creating paths and patios out of materials that allow water to penetrate the soil rather than run off. Bricks in sand, flagstone in decomposed granite, and interlocking pavers that sit on a sandy base are all ways to allow groundwater to be recharged.
I know this may seem like a lot of information to absorb, but awareness of the vulnerability of our water supply helps us become better gardeners. Whether you realize it or not, your healthy gardening practices do have an effect – not only on neighbors and entire communities but on the larger environment well beyond.
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