Smart Landscape Design & Water Conservation
Recent rains in the San Francisco Bay Area have been a very welcome turn of events in our on-going multi-year drought. While state officials have said these recent rains will help, they still fall short of annual averages, and our need for water conservation continues to grow. Living in this particular region of the country we experience a Mediterranean-type climate, so regardless of whether we are in a drought or not water will always be an issue due to our distinctive rainy and dry periods. Just as we are tightening our money budgets in these hard economic times; likewise, we can save money by learning to work within a water budget so that household needs are met and a reasonably lush landscape is maintained.
In order to accomplish this Water-Wise landscaping, home owners, gardeners, and landscaper designers can implement a number of procedures to save water and water costs. On average, the largest amount of water used by households is for watering gardens and landscapes. For example it takes 50,000 gallons of water to irrigate a 2,000 square foot lawn. If you have a swimming pool with a nice green lawn around it, then water usage increases dramatically. A conventional large pool holds about 40,000 gallons of water.
One of your first Water-Wise practices to look at is designing the “planting palette.” Most nurseries offer a wide variety of plants from around the world, but Native and Mediterranean plants are best suited for our region’s rain patterns. You might think this would be very limiting to one’s options, but besides our wealth of native plants, this includes plants from the Mediterranean Basin, Western and South Australia, Southwestern South Africa, and parts of Central Chile. With the number of plant choices available it helps to have a professional designer assist you with a planting plan.
If you are in love with Japanese maples, fruit trees and other plants that require more water, you can still have them by creating a planting plan that carefully sites them in a somewhat shadier spot and combines a limited number of them with Native and Mediterranean plants. As you allocate water wisely, you’ll be able to create landscapes that are meaningful to you, lush, beautiful, and more sustainable!
One of the most important Water-Wise landscaping practices is to mulch planting areas. Generally mulching is one of the last things done in constructing landscapes and often considered optional. Mulching is not optional. Mulch holds moisture in the soil during our dry times and slows rapid rainwater runoff in wet periods, allowing the soil to absorb the water slowly, and thus reduces erosion.
There are many kinds of mulches, ranging from the inexpensive choice of wood chips to more expensive materials like pebbles, stones, and boulders. Perhaps the least expensive, however, is one many homes already have plenty of—simple leaf litter. Letting leaf litter lie where it falls in planting areas, and adding to it from the areas you don’t want it, can make a blanket of organic material. This blanket needs to be a minimum of 2” thick to be effective. Once this depth is achieved, the leaf mulch will keep the daily temperature of the soil within a limited range, keeping plant roots from baking in hot soil during the day. Other benefits to mulching include weed reduction, creating an environment for beneficial soil microorganisms and fauna to prosper, and helping to define spaces and paths by adding different colors and textures.
Another Water-Wise landscape practice is rainwater harvesting for irrigation. In short, this is the collection and storage of rainwater to be used in the landscape (this storage can be as simple as recharging ground water). Depending on how the system is designed, and how much storage capacity there is, thousands of gallons of water can be harvested. Rainwater can be the sole source of water you collect and use for irrigation, or you could also divert “graywater” from sources like the clothes washer, the bath tub, or even condensation from your AC unit to increase your water budget. If you live in an area that has heavy summer fog, you can even collect that!
The first place to start before installing a rainwater harvesting system or graywater diversion system is to check with your local municipality for relevant codes and ordinances. Once you decide to collect this water for irrigation, you’ll need to consider how to store it. There are many options including retention ponds, cisterns and tanks (of which there are many kinds, from simple wine barrels to prefabricated metal or plastic). You can also direct this water, using swales (planted water channels) and berms (planted mounds of soil), into tree basins or detention ponds (infiltration areas), thereby replenishing ground water. These are practices that have been used to sustain landscapes for eons, they are widely practiced in many dry lands around the world today.
It is important to remember, however, that swales and berms and tanks all have significant impacts on the aesthetics of landscape design. Swales and berms are inherently sculptural in form and require careful consideration of placement in the landscape. Tanks too are sculptural in form, and incorporating them to complement the architecture of a house and landscape must also be carefully considered to achieve truly graceful landscapes.
Finally, if you choose not to install a rainwater harvesting system you can provide the most up-to-date technology to conserve water by installing a drip irrigation system with soil moisture sensors, rain sensors, and timers. These systems are very efficient with allocating water precisely, but can be complex, so enlisting the services of a professional is advised.
We may get more rain in the coming months and years, but even if we do, it will not end our periodic droughts. Consequently, for those of us who love gardening, or make a living designing gardens and landscapes, we have to work with limited water resources–within a water budget. I’ve outlined throughout this article various Water Wise practices to do that, starting with a smart planting plan, always mulching, harvesting rainwater–storing it and directing it with swales and berms for irrigation, using a graywater diversion system to supplement irrigation and finally, installing a high-tech irrigation system, if needed. During these hard economic times, it makes sense to save money by saving water in such a sustainable manner.