July 24, 2010
Marin averages 52 inches of rain each year at Lake Lagunitas, and we've been fortunate to get enough to fill the Marin Municipal Water District reservoirs this season. The rest of Marin receives much less water than our watershed on Mount Tamalpais, usually between 22 inches and 40 inches depending on where you live in relation to the mountain. Our area is Mediterranean in nature and prone to periodic drought. Our climate gets 90 percent of our precipitation between November and March, and we have seven to nine months with little to no rain.
From a gardener's perspective, this climate allows us to grow a wonderful and growing number of Mediterranean plants: California natives and plants from the Mediterranean Basin, the Western Cape of Africa, and parts of Australia and Chile. Gardeners can choose plants from our local plant communities such as grasslands, coastal bluff, chaparral, oak woodland and even redwood forests, depending on the microclimate. California has a rich cultural heritage from indigenous Indians, Mexicans, Spanish missionaries and European settlers.
Along with all of our wonderful blended cultures, many of us and our ancestors also brought with us a desire for plants that prefer much wetter summers that are not appropriate given our local climate. On top of this list is the typical lawn, requiring immense amounts of summer water.
In general, unless you've got kids or pets actively playing on a lawn, it would be prudent to consider changing that planting to something less wasteful. Even a pond or water feature can use less water than the same-sized lawn over the growing season. Synthetic lawns are a viable option if a place to play is still the main function of the space. The choices today are not at all like the old AstroTurf.
If you must keep your lawn, consider reducing its size and be sure to irrigate it with efficient multistream, multitrajectory rotors that maintain the highest uniformity over the lawn area, or consider sub-surface drip irrigation. If you still have the old impact heads in your system, it's time to upgrade.
Eliminate all runoff by cycling your run times, let the lawn grow to a taller height, and don't over fertilize.
There are many wonderful alternatives to a lawn. A meadow appearance can be created using one of the many "no-mow" grass blends, some of which are completely native and available as sod. Carex and other sedges are another option. Many people are opting to replace their lawn area with a habitat garden for local wildlife or even productive vegetable gardens, both of which take less water than the traditional lawn.
Once the big water-wasting culprit is out of the way or mitigated, think about your irrigation system. With seven months of no rain, having a garden without an automated irrigation system is time consuming, to put it mildly.
A modern ET or weather-based controller can help save lots of water, usually at least 35 percent over the season. MMWD sends out weekly ET (evapotranspiration) data and programming suggestions for the three Marin watering zones, but a controller that does it for you every day is the way to go.
Your system should be organized so that each valve is a hydrozone that has the same water needs; this allows maximum efficiency. Of course, no system will save water if there are leaks. A regular checkup is essential to any system. Each valve is only as efficient as its weakest point and any increase in uniformity within a hydrozone can make a big increase in water efficiency.
We now have other options: Graywater can be legally diverted from showers, sinks and washing machines into the garden for lush summer growth - all from water that would have gone down the sewer. Rain harvesting, captured from our downspouts and stored for summer garden use or diverted from the gutter into bioswales, can help to slow, spread and sink water into our aquifers and reduce the amount of water that flows to our storm drains. Permeable pavers will reduce runoff from hardscape areas.
Regular mulching in the garden goes a long way toward saving water as well. Mulch can increase the infiltration rate of the soil, increase the water holding capacity and reduce the erosion of our precious topsoil.
If we plant appropriately, eliminate or reduce lawn areas, use high-efficiency irrigation systems, re-use house water, capture rain water from our roofs and regularly mulching our landscape, we can all do our part to conserve our precious resource.
The University of California Marin Master Gardeners are sponsored by UC Cooperative Extension. For questions about gardening, plant pests or diseases, or to arrange a free water walk, call 499-4204 from 9 a.m. to noon and 1 to 4 p.m. weekdays, or bring in samples or pictures to 1682 Novato Blvd., Suite 150B, Novato.