This is a particularly useful concept in arid climate regions where any water is beneficial, though gray water should not be used for root or potted plants. If irrigation is used to supplement this, then it should be designed on the basis of different requirement zones as a means of conserving water (Figure 3-37). Lawns (also see “Select Plants for Regional Precipitation”) should be regularly aerated to create air space within the soil and encourage the infiltration of surface water. With proper plumbing changes, the water from sinks, showers, dishwashers, and laundry machines can be drained to a holding tank where it can be a source for watering plants. Average rainfall is about 59" in Miami, 42" in Boston, 36" in Seattle, and 7-1/2" in Phoenix. May through October
Site irrigation should be organized into zones of different water needs to conserve water
are the wettest months in Miami, whereas April through June are the driest months in Phoenix. Mulch reduces the amount of water that evaporates from the soil, lowers soil temperatures, reduces weeds that are unsightly and take moisture from landscape plants, and decomposes to form organic material. These systems use a small tube that is connected to a matlike material below the ground’s surface as a means of moistening the soil. Lastly, an irrigation system should have a rain-shutoff device and undergo regular maintenance to repair leaks, adjust volume, and correct aim of the sprinkler heads. It should be noted that gray water is not sewage that originates from toilets. Other maintenance practices that conserve water include putting mulch on planting beds where there is exposed soil. A landscape designed for minimal use of water is called a xeriscape and is most commonly used in arid regions, though it has applications in all areas that experience periodic droughts. A well-conceived master plan, proper selection of plant materials (see “Select Plants for Regional Precipitation” in this chapter), efficient irrigation, and good maintenance practices can all contribute to a xeriscape. Sprinkler – or spray-type irrigation should be minimized because some water is lost through evaporation and wind dispersal. A low-water zone should be as large as possible and located the greatest distance from the residence because it would not need pipes and other connections to support it. Water harvesting is a different technique for conserving water by catching precipitation on a hard surface such as a roof or pavement and then storing it as a source for watering plants. The optimal xeriscape relies only on naturally occurring precipitation. Natural precipitation is often supplemented in the residential landscape with various forms of watering to help plants and lawns survive dry spells. Another naturally occurring event is precipitation, a necessary source of water for all life on the residential site. This zone should be kept as small as possible to conserve water. A moderate or mesic water zone would require some irrigation during dry spells but little to no extra water the remainder of the time. A moist water zone, often including the lawn, would require the most irrigation and should be relatively close to the residence to reduce the length of pipe or hose to service it. Ideal in planting beds and containers, drip irrigation or soaker hoses are the best methods of irrigation because water enters directly into the ground. This provisional water can be substantial in terms of both volume and cost. Gray water originatesfrom various household washing practices such as dishwashing, laundry, and showers and is typically drained into a septic system or municipal sewer. A cistern was a common method for storing water on farms before electric pumps became commonplace in wells. While essential, precipitation is not predictable in occurrence and varies widely in seasonal and regional amounts. The master plan should incorporate a host of concepts so that water conservation is integral to the entire design.