Rainwater Harvesting and Stormwater Reuse for Arid Environments - Design with the Desert: Conservation and Sustainable Development - page 377

21.5.2.7 Using Xeriscape Principles and Native Plants
Most urban landscapes are irrigated with municipal supplies, treated to potable/drinking
water standards unnecessary for most landscapes. More sustainable landscapes can be
maintained on what is naturally provided, in an efficient manner using water harvest-
ing techniques. Xeriscape, a water-conserving landscape design approach, promotes seven
basic principles:
1. Planning and design
2. Soil analysis and improvement
3. Practical areas of turf
4. Appropriate plants
5. Efficient irrigation
6. Mulching
7. Proper maintenance
This approach groups plants with similar water requirements. These planting zones typi-
cally include a native zone where once plants are established they can survive on natural
rainfall.
In some cases, landscape designs are created entirely with plants that can survive on
rainfall once established, often termed natural landscaping . The purpose of natural land-
scaping is to preserve and reintroduce indigenous plants from the site, a practice that may
eliminate the need for supplemental watering after plants are established. This movement
is especially appropriate in arid locations where water is scarce. The water-saving benefits
of a natural landscape supplemented with harvested rainwater irrigation include
• Reduced peak water demand
• Reduced groundwater overdraft and contamination
• Reduced water costs
• Improved long-term water utility revenue stability
• Reduced runoff, soil erosion, and costs for stormwater management
• Creation of distinctive landscapes that represent the natural biotic characteristics
where the site is located
• Reduced energy costs for landscape maintenance
• Reduced plant disease, rot, and mortality caused by over watering
21.5.3 Active Systems
Buildings with expansive rooftops can be considered a watershed within a site and typi-
cally provide a fairly clean water source for supplemental irrigation water and possibly
other nonpotable water uses. A few of these uses are discussed to illustrate how active
systems can be designed (Figures 21.6 and 21.7).
21.5.3.1 Vehicle Washing and Automated Carwashes
According to the International Carwash Association, water used to wash a vehicle can range
from 15 gal per vehicle for self-serve washes to 50-60 gal per vehicle for in-bay (stationary)