Rainwater Harvesting and Stormwater Reuse for Arid Environments - Design with the Desert: Conservation and Sustainable Development - page 365

Pollutant Discharge Elimination Systems (NPDES). The NPDES program, administered
nationally by the Environmental Protection Agency (EPA), requires a permit for the dis-
charge of any pollutant from a point source into the waters of the United States. In Arizona,
the Arizona Department of Environmental Quality (ADEQ) requires an Arizona Pollutant
Discharge Elimination System (AZPDES) general permit authorizing stormwater discharges
from development activities into waters of the United States. AZPDES requires best manage-
ment practices be implemented to minimize pollutant runoff from development activities.
Other states may have similar independent pollutant discharge regulations. The implemen-
tation of rainwater harvesting and stormwater reuse approaches will assist with meeting the
required best management practices as it is highly feasible that the impermeable surfaces
proposed for most urban environments will be coated with vehicle oil, pollens, and settled
air pollutants or dirt, all of which would be released to the site's retention basins and adja-
cent watercourses during a major rainstorm. By managing runoff close to its source through
site design, low-impact techniques focused on rainwater harvesting and stormwater reuse
mitigate these disturbances to the local environment. These water-conserving techniques for
nonpotable needs are essential to maintaining growing clean water demands. For example,
municipalities and industries combined accounted for the second highest water use—31%
in 2006—as reported by the Arizona Department of Water Resources.* Freshwater supplies
used for nonpotable requirements can be reduced or even replaced with an alternate nonpo-
table water source such as harvested rainwater to help limit the overall freshwater/ground-
water usage by municipalities and industries. The following discussions focus on the details
to consider when planning and designing, and implementing water harvesting techniques.
21.2 Determining Reuse Level of Commitment
Before an actual rainwater harvesting or stormwater reuse system can be designed, several
basic questions must be answered regarding the following:
• Retroit existing building or use a new integral system
• System size—large, medium, or small
• Complexity—passive or active collection systems
• Cost—low cost or complex
• Intensity of use and level of commitment or water security required
• Intended use—landscape irrigation, other uses, and/or potable water needs
• Water quality required (mosquito control)
Retrofitting an existing building or landscape generally is more expensive and costly than
it is to design a new integral system. Water storage systems can range in size from small
to very large:
• Small: <5,000 gal
• Medium: 5,001-25,000 gal
• Large: 25,001-50,000 gal
• Very large: >50,000 gal
* http://www.water.az.gov/adwr (accessed August 18, 2011).