4.1 Supply of fresh water is limited and demand is increasing.

4.1.1 The United Nations Population Fund estimates that only 2.5 percent of the water on the Earth is fresh, and only about 0.5 percent is accessible ground or surface water.

4.1.2 While world population tripled in the 20th century, the use of water increased six-fold. The United Nations estimates that in the year 2017, close to 70 percent of the global population will have problems accessing fresh water. Additionally, more than 2 billion people around the world lack basic sanitation facilities.

4.1.3 According to WWAP, agriculture use accounts for 70 percent of annual worldwide water use, industrial use accounts for 22 percent and domestic use accounts for 8 percent (1) .5

4.2 Increased demand has put additional stress on water supplies and distribution systems, threatening both human health and the environment.

4.3 Increased demand has intensified energy use and the associated greenhouse gas emissions. Significant energy is expended for treatment and distribution of water. According to WaterSense, American public water supply and treatment facilities consume about 56 billion kilowatt-hours (kWh) per year—enough electricity to power more than 5 million homes for an entire year. In California, an estimated 19 percent of electricity, 32 percent of natural gas consumption, and 88 billion gallons of diesel fuel annually power the treatment and distribution of water and wastewater (2).

4.4 The building industry diverts an estimated 16 percent of global fresh water annually (3). It is imperative that design and construction address water efficiency. The estimate of annual usage of available fresh water by the building industry accounts for the quantity of water that is required to manufacture building materials and to construct and operate buildings. It does not reflect the impact of the building industry on the quality of water.

4.5 This guide provides information regarding ideal sustainability and water use.

4.6 This guide provides general options for applied sustainability and water use.

1.1 This guide is intended to inform sustainable development in the building industry. It outlines ideal sustainability and applied sustainability for water management, consistent with Guide E2432. Both ideal sustainability and applied sustainability should inform decisions regarding water management.

1.1.1 Ideal sustainability is patterned on the hydrological cycle. This provides the concept goals and direction for continual improvement.

1.1.2 Applied sustainability outlines current best practices. This identifies available options considering environmental, economic, and social opportunities and challenges. The most appropriate option(s) are likely to vary depending on the location of the project.

1.2 Water management challenges differ enormously depending on the type of built environment and the available water resources.

1.2.1 The general demands of the built environment vary from very low density rural development to crowded urban development. Large cities present a particular challenge, with 400 cities worldwide housing over 1 million inhabitants.

1.2.2 Successfully meeting the challenges of uneven distribution of water around the world, depletion of groundwater, changing rainfall patterns, and other water industry trends requires sustainable solutions for the effective management of the entire water cycle.

1.2.3 Sustainable design, construction, and operation of water and wastewater services for the built environment are critical components of water stewardship and global sustainable water management.

1.3 Water stewardship encompasses both pollution prevention (quality issues) and conservation (quantity issues).

1.4 The values stated in inch-pound units are to be regarded as standard. No other units of measurement are included in this standard.

1.5 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety, health, and environmental practices and to determine the applicability of regulatory limitations prior to use.

1.6 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.