THe National Resources Defense Council (NRDC) just issued a report titled "Capturing Rainwater from Rooftops" highlighting the potential for rainwater re-use or rainwater harvesting as its sometimes referred to for complementing municipal water supply needs.
The NRDC analyzed the total volume of rooftop rainwater potentially available for capture and use (based on rooftop area and average annual rainfall) in eight U.S. cities, as well as the volume of water potentially available for use under various capture, storage and usage scenarios. The result of the analyses showed that the volume of rooftop runoff, if it were to be completely captured, would be enough to meet the annual water supply needs of between 21 percent and 75 percent of each city’s population.
NRDC’s study shows that a substantial opportunity exists to use rooftop rainwater capture as an efficient, effective water resource management approach.
There are several factors that could affect the use and benefit of re-using rooftop runoff (local regulations, existing infrastructure, etc.) however this study shows the potential is there, and rainwater harvesting represents a valuable tool municipalities, developers, property managers and homeowners can use to meet their water supply needs.
To read the entire report from the NRDC please click this link.
For questions or more information about Rainwater re-use, please contact John B. McAllister, P.E. at (508) 747-7900 extension 117.
Water has been considered as an inexhaustible resource for a long time. Its use was not really controlled or limited. The overusage inevitably led to shortages, and scarcity of potable water is now a reality that our world has to cope with. Only 1% of the world’s water is suitable for consumption and one-third of the world’s population lives in a region experiencing water shortages and does not have access to fresh drinking water, which accounts for 1.1 billion people in developing countries.
This scarcity comes from:
- Drought and unusually dry conditions, like in 2007 in the Southeastern United States
- Population growth, above all in regions where there are a few inches of rain per year like in the Sun Belt
The scarcity of potable water has led to a rise in water prices throughout the United States. It has become obvious and inevitable that there is a need to find another way to use water in order to spare this resource.
The first practice affected by new restrictions and conservation measures is landscape irrigation. Landscape-watering restrictions were introduced in the US: just one-third of all domestic water use can be allocated for irrigation. However, landscapes are valuable properties: they increase property values, decrease pollution and boost tourism. A solution had to be found in order to balance a decrease in potable water and the desire for irrigation. The best solution seemed to substitute the water supply with an alternative source: non-potable water.
Non-potable water is a term that includes: water from air-conditioning condensate, rainwater, stormwater runoff, treated residential wastewater, and brackish water (combination of sea and fresh water).
There are different ways and reasons of using non- potable water:
- The United State Green Building Council’s (USGBC) Leadership in Energy and Environmental Design program (LEED), part of the Green Building Movement, made the use of non-potable water for landscape irrigation a popular practice. This program gives the opportunity of sites who want to have LEED certification to receive six to ten certification points by using recycled water and implementing efficient irrigation systems. Having the LEED-certification is advantageous to properties because they save money and energy. This program aims at giving site the incentive to use non-potable water for irrigation, but it is completely voluntary.
- Using non-potable water is now required by some states and local agencies for new commercial properties and government facilities.
- There are tax incentives and rebates for residential and commercial buildings if non-potable water is used. This is always an appealing means at a time when the cost of municipal water and sewer services are increasingly high.
Using non- potable water for landscape irrigation includes some requirements to observe:
- Brackish water : may require a reverse osmosis to remove excess salinity, which can be very expensive
- Harvested water : systems to collect, filter, store and recycle stormwater
- Reclaimed water: in Massachusetts, must be treated to the Massachusetts Department of Environmental Protection (MA DEP) water re-use standards.
If the type of water used for irrigation changes, the irrigation system itself is going to change. Specifiers, landscape architects and contractors are going to design and implement new irrigation systems because non-potable water has different chemical properties than fresh water and non-potable water affects differently irrigation system components and design.
Research and development has revealed the components and priorities of reclaimed water. This water is unfit for consumption and can have a harsh effect on water transfer lines and irrigation system components. The challenge in designing irrigation systems for use with non-potable water is to make products that withstand all sources of non-potable water. Reclaimed water’s composition has been carefully analyzed by engineers and they found out that chemicals and compounds have a damaging effect on the performance of products like valves, rotors or sprays and they reduce their life expectancy. Engineers know that they now have to design and specify efficient and more durable products.
The use of reclaimed water for landscape irrigation is not just a trend, it is a new practice that will keep on spreading all over the world in order to face the shortage of potable water. Architects, specifiers, builders, legislators, and programs like the LEED program, will all contribute to promoting this new way of using water efficiently and wisely, and to educating customers. This new practice enables the customer to save water and money, and to act sustainably. Water savings and sustainable design meet an increased demand and this is not going to stop, because everyone recognizes the benefits of these products.
Norfolk will follow this blog posting with a posting providing more information on rainwater harvesting.
If you have any questions about rainwater harvesting or water re-use, please contact John McAllister at firstname.lastname@example.org or at (508) 747 - 7900 x 117.
Information in this article taken from November/December 2011, article by Lynette Von minden, published in Water Efficiency.