Municipal Water Systems: Closing the Loop

Municipal Water Systems: Closing the Loop

What government initiatives and standards exist for metropolitan rainwater harvesting and reuse?

Short answer: It depends on your government!

More seriously: We've found lots of information on rainwater harvesting (just Google it), but we've been unable to find much information on standards, except this note that rainwater harvesting is mandatory in Tamil Nadhu, the first state in India to take that step (though not without controversy), as well as in Bermuda and a number of other areas.

Says the Arizona Water Resources Research Center:
"A rainwater harvesting system concentrates and collects rain falling on house roofs and grounds for direct use and storage. Water is collected or harvested from concrete patios, driveways and other paved areas. Also harvested is the flow from the roof and from catchments such as gutters. Houses can be designed to maximize the amount of catchment area, thereby increasing rainwater harvesting possibilities."
The LA MWD has provided small grants for rainwater harvesting systems, according to the Rainwater Harvesting Web site. A more ambitious city-wide scheme is afoot in LA -- a city with an interesting challenge: rainfall delivers half the city's water demand, but since 75% the city is impermeable buildings and roads most of the water runs to sewers and to the sea. The city spends billions to acquire water, and billions to throw it away. The not-for-profit TreePeople proposes to change that, with an integrated water management system that could save the city hundreds of billions of dollars, cut water imparts in half, and creates then of thousands of jobs in the process.

Australia's GreenPlumbers says:
"In Metropolitan areas there are other factors that need to be considered to ensure that the rainwater you harvest can be used to its full potential. Water quality is a potential problem with all roof water systems due to:
  • atmospheric pollution;
  • bird and possum droppings;
  • insects and other small animals;
  • roofing materials and paints;
  • detergents and other chemicals (i.e., fibrous cement roofs -- lime contamination)."
Another constraints: legality varies. In Texas, there are financial incentives (PDF) for rainwater harvesting systems and a law (HB 645) making it illegal for homeowner associations to ban rainwater harvesting systems. Moreover, rainwater harvesting materials (and all water-saving devices) are tax-free (PDF).

On the other hand, "The use of water in this state and other western states," according to the Colorado Extension Service, "is governed by what is known as the prior appropriation doctrine. This system of water allocation controls who uses how much water, the types of uses allowed, and when those waters can be used. A simplified way to explain this system is often referred to as the priority system or "first in time, first in right.'... The diversion and use of rainwater is subject to Colorado water law, making it difficult to use without a plan for augmentation that replaces depletions to surface water flows. In most areas of Colorado, the most common way to use rainwater is to direct roof gutter downspouts to landscape areas you wish to water."

Bottom line: a great idea in concept, but as with all ecological design strategies, there is no one-size-fits-all panacea; design must always be suited to place.

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Gil Friend, systems ecologist and business strategist, is president and CEO of Natural Logic, Inc. -- offering advisory services and tools that help companies and communities prosper by embedding the laws of nature at the heart of enterprise. Sign up online to receive his monthly column via email. Read Gil's blog here.