The Case for Rainwater Harvesting

Posted on Tuesday, April 14th, 2009 at 4:28 pm by admin

Yee Huang, from the Center for Progressive Reform, posted a great article on Alternet today about the absurdity of states outlawing rainwater harvesting. It seems that some backward-thinking states such as Colorado, in an effort to control and sell their water resources, have made the ancient practice of capturing rainwater illegal.

I thought I would add to the conversation by posting this excerpt from The Carbon-Free Home: 36 Remodeling Projects to Help Kick the Fossil-Fuel Habit, by Stephen and Rebekah Hren, in which they make the case for rainwater harvesting. Enjoy.

The following is an excerpt from The Carbon-Free Home. It has been adapted for the web.

Letting water fall on your roof and run off your yard into the storm drain, and then pumping an equivalent amount of water from miles away for use inside your home doesn’t make a lot of sense. Like other wasteful and inefficient modern city systems, the failure to harvest and use the water that rains down on our houses results in wasted energy, almost invariably fossil energy, with the concomitant carbon emissions.

Much urban and rural water arrives at taps after being pumped (using fossil energy) from underground aquifers. Some of these aquifers are now stranded, meaning they are not being recharged. Water from these aquifers is often referred to as fossil water, because it accumulated over thousands if not millions of years and will not be replenished in a humanly relevant time frame once depleted. Aquifers that are capable of being recharged do so faster when water is released slowly over a long period of time so that less is lost to runoff. In other areas, water is obtained from dams that cause massive ecological disruption and greenhouse gas emissions (due to the organic matter that settles and decomposes anaerobically on the bottom of the lake, methane is released as water flows over the dam).

Water and fossil fuels are increasingly intertwined as they both become scarce, from overuse and ever rising human populations. Industrial agriculture depends heavily on both water and fossil fuels for the manufacture, packaging, distribution, and refrigeration of its “products.” Depleting aquifers take geometrically increasing amounts of energy to keep the pumps running as the depth of the wells increase. With the biofuels boom, many of the grains grown are then being turned back into fuel to run our hundreds of millions of automobiles and transport trucks (more on this in chapter 11). Beyond realizing the energy required in the capture, treatment, and pumping of a typical municipality’s water, an understanding of the precarious state of the world’s water supply and how dependent it has become on fossil fuels is important to making informed decisions. (Read Lester Brown’s Plan B 3.0 for a detailed analysis of the world situation. See resources for more information.)

On a local level, nothing will make you think more about the status of your area’s water supply, the fundamental requirement for all life, than becoming a personal steward of your water resources by capturing rainwater and using it in your home. As we write this chapter, much of the Southeast, including our hometown of Durham, North Carolina, is in extreme drought conditions. Durham currently has only 39 days of readily accessible water supply. We don’t know when or if the rains will begin again in earnest, but we do think about every drop of water that we take from our taps and are thankful for even the minimal amount of water we’ve been able to catch in our rainwater barrels this year.

Please note that some jurisdictions, especially in the western United States, limit or prohibit rainwater catchment, as rainwater is counted in downstream water calculations when those water rights are sold. Despite how ridiculous we think this is, it is something to be wary of.

Rainwater can obviously be used to water gardens, but depending on the complexity of the system it can also be used for flushing toilets, washing clothes and dishes, and drinking water. Paradoxically, some folks consider the idea of drinking rainwater unpleasant. All the water we use has been rainwater many times, lots of it quite recently, and the process of evaporation (also called “distillation”) that creates rainwater purifies it of salts, man-made contaminants, and bacteria. Understanding the main components of a rainwaterharvesting system and integrating a proper filtering system should alleviate any concerns you might have about the potability of your water.

While building your own rainwater-catchment system entails a fair amount of up-front costs, it nevertheless provides many benefits over the long term. Rainwater catchment:

  • Provides water security.
  • Makes us conscious of the amount of water our site would naturally receive.
  • Will likely provide water that is much cleaner and purer than city water. Rainwater has been naturally purified of pollutants and microbes by distillation.
  • Can be used for moderating temperature.
  • Puts much less strain on municipal stormwater systems during heavy rains.
  • Improves the ecology of our site by slowly releasing the water so that more of it can be used.
  • Makes sure the “purifying” chemicals in your municipality’s water don’t kill off the vital bacteria in your compost, biogas digester, yogurt maker, or stomach.

While a whole-house rainwater-catchment system can be quite involved, it will operate synergistically with many other components of a carbon-free home, making its incorporation worthwhile over the long term. For example, installing a metal roof provides the best surface for water catchment, while helping keep your home cool with a roofing material that will last as long as your solar electric or hot-water systems.

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