Resilient Design: Water in a Drought-Prone Era
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July, 2011 dust storm in Phoenix, Arizona. Photo: Militec, Inc. Click on image to enlarge. Periodic drought is something that a significant portion of the U.S. will have to get used to in the coming decades. Climate scientists tell us that while pre... As we think of adaptation to climate change and resilience, dealing with water has to be a part of our focus. In this blog I'll cover how to improve the efficiency with which we use water and measures to ensuring access to water during shortages. The Niagara Stealth toilet, which uses just o.8 gallons per flush. Photo: Niagara Conservation. Click on image to enlarge. Use water efficiently When water becomes scarce, it is all the more important to use that water efficiently. During drought emergencies, restrictions in certain water uses (such as outdoor irrigation) are commonly instituted. By planning ahead and replacing water-intensive lawns with low-water-use native landscaping (often called "xeriscaping"), your grounds will likely do just fine without water. If you want to be able to get by with stored water during interruptions in water supply (see below), you need to make that stored water go as far as possible. This means ultra-low-flush toilets, such as the new generation of high-efficiency toilets (HETs) that use no more than 1.28 gallons per flush or that offer two flush volumes, showerheads using as little as 1.5 gallons per minute, bathroom faucets with flow rates as low as 0.5 gallons per minute, water-conserving horizontal-axis (front-loading) clothes washers, and top-efficiency dishwashers. One can go even further with water-efficiency using composting toilets that don't use any water, waterless urinals, and graywater systems that capture water from a lavatory sink to re-fill the toilet. Relying on a spring on a hill Rural homeowners with springs that gravity-feed water to the house are at a distinct advantage when it comes to resilience. Our home in Dummerston used to be served by a spring on the hill above our house that relied on gravity to deliver water to a cistern in our basement. The vertical drop from the spring wasn't enough to deliver a strong shower, so we had a shallow-well pump in the basement to charge a pressure tank, but during power outages I could turn a few valves and switch over to gravity-pressure for our home water system; the 20 psi of pressure provided a weak shower--but a lot better than none. Unfortunately, after several years of the spring running dry in August, we drilled a well and pretty-much abandoned the spring. On-site water storage If your water supply is interrupted for whatever reason, the only real option is to have stored water on-site. Rural homeowners who face periodic power interruptions are familiar with this issue. Unless we have back-up generators, when we lose power we lose our water, because our deep-well pumps don't work. This is my situation. We have a pressure tank in the basement, so we may still have a few gallons of available water after a power outage, but not much. It's always a good idea to have stored water on hand for emergency use. Those five-gallon carboys used with drinking-water dispensers work well for storing potable water. Fill them, seal them to keep insects and dust out, and keep them in a dark location to prevent algae growth. Open containers may be fine for storing non-potable water that can be used to flush toilets. When we lose power, we shut off the fill-valve to one of our toilets, and fill it manually after flushing. You can carry water from a stream, collect water from your roof in buckets positioned under the eaves, or rely on a full-blown rainwater harvesting system (see below). Rainwater storage tanks at the Chesapeake Bay Foundation in Annapolis, Maryland. Photo: Alex Wilson. Click on image to enlarge. Rainwater harvesting A greater level of resilience can be achieved with a rainwater harvesting system. The simplest of these systems is a rain barrel positioned under a downspout at the corner of your house. With larger systems, multiple downspouts feed rainwater into a large tank, or cistern, that stores the water. Many types of cisterns are available, made from plastic, fiberglass, galvanized steel, wood, or cement. I've seen rainwater systems with buried cisterns that hold tens of thousands of gallons, but more common are tanks holding a few thousand gallons in an outdoor shed or basement. Being able to gravity-feed water from a cistern is an advantage, but that's often hard to do in cold climates, since the tank has to be kept from freezing. Simple rainwater harvesting systems are typically used (during non-emergency times) for outdoor irrigation. More sophisticated systems are designed to provide potable water and include first-flush systems (to discard the first water that comes off a room during a rainstorm), filtration, and purification systems to ensure safe water. When used for potable water, a metal roof is usually the best surface, since less detritus is held in the roof surface. About this series Throughout this resilient design series , I'm covering how our homes and communities can continue to function in the event of extended power outages, interruptions in heating fuel, or shortages of water. Resilient design is a life-safety issue that is critical for the security and wellbeing of families in a future of climate uncertainty. Alex is founder of BuildingGreen, Inc. and executive editor of Environmental Building News . To keep up with his latest articles and musings, you can sign up for his Twitter feed .