Solving the Water-Energy Supply Challenge

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Judy Dorsey

Speaking at the Net Zero Cities Symposium in Fort Collins, Colo., Oct. 16 and 17, Brendle Group President and Principal Engineer Judy Dorsey noted the similarities between delivering clean, safe and affordable water and delivering clean, safe and affordable energy. More people in the world have a cell phone than have access to sanitary toilet facilities, she said. This lack of access to clean water and sanitation kills children at a rate equivalent to a jumbo jet crashing every four hours.

Here in the United States, 70 percent of water use is for agriculture, yet half of the food produced is wasted. One-fifth of the water we distribute is lost to leakage. Almost all of our energy is produced from thermoelectric (89 percent) or hydroelectric (9 percent) systems — systems that, combined, use roughly 2 gallons of water per kilowatt-hour of energy produced. Dorsey described Brendle Group’s work to develop solutions to these problems. She has led the Fort Collins-based firm in more than 200 sustainability projects, and demonstrates on their LEED Gold headquarters many of the technologies Brendle Group investigates.

The group’s activities include combined energy/water audits, developing water footprints and pushing for net-zero planning for both water and energy. A water footprint analysis considers both the water quantity (e.g., consumption) and water quality (e.g., stormwater runoff) impacts for an entity (facility, district, city, etc.). The quantity portion of the footprint involves establishing both the regional annual average precipitation and the annual minimum precipitation (the “dry” years), then determining the existing “business as usual” water usage for the entity over a specified planning horizon (see chart, below, water quantity makes up 60 percent of the total water footprint for this entity). The impact on usage can then be evaluated across various measures, including improved conservation, grey water, landscaping, rainwater harvesting and even water supply credits. These impacts are plotted on the footprint plot to determine which measure has the biggest or most immediate impact, when the cumulative effect of these impacts will result in a usage number below the minimum annual average supply level, and when the facility would reach net-zero water consumption. A similar method is also used for addressing the quality portion of the footprint and could include measures such as reduced impervious area and onsite stormwater management.

The Net Zero Cities Symposium focused on systems thinking about a community-based approach to carbon emission reduction by investigating the two major sources of carbon emission: energy and transportation. Working sessions allowed the sharing of business and community strategies associated with the gradual transition from largely coal and oil-based fuels to those of conservation and alternative modalities. For more information, visit netzerocities.net.

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