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<br />..-,. ..... . "'i~ <br /> <br />Holistic Approach to Sustainable Water Management in Northwest Douglas County <br />page 2 <br /> <br />3. Significant savings can be realized by managing the outdoor water demand through limiting . <br />irrigated area, using water efficient landscaping, and improving irrigation techniques. The <br />outdoor water demand can be reduced by over 50% with moderate conservation and by over <br />75% with water wise conservation. With rainwater harvesting, outdoor water demand is <br />reduced by approximately 65% with moderate conservation and approximately 88% with <br />water wise conservation. <br /> <br />4. For existing well users, rainwater harvesting provides an opportunity to reduce withdrawals <br />from non-tributary aquifers with declining water levels and to provide a supplemental <br />supply, especially for irrigation and fire suppression. <br /> <br />5. Individual residential cisterns were evaluated in this study~ other rainwater capture methods <br />on a regional basis may provide additional options for particular projects. <br /> <br />6. Credit for the portion of precipitation that did not historically return to the stream system <br />(Le., lost to ET and sublimation) can be incorporated into augmentation plans without <br />injuring existing water rights. <br /> <br />Although this study focuses on the water supply needs in northwest Douglas County, the methods <br />presented are anticipated to be applicable throughout the county and state. A toolbox of algorithms <br />is presented that can be used to: (a) calculate water supplies created through rainwater harvesting <br />and the use of outdoor water demand management, and (b) calculate augmentation requirements that <br />reflect historic stream contributions. <br /> <br />Study Recommendations . <br /> <br />In summary, the study found that rainwater harvesting does have potential as a sustainable water <br />management approach in northwest Douglas County, particularly when paired with outdoor water <br />demand management practices. Existing literature shows that physically, not all of the precipitation <br />falling on an undeveloped site returns to the stream system. However, current Colorado law does <br />not allow rainwater harvesting to be utilized to its full advantage as one source of a sustainable water <br />supply. Recommendations from the study include: <br /> <br />1. Douglas County should provide alternative water demand assumptions that recognize <br />reduced outdoor water demand. Results of this study show that outdoor water demand can <br />be reduced by more than 75% using only outdoor water demand management. Additional <br />savings are possible with rainwater harvesting. <br /> <br />2. A pilot project should be identified that would incorporate rainwater harvesting with <br />efficient landscaping and irrigation practices to verify the conclusions in this study. The <br />pilot project would measure actual precipitation consumption and runoff patterns and verify <br />the water savings created through outdoor demand management techniques. <br /> <br />3. Legislative action should be pursued to authorize a pilot program that would codify <br />rainwater harvesting in a way that incorporates appropriate balancing and control <br />considerations and harmonizes rainwater harvesting with protection of other valuable state <br />resources. <br /> <br />. <br /> <br />{j Leonard Rice Engineers, Inc. <br /> <br />January 2007 - J 234C'PN <br />