Southwest Hydrology: The Resource of Semi-Arid Hydrology Volume 4 Number 2

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the country. Prior source tracking research reports cite accuracy ranges from 60 to 90 percent for various source tracking methods. The authors of the USGS study attribute the discrepancy between the 60 -90 percent rates and the 20 -30 percent rates they reported to a number of factors: • Different bacteria may be present in animals in different seasons. In the USGS study, challenge isolates were collected nine months after the reference feces were collected; • Too many strains of E. coli bacteria may exist in each animal species for effective application with small reference libraries, such as the 900 reference strains in the USGS study. At a cost of $10 to $100 to analyze one reference strain, building large source libraries gets expensive rather quickly. • E. coli strains may not be truly specific to one animal source. Some strains have been found in more than one animal source, such as when animals live in close proximity with one another, although no evidence to support this premise was found in the USGS study. Further research may lead to improvements in current source tracking methods or development of better methods. For the immediate future, researchers and end users would be prudent to use caution and incorporate quality- control measures to validate the accuracy of source tracking results. The report, "Comparison of Seven Protocols to Identify Fecal Contamination Sources Using Escherichia coli," is available on the USGS website at oh. water. usgs.gov/ reports /Abstraets/est- v38- 22.pdf. Report Considers Energy Cost of CA Water The Natural Resources Defense Council and the Pacific Institute recently released a report, "Energy Down the Drain: The Hidden Costs of California's Water Supply." The report points out the lack of understanding many western U.S. residents may have regarding the close connection between water and power resources, and further, that water planners at all levels "have largely failed to consider the energy implications of their decisions." The researchers focused on the power used in California to provide water to residents and industry. As an example, in delivering water from the San Francisco Bay -Delta to Southern California, the California State Water Project consumes two to three percent of all electricity used in the state. The report presents a model for how policymakers can calculate the amount of energy consumed in water use, and then demonstrates the application of the model to three specific areas to show how water planners could use this model in their own regions. The example of San Diego County's search for future water supply options highlighted energy use in urban water systems; examples of the Westlands Water District in Central California and the Columbia River Basin in Northern California illustrated energy use in agricultural settings. Key findings include: Water conservation lowers energy use and energy bills. —a • Water recycling is a highly energy efficient water source. • Retiring agricultural land may increase energy use if the water is transferred to other agricultural or urban uses. • Retiring agricultural land can save energy if the water is dedicated to the environment. • Diverting water above dams costs power and money. The report concludes that conservation has much greater potential, and stronger energy - related economic and environmental benefits than has been recognized to date. In addition, the energy benefits of conservation can generate air quality and climate change benefits. Final recommendations include: prioritize conservation funding, enforce existing conservation requirements, require water measurement, promote conservation through conservation pricing, offer conservation incentives, and implement measures to ensure conservation savings. The 86 -page report is available at wwwnrdc.org/ water / conservation /edrain/contents.asp. e�5� Engineers, Geologists, Environmental GEOMATRIX Scientists, and Decision Analysts • Regional Groundwater Studies • Water Resources Engineering • Groundwater Modeling > Watershed Management > Subsidence Analysis /Geohazard Evaluations > Conjunctive Use > Water Quality Evaluations > Environmental Assessments Costa Mesa, CA (949) 642 -0245 Scottsdale, AZ (480) 348 -1283 Please visit www.geomatrix.com for career opportunities - EOE March /April 2005 • Southwest Hydrology • 37