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Urban Areas 295Quevauviller, P. 2011. Adapting to climate change: Reducing water-related risks in Europe—EUpolicy and research considerations. Environmental Science and Policy 14:722–729.Ramamurthy, P., and E. R. Pardyjak. 2011. Toward understanding the behavior of carbon dioxideand surface energy fluxes in the urbanized semi-arid Salt Lake Valley, Utah, USA. AtmosphericEnvironment 45:73–84.Ruddell, D., D. Hoffman, O. Ahmad, and A. Brazel. Forthcoming. An analysis of historicalthreshold temperatures for Phoenix (urban) and Gila Bend (desert). Climate Research 54.Sailor D. J., and L. Lu. 2004. A top-down methodology for developing diurnal and seasonalanthropogenic heating profiles for urban areas. Atmospheric Environment 38:2737–2748.Salt Lake City Department of Public Utilities (SLCDPU). 2010. 2009 Water master conservation plan.Salt Lake City: SLCDPU.U.S. Environmental Protection Agency (EPA). 2009. Assessment of the impacts of global change onregional U.S. air quality: A synthesis of climate change impacts on ground-level ozone; An interimreport of the U.S. EPA Global Change Research Program. EPA/600/R-07/094F.Velasco E., and M. Roth. 2010. Cities as net sources of CO 2: Review of atmospheric CO 2exchangein urban environments measured by eddy covariance technique. Geography Compass4:1238–1259.Webb, M. D., and K. W. F. Howard. 2011. Modeling the transient response of saline intrusion torising sea-levels. Ground Water 49:560–569.Zhao, Z., S. Chen, M. J. Kleeman, and A. Mahmud. 2011. The impact of climate change on airquality related meteorological conditions in California – Part II: Present versus future timesimulation analysis. Journal of Climate 13:3362–3376.EndnotesiiiiiiivvviviiAn urban metabolism refers to the total urban systems flows of materials, energy and inputs, andoutputs in the form of waste. Supply chains are components of the urban metabolism.Urban heat island effect was defined as “the relative warmth of a city compared with surroundingrural areas, associated with changes in runoff, the concrete jungle effects on heat retention,changes in surface albedo, changes in pollution and aerosols, and so on” by the IPCC (2007).See http://www.water.ca.gov/floodsafe/.The EC method is a widely used micrometeorological technique designed to measure turbulentexchanges of mass, momentum, and heat between an underlying surface and the atmosphere(see Aubinet, Vesala and Papale 2012 and references within). For CO 2exchange, rapid measurementsof vertical velocity fluctuations and CO 2mixing ratio are made on a tower well above thebuildings and trees of an urban surface in the so-called constant flux layer. From these quantities,a covariance is computed (Baldocchi 2003). If appropriate assumptions are satisfied, the covarianceis a measure of the net differences between the uptake of CO 2by photosynthesis and theemission of CO 2by anthropogenic and biological processes.Difficulties are both practical and technical. Practical difficulties include funding for such equipmentas flux towers, their siting in urban areas, and funds to conduct the monitoring and dataanalysis. Additional technical difficulties exist related to quantifying important contributions tofluxes, such as those related to complex distributions of sources and sinks and their relationshipto advection and non-homogeneous surfaces that are common in urban areas (Feigenwinter,Vogt, and Christen 2012).A source is a process or activity through which a greenhouse gas is released into the atmosphere.A sink is something that acts as a reservoir to absorb it on a short- or long-term basis.See http://www.urban-climate.org.