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This study addresses a classic sustainability challenge--the tradeoff between water conservation and temperature amelioration in rapidly growing cities, using Phoenix, Arizona and Portland, Oregon as case studies. An urban energy balance model-- LUMPS (Local-Scale Urban Meteorological Parameterization Scheme)--is used to represent the tradeoff between outdoor water use and nighttime cooling during hot, dry summer months. Tradeoffs were characterized under three scenarios of land use change and three climate-change assumptions. Decreasing vegetation density reduced outdoor water use but sacrificed nighttime cooling. Increasing vegetated surfaces accelerated nighttime cooling, but increased outdoor water use by ∼20%. Replacing impervious surfaces with buildings achieved similar improvements in nighttime cooling with minimal increases in outdoor water use; it was the most water-efficient cooling strategy. The fact that nighttime cooling rates and outdoor water use were more sensitive to land use scenarios than climate-change simulations suggested that cities can adapt to a warmer climate by manipulating land use [ABSTRACT FROM AUTHOR]

Abstract: We investigated the impacts of temperature changes derived from climate change scenarios and land cover change on patterns of external residential water consumption and nighttime cooling in suburban Hillsboro, Oregon. Three downscaled climate warming scenarios and two land cover change scenarios (sprawl and dense) for the 2040s were used as inputs for an urban energy balance model, the Local-Scale Urban Meteorological Parameterization Scheme (LUMPS). Based on the surface energy fluxes simulated by the LUMPS model, we calculate that the combination of the sprawl scenario with the 3°C temperature rise increases external water consumption by 4061L per household for August. Alternately, dense development concomitant with temperature increase constrains increases in water consumption, but reduces nighttime cooling rates by more than 0.3°C. Increasing the fraction of trees would increase efficiency in promoting urban cooling while reducing external water consumption. This study demonstrates that urban land cover and water use are naturally intertwined at the neighborhood scale, suggesting that urban land-use planning and water management should be fully integrated to design cities that can accommodate future population growth and development while minimizing negative impacts of potential climate change. [Copyright &y& Elsevier]

In this paper, we use a theoretical framework of coupled human and natural systems to review the methodological advances in urban water demand modeling over the past 3 decades. The goal of this review is to quantify the capacity of increasingly complex modeling techniques to account for complex human and natural processes, uncertainty, and resilience across spatial and temporal scales. This review begins with coupled human and natural systems theory and situates urban water demand within this framework. The second section reviews urban water demand literature and summarizes methodological advances in relation to four central themes: (1) interactions within and across multiple spatial and temporal scales, (2) acknowledgment and quantification of uncertainty, (3) identification of thresholds, nonlinear system response, and the consequences for resilience, and (4) the transition from simple statistical modeling to fully integrated dynamic modeling. This review will show that increasingly effective models have resulted from technological advances in spatial science and innovations in statistical methods. These models provide unbiased, accurate estimates of the determinants of urban water demand at increasingly fine spatial and temporal resolution. Dynamic models capable of incorporating alternative future scenarios and local stochastic analysis are leading a trend away from deterministic prediction. [ABSTRACT FROM AUTHOR]