Patricia Gober

Credibility, salience, and legitimacy of boundary objects: water managers' assessment of a simulation model in an immersive decision theater

The connection between scientific knowledge and environmental policy is enhanced through boundary organizations and objects that are perceived to be credible, salient, and legitimate. In this study, water resource decision-makers evaluated the knowledge embedded in WaterSim, an interactive simulation model of water supply and demand presented in an immersive decision theater. Content analysis of individual responses demonstrated that stakeholders were fairly critical of the models validity, relevance, and bias. Differing perspectives reveal tradeoffs in achieving credible, salient, and legitimate boundary objects, along with the need for iterative processes that engage them in the co-production of knowledge and action. Copyright , Beech Tree Publishing.

The Impact of the Phoenix Urban Heat Island on Residential Water Use

Abstract One goal of the smart growth movement is a more compact urban form, intended to reduce energy use and the cost of moving materials, products, and people. The benefits of compactness are compromised, however, if higher densities and more intense land use create urban heat islands, which increase water and energy use. This study examines the effects of Phoenixs urban heat island on water use by single-family residences, controlling for relevant population and housing attributes. Our statistical analysis demonstrates that increasing daily low temperatures by 1° Fahrenheit is associated with an average monthly increase in water use of 290 gallons for a typical single-family unit. These results suggest that planners should consider effects on water demand as well as other environmental consequences when they evaluate growth strategies, and use incentives to encourage efficiency and sustainability.

Using watered landscapes to manipulate urban heat island effects: How much water will it take to cool phoenix?

Problem: The prospect that urban heat island (UHI) effects and climate change may increase urban temperatures is a problem for cities that actively promote urban redevelopment and higher densities. One possible UHI mitigation strategy is to plant more trees and other irrigated vegetation to prevent daytime heat storage and facilitate nighttime cooling, but this requires water resources that are limited in a desert city like Phoenix. Purpose: We investigated the tradeoffs between water use and nighttime cooling inherent in urban form and land use choices. Methods: We used a Local-Scale Urban Meteorological Parameterization Scheme (LUMPS) model to examine the variation in temperature and evaporation in 10 census tracts in Phoenixs urban core. After validating results with estimates of outdoor water use based on tract-level city water records and satellite imagery, we used the model to simulate the temperature and water use consequences of implementing three different scenarios. Results and conclusions: We found that increasing irrigated landscaping lowers nighttime temperatures, but this relationship is not linear; the greatest reductions occur in the least vegetated neighborhoods. A ratio of the change in water use to temperature impact reached a threshold beyond which increased outdoor water use did little to ameliorate UHI effects. Takeaway for practice: There is no one design and landscape plan capable of addressing increasing UHI and climate effects everywhere. Any one strategy will have inconsistent results if applied across all urban landscape features and may lead to an inefficient allocation of scarce water resources. Research Support: This work was supported by the National Science Foundation (NSF) under Grant SES-0345945 (Decision Center for a Desert City) and by the City of Phoenix Water Services Department. Any opinions, findings, and conclusions or recommendations expressed in this material are those of the authors and do not necessarily reflect the views of NSF.

Climate variability and residential water use in the city of Phoenix, Arizona

Abstract In this investigation, how annual water use in the city of Phoenix, Arizona, was influenced by climatic variables between 1980 and 2004 is examined. Simple correlation coefficients between water use and annual mean temperature, total annual precipitation, and annual mean Palmer hydrological drought index values are +0.55, −0.69, −0.52, respectively, over the study period (annual water use increases with higher temperature, lower precipitation, and drought). Multivariate analyses using monthly climatic data indicate that annual water use is controlled most by the overall state of drought, autumn temperatures, and summer-monsoon precipitation. Model coefficients indicate that temperature, precipitation, and/or drought conditions certainly impact water use, although the magnitude of the annual water-use response to changes in climate was relatively low for an urban environment in which a sizable majority of residential water use is for outdoor purposes. People’s perception of the landscape’s water n...

Water Planning Under Climatic Uncertainty in Phoenix: Why We Need a New Paradigm

The uncertainties associated with global climate models pose substantial hurdles for urban water planning. Despite growing consensus among climatologists that the American Southwest is headed for a warmer and drier future, water planners in metropolitan Phoenix and elsewhere are reluctant to consider long-term climate change as a significant factor in increased risk of future water scarcity. A new paradigm for climate research and water planning is needed—one that is based on an assumption of uncertainty and a vision of multiple plausible futures, managing risk, and adaptive behaviors. To this end, we downscaled global climate models from the Intergovernmental Panel on Climate Change Third and Fourth Assessment Reports for the watersheds north of Phoenix and estimated changes in runoff using a hydrological model. Results then were used as inputs to WaterSim, an integrated simulation model of water supply and demand in Phoenix. The model simulated “what if” scenarios under varying policy decisions and future climates. Results of simulation experiments suggest that (1) current levels of per capita water consumption cannot be supported without unsustainable groundwater use under most climate model scenarios, (2) feasible reductions in residential water consumption allow the region to weather the most pessimistic of the climate projections, (3) delaying action reduces long-term sustainability of the groundwater resource under some climate scenarios, and (4) adaptive policy with appropriate monitoring to track groundwater provides warning that the need for use restrictions is approaching and avoids the need for drastic, ad hoc actions.

Determinants of short- and long-term mobility expectations for home owners and renters.

Confusion about the role of residential satisfaction vis-a-vis structural factors in the mobility process stems from the failure to examine the determinants of mobility over varying time frames and housing tenures. Using survey data for a random sample of 580 Phoenix-area households, we test models of short-term (l year) and long-term (5 years) mobility expectations for home owners and renters. The results show that residential satisfaction mediates the effects of structural variables on mobility expectations in the short term for home owners. In the long-term model for home owners and the short-term model for renters, the role of satisfaction as an intervening force declines in relative importance. Among renters, structural variables operate directly on long-term mobility expectations.

Vulnerability assessment of climate-induced water shortage in Phoenix

Global warming has profound consequences for the climate of the American Southwest and its overallocated water supplies. This paper uses simulation modeling and the principles of decision making under uncertainty to translate climate information into tools for vulnerability assessment and urban climate adaptation. A dynamic simulation model, WaterSim, is used to explore future water-shortage conditions in Phoenix. Results indicate that policy action will be needed to attain water sustainability in 2030, even without reductions in river flows caused by climate change. Challenging but feasible changes in lifestyle and slower rates of population growth would allow the region to avoid shortage conditions and achieve groundwater sustainability under all but the most dire climate scenarios. Changes in lifestyle involve more native desert landscaping and fewer pools in addition to slower growth and higher urban densities. There is not a single most likely or optimal future for Phoenix. Urban climate adaptation involves using science-based models to anticipate water shortage and manage climate risk.

Vulnerability to Extreme Heat in Metropolitan Phoenix: Spatial, Temporal, and Demographic Dimensions

This study assessed the spatial distribution of vulnerability to extreme heat in 1990 and 2000 within metropolitan Phoenix based on an index of seven equally weighted measures of physical exposure and adaptive capacity. These measures were derived from spatially interpolated climate, normalized differential vegetation index, and U.S. Census data. From resulting vulnerability maps, we also analyzed population groups living in areas of high heat vulnerability. Results revealed that landscapes of heat vulnerability changed substantially in response to variations in physical and socioeconomic factors, with significant alterations to spatial distribution of vulnerability especially between eastern and western sectors of Phoenix. These changes worked to the detriment of Phoenixs Hispanic population and the elderly concentrated in urban-fringe retirement communities.

The Size and Shape of Phoenix’s Urban Fringe:

Annual changes in the amount and location of residential fringe development in metropolitan Phoenix are tracked from 1990 to 1998 using local records of housing completions. New development covered a wide geographic area in 1990 but became more geographically concentrated with time. Metropolitan Phoenix is organized into five belts: (1) an outer rural zone, (2) an area of pioneer settlement where the construction of single-family housing began in 1990, (3) a peak zone of intensive development, (4) a zone of infill, and (5) a built-up area where little new construction occurs. Multiple-family housing construction occurs primarily in the infill zone. Between 1995 and 1998, new home construction moved outward at the pace of almost one-half mile per year to an average distance of 18.94 miles from the metropolitan center. Planners can use information about the size, shape, type, and timing of urban fringe development to anticipate infrastructure and service needs.

Spatial Patterns and Determinants of Winter Atmospheric Carbon Dioxide Concentrations in an Urban Environment

The purpose of this article is to describe determinants and spatial patterns of atmospheric carbon dioxide (CO2) in Phoenix, Arizona. Specifically, we use geographic information systems (GIS) and regression-based analyses to identify the human and biological factors that contribute to spatial and temporal variations in near-surface (2-meter height) atmospheric CO2 levels. We use these factors to create estimated surfaces of CO2 concentrations for the area. We evaluate the surfaces using records of CO2 from independent monitoring stations and transects. To investigate the temporal patterns and variations in CO2 concentrations, we estimate CO2 surfaces for the early mornings and the afternoons, on weekdays when traffic is heavy and spatially focused and on weekends when it is lighter and more spatially dispersed. Findings suggest there is a distinct relationship between the structure of Phoenix CO2 levels and spatial patterns of human activities and vegetation densities. Morning CO2 levels are higher than afternoon levels and correspond closely to the density of traffic, population, and employment. The spatial structure of human activity explains the pattern of CO2 better on weekdays than on weekends. CO2 surfaces reflect declining densities of human activity with distance from the city center, the pattern of irrigated agriculture in the Phoenix area, and riparian habitats on the urban fringe. Spatial and temporal patterns of CO2 concentrations are useful in understanding urban climate and ecosystem processes.