Satellites to Sprinklers: Assessing the Role of Climate and Land Cover Change on Patterns of Urban Outdoor Water Use

Abstract

Outdoor water use represents over 50% of total water demand in semiarid and arid cities and presents both challenges to and opportunities for improved efficiency and water resilience. The current work adapts a remote sensing‐based methodology to estimate growing season irrigation rates at the census block group scale in Denver, Colorado. Results show that city‐wide outdoor water use does not change significantly from 1995 to 2018, while per capita water use and total water use significantly decrease from 2000 to 2018. Because total water use, but not outdoor use, is decreasing, the percent of water used outdoors significantly increases across the city from 2000 to 2018. Climate variables account for one‐quarter of interannual variation in mean irrigation rates due primarily to changes in temperature, not precipitation. Percent impervious land cover exhibits a significant inverse nonlinear relationship with irrigation rates at the census block group scale. Finally, 38% of Denver census block groups show significantly increasing irrigation rates between 1995 and 2018 driven primarily by increasing temperatures. The increasing proportion of water used for irrigation highlights the importance of outdoor demand management for urban water systems as indoor efficiencies improve. We advocate that resilient water systems necessitate integrated land use, infrastructure, and water planning in the face of urban growth and climate change. While minimizing irrigated urban areas may reduce demand, remaining green spaces should be designed to maximize multiple benefits including reductions in water demand and urban heat islands, stormwater management, and recreation to improve the sustainability of growing cities.

Advancing a Net Zero Urban Water Future in the United States Southwest: Governance and Policy Challenges and Future Needs

“…Another issue with moving toward NZUW in the water scarce Southwest involves outdoor irrigation and landscaping, which often accounts for half of municipal urban water use. − The trees and vegetation growing in many areas of the Southwest are largely non-native species and have higher water requirements, especially when not adapted to hot dry summers and needing irrigation . Because outdoor water use is a consumptive water use, for urban areas to maintain outdoor vegetation under NZUW, landscaping in the urban Southwest will need to survive with little to no supplemental irrigation, implying a major transformation in some cities toward native and/or drought-tolerant plants and landscapes and streets designed to optimize passive stormwater harvesting.…”

Individualized and Combined Effects of Future Urban Growth and Climate Change on Irrigation Water Use in Central Arizona

“…2014; Vahmani and Ban‐Weiss 2016; Blount et al. 2021). For example, urban irrigators can often exceed plant watering needs (e.g., Volo et al.…”

“…While the distribution of irrigation fraction was obtained from historical remotely sensed data, actual irrigator behavior is not fully captured in the model nor are uncertainties related to future irrigation practices, such as plant selection and irrigation efficiency, accounted for in this and other similar studies in the southwestern U.S. (e.g., Mini et al 2014;Vahmani and Ban-Weiss 2016;Blount et al 2021). For example, urban irrigators can often exceed plant watering needs (e.g., Volo et al 2014;Vivoni et al 2020).…”