Changes to Outdoor Water Demand Associated with Residential Redevelopment Highlight the Importance of Integrated Land Use and Urban Water Planning

Abstract:

Outdoor water use represents over half of total demand in many water-limited cities in the western U.S. and is becoming a larger portion of consumptive demand as indoor efficiencies improve and urban reuse increases. Outdoor use also presents a climate adaptation challenge as rising temperatures are projected to increase urban irrigation demand. Infill development, which increases the density of residential land uses, may provide an opportunity to reduce outdoor demand. However, the quantification of changes in outdoor use associated with redevelopment is poorly understood. The current work uses a remote sensing-based approach to calculate parcel-level irrigation rates for 2018 in Denver, Colorado, and applies a novel stochastic methodology to model the impacts of redevelopment on outdoor water demand. Results show that mean single-family irrigation rates exceed those of multifamily residences by 70 mm (46%) during the growing season. Citywide analyses of redevelopment in Denver show reductions of 141,000 m³ (114 acre-feet, or 0.76% of total residential demand) per one percent of single-family parcels redeveloped. Denver Water projects a 5.4% increase in total urban demand associated with a 1℉ increase in temperature, which could be offset by the redevelopment of 48.8% of single-family parcels in Denver based on our research. These results highlight the significant contributions redevelopment can have in urban water management towards both reducing outdoor demand and promoting climate adaptation solutions. However, redevelopment decisions – and the policies that promote or discourage infill – should consider a range of factors associated with more dense cities, including urban heat islands, stormwater management, the social and health benefits of green space, and equity. Integrating land use and water planning in water scarce urban areas can streamline varied goals, including demand management, climate adaptation, and efficient, multi-benefit urban green spaces. This is a necessary step to creating resilient, sustainable urban systems, especially in arid and semi-arid regions.