Is Rainwater Harvesting Worthwhile? A Benefit-Cost Analysis

Authors: Suzanne Dallman*, California State University - Long Beach, Anita M. Chaudhry, California State University - Chico, Misgana K. Muleta, CA Polytechnic State University, San Luis Obispo, Juneseok Lee, Manhattan College
Topics: Water Resources and Hydrology, Resources
Keywords: Rainwater harvesting, benefit-cost analysis, urban water supply
Session Type: Poster
Day: 4/5/2019
Start / End Time: 1:10 PM / 2:50 PM
Room: Lincoln 2, Marriott, Exhibition Level
Presentation File: No File Uploaded

Rainwater harvesting is increasingly viewed as a practical means of supplementing water supply in water-scarce regions. Distributed solutions based on many small capture devices are often viewed as inefficient in terms of both cost and volume of water captured, particularly in semi-arid regions such as southern California, with relatively few storms and long dry summers. This poster presents the results of a benefit-cost analysis of distributed rainwater capture at residential and commercial buildings to substitute portions of potable water supplied from the water utility. We applied this to the Ballona Creek watershed in Los Angeles County, California, evaluating several cistern sizes and participation rates to estimate the magnitude of water, energy and carbon savings for indoor and outdoor use of captured water. Results show that rainwater capture may be an efficient approach to augmenting water supply under certain conditions. From the perspective of the water supplier, capturing water for outdoor use is cost-effective, but including indoor use is not due to installation and maintenance costs. From the perspective of the homeowner, installing a cistern for landscape irrigation would result in net cost savings over time, with higher benefits realized from larger cisterns. This research can inform public policy on a potentially cost effective way to supplement water supplies, enhance water conservation and reduce resource use without increasing investment in piped water infrastructure.

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