AbstractWater demand forecasting is an important tool for integrated water management. Long-term demand predictions include inherent uncertainty, but few studies have investigated empirical methods to forecast water demand that include uncertainty from many driving factors or evaluate how changes in demand affect linked systems such as wastewater conveyance and treatment. This study presents a novel approach for long-term urban water demand forecasting that (1) integrates uncertainty in technology, behavior, and climate; and (2) estimates effects of demand changes on wastewater management systems. We demonstrate this using a case study of 350 urban water supply agencies and more than 300 wastewater treatment systems in California serving 31 million people. For the period from 2020 to 2030, we used modeling with Monte Carlo simulations to estimate future scenarios of urban water demand given changes in efficiency, climate, water rates, and population. Effects of demand changes on wastewater management were estimated using network modeling and novel evaluation metrics. In modeled scenarios, future per capita water demand in California cities decreases by 8% to 12% depending on the included factors, while total volumetric demand declines by up to 11%. Efficiency changes had the largest impact. Wastewater agencies experience up to a 10% reduction in wastewater influent flow, but differences exist across regions and facilities. Aligning future water supply investments with integrated demand forecasts could forgo as much as $860 million in investments for new water supply capacity, but tradeoffs exist if such new capacity is important for future supply reliability with severe drought. Results demonstrate the value of incorporating social, technological, and climate factors in demand forecasting through stochastic approaches.
- Forecasting Urban Water Demand and Effects on Wastewater Management: An Integrated Systems Approach with Uncertainty
- Erik Porse - University of California Division of Agriculture and Natural ResourcesJonathan D. Kaplan - California State University, SacramentoHarold Leverenz - California State University, SacramentoCaitlyn Leo - California State University, SacramentoJoanna Solins - Virginia Cooperative ExtensionMary Cadenasso - University of California, DavisStephanie Pincetl - University of California, Los AngelesDakota Keene - California State University, SacramentoDavid Babchanik - University of California, DavisKhalil Lezzaik - California State University, SacramentoPatrick Maloney - Wacker (United States)
- Economics Department
- American Society of Civil Engineers; RESTON
- 09/01/2026
- California Institute for Water Resources within the University of California Agriculture - California State Water Resources Control Board: 19-058-240
Erick Eschker and John Johnston made significant contributions to methods presented here and provided helpful comments to versions of the manuscript. We thank Charlotte Ely, Karina Herrera, Marielle Rhodeiro, Paola Gonzalez, and Chris Martinez for important contributions to methods presented in the manuscript and for the review of draft versions. The analysis benefited from outreach with experts from industry, research, and community organizations throughout California, collected through interviews, surveys, and data sharing. The methods and findings reflected in this paper are solely attributable to the authors. This paper was developed with support from the California Institute for Water Resources within the University of California Agriculture and Natural Resources and was derived in part from research funded by the California State Water Resources Control Board (Agreement #19-058-240). The contents reflect the view of the authors and not the views or policies of the State of California.
- 99258329869201671; https://hdl.handle.net/20.500.12741/rep:14193; https://doi.org/10.1061/JWRMD5.WRENG-7105
- English
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