Mack, E. A. & Wrase, S. A burgeoning crisis? A nationwide assessment of the geography of water affordability in the United States. PLoS ONE 12, e0169488 (2017).

Article 

Google Scholar
 

Jones, P. A. & Moulton, A. The invisible crisis: water unaffordability in the United States. SCRIBD https://www.scribd.com/document/315199865/The-Invisible-Crisis-Water-Unaffordability-In-The-United-States (2016).

Teodoro, M. P. Measuring household affordability for water and sewer utilities. J. Am. Water Works Assoc. 110, 13–24 (2018).

Article 

Google Scholar
 

Teodoro, M. P. & Thiele, R. Water and sewer price and affordability trends in the United States, 2017–2023. J. Am. Water Works Assoc. 116, 14–24 (2024).

Article 

Google Scholar
 

Patterson, L. A., Bryson, S. A. & Doyle, M. W. Affordability of household water services across the United States. PLoS Water 2, e0000123 (2023).

Article 

Google Scholar
 

Raucher, R., Clements, J., Rothstein, E., Mastracchio, J. & Green, Z. Developing a New Framework for Household Affordability and Financial Capability in the Water Sector (AWWA, 2019).

Cardoso, D. S. & Wichman, C. J. Water affordability in the United States. Water Resour. Res. 58, e2022WR032206 (2022).

Article 

Google Scholar
 

Doyle, M. W., Patterson, L., Smull, E. & Warren, S. Growing options for shrinking cities. J. Am. Water Works Assoc. 112, 56–66 (2020).

Article 
CAS 

Google Scholar
 

Hanak, E. et al. Paying for Water in California (Public Policy Institute of California, 2014).

Sarango, M., Senier, L. & Harlan, S. L. The high health risks of unaffordable water: an in-depth exploration of pathways from water bill burden to health-related impacts in the United States. PLoS Water 2, e0000077 (2023).

Article 

Google Scholar
 

Rosinger, A. Y. Biobehavioral variation in human water needs: how adaptations, early life environments, and the life course affect body water homeostasis. Am. J. Hum. Biol. 32, e23338 (2020).

Article 

Google Scholar
 

Gleick, P. H. Water: the Potential Consequences of Climate Variability and Change for the Water Resources of the United States (Pacific Institute for Studies in Development, Environment, and Security, 2000).

Gleick, P. H. & Cooley, H. Freshwater scarcity. Annu. Rev. Environ. Resour. 46, 319–348 (2021).

Article 

Google Scholar
 

IPCC. Climate Change 2022: Impacts, Adaptation and Vulnerability (eds Pörtner, H.-O. et al.) 4-1–4-21 (Cambridge Univ. Press, 2022).

Wang, X. et al. Adaptation to climate change impacts on water demand. Mitig. Adapt. Strateg. Glob. Change 21, 81–99 (2016).

Article 

Google Scholar
 

Blount, K., Wolfand, J. M., Bell, C. D., Ajami, N. K. & Hogue, T. S. Satellites to sprinklers: assessing the role of climate and land cover change on patterns of urban outdoor water use. Water Resour. Res. 57, e2020WR027587 (2021).

Article 

Google Scholar
 

Lee, J. H. & Kim, C. J. A multimodel assessment of the climate change effect on the drought severity–duration–frequency relationship. Hydrol. Process. 27, 2800–2813 (2013).

Article 

Google Scholar
 

Spinoni, J., Naumann, G., Carrao, H., Barbosa, P. & Vogt, J. World drought frequency, duration, and severity for 1951–2010. Int. J. Climatol. 34, 2792–2804 (2014).

Article 

Google Scholar
 

Diffenbaugh, N. S., Swain, D. L. & Touma, D. Anthropogenic warming has increased drought risk in California. Proc. Natl Acad. Sci. USA 112, 3931–3936 (2015).

Article 
CAS 

Google Scholar
 

Cooley, H., Shimabuku, M. & DeMyers, C. Advancing Affordability through Water Efficiency (Pacific Institute, 2022).

Luthy, R. G., Wolfand, J. M. & Bradshaw, J. L. Urban water revolution: sustainable water futures for California cities. J. Environ. Eng. 146, 04020065 (2020).

Article 
CAS 

Google Scholar
 

Rachunok, B. & Fletcher, S. Socio-hydrological drought impacts on urban water affordability. Nat. Water 1, 83–94 (2023).

Article 

Google Scholar
 

Goddard, J. J., Ray, I. & Balazs, C. How should water affordability be measured in the United States? A critical review. WIREs Water 9, e1573 (2022).

Article 

Google Scholar
 

Patterson, L. A. & Doyle, M. How sensitive is household affordability to changes in water bills?. J. Am. Water Works Assoc. 115, 14–26 (2023).

Article 

Google Scholar
 

Goddard, J. J., Ray, I. & Balazs, C. Water affordability and human right to water implications in California. PLoS ONE 16, e0245237 (2021).

Article 
CAS 

Google Scholar
 

House-Peters, L., Pratt, B. & Chang, H. Effects of urban spatial structure, sociodemographics, and climate on residential water consumption in Hillsboro, Oregon. J. Am. Water Resour. Assoc. 46, 461–472 (2010).

Article 

Google Scholar
 

Lempert, R. J. & Groves, D. G. Identifying and evaluating robust adaptive policy responses to climate change for water management agencies in the American west. Technol. Forecast. Soc. Change 77, 960–974 (2010).

Article 

Google Scholar
 

Herman, J. D., Zeff, H. B., Reed, P. M. & Characklis, G. W. Beyond optimality: multistakeholder robustness tradeoffs for regional water portfolio planning under deep uncertainty. Water Resour. Res. 50, 7692–7713 (2014).

Article 

Google Scholar
 

Jeuland, M. & Whittington, D. Water resources planning under climate change: assessing the robustness of real options for the Blue Nile. Water Resour. Res. 50, 2086–2107 (2014).

Article 

Google Scholar
 

Fletcher, S., Lickley, M. & Strzepek, K. Learning about climate change uncertainty enables flexible water infrastructure planning. Nat. Commun. 10, 1782 (2019).

Article 

Google Scholar
 

Zeff, H., Herman, J. D., Reed, P. M. & Characklis, G. W. Cooperative drought adaptation: integrating infrastructure development, conservation, and water transfers into adaptive policy pathways. Water Resour. Res. 52, 7327–7346 (2016).

Article 

Google Scholar
 

Zeff, H., Kasprzyk, J. R., Herman, J. D., Reed, P. M. & Characklis, G. W. Navigating financial and supply reliability tradeoffs in regional drought management portfolios. Water Resour. Res. 50, 4906–4923 (2014).

Article 

Google Scholar
 

Heyman, J. M., Mayer, A. & Alger, J. Predictions of household water affordability under conditions of climate change, demographic growth, and fresh groundwater depletion in a southwest US city indicate increasing burdens on the poor. PLoS ONE 17, e0277268 (2022).

Article 
CAS 

Google Scholar
 

Nayak, A., Rachunok, B., Thompson, B. & Fletcher, S. Socio-hydrological impacts of rate design on water affordability during drought. Environ. Res. Lett. 18, 124027 (2023).

Article 

Google Scholar
 

Water conservation portal. State Water Resources Control Board. https://www.waterboards.ca.gov/water_issues//programs/conservation_portal/conservation_reporting.html (2025).

Perez, S. E. 2020 Urban Water Management Plan (City of Santa Cruz Water Department, 2021); https://www.santacruzca.gov/files/assets/city/v/1/wt/documents/water-mgmt/final-adopted-2020-urban-water-management-plan-including-water-shortage-contingency-plan-without-appendices.pdf

Water Affordability Needs Assessment: Report to Congress (United States Environmental Protection Agency, 2024).

House-Peters, L. & Chang, H. Urban water demand modeling: review of concepts, methods, and organizing principles. Water Resour. Res. 47, W05401 (2011).

Article 

Google Scholar
 

Raucher, R., Wagner, C. & Donovan, C. The Economic Impacts of Water Supply Curtailments as May Need to Be Implemented by the Santa Cruz Water Department (City of Santa Cruz Water Department, 2022).

Giang, A. Equity and modeling in sustainability science: examples and opportunities throughout the process. Proc. Natl Acad. Sci. USA 121, Water Resour. Res. (2024).

Article 

Google Scholar
 

Pierce, G., Chow, N. & DeShazo, J. R. The case for state-level drinking water affordability programs: conceptual and empirical evidence from California. Util. Policy 63, 101006 (2020).

Article 

Google Scholar
 

Howe, C. W. & Goemans, C. The simple analytics of demand hardening. J. Am. Water Works Assoc. 99, 24–25 (2007).

Article 

Google Scholar
 

Medwid, L. & Mack, E. A. A scenario-based approach for understanding changes in consumer spending behavior in response to rising water bills. Int. Reg. Sci. Rev. 44, 487–514 (2021).

Article 

Google Scholar
 

Understanding Proposition 218. California Legislative Analyst’s Office https://lao.ca.gov/1996/120196_prop_218/understanding_prop218_1296.html (1996).

Moser, S. C. & Ekstrom, J. A. A framework to diagnose barriers to climate change adaptation. Proc. Natl Acad. Sci. USA 107, 22026–22031 (2010).

Article 
CAS 

Google Scholar
 

Helmrich, A., Chester, M., Miller, T. R. & Allenby, B. Lock-in: origination and significance within infrastructure systems. Environ. Res. Infrastruct. Sustain. 3, 032001 (2023).

Article 

Google Scholar
 

Palmer, R. N. & Characklis, G. W. Reducing the costs of meeting regional water demand through risk-based transfer agreements. J. Environ. Manage. 90, 1703–1714 (2009).

Article 

Google Scholar
 

Hansen, K. & Mullin, M. Barriers to water infrastructure investment: findings from a survey of US local elected officials. PLoS Water 1, e0000039 (2022).

Article 

Google Scholar
 

Wichman, C. J. The economics of equity and affordability in residential water pricing. Water Econ. Policy 11, 2530002 (2025).

Article 

Google Scholar
 

Bardeen, S. Prop 218’s ongoing impacts on California water. Public Policy Institute of California https://www.ppic.org/blog/prop-218s-ongoing-impacts-on-california-water/ (2025).

Clements, J. et al. Customer Assistance Programs for Multi-Family Residential and Other Hard-to-Reach Customers (Water Research Foundation, 2017).

Guzman, G. & Kollar, M. Income in the United States: 2023 (2024).

Shrider, E. A. Poverty in the United States: 2023. (United States Census Bureau, 2023). https://www.census.gov/library/publications/2024/demo/p60-283

2019 American Community Survey Five-Year Estimates. American Community Survey (United States Census Bureau, 2019).

Menard, R. Long Range Financial Plan (WT). City of Santa Cruz Water Department (2016).

Menard, R. 2021 Water Department Long-Range Financial Plan and Water Rate Schedule for FY 2023 to FY 2027 (WT). City of Santa Cruz Water Department (2021).

Vulnerability Assessment and Adaptation Planning for Santa Cruz Water Department (Hydrosystems Research Group, 2023).

Tomlinson, J. E., Arnott, J. H. & Harou, J. J. A water resource simulator in Python. Environ. Modell. Softw. 126, 104635 (2020).

Article 

Google Scholar
 

Loucks, D. P. & van Beek, E. Water Resource Systems Planning and Management: an Introduction to Methods, Models, and Applications (Springer, 2017).

Eyring, V. et al. Overview of the Coupled Model Intercomparison Project Phase 6 (CMIP6) experimental design and organization. Geosci. Model Dev. 9, 1937–1958 (2016).

Article 

Google Scholar
 

Steinschneider, S. & Brown, C. A semiparametric multivariate, multisite weather generator with low-frequency variability for use in climate risk assessments. Water Resour. Res. 49, 7205–7220 (2013).

Article 

Google Scholar
 

Portfolio Schedules and Costs (Kennedy Jenks, 2024).

Trindade, B., Reed, P. M., Herman, J., Zeff, H. B. & Characklis, G. W. Reducing regional drought vulnerabilities and multi-city robustness conflicts using many-objective optimization under deep uncertainty. Adv. Water Res. 104, 195–209 (2017).

Article 

Google Scholar
 

Hadka, D. & Reed, P. Borg: an auto-adaptive many-objective evolutionary computing framework. Evol. Comput. 21, 231–259 (2013).

Article 

Google Scholar
 

Olmstead, S. M., Michael Hanemann, W. & Stavins, R. N. Water demand under alternative price structures. J. Environ. Econ. Manag. 54, 181–198 (2007).

Article 

Google Scholar
 

Klassert, C., Sigel, K., Klauer, B. & Gawel, E. Increasing block tariffs in an arid developing country: a discrete/continuous choice model of residential water demand in Jordan. Water 10, 248 (2018).

Article 

Google Scholar
 

Worthington, A. C. & Hoffman, M. An empirical survey of residential water demand modelling. J. Econ. Surv. 22, 842–871 (2008).

Article 

Google Scholar
 

Bohn, S., Danielson, C., Kimberlin, S., Malagon, P. & Wimer, C. Poverty in California. PPIC https://www.ppic.org/wp-content/uploads/JTF_PovertyJTF.pdf (2023).

M1 Principles of Water Rates, Fees and Charges. 7th ed. (AWWA, 2017).

Reed, P. M. et al. Addressing Uncertainty in MultiSector Dynamics Research—Addressing Uncertainty in MultiSector Dynamics Research Documentation (2022).

Saltelli, A. et al. Global Sensitivity Analysis: the Primer (Wiley, 2008).

County of Santa Cruz Assessor’s Office Database (County of Santa Cruz, 2023).

American Community Survey (ACS), Five-Year Public Use Microdata Sample (PUMS), 2015–2019 (United States Census Bureau, 2020).

Maurer, E. P., Wood, A. W., Adam, J. C., Lettenmaier, D. P. & Nijssen, B. A long-term hydrologically based dataset of land surface fluxes and states for the conterminous United States. AMS https://journals.ametsoc.org/view/journals/clim/15/22/1520-0442_2002_015_3237_althbd_2.0.co_2.xml (2002).

San Lorenzo R a Big Trees CA (United States Geological Survey, 2024).

Exploring Next-Gen Climate Data. Cal-Adapt https://cal-adapt.org/ (2022).

Mitchell, K. E. et al. The multi-institution North American Land Data Assimilation System (NLDAS): utilizing multiple GCIP products and partners in a continental distributed hydrological modeling system. J. Geophys. Res. Atmos. 109, D07S90 (2004).

Article 

Google Scholar
 

Rodell, M. et al. The Global Land Data Assimilation System. Bull. Am. Meteorol. Soc. 85, 381–394 (2004).

Article 

Google Scholar
 

Skerker, J. et al. Stochastic flow and weather data. Zenodo https://doi.org/10.5281/zenodo.18752509 (2026).

Skerker, J. jskerker/SantaCruz_Integrated_Model: updated code for paper revisions—Skerker et al. 2026. Zenodo https://zenodo.org/records/18752481 (2026).

Pascale, S., Kapnick, S. B., Delworth, T. L. & Cooke, W. F. Increasing risk of another Cape Town ‘day zero’ drought in the 21st century. Proc. Natl Acad. Sci. USA 117, 29495–29503 (2020).

Article 
CAS 

Google Scholar
 

Fletcher, S. et al. Water supply infrastructure planning: decision-making framework to classify multiple uncertainties and evaluate flexible design. J. Water Resour. Plan. Manag. 143, 04017061 (2017).

Article 

Google Scholar
 

Kramer, I., Tsairi, Y., Roth, M. B., Tal, A. & Mau, Y. Effects of population growth on Israel’s demand for desalinated water. npj Clean Water 5, 67 (2022).

Article 

Google Scholar
 

Naseri, M. Y., Bernosky, G., Mayer, P. W. & Marston, L. T. Patterns and predictors of residential indoor water use across major US cities. Earths Future 13, e2024EF005467 (2025).

Article 

Google Scholar
 

Fagundes, T. S., Marques, R. C., Ferreira, D. F., da, C. & Malheiros, T. F. Exploring water affordability through subsidy policies. Water Res. 286, 124251 (2025).

Article 
CAS 

Google Scholar