A Systems Approach to Municipal Water Portfolio Security: A Case Study of the Phoenix Metropolitan Area

Richard R Rushforth,Benjamin L Ruddell,Maggie Messerschmidt

doi:10.3390/w12061663

Richard R Rushforth, Benjamin L Ruddell + Show 1 more

Open Access

https://doi.org/10.3390/w12061663

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Abstract

We present a rigorous quantitative, systems-based model to measure a municipality’s water portfolio security using four objectives: Sustainability, Resilience, Vulnerability, and Cost (SRVC). Water engineers and planners can operationalize this simple model using readily available data to capture dimensions of water security that go far beyond typical reliability and cost analysis. We implement this model for the Phoenix Metropolitan Area under several scenarios to assess multi-objective water security outcomes at the municipal-level and metropolitan area-level to water shocks and drought. We find the benefits of adaptive water security policies are dependent on a municipality’s predominant water source, calling for a variegated approach to water security planning across a tightly interrelated metropolitan area. Additionally, we find little correlation between sustainability, resilience, and vulnerability versus cost. Therefore, municipalities can enhance water security along cost-neutral, adaptive policy pathways. Residential water conservation and upstream flow augmentation are cost-effective policies to improve water security that also improve sustainability, resilience, and vulnerability and are adequate adaptations to a short-term Colorado River shortage. The Phoenix Metropolitan Area’s resilience to drought is higher than that of any of its constituent municipalities, underscoring the benefits of coordinated water planning at the metropolitan area-level.

Highlights

Facing growing urban water demand and nonstationary water availability due to climate change, a key challenge for municipal water planning is the development of theoretically and empirically robust frameworks that are actionable for decision-making [1]
Standard methods break down when there are multiple independent planning timescales and decision boundaries. When we neglect these confounding factors, we develop water portfolios biased toward cost efficiency and presume rational technocratic decision-making at the expense of increased vulnerability, along with decreased sustainability and resilience [8,9,10]
Structural water deficits vary dramatically depending on the scenario and the municipality, ranging from a surplus or no deficit to 27% water supply deficits for a single municipality (Tolleson) and across several orders of magnitude across the Phoenix metropolitan area (PMA) for a single scenario

Summary

Introduction

Facing growing urban water demand and nonstationary water availability due to climate change, a key challenge for municipal water planning is the development of theoretically and empirically robust frameworks that are actionable for decision-making [1]. Municipalities within a MA may differ in history, political and economic power or structure, or demographics or have distinct locational advantages within the conurbation. These municipal characteristics may influence water rights seniority, the ability to finance or build new infrastructure, acquire new water rights, or receptivity toward water resource cooperation. These conditions create the potential for zero-sum water decisions amongst municipalities within a MA. Water portfolio security is a systems-level characteristic manifest at multiple adaptive decision scales from the municipal scale to the MA scale.

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