skip to main content

Title: Learning and flexibility for water supply infrastructure planning under groundwater resource uncertainty

Water supply infrastructure planning in groundwater-dependent regions is often challenged by uncertainty in future groundwater resource availability. Many major aquifer systems face long-term water table decline due to unsustainable withdrawals. However, many regions, especially those in the developing world, have a scarcity of groundwater data. This creates large uncertainties in groundwater resource predictions and decisions about whether to develop alternative supply sources. Developing infrastructure too soon can lead to unnecessary and expensive irreversible investments, but waiting too long can threaten water supply reliability. This study develops an adaptive infrastructure planning framework that applies Bayesian learning on groundwater observations to assess opportunities to learn about groundwater availability in the future and adapt infrastructure plans. This approach allows planners in data scarce regions to assess under what conditions a flexible infrastructure planning approach, in which initial plans are made but infrastructure development is deferred, can mitigate the risk of overbuilding infrastructure while maintaining water supply reliability in the face of uncertainty. This framework connects engineering options analysis from infrastructure planning to groundwater resources modeling. We demonstrate a proof-of-concept on a desalination planning case for the city of Riyadh, Saudi Arabia, where poor characterization of a fossil aquifer creates uncertainty in how long current groundwater resources can reliably supply demand. We find that a flexible planning approach reduces the risk of over-building infrastructure compared to a traditional static planning approach by 40% with minimal reliability risk (<1%). This striking result may be explained by the slow-evolving nature of groundwater decline, which provides time for planners to react, in contrast to more sudden risks such as flooding where tradeoffs between cost and reliability risk are heightened. This Bayesian approach shows promise for many civil infrastructure domains by providing a method to quantify learning in environmental modeling and assess the effectiveness of adaptive planning.

more » « less
Author(s) / Creator(s):
; ; ;
Publisher / Repository:
IOP Publishing
Date Published:
Journal Name:
Environmental Research Letters
Page Range / eLocation ID:
Article No. 114022
Medium: X
Sponsoring Org:
National Science Foundation
More Like this
  1. Uncertainty in future climate change challenges water infrastructure development decisions. Flexible infrastructure development, in which infrastructure is proactively designed to be changed in the future, can reduce the risk of overbuilding unnecessary infrastructure while maintaining reliable water supply. Flexible strategies assume that water planners will learn over time, updating future climate projections and using that new information to change plans. Previous work has developed methods to incorporate learning using climate observations into flexible planning but has not quantified the impact of different amounts of learning on the effectiveness of flexible planning. In this work, we develop a framework to assess how differences in the amount of learning about climate uncertainty affect the value of flexible water infrastructure planning. In the first part of our framework, we design climate scenarios with different amounts of learning using an exploratory Bayesian modeling approach. Then, we quantify the impacts of learning on flexibility using simulated costs and infrastructure decisions. We demonstrate this framework on a stylized case study of the Mwache Dam near Mombasa, Kenya. Flexible planning is more effective in avoiding over‐ or underbuilding under high‐learning scenarios, especially in avoiding overbuilding in wet climates. This framework provides insight on the climate conditions and learning scenarios that make flexible infrastructure most valuable. 
    more » « less
  2. Abstract

    Uncertainty arising from climate change poses a central challenge to the long‐term performance of many engineered water systems. Water supply infrastructure projects can leverage different types of flexibility, in planning, design, or operations, to adapt infrastructure systems in response to climate change over time. Both flexible planning and design enable future capacity expansion if‐and‐when needed, with flexible design proactively incorporating physical design changes that enable retrofits. All three forms of flexibility have not previously been analyzed together to explicitly assess their relative value in mitigating cost and water supply reliability risk. In this paper, we propose a new framework to evaluate combinations of flexible planning, design, and operations. We develop a nested stochastic dynamic optimization approach that jointly optimizes dam development and operating policies under dynamic climate uncertainty. We demonstrate this approach on a reservoir project near Mombasa, Kenya. Our results find that flexible operations have the greatest potential to reduce costs. Flexible design and flexible planning can amplify the value of flexible operations under higher discounting scenarios and when initial infrastructure capacities are undersized. This approach provides insight on the climate change and techno‐economic conditions under which flexible planning, design, and operations can be best leveraged individually or in combination to reduce climate change uncertainty risks in water supply infrastructure projects.

    more » « less
  3. Climate oscillations ranging from years to decades drive precipitation variability in many river basins globally. As a result, many regions will require new water infrastructure investments to maintain reliable water supply. However, current adaptation approaches focus on long-term trends, preparing for average climate conditions at mid- or end-of-century. The impact of climate oscillations, which bring prolonged and variable but temporary dry periods, on water supply augmentation needs is unknown. Current approaches for theory development in nature-society systems are limited in their ability to realistically capture the impacts of climate oscillations on water supply. Here, we develop an approach to build middle-range theory on how common climate oscillations affect low-cost, reliable water supply augmentation strategies. We extract contrasting climate oscillation patterns across sub-Saharan Africa and study their impacts on a generic water supply system. Our approach integrates climate model projections, nonstationary signal processing, stochastic weather generation, and reinforcement learning–based advances in stochastic dynamic control. We find that longer climate oscillations often require greater water supply augmentation capacity but benefit more from dynamic approaches. Therefore, in settings with the adaptive capacity to revisit planning decisions frequently, longer climate oscillations do not require greater capacity. By building theory on the relationship between climate oscillations and least-cost reliable water supply augmentation, our findings can help planners target scarce resources and guide water technology and policy innovation. This approach can be used to support climate adaptation planning across large spatial scales in sectors impacted by climate variability.

    more » « less
  4. Abstract

    To bolster freshwater supplies, water managers are increasingly interested in recharging groundwater using storm water and recycled water. However, such multisupply groundwater recharge projects are hindered by the lack of planning tools to evaluate system design costs and trade‐offs. This study presents modeling advancements that provide enhanced insights into multisupply spreading basin systems (i.e., spreading basins that accommodate both advanced treated recycled water and dynamically available storm water), a form of managed aquifer recharge. The model identifies system designs that optimize infrastructure life cycle cost and water volumes infiltrated for groundwater recharge. To illustrate the model's application under realistic conditions, we present a case study of Los Angeles, California. In this case study, we find that competition between storm water and recycled water for spreading basin use is relatively minor. Moreover, compared to systems based on existing conservative assumptions, our methods identify optimal dynamic system designs that are 5%–20% more cost‐effective, primarily resulting from higher water recycling facility utilization. Overall, this approach, which considers the dynamic nature of storm water availability and variable recycled water production, can inform water planners of the cost, water volume, and energy trade‐offs associated with different multisupply spreading basin system designs, including varying levels of centralization.

    more » « less
  5. Abstract

    Water scarcity is a growing problem around the world, and regions such as California are working to develop diversified, interconnected, flexible, and resilient water supply portfolios. To meet these goals, water utilities, irrigation districts, and other organizations will need to cooperate across scales to finance, build, and operate shared water supply infrastructure. However, planning studies to date have generally focused on partnership‐level outcomes (i.e., highly aggregated cost‐benefit analyses), while ignoring the heterogeneity of benefits, costs, and risks across the individual partners. This study contributes an exploratory modeling analysis that tests thousands of alternative infrastructure partnerships in the Central Valley of California, using a daily scale simulation model (CALFEWS) to evaluate the effects of new infrastructure on individual water providers. The viability of conveyance and groundwater banking investments are as strongly shaped by partnership design choices (i.e., which water providers are participating, and how is the project's debt distributed?) as by extreme hydrologic conditions (i.e., floods and droughts). Importantly, most of the analyzed partnerships yield highly unequal distributions of water supply and financial risks across the partners, so that only 8% of the partnerships explored are capable of providing water to each partner for under $200/ML. Partnership viability is especially rare in the absence of groundwater banking facilities (1%), or under dry hydrologic conditions (1%), even under explicitly optimistic assumptions regarding climate change. Given these results, we outline several major policy implications for institutionally complex regions such as California, which are currently investing heavily in cooperative approaches to resilient water portfolio design.

    more » « less