The cost of alternative urban water supply and efficiency options in California

Environmental Research Communications (IOP) | May 28th, 2019

Urban communities, farms, businesses, and natural ecosystems depend upon adequate, reliable, and affordable supplies of clean water. As populations and economies

Urban communities, farms, businesses, and natural ecosystems depend upon adequate, reliable, and affordable supplies of clean water. As populations and economies grow and as climatic changes alter both water supply and demand, traditional options for meeting freshwater needs are becoming less available, reliable, and effective. As we approach peak water constraints on traditional water supplies, more efforts needed to reduce water demands through a wide range of conservation and efficiency technologies and policies, and to develop alternative, non-traditional water sources. A key factor in the adoption of these strategies is their economic feasibility; yet, only limited and often confusing data are available on their relative costs. To fill this gap, this analysis evaluates the costs of four groups of alternatives for urban supply and demand based on data and analysis in the California context: stormwater capture; water recycling and reuse; brackish and seawater desalination; and a range of water conservation and efficiency measures. We also describe some important co-benefits or avoided costs, such as reducing water withdrawals from surface water bodies or polluted runoff in coastal waterways. While difficult to quantify, such benefits are economically relevant, and we highlight areas where further research and analysis are needed to improve estimates presented here. All of the water- use efficiency options are far less costly than traditional or alternative supply systems with the exception of some of the most expensive landscape water reduction options. The water treatment and reuse systems and the urban stormwater capture projects are more costly per unit of water produced but still less expensive than seawater desalination—the most expensive option evaluated.

The economic value of local water supplies in Los Angeles

Nature Portfolio (Springer Nature) | May 21st, 2018

Los Angeles imports water over long distances to supplement local supplies. Reduced reliability of the available imports is driving many local agencies to promote conserv

Los Angeles imports water over long distances to supplement local supplies. Reduced reliability of the available imports is driving many local agencies to promote conservation and enhance local water sources. These include stormwater capture, water reuse and groundwater. But financial considerations are often a significant impediment to project development, especially when comparing new and existing sources. Here we demonstrate a comprehensive approach for evaluating the economic implications of shifting to local water reliance in Los Angeles County. We show that local water supplies are economically competitive. Results from integrated hydroeconomic modelling of urban water in Los Angeles identify cost-effective water supply portfolios and conservation targets. Considering costs across the ‘full-cycles’ of urban water supply that span agency boundaries yields better comparisons of planning alternatives. Throughout the region, many water retailers could successfully mitigate effects of imported water cuts while still supporting drought-tolerant landscapes, but some would suffer due to over-reliance on imports. Updating economic assessment methods would support needed innovations to achieve local reliance in Los Angeles, including infrastructure investments, institutional reforms, many more drought-tolerant landscapes and reallocated groundwater rights.

The impact of pricing structure change on residential water consumption: A long-term analysis of water utilities in California

Water Resources and Economics (Elsevier) | February 10th, 2024

California's demand-side urban water management policies, such as shifting water pricing structures from non-conservation to conservation-based rates, have received much

California's demand-side urban water management policies, such as shifting water pricing structures from non-conservation to conservation-based rates, have received much attention in terms of meeting the state's short- and long-term water conservation policies. This paper quantifies the effect of pricing structure changes on residential water consumption using a survey dataset of 189 major California water utilities from 1994 to 2019. Results of our study demonstrate that residential per capita per day water consumption was reduced by an average of 2.6% when water agencies switched from non-conservation-based to conservation-based pricing structures. We also found evidence that the longer a utility maintained a non-conservation-based rate structure before switching to conservation-based pricing, the larger the water consumption reduction in that utility's service area. In addition, utilities that reverted to non-conservation rates after having longer-term conservation pricing structures experienced smaller increases compared to having long-term non-conservation ones in water use in their service areas. This suggests evidence of a crowding-in effect for transitions from conservation-based to non-conservation-based pricing structures.

The implications of drought and water conservation on the reuse of municipal wastewater: Recognizing impacts and identifying mitigation possibilities

Water Research, Elsevier | November 1st, 2017

As water agencies continue to investigate opportunities to increase resilience and local water supply reliability in the face of drought and rising water scarcity, wa

As water agencies continue to investigate opportunities to increase resilience and local water supply reliability in the face of drought and rising water scarcity, water conservation strategies and the reuse of treated municipal wastewater are garnering significant attention and adoption. Yet a simple water balance thought experiment illustrates that drought, and the conservation strategies that are often enacted in response to it, both likely limit the role reuse may play in improving local water supply reliability. For instance, as a particular drought progresses and agencies enact water conservation measures to cope with drought, influent flows likely decrease while influent pollution concentrations increase, particularly salinity, which adversely affects wastewater treatment plant (WWTP) costs and effluent quality and flow. Consequently, downstream uses of this effluent, whether to maintain streamflow and quality, groundwater recharge, or irrigationmay be impacted. This is unfortunate since reuse is often heralded as a drought-proof mechanism to increase resilience. The objectives of this paper are two-fold. First, we illustrate—using a case study from Southern California during its most recent drought— how drought and water conservation strategies combine to reduce influent flow and quality and, subsequently, effluent flow and quality. Second, we use a recently developed regional water reuse decision support model (RWRM) to highlight cost-effective strategies that can be implemented to mitigate the impacts of drought on effluent water quality. While the solutions we identify cannot increase the flow of influent or effluent coming into or out of a treatment plant, they can improve the value of the remaining effluent in a cost-effective manner that takes into account the characteristics of its demand, whether it be for landscaping, golf courses, agricultural irrigation, or surface water augmentation.

The importance of system configuration for distributed direct potable water reuse

Nature Portfolio (Springer Nature) | April 27th, 2020

Water and wastewater infrastructure worldwide faces unprecedented demand and supply conflicts that require unconventional solutions. In this study, we develop a novel mod

Water and wastewater infrastructure worldwide faces unprecedented demand and supply conflicts that require unconventional solutions. In this study, we develop a novel modelling framework to assess the environmental and economic implications of a hybrid water supply system that supplements a centralized surface water supply with distributed direct potable reuse (DPR) of municipal wastewater, as a strategy to address such challenges. The model is tested with real water and wastewater systems data from the City of Houston, Texas. Results show that supplementing the conventional centralized water supply with distributed DPR would reduce water age in the drinking-water distribution network and hence improve water quality; properly designed system configurations attain system-wide net energy savings even with the high energy consumption of existing technologies used for advanced treatment of the wastewater. A target energy efficiency for future advanced treatment technologies is identified to achieve net energy saving with all hybrid system configurations. Furthermore, distributed DPR remains financially competitive compared with other unconventional water supply solutions. The modelling framework and associated databases developed in this study serve an important research need for quantitatively characterizing distributed and hybrid water systems, laying the necessary foundation for rational design of integrated urban water systems.

The potential of urban irrigation for counteracting carbon-climate feedback

Nature Portfolio (Springer Nature) | March 18th, 2024

The Resilience Value of Recycled Water for Los Angeles

University of California, Los Angeles (UCLA) | November 13th, 2024

In 2019, the City of Los Angeles (City) announced the development of the Operation NEXT Water Supply Program (Operation NEXT or Program) (City of Los Angeles, 2019), an a

In 2019, the City of Los Angeles (City) announced the development of the Operation NEXT Water Supply Program (Operation NEXT or Program) (City of Los Angeles, 2019), an advanced water recycling project aimed at expanding the use of purified recycled water. The current approach for Operation NEXT (now Pure Water Los Angeles) encompasses several distinct water infrastructure components. One is the construction and operation of an advanced water treatment purification facility at the Hyperion Wastewater Treatment Plant, the largest wastewater treatment facility west of the Mississippi. This project, in partnership with Los Angeles Sanitation & Environment comprises the Hyperion 2035 Program (Hyperion 2035) (LADWP, 2024; LASAN, 2024). Once constructed, potable recycled water flows from this facility will further diversify the City’s water supply portfolio, adding up to 257,636 acre-feet of supply each year once it is fully operational. A second component of Operation NEXT is a conveyance system that will transport this purified recycled water to groundwater basins or further treatment facilities, where it will be stored or blended with other water supplies. Currently, the construction and operation of Operation NEXT is still being estimated, and costs range between $6.4 billion and $24.0 billion USD as of 2020.

The Untapped Potential of California’s Urban Water Supply: Water Efficiency, Water Reuse, and Stormwater Capture

Pacific Institute | April 12th, 2022

In this assessment, we quantify the potential for a range of water strategies in urbanized parts of California to both reduce inefficient and wasteful water uses and expa

In this assessment, we quantify the potential for a range of water strategies in urbanized parts of California to both reduce inefficient and wasteful water uses and expand local water supplies. This assessment finds that urban water-use efficiency improvements could reduce statewide urban water use by 2.0 million to 3.1 million acre-feet per year (AFY). The reuse potential of municipal wastewater is 1.8 million to 2.1 million AFY, and the stormwater capture potential is 580,000 AFY in a dry year to as much as 3.0 million AFY in a wet year. Previous assessments have shown that these efficiency and supply options are more cost effective than traditional – and increasingly hard to implement – options to expand supply. Programs to tap this potential would tremendously help solve California’s long-standing water problems.

The Untapped Potential of California’s Water Supply

Pacific Institute | June 10th, 2014

California could be saving up to 14 million acre-feet of untapped water – providing more than the amount of water used in all of California’s cities in one year – w

California could be saving up to 14 million acre-feet of untapped water – providing more than the amount of water used in all of California’s cities in one year – with an aggressive statewide effort to use water-saving practices, reuse water, and capture lost stormwater, according to a new analysis released by the Pacific Institute and the Natural Resources Defense Council. “Our current approach to water use is unsustainable, but that doesn’t mean there isn’t enough water to meet our needs,” said Kate Poole, NRDC senior attorney with the water program. “At a time when every drop counts, we need to employ sensible and cost-effective 21st century solutions that will help us reduce uses today while promising new, resilient supplies for cities and farms tomorrow.” “As climate change brings more extreme weather, including droughts, ramping up forward-thinking solutions now will help us be more resilient,” said Peter Gleick, president of the Pacific Institute. “With widespread adoption of available water conservation and efficiency improvements, demand can be met more readily, less expensively, and with less pressure on our tapped-out rivers and groundwater basins. Moreover, water reuse and stormwater capture can help boost local supplies.”

The water footprint of water conservation using shade balls in California

Nature Portfolio (Springer Nature) | July 16th, 2018

The interest in quick technologic fixes to complex water problems increases during extreme hydroclimatic events. However, past evidence shows that such fixes might be ass

The interest in quick technologic fixes to complex water problems increases during extreme hydroclimatic events. However, past evidence shows that such fixes might be associated with unintended consequences. We revisit the idea of using shade balls in the Los Angeles reservoir to reduce evaporation during the recent drought in California, and question its sustainability by revealing the water footprint of this technologic water conservation solution.