Water conservation benefits of urban heat mitigation

Nature Portfolio (Springer Nature) | October 20th, 2017

Many cities globally are seeking strategies to counter the consequences of both a hotter and drier climate. While urban heat mitigation strategies have been sho

Many cities globally are seeking strategies to counter the consequences of both a hotter and drier climate. While urban heat mitigation strategies have been shown to have beneficial effects on health, energy consumption, and greenhouse gas emissions, their implications for water conservation have not been widely examined. Here we use a suite of satellite- supported regional climate simulations in California to show that broad implementation of cool roofs, a heat mitigation strategy, not only results in significant cooling, but can also meaningfully decrease outdoor water consumption by reducing evaporative and irrigation water demands. Irrigation water consumption across the major metropolitan areas is reduced by up to 9% and irrigation water savings per capita range from 1.8 to 15.4 gallons per day across 18 counties examined. Total water savings are found to be the highest in Los Angeles county, reaching about 83 million gallons per day. Cool roofs are a valuable solution for addressing the adaptation and mitigation challenges faced by multiple sectors in California.

Water Footprint Outcomes and Policy Relevance Change with Scale Considered: Evidence from California

Pacific Institute | September 1st, 2014

A new article by Julian Fulton, Heather Cooley, and Peter Gleick evaluates California’s water footprint, finding that California’s water footprint demonstrate a set o

A new article by Julian Fulton, Heather Cooley, and Peter Gleick evaluates California’s water footprint, finding that California’s water footprint demonstrate a set of vulnerabilities and policy options that do not emerge in national-level assessments. The article, published in Water Resources Management, demonstrates that water footprint assessments may find greater policy relevance when scaled to analytical units where water-related decision making occurs. Abstract: Methods and datasets necessary for evaluating water footprints have advanced in recent years, yet integration of water footprint information into policy has lagged. One reason for this, we propose, is that most studies have focused on national units of analysis, overlooking scales that may be more relevant to existing water management institutions. The authors of Water Footprint Outcomes and Policy Relevance Change with Scale Considered: Evidence from California illustrate this by building on a recent water footprint assessment of California, the third largest and most populous state in the United States. While California contains diverse hydrologic regions, it also has an overarching set of water institutions that address statewide water management, including ensuring sustainable supply and demand for the state’s population and economy. The water footprint sheds new light on sustainable use and, in California, is being considered with a suite of sustainability indicators for long-term state water planning. Key to this integration has been grounding the method in local data and highlighting the unique characteristics of California’s water footprint, presented here. Compared to the U.S., California’s water footprint was found to be roughly equivalent in per-capita volume (6 m3d-1) and constituent products, however two  policy-relevant differences stand out: (1) California’s water footprint is far more externalized than the U.S.’s, and (2) California depends more on “blue water” (surface and groundwater) than on “green water” (rainwater and soil moisture). These aspects of California’s water footprint suggest a set of vulnerabilities and policy options that do not emerge in national-level assessments. Such findings demonstrate that water footprint assessments may find more policy relevance when scaled to analytical units where water-related decision making occurs.

Water Loss Audit Manual

California Department of Water Resources (DWR) | February 11th, 2016

This document is intended to provide guidance on preparing a distribution system water loss audit in accordance with the American Water Works Association (AWWA) Manual 36

This document is intended to provide guidance on preparing a distribution system water loss audit in accordance with the American Water Works Association (AWWA) Manual 36. The guidance was prepared specifically as a reference for California water suppliers. To improve water loss reporting in California, SB 1420 (2014) was passed requiring water suppliers to submit water loss audits as part of urban water management plans prepared once every five years. SB 555 (2015) builds on SB 1420 and requires, beginning in 2017, the submittal of annual water loss reports to the California Department of Water Resources (DWR) that have been validated for data accuracy. This guide should be helpful, but is not intended to be a substitute for the AWWAs Manual 36. Water loss audits are a valuable tool in identifying and prioritizing distribution system leaks that when addressed can improve the efficiency of water production and delivery for all water suppliers by reducing losses.

Water Partnerships between Cities and Farms in Southern California and the San Joaquin Valley

Public Policy Institute of California (PPIC) | October 29th, 2020

The San Joaquin Valley and urban Southern California are worlds apart in many ways. Yet each face growing water challenges and a shared interest in ensuring reliable, aff

The San Joaquin Valley and urban Southern California are worlds apart in many ways. Yet each face growing water challenges and a shared interest in ensuring reliable, affordable water supplies to safeguard their people and economies. Both regions’ water futures could be more secure if they take advantage of shared water infrastructure to jointly develop and manage some water supplies.  Increasing climate volatility is heightening concerns about droughts of the future. And two major shifts in California’s water landscape have generated new opportunities for collaboration between urban and agricultural interests. For urban areas, significant declines in water demand have reduced pressure on supplies during normal and wet years for many agencies, making reliability for future droughts the primary concern. For the overdrafted San Joaquin Valley, the requirement to manage groundwater sustainably has heightened interest in expanding water supplies and underground storage.  Partnerships between Southern California cities and San Joaquin Valley farms could help alleviate groundwater overdraft in the valley while building drought resilience in Southern California. More flexible supplies can help agencies adapt to changing conditions. By coordinating the location of infrastructure investments, agencies can use partnerships to bring the water where and when it is most needed, at least cost.  This report explores a variety of solutions that could benefit both regions. For the San Joaquin Valley, we look for ways to augment water supplies to ease the transition to groundwater sustainability, while for Southern California we explore options that would increase cities’ ability to deal effectively with extended droughts. By diversifying water supplies, building connections to share water more flexibly, and preparing for the extreme events to come, such partnerships would support Governor Newsom’s Water Resilience Portfolio, and pave the way for a shared effort to make the state’s water system more resilient to a changing climate. 

Water Recommendations to the Next President

Pacific Institute | September 14th, 2020

The United States faces several severe and worsening water problems. Continuing to neglect these problems will impoverish and sicken this and future generations,

The United States faces several severe and worsening water problems. Continuing to neglect these problems will impoverish and sicken this and future generations, destroy beneficial aquatic ecosystems, and threaten our economy and food supply. Smart water policies will create hundreds of thousands of jobs, improve public health, and speed our economic recovery. In this letter, we offer a short assessment of four key problems and specific recommendations for addressing them.

Water requirement of Urban Green Infrastructure under climate change

Science of the Total Environment (Elsevier) | June 16th, 2023

The increased uncertainty of rainfall and high urban temperatures resulting from climate change present challenges for water management in Urban Green Infrastructure (UGI

The increased uncertainty of rainfall and high urban temperatures resulting from climate change present challenges for water management in Urban Green Infrastructure (UGI). UGI is an important component of cities, and it plays a crucial role in addressing various environmental issues (e.g., floods, pollutants, heat islands, etc.). Effective water management of UGI is essential to ensure its environmental and ecological benefits in the face of climate change. However, previous studies have not adequately investigated water management strategies for urban-scale GI under climate change scenarios. This study aims to estimate the current and future water requirement and effective rainfall (rainwater stored in the soil and plant roots available for plant evaporation) to determine the irrigation requirement of UGI during periods of rainfall deficit under current and future climate conditions. The results indicate that the water requirement for UGI will continue to increase under both RCP4.5 and RCP8.5 climate scenarios, with a higher increase projected under RCP8.5. For instance, the average water requirement for UGI is currently 731.29 mm, and it is projected to increase to 756.45 mm (RCP4.5) and 816.47 mm (RCP8.5) in summer during the period of 2081–2100, assuming low managed water stress condition. In addition, the water requirement of UGI in Seoul is the highest in June (approximately 125–137 mm) and the lowest in December or January (about 5–7 mm). While irrigation is unnecessary in July and August due to sufficient rainfall, other months in Seoul require irrigation when rainfall is insufficient. For example, continuous insufficient rainfall from May to June 2100 and April to June 2081 would need >110 mm (RCP4.5) of irrigation requirement even under high managed water stress condition. The findings of this study provide a theoretical foundation for water management strategies in current and future UGI settings.

Water Resilience Plan: Rapid Assessment -- Preliminary Identification of Needs and Strategies with Significant Impact on the Region’s Water

Los Angeles County Department of Public Works (LACDPW) | May 1st, 2017

This document represents one of the items set forth in the Water Resilience Work Plan presented to the Board of Supervisors in June 2016. The Rapid Assessment pre

This document represents one of the items set forth in the Water Resilience Work Plan presented to the Board of Supervisors in June 2016. The Rapid Assessment presents some of the early findings of the research to identify the most promising approaches and related financial need. As a piece of the larger Water Resilience Plan, a first draft of which Public Works plans to present to the Board in summer 2017, the Rapid Assessment provides a targeted snapshot of the research outcomes and underscores the greatest perceived needs relevant to building regional water resilience. The context of climate change and unpredictable rainfall in Southern California has greatly diminished the reliability of imported water supplies and our ability to replenish groundwater in recent years. This new reality calls for practical, effective strategies to access significant amounts of locally available water to supplement and build resilience in the region’s water supply . Currently, the County of Los Angeles manages to capture and store enough stormwater to meet the demand of one and a half million residents each year. Research has shown that implementation of a portfolio of regional stormwater capture projects could increase this amount between two- and three-fold by ensuring the region can capitalize on less regular, more intense rain events. While other sustainable sources of water should be considered and integrated into a comprehe nsive water management strategy for the region, stormwater represents an accessible, abundant resource with limited funding opportunities. Potable and recycled water are underwritten by ratepayer revenue that also supports improvement and expansion of related infrastructure. Available funding for existing stormwater capture supports current County operations and maintenance, but is insufficient for any significant expansion. Desalination has limited dedicated funding , but relies on costly treatment options that have unclear environmental impacts for the region. Significant investment in regional stormwater capture projects would have substantial impact on local water supply while contributing to improvements in overall watershed health. Stormwater capture strategies, in particular, provide unparalleled opportunities to improve water quality and enhance communities through the integration of multi-benefit approaches. New funding opportunities will be necessary to facilitate the design, implementation, and operations of centralized projects with regional benefits.

Water shortage risks from perennial crop expansion in California’s Central Valley

Environmental Research Letters (IOP) | October 15th, 2019

California’s Central Valley is one of the world’s most productive agricultural regions. Its high-value fruit, vegetable, and nut crops rely on surface water imports

California’s Central Valley is one of the world’s most productive agricultural regions. Its high-value fruit, vegetable, and nut crops rely on surface water imports from a vast network of reservoirs and canals as well as groundwater, which has been substantially overdrafted to support irrigation. The region has undergone a shift to perennial (tree and vine) crops in recent decades, which has increased water demand amid a series of severe droughts and emerging regulations on groundwater pumping. This study quantifies the expansion of perennial crops in the Tulare Lake Basin, the southern region of the Central Valley with limited natural water availability. A gridded crop type dataset is compiled on a 1-square mile spatial resolution from a historical database of pesticide permits over the period 1974–2016 and validated against aggregated county-level data. This spatial dataset is then analyzed by irrigation district, the primary spatial scale at which surface water supplies are determined, to identify trends in planting decisions and agricultural water demand over time. Perennial crop acreage has nearly tripled over this period, and currently accounts for roughly 60% of planted area and 80% of annual revenue. These trends show little relationship with water availability and have been driven primarily by market demand. From this data, we focus on the increasing minimum irrigation needs each year to sustain perennial crops. Results indicate that under a range of plausible future regulations on groundwater pumping ranging from 10% to 50%, water supplies may fail to consistently meet demands, increasing losses by up to 30% of annual revenues. More broadly, the datasets developed in this work will support the development of dynamic models of the integrated water-agriculture system under uncertain climate and regulatory changes to understand the combined impacts of water supply shortages and intensifying irrigation demand.

Water Surplus and Drought Management Update - Conditions as of 11/29/2022

Metropolitan Water District of Southern California (MWD) | December 13th, 2022

Water Use by Urban Lawns and Trees in Los Angeles

University of California, Los Angeles (UCLA) | July 24th, 2017