Moving Toward a Multi-Benefit Approach for Water Management

Pacific Institute | April 11th, 2019

There is broad recognition that adapting to climate change, coupled with the need to address aging infrastructure, population growth, and degraded ecosystems, will re

There is broad recognition that adapting to climate change, coupled with the need to address aging infrastructure, population growth, and degraded ecosystems, will require rethinking programs and policies and investing in our natural and built water systems. There are a variety of strategies for addressing water challenges, from watershed restoration and efficiency improvements to vegetated swales and green roofs. Because water is deeply linked with economic, environmental, and community wellbeing, many of these strategies can also provide other benefits, such as reducing energy use and greenhouse gas emissions, providing wildlife habitat, and enhancing community livability.

Multiyear Water Quality Performance and Mass Accumulation of PCBs, Mercury, Methylmercury, Copper, and Microplastics in a Bioretention Rain Garden

American Society of Civil Engineers (ASCE) | November 1st, 2019

A multiyear water quality performance study of a bioretention rain garden located along a major urban transit corridor east of San Francisco Bay was conducted to assess t

A multiyear water quality performance study of a bioretention rain garden located along a major urban transit corridor east of San Francisco Bay was conducted to assess the efficacy of bioretention rain gardens to remove pollutants. Based on data collected in three years between 2012 and 2017, polychlorinated biphenyls (PCBs) and suspended sediment concentrations (SSCs) were reduced (>90%>90%), whereas total mercury (Hg), methylmercury (MeHg), and copper (Cu) were moderately captured (37%, 49%, and 68% concentration reduction, respectively). Anthropogenic microparticles including microplastics were retained by the bioretention rain garden, decreasing in concentration from 1.6particles/L1.6  particles/L to 0.16particles/L0.16  particles/L. Based on subsampling at 50- and 150-mm intervals in soil cores from two areas of the unit, PCBs, Hg, and MeHg were all present at the highest concentrations in the upper 100 mm in the surface media layers. Based on residential screening concentrations, the surface media layer near the inlet would need to be removed and replaced annually, whereas the rest of the unit would need replacement every 8 years. The results of this study support the use of bioretention in the San Francisco Bay Area as one management option for meeting load reductions required by San Francisco Bay total maximum daily loads, and provide useful data for supporting decisions about media replacement and overall maintenance schedules.

Natural infrastructure in sustaining global urban freshwater ecosystem services

Nature Portfolio (Springer Nature) | October 21st, 2021

Rapid urbanization throughout the globe increases demand for fresh water and the ecosystem services associated with it. This need is conventionally met through the constr

Rapid urbanization throughout the globe increases demand for fresh water and the ecosystem services associated with it. This need is conventionally met through the construction of infrastructure. Natural infrastructure solutions have increased to provide freshwater ecosystem services, but little global research has examined the intricate relationships between built and natural infrastructure for providing freshwater ecosystem services to cities across the globe. Using network analysis, here we examine the interrelationships between built and natural infrastructure in 2,113 watersheds for 317 cities worldwide, focusing on four key freshwater ecosystem services: freshwater provision, sediment regulation, flood mitigation and hydropower production. Our results indicate that protected wetlands contribute to sustaining freshwater provision to cities. Forest cover in protected areas can improve the capacity of large dams in reducing sediment loads and producing hydropower, but cities mainly depend on reduced impervious surfaces and more green spaces within urban areas for flood mitigation. Improved understandings of the role of natural infrastructure in urban water networks must underpin strategic decision-making to sustainably provide freshwater ecosystem services to global cities.

Observational Study of Sycamore Regeneration at two sites in Santa Clara County after the 2016-2017 Water Year

San Francisco Estuary Institute (SFEI) | June 1st, 2018

This memo serves as an update to the Sycamore Alluvial Woodland Habitat Mapping and Regeneration Study (Beagle et al. 2017), and describes changes seen at the two study s

This memo serves as an update to the Sycamore Alluvial Woodland Habitat Mapping and Regeneration Study (Beagle et al. 2017), and describes changes seen at the two study sites, Upper Coyote Creek and Pacheco Creek, between fall 2015 and fall 2017. We were tasked with augmenting tree core data as reported in 2017 by adding additional trees to further investigate the relationship between sycamore establishment and geomorphic position, which partially serves as a proxy for the role flood processes play in improving the suitability of conditions for sycamore seedling establishment and growth. Coincidentally, major flooding during water year 2016-2017 provided us with an exciting opportunity to observe sycamore regeneration at these two study sites. This memo reports on tree coring results; documents and maps sycamore seedlings and other observed regeneration strategies of sycamores during 2018 related to geomorphic change at the two study sites; proposes natural and anthropogenic drivers of sycamore regeneration; and outlines next steps for further investigation. 

Opportunities to Accelerate Nature-Based Solutions: A Roadmap for Climate Progress, Thriving Nature, Equity, and Prosperity

White House Domestic Climate Policy Office | November 30th, 2022

Optimal Selection and Placement of Green Infrastructure in Urban Watersheds for PCB Control

American Society of Civil Engineers (ASCE) | May 1st, 2019

San Francisco Bay and its watersheds are polluted by legacy polychlorinated biphenyls (PCBs), resulting in the establishment of a total maximum daily load (TDML) that req

San Francisco Bay and its watersheds are polluted by legacy polychlorinated biphenyls (PCBs), resulting in the establishment of a total maximum daily load (TDML) that requires a 90% PCB load reduction from municipal stormwater. Green infrastructure (GI) is a multibenefit solution for stormwater management, potentially addressing the TMDL objectives, but planning and implementing GI cost-effectively to achieve management goals remains a challenge and requires an integrated watershed approach. This study used the nondominated sorting genetic algorithm (NSGA-II) coupled with the Stormwater Management Model (SWMM) to find near-optimal combinations of GIs that maximize PCB load reduction and minimize total relative cost at a watershed scale. The selection and placement of three locally favored GI types (bioretention, infiltration trench, and permeable pavement) were analyzed based on their cost and effectiveness. The results show that between optimal solutions and nonoptimal solutions, the effectiveness in load reduction could vary as much as 30% and the difference in total relative cost could be well over $100 million. Sensitivity analysis of both GI costs and sizing criteria suggest that the assumptions made regarding these parameters greatly influenced the optimal solutions.

Patterns and controlling factors of residential water use in Los Angeles, California

International Water Association (IWA) Publishing | May 19th, 2014

The current study evaluates residential water use patterns and driving factors across Los Angeles, California. Ten years of monthly residential water data were obtained f

The current study evaluates residential water use patterns and driving factors across Los Angeles, California. Ten years of monthly residential water data were obtained from the Los Angeles Department of Water and Power. Socio-economic, vegetation characteristics, climate, and water pricing data were utilized to develop a statistical model to determine controlling factors of single-family residential water use. Key drivers were found to be household income, landscape greenness, water pricing, household volume allocation, precipitation and temperature. Results show that low water users are less sensitive to climate variability than high water users, likely because these customers have reduced outdoor water use. In the lower income group, average household size is a predictor for household water consumption, which increases with more residents. Lower water users are also more sensitive to changes in their first level household water allocation (Tier 1). However, low, medium and high water users all respond more to changes in the Tier 1 rate than the Tier 2 rate, and generally reduce consumption if this block rate is increased.

Prioritizing Candidate Green Infrastructure Sites within the City of Ukiah: A Demonstration of the Site Locator Tool of GreenPlan-IT. Report prepared for the City of Ukiah Department of Public Works under Supplemental Environmental Project # R1-018-0024

San Francisco Estuary Institute (SFEI) | April 1st, 2019

Green infrastructure (GI), also known as Low Impact Development (LID), has emerged as an integral aspect of multi-benefit, watershed approaches to address concerns about

Green infrastructure (GI), also known as Low Impact Development (LID), has emerged as an integral aspect of multi-benefit, watershed approaches to address concerns about stormwater quality and quantity in an urban environment. When carefully applied, GI installations, such as rain gardens, tree-well planters, and permeable pavement, can be cost-effective, resilient ways to manage storm water at its source with measurable, cumulative environmental and community benefits. 

Quantifying the Multiplier Effect of Southern California’s Turf Removal Rebate Program with Time-Series Aerial Imagery

American Water Resources Association (AWRA) | December 30th, 2020

From 2014 to 2016, water agencies in Southern California provided more than $350 million in rebates to owners who converted their turf to drought-tolerant landscaping. In

From 2014 to 2016, water agencies in Southern California provided more than $350 million in rebates to owners who converted their turf to drought-tolerant landscaping. In order to provide a fuller understanding of the water savings of this program, this study establishes that there was a behavioral contagion, or a multiplier effect, from rebate participants in the program. An imagery-based, time-series analysis of 20 Southern California neighborhoods from 2012 to 2018 was performed to detect what parcels converted their lawns without a rebate and how they were spatially correlated with rebate participants. This correlation was then used on almost 55,000 rebate participants to estimate the multiplier benefits for the entire program at 132%. For every 100 rebate participants, the multiplier effect helped contribute to an additional 132 parcels to convert to drought-tolerant landscaping. This methodology was compared with a previous study in the Irvine Ranch Water District providing similar results. This study provides the Metropolitan Water District of Southern California a better understanding of the water savings per rebate dollar of the Turf Removal Rebate Program as well as providing a robust approach for cities or water agencies to estimate the multiplier effect of their turf rebate programs.

Re-Oaking North Bay: A strategy for restoring native oak ecosystems, focusing on Napa and Sonoma valleys

San Francisco Estuary Institute (SFEI) | July 7th, 2020

Oaks are iconic trees in California, the defining feature of savannas and woodlands in many parts of the state. For millennia, these majestic trees have provided the e

Oaks are iconic trees in California, the defining feature of savannas and woodlands in many parts of the state. For millennia, these majestic trees have provided the ecological foundation upon which thousands of other organisms depend. Their cultural significance is equally profound: they are of central importance to diverse indigenous groups, and are prized for the many benefits they provide California residents. Vast expanses of oak savanna historically occupied the rich alluvial soils of Napa and Sonoma valleys. The immense and long-lived valley oak (Quercus lobata) dominated these savannas, accounting for more than 65% of trees (Dawson 2008, Grossinger et al. 2012). Early observers described the valleys as “studded with groups of oaks” (Marryat 1850), and extolled the “magnificent oaks” that were “the glory of the landscape scenery” (Smith and Elliott 1878). Black oak (Q. kelloggii), coast live oak (Q. agrifolia), and other oak species were present in smaller numbers on the valley floors and were more abundant in the hillsides (Dawson 2008, Grossinger et al. 2012). Over the past two centuries, however, much of this oak savanna has been cleared to make way for orchards, vineyards, and towns. In Napa Valley, the number of mature trees has declined from an estimated 45,000 in the early 1800s to less than 1,000 today (Grossinger et al. 2012). Valley oak habitat has been particularly affected by clearing and fragmentation: in many areas of the state, loss of valley oak woodland exceeds 90% (Kelly et al. 2005, Whipple et al. 2011). Documentation of this loss, and recognition of the value of oaks for both people and nature, has led to a growing desire to restore this unique ecosystem and bring back many of the benefits that oaks provide. Despite the significant changes the North Bay landscape has experienced since European settlement, there are opportunities to restore oaks in settings as diverse as backyards, parks, streets, farms, vineyards, and creeksides.