Wetland service or values are often assumed to occur at a comparable level to wetland function (i.e., higher functioning wetlands provide more services). However, services are seldom directly evaluated because of the lack of structured assessment approaches. For wetland ecosystem service to be effectively incorporated in regulatory and monitoring programs, there needs to be parsimonious assessment tools that can be applied systematically, repeatably, and rapidly. This approach begins by disentangling existing terminology and clearly defining all the terms necessary to support the assessment of ecosystem services (ES). We provide context to illustrate how these terms have been variously employed in wetland science and policy, and follow with a conceptual framework for a rapid wetland ES assessment tool that is implemented as a module to existing rapid wetland function or condition assessment tools. We employ a service capacity index (SCI) that builds on existing concepts of functional capacity indices (FCIs) by incorporating the opportunity for beneficiaries to avail themselves of the source and sink ecological products provided by wetlands. We argue that if the goal of assessment is to meet compensatory mitigation requirements of unavoidable loss of wetland service, an SCI is an appropriate complement to an FCI. We illustrate the application of the proposed approach using Montana floodplain wetlands as an example.

Adaptive management is a widely used approach for supporting decision making in the face of uncertainty, but its success relies on the timely refinement of management strategies in response to monitoring outcomes. In this study, we demonstrate the role of modeling to inform implementation of an adaptive management plan for flow management in the urbanized San Gabriel River, California, USA. We applied modeling techniques to assess the impact of reduced discharge from water reclamation plants on the condition of riparian vegetation. Using stem water potential and canopy volume as indicators of plant stress, we examined their responses to changes in managed discharge over 5 years. Our results showed that stem water potential was more responsive based on environmental conditions than canopy volume, although no significant relationship was found between reduced discharge and overall plant stress. This lack of significant relationship is likely due to inherent variability within the system, including differences among riparian species and their proximity to the managed discharge and other stressors, which may obscure potential effects of flow reduction. By incorporating these findings into the adaptive management plan, we refined the monitoring strategy early on, optimizing resource reallocation and focusing on the most sensitive indicators of plant stress. Our study demonstrates the value of early implementation of modeling in adaptive management, allowing for more timely decision-making and improved management outcomes in flow-regulated systems.

Vegetation surveys provide key information for evaluating functions within and across estuaries. However, survey methods and analyses are often highly variable, site-specific, and driven by monitoring program goals and objectives, making regional comparisons that include multiple programs difficult. This study compared multiple transect- and quadrat-based vegetation monitoring methods within eight southern California estuaries to assess variability and comparability among methods within programs and to provide recommendations for the development of regional and statewide coastal wetland monitoring programs. Using data from established monitoring programs with distinct, non-overlapping goals, vegetation percent cover, species richness, and community composition across five commonly used methods (line intercept, point contact, swath intercept, standard (visually assessed) quadrat, and laser quadrat) were compared. Of the seven vegetation cover comparisons made within programs (n = 2) and methods (n = 5), estimates did not vary by more than 7

Establishing appropriate restoration targets, tracking progress toward those targets, and determining appropriate adaptive intervention are some of the greatest challenges to successful ecosystem restoration. Addressing these challenges is often informed by the use of “reference sites” that represent relatively unaltered or historical conditions and conceptually can be used to provide context and comparison for restoration projects. In reality, contemporary “unaltered” sites have often been manipulated by centuries of cultural practices and “pristine” conditions cannot be defined. Moreover, in highly altered landscapes or where stressors are continuing to rapidly reshape ecosystem structure, few or no sites may be unaltered enough to serve as pristine or aspirational reference standard sites for restoration. To address this challenge, we adapted the concept of “reference sites” to a framework for developing sentinel site networks, which consist of sites along a gradient of condition. These sites are selected for long‐term monitoring to track ecological conditions through time, to evaluate the effect of regional trends in external conditions or stressors, and to document progress toward site‐specific goals and regional objectives. Developing a sentinel site network involves screening sites based on condition, stressors, representativeness, and feasibility for long‐term monitoring, informed by input from regional experts and stakeholders. The resultant network includes sites along a gradient of condition, geographical representation, and management that can be customized or regionally based on local constraints. We demonstrate the application of this process through the development of a sentinel site network for coastal wetlands in the highly developed southern California (U.S.A.) region. This process can be readily adapted to other habitats globally and may be particularly useful in habitats that have been highly impacted by human activities.

Climate change significantly affects precipitation patterns at multiple scales, which influences river and other hydrologic flow regimes. However, the impacts of climate-driven changes to hydrologic regimes on the vulnerability of species associated with riparian areas remain largely unexplored. Not considering the effect of flow alteration compromises the ability to identify and protect critical habitat areas. We developed a species distribution model to predict the distribution of an endangered amphibian (arroyo toad, Anaxyrus californicus) under current and future climate-impacted flow scenarios to better understand its vulnerability to altered conditions. The current modeled distribution of the arroyo toad was compared to models that estimated flows altered through stochastic changes in air temperature and precipitation associated with climate change. To analyze vulnerability, we investigated disparities in elevation, range size, range overlap, protected range, and predicted probability of occurrence. The study identified key flow metrics associated with toad habitats, emphasizing a negative relationship with most, aligning with arroyo toad breeding requirements. Vulnerability assessments demonstrated a potential reduction in toad range and shifts in elevational range potentially due to climate-induced flow alterations. Our study underscores the importance of managing altered flow to support freshwater ecosystems, allowing managers to prioritize conservation efforts, protect vulnerable streams, and address problematic areas. However, additional factors like geomorphology and human activities also play significant roles, suggesting the need for diverse management strategies.

The future of coastal wetlands will depend on the combined effects of climate change and human impacts from urbanization and coastal management. Disentangling the effects of these factors is difficult, but satellite imagery archives provide a way to track biological and physical changes in wetlands over recent decades to reveal how coastal wetlands have been changing in response to climate and human drivers. In this study, we used Landsat to monitor the conditions of 32 coastal wetlands in southern California from 1984 to 2019 and identify environmental and human drivers of these trends. Wetland conditions were characterized by vegetation greenness, using the normalized difference vegetation index (NDVI), and by habitat composition, derived from areal estimates of wetland and subtidal habitats. Overall, wetlands displayed three types of long-term response: greening and gaining wetland (10), greening and losing wetland (16), and browning and losing wetland (6). Regional environmental drivers with overall positive effects on wetland NDVI were sea level, wave height, and precipitation, whereas stream discharge, vapor pressure deficit, and air temperature had negative or nonlinear effects. Wetland area change was primarily correlated with sea level, but response was highly contextual among sites. Negative trends in wetland NDVI and area were more common in larger sites with low elevations and in sites with open inlets. Restoration had mixed effects, with only half of the restored sites showing positive changes in NDVI and wetland area post-restoration. The important work of managing and restoring urban coastal wetlands is complicated by variability and context and requires us to account for the influence of humans and climate as we build a regional understanding of historic, present, and future wetland health.

Restoration of urban rivers must simultaneously design for ecological habitat while accounting for altered flow regimes associated with urban runoff, flood protection, and industrial/wastewater discharge. The goal of this study was to use ecological flow targets to guide channel restoration of the Los Angeles (LA) River across potential future flow regimes. Using a one-dimensional hydraulic model, we simulated a range of channel cross section configurations subject to different flow management decisions (wastewater reuse, low-flow [LF] treatment, and baseflow augmentation). Hydraulic results were assessed relative to ecohydraulic targets for desirable aquatic species in the LA River (willow, steelhead trout, and Santa Ana sucker). Results suggest that, along the mainstem of the LA River, restoration designs that include narrow LF channels may support Santa Ana sucker habitat and steelhead migration if management decisions decrease instream flows (e.g., by reusing treated wastewater). However, the same channel design and management decisions may not provide conditions needed to propagate floodplain vegetation such as willows. In tributary reaches, flows are too low to support habitat conditions for Santa Ana sucker or steelhead but may be able to support riparian habitat if a soft-bottom LF channel and active floodplain are present. In general, results illustrate the trade-offs between water management goals and habitat requirements for target species.

Environmental DNA (eDNA) data make it possible to measure and monitor biodiversity at unprecedented resolution and scale. As use-cases multiply and scientific consensus grows regarding the value of eDNA analysis, public agencies have an opportunity to decide how and where eDNA data fit into their mandates. Within the United States, many federal and state agencies are individually using eDNA data in various applications and developing relevant scientific expertise. A national strategy for eDNA implementation would capitalize on recent scientific developments, providing a common set of next-generation tools for natural resource management and public health protection. Such a strategy would avoid patchwork and possibly inconsistent guidelines in different agencies, smoothing the way for efficient uptake of eDNA data in management. Because eDNA analysis is already in widespread use in both ocean and freshwater settings, we focus here on applications in these environments. However, we foresee the broad adoption of eDNA analysis to meet many resource management issues across the nation because the same tools have immediate terrestrial and aerial applications.

The economic and methodological efficiencies of environmental DNA (eDNA) based survey approaches provide an unprecedented opportunity to assess and monitor aquatic environments. However, instances of inadequate communication from the scientific community about confidence levels, knowledge gaps, reliability, and appropriate parameters of eDNA-based methods have hindered their uptake in environmental monitoring programs and, in some cases, has created misperceptions or doubts in the management community. To help remedy this situation, scientists convened a session at the Second National Marine eDNA Workshop to discuss strategies for improving communications with managers. These include articulating the readiness of different eDNA applications, highlighting the strengths and limitations of eDNA tools for various applications or use cases, communicating uncertainties associated with specified uses transparently, and avoiding the exaggeration of exploratory and preliminary findings. Several key messages regarding implementation, limitations, and relationship to existing methods were prioritized. To be inclusive of the diverse managers, practitioners, and researchers, we and the other workshop participants propose the development of communication workflow plans, using RACI (Responsible, Accountable, Consulted, Informed) charts to clarify the roles of all pertinent individuals and parties and to minimize the chance for miscommunications. We also propose developing decision support tools such as Structured Decision-Making (SDM) to help balance the benefits of eDNA sampling with the inherent uncertainty, and developing an eDNA readiness scale to articulate the technological readiness of eDNA approaches for specific applications. These strategies will increase clarity and consistency regarding our understanding of the utility of eDNA-based methods, improve transparency, foster a common vision for confidently applying eDNA approaches, and enhance their benefit to the monitoring and assessment community.

The value of sediment for helping coastal habitats and infrastructure respond to sea level rise is widely recognized. Across the country, coastal managers are seeking ways to beneficially use sediment sourced from dredging and other projects to counter coastal erosion and protect coastal resources. However, these projects are difficult to permit and have been slow to actualize. This paper draws on interviews with sediment managers and regulators in California to explore the challenges and opportunities for habitat restoration and beach nourishment within the current permitting regime. We find that permits are costly, difficult to obtain, and sometimes stand as a barrier to more sustainable and adaptive sediment management. We next characterize streamlining approaches and describe entities and ongoing efforts within California that apply them. Finally, we conclude that to keep pace with coastal losses due to climate change impacts, efforts toward efficient permitting must be accelerated and approaches diversified to support coastal resilience practices state-wide, in a timeframe that will allow coastal managers to innovate and adapt.

Abstract. Environmental streamflow management can improve the ecological health of streams by returning modified flows to more natural conditions. The Ecological Limits of Hydrologic Alteration (ELOHA) framework for developing regional environmental flow criteria has been implemented to reverse hydromodification across the heterogenous region of coastal southern California (So. CA) by focusing on two elements of the flow regime: streamflow permanence and flashiness. Within ELOHA, classification groups streams by hydrologic and geomorphic similarity to stratify flow-ecology relationships. Analogous grouping techniques are used by hydrologic modelers to facilitate streamflow prediction in ungaged basins (PUB) through regionalization. Most watersheds, including those needed for stream classification and environmental flow development, are ungaged. Furthermore, So. CA is a highly heterogeneous region spanning a gradient of urbanization, which presents a challenge for regionalizing ungaged basins. In this study, we develop a novel classification technique for PUB modeling that uses an inductive approach to group regional streams by modeled hydrologic similarity followed by deductively determining class membership with hydrologic model errors and watershed metrics. As a new type of classification, this “Hydrologic Model-based Classification” (HMC) prioritizes modeling accuracy, which in turn provides a means to improve model predictions in ungaged basins, while complementing traditional classifications and improving environmental flow management. HMC is developed by calibrating a regional catalog of process-based rainfall-runoff models, quantifying the hydrologic reciprocity of calibrated parameters that would be unknown in ungaged basins, and grouping sites according to hydrologic and physical similarity. HMC was applied to 25 USGS streamflow gages in the south coast region of California and was compared to other hybrid PUB approaches combining inductive and deductive classification. Using an Average Cluster Error metric, results show HMC provided the most hydrologically similar groups according to calibrated parameter reciprocity. Hydrologic Model-based Classification is relatively complex and time-consuming to implement, but it shows potential for advancing ungaged basin management. This study demonstrates the benefits of thorough stream classification using multiple approaches, and suggests that Hydrologic Model-based Classification has advantages for PUB and building the hydrologic foundation for environmental flow management.

Contaminants of emerging concern such as pharmaceuticals, personal care products, per- and polyfluoroalkyl substances, and plasticizers, are ubiquitous in effluent-dominated rivers and have potential adverse effects on humans and aquatic life. Demands on water supply have prompted conservation and water reuse measures, impacting the discharge in these rivers, yet the effects of these management decisions on water quality are largely intuited and not quantified. This research examines how changes in water reuse practices will impact concentrations of contaminants of emerging concern, specifically carbamazepine, diclofenac, galaxolide, gemfibrozil, 4-nonylphenol, and perfluorooctane sulfonic acid (PFOS), in the effluent-dominated Los Angeles River (Los Angeles County, California). A water quality module was added to a calibrated hydrologic model of the system and parametrized with observed water quality monitoring data in EPA SWMM. Results indicate that water reuse (i.e., reduced effluent flow) will consistently improve in-stream water quality for all compounds studied except PFOS. However, the improvements are often not substantial enough to mitigate high concentrations directly downstream of treated effluent discharge points. Concentrations of these pharmaceuticals are substantially reduced through attenuation as dilution and degradation occur downstream, though the rate of this attenuation is variable and based on the contaminant. In contrast, concentrations of PFOS increase under some wastewater reuse scenarios and decrease under others but remain below the recommended environmental screening levels. Our work also highlights that management decisions regarding water quantity should integrate water quality modeling to help identify priority monitoring locations and constituents.

Anthropogenic development has adversely affected river habitat and species diversity in urban rivers, and existing habitats are jeopardized by future uncertainties in water resources management and climate. The Los Angeles River (LAR), for example, is a highly modified system that has been mostly channelized for flood control purposes, has altered hydrologic and hydraulic conditions, and is thermally altered (warmed), which severely limits the habitat suitability for cold water fish species. Efforts are currently underway to provide suitable environmental flows and improve channel hydraulic conditions, such as depth and velocity, for adult fish migration from the Pacific Ocean to upstream spawning areas. However, the thermal responses of restoration alternatives for resident and migrating cold water fish have not been fully investigated. Using a mechanistic model, we simulated the LAR’s water temperature under baseline conditions and future alternative restoration scenarios for migration of the native, anadromous steelhead trout in Southern California and the historically resident Santa Ana sucker. We considered three scenarios: 1) increasing roughness of the low-flow channel, 2) increasing the depth and width of the low-flow channel, and 3) allowing subsurface inflow to the river at a soft bottom reach in the LA downtown area. Our analysis indicates that the maximum weekly average temperature (MaxWAT) in the baseline condition was 28.9°C, suggesting that the current river temperatures would act as a limiting factor during the steelhead migration season and habitat for Santa Ana sucker. The MaxWAT dropped about 3%–28°C after applying all the considered scenarios at the study site, which is 3°C higher than the determined steelhead survival threshold. Our simulations suggest that without consideration of thermal restoration, restoring hydraulic conditions may be insufficient to support cold water fish migration or year-round resident native fish populations, particularly with potential river temperature increases due to climate change.

Coastal marsh within Mediterranean climate zones is exposed to episodic watershed runoff and sediment loads that occur during storm events. Simulating future marsh accretion under sea level rise calls for attention to: (a) physical processes acting over the time scale of storm events and (b) biophysical processes acting over time scales longer than storm events. Using the upper Newport Bay in Southern California as a case study, we examine the influence of event‐scale processes on simulated change in marsh topography by comparing: (a) a biophysical model that integrates with an annual time step and neglects event‐scale processes (BP‐Annual), (b) a physical model that resolves event‐scale processes but neglects biophysical interactions (P‐Event), and (c) a biophysical model that resolves event‐scale physical processes and biophysical processes at annual and longer time scales (BP‐Event). A calibrated BP‐Event model shows that large (>20‐year return period) episodic storm events are major drivers of marsh accretion, depositing up to 30 cm of sediment in one event. Greater deposition is predicted near fluvial sources and tidal channels and less on marshes further from fluvial sources and tidal channels. In contrast, the BP‐Annual model poorly resolves spatial structure in marsh accretion as a consequence of neglecting event‐scale processes. Furthermore, the P‐Event model significantly overestimates marsh accretion as a consequence of neglecting marsh surface compaction driven by annual scale biophysical processes. Differences between BP‐Event and BP‐Annual models translate up to 20 cm per century in marsh surface elevation.

Environmental flows, or the practice of allocating water in river systems for ecological purposes, is a leading strategy for conserving aquatic species and improving river health. However, consideration of surface-groundwater connectivity is seldom addressed in environmental flow development due to a lack of methodologies that account for groundwater contributions to instream flow. Groundwater-influenced streams have been identified as key refugia for native biota under a rapidly changing climate. These ecosystems are anticipated to be more resistant to climate change because groundwater input buffers the adverse effects of low flows and high temperatures, particularly in the dry season. Less understood, however, is the relative contribution of groundwater inputs to streamflow and how these surface-groundwater water interactions should be accounted for in environmental flow assessments and management actions. In order to assess ecological flow needs in groundwater-influenced streams, we applied the California Environmental Flows Framework (CEFF) in two river systems in California, United States. The Little Shasta River and the lower Cosumnes River are representative of many groundwater-influenced streams throughout the semi-arid western United States. Historically, perennial streamflow once sustained diverse native aquatic species in these ecosystems, but water withdrawals for irrigated agriculture has resulted in periodic stream dewatering. We found CEFF was useful in quantifying ecological flow needs for seasonal components of the flow regime that support ecosystem functionality. In particular, CEFF offered flexibility to incorporate information on the seasonal and spatial dimensions of groundwater influences in the development of ecological flow targets. The focus on ecosystem functions in CEFF, and ability to account for groundwater influences on those functions, creates opportunities for integrated surface-groundwater management strategies that support the recovery and protection of streamflows in groundwater-influenced streams.

Watersheds are often degraded by human activities, reducing their ability to provide ecosystem functions and services. While governmental agencies have put forward plans for improving watershed health, resources are limited, and choices must be made as to which watersheds to prioritize and what actions to take. Prioritization tools with sufficient specificity, resolution, and automation are needed to guide decisions on restoration and management actions across large scales. To address this need, we developed a set of tools to support the protection of streams and associated riparian habitats across the state of California. We developed and tested watershed condition estimation models based on bioassessment data, used the EPA’s StreamCat dataset to identify stressors, incorporated environmental justice factors and developed reach-specific models to prioritize actions. We applied the prioritization tools statewide and were able to identify 18% of stream reaches that are in good condition but that are most vulnerable to existing stressors and an additional 19% of stream reaches that are degraded and are highest priority for restoration and management. The remaining 63% of stream reaches were prioritized for protection and periodic monitoring or minor remedial actions. The results of this project can help regional stakeholders and agencies prioritize hundreds of millions of dollars being spent to protect, acquire, and restore stream and riparian habitats. The methods are directly transferable by using any regional condition and stress data that can be readily obtained.

A key challenge in managing flow alteration is determining the severity and pattern of alteration associated with the degradation of biological communities. Understanding these patterns helps managers prioritize locations for restoration and flow management actions. However, the choices made about how to use these flow-ecology relationships can have profound implications on management decisions (e.g., which biological endpoints, which thresholds, which seasonal flow components to use). We describe a process for using flow-ecology relationships to prioritize management actions that 1) Represents the most relevant components of the annual hydrograph, 2) Demonstrates an appropriate level of sensitivity in order to discriminate locations to inform decision making, 3) Aims to protect multiple biological assemblages, 4) Reduces misclassification of priority areas (i.e., error of omission). Our approach is based on the functional flows approach which uses multiple flow metrics that describe the frequency, timing, magnitude, duration, and rate of change of seasonal process-based components of the annual hydrograph. Using this approach, we performed a flow-ecology analysis of regional bioassessment data, through which we determined where flow alteration impacts biology and prioritized reaches for changes in flow management to protect aquatic resources in a highly urbanized region of southern California, where managing scarce water resources leads to difficult decisions about tradeoffs that require technical information. We identified three important functional flow metrics for each of two bioassessment indices, one based on benthic macroinvertebrates, and another based on benthic algae. Based on thresholds that describe levels of alteration as well as thresholds describing the probability of achieving a healthy biological condition, we compared nine biological threshold combinations for each index. We found instances of flow alteration that impact biological condition highly variable (0–100% of subbasins) between combinations and we present a method for finding the most appropriate combination for prioritizing locations for flow management. We apply the final thresholds to the study region and propose 16 subbasins of high priority for implementing flow management and restoration. Importantly, we show that focusing on a single biological group would result in biologically altered locations being effectively ignored.

Southern California Coastal Water Research Project, Costa Mesa, CA, United States, Water, Agriculture and Environment program, Jonathan Tonkin Population and Community Ecology, The University of Melbourne, Parkville, VIC, Australia, Riverfutures, Derbyshire, United Kingdom, Australian Rivers Institute, Griffith University, Nathan, QLD, Australia, University of Canterbury, Christchurch, New Zealand

Flows in urban rivers are increasingly managed to support water supply needs while also protecting and/or restoring instream ecological functions, goals that are often in opposition to each other. Effluent-dominated rivers (i.e., rivers that consist primarily of discharged treated wastewater) pose a particular challenge because changes in effluent discharge may impact river ecology. A functional flows approach, in which metrics from the annual hydrograph correspond to ecological processes, was applied to understand the hydro-ecological implications of wastewater reuse in the Los Angeles River watershed (Los Angeles County, California, USA). The Los Angeles River, like many urban rivers, is dominated by effluent, particularly during dry weather. An hourly hydrologic model was created, calibrated, and validated in EPA SWMM for the Los Angeles River watershed to investigate how increases in wastewater reuse (i.e., decreases in discharge to the river) may impact river flows and subsequently ecology and recreation in the river. Current flows are shown to support freshwater marsh, riparian habitat, fish migration, and wading shorebird habitat, in addition to recreational kayaking. Functional flow metrics were assessed under future management scenarios including reducing discharge to increase recycling at three wastewater treatment plants within the watershed. Both wet-season and dry-season baseflows were most sensitive to increasing wastewater reuse, with an average decrease of 51–56% (0.93 cms) from current baseflows. Sensitivity curves that relate potential changes in wastewater discharge to changes in functional flows show that a 4% decrease in current wastewater discharge may negatively impact habitat for indicator species during the dry season. More opportunity exists for wastewater reuse during the wet season, when current wastewater discharge may be reduced by 24% with minimal impacts to ecology and recreation. The developed approach has the potential to inform similar tradeoff decisions in other urban rivers where flows are dominated by wastewater or stormdrain discharge.

Large state or regional environmental flow programs, such as the one based on the California Environmental Flows Framework, rely on broadly applicable relationships between flow and ecology to inform management decisions. California, despite having high flow and bioassessment data density, has not established relationships between specific elements of the annual hydrograph and biological stream condition. To address this, we spatially and temporally linked USGS gage stations and biological assessment sites in California to identify suitable paired sites for comparisons of streamflow alteration with biological condition at a statewide scale. Flows were assessed using a set of functional flow metrics that provide a comprehensive way to compare alteration and seasonal variation in streamflow across different locations. Biological response was evaluated using the California Stream Condition Index (CSCI) and Algal Stream Condition Index (ASCI), which quantify biological conditions by translating benthic invertebrate or algal resources and watershed-scale environmental data into an overall measure of stream health. These indices provide a consistent statewide standard for interpreting bioassessment data, and thus, a means of quantitatively comparing stream conditions throughout the state. The results indicate that indices of biological stream condition were most closely associated with flow alteration in seasonality and timing metrics, such as fall pulse timing, dry-season timing, and wet season timing. Magnitude metrics such as dry-season baseflow, wet season baseflow, and the fall pulse magnitude were also important in influencing biological stream conditions. Development of ecological flow needs in large-scale environmental programs should consider that alteration to any of the seasonal flow components (e.g., dry-season baseflow, fall pulse flow, wet-season baseflow, spring recession flow) may be important in restructuring biological communities.