California Delta Research Articles

Assessment of Potential Recovery Viability for Colorado Pikeminnow Ptychocheilus lucius in the Colorado River in Grand Canyon

Abstract Colorado Pikeminnow Ptychocheilus lucius, the Colorado River's top native predatory fish, was historically distributed from the Gulf of California delta to the upper reaches of the Green, Colorado, and San Juan rivers in the Colorado River basin in the Southwestern United States. In recent decades Colorado Pikeminnow population abundance has declined, primarily as a result of predation by warmwater nonnative fish and habitat modification following dam construction. Small, reproducing populations remain in the Green and upper Colorado rivers, but their current population trajectory is declining and the San Juan River population is maintained primarily through stocking. As such, establishment of an additional population could aid recovery efforts and increase the species' resilience and population redundancy. The Colorado River in Grand Canyon once supported Colorado Pikeminnow, but until recently habitat suitability in this altered reach was considered low as a result of depressed thermal regime and abundant nonnative predators. Climate change and ongoing drought has presented an opportunity to evaluate the feasibility of native fish restoration in a system where declining reservoir storage has led to warmer releases and re-emergence of riverine habitat. These changes in the physical attributes of the river have occurred in concert with a system-wide decline in nonnative predators. Conditions 10 y ago were not compatible with reintroduction feasibility in Grand Canyon; however, as a result of rapidly changing conditions an expert Science Panel was convened to evaluate whether the physical and biological attributes of this reach could now support various life stages of Colorado Pikeminnow. Here, we report on the evaluation process and outcome from the Science Panel, which developed a science-based recommendation to the U.S. Fish and Wildlife Service on reintroduction feasibility. The Science Panel concluded that current habitat attributes in Grand Canyon could satisfy some, but perhaps not all, Colorado Pikeminnow life history requirements. This reach has the potential to support adult and subadult growth, foraging, migrations, and spawning, but low juvenile survival may limit recruitment. However, populations of other native species are successfully reproducing and increasing in western Grand Canyon, even in areas once considered suboptimal habitat. Should managers decide to move to the next phase of this process, actions such as experimental stocking and monitoring, telemetry studies, bioenergetics modeling, and laboratory-based research may provide additional information to further evaluate a potential reintroduction effort in this rapidly changing but highly altered system.

Toxicity of herbicides used for control of waterhyacinth in the California Delta towards the planthopper Megamelus scutellaris released for biological control

ABSTRACT The water hyacinth planthopper Megamelus scutellaris has been released for biological control of waterhyacinth (Eichhornia crassipes or Pontederia crassipes) in Florida and is widely established there, with additional releases in Louisiana and California, USA, and in South Africa. Management still often requires the use of herbicides. Knowledge of their direct toxicity to M. scutellaris would aid in integrated management. We tested the contact toxicity of 2,4-D, diquat, glyphosate, imazamox and penoxsulam as well as a paraffinic oil-based and a vegetable oil-based adjuvant, by exposing planthoppers to dipped leaves in the laboratory, and by applying chemicals to infested mesocosms in the field. Exposure to 2,4-D, glyphosate, imazamox and penoxsulam did not cause significant mortality to M. scutellaris compared to exposure to water-dipped leaves in the laboratory, and did not consistently reduce final counts of M. scutellaris compared to counts in water-sprayed mesocosms in field trials. Laboratory exposure to diquat-dipped leaves caused significantly (45%–69%) higher mortality than did exposure to water-dipped leaves, and exposure to leaves dipped in paraffinic-oil based adjuvant also increased mortality (40–50%). In field mesocosms, application of diquat reduced recovery of live M. scutellaris by 64% in one trial, and the same adjuvant reduced recovery by 36%–49% in two trials. The results suggest that biological and chemical control of water hyacinth using M. scutellaris can be safely integrated using most of the herbicides applied for control of this weed in California.

Governing Science: Learning and Adaptive Management in the California Delta

Governing Science: Learning and Adaptive Management in the California Delta

Conflict Contagion: How Interdependence Shapes Patterns of Conflict and Cooperation in Polycentric Systems

Abstract In this article, we bridge and extend concepts from behavioral game theory and the Ecology of Games Theory of Polycentricity (EGT) to test possible mechanisms for conflict contagion across the array of actors and policy forums that constitute a polycentric governance system. We argue that actors who experience conflict in one forum will develop similar strategies in other forums, which then impacts the level of conflict exhibited in within-forum interactions. This behavioral spillover of conflict is a different mechanism than conflict that might be experienced when two forums are addressing the same policy issue(s), which may be characterized by higher or lower levels of conflict. We use survey data collected in the Tampa Bay (FL) and California Delta (CA) water governance systems to examine conflict contagion across forums. Using a series of spatial autoregressive models, we find evidence that co-membership networks serve as a conduit for conflict contagion among forums. Our results show that forum deliberations can be strongly impacted by interactions from other institutions and processes. Consistent with the idea of path dependence, “new” forums are not necessarily independent of the forums they replace, but rather, preexisting levels of conflict and cooperation may constrain available outcomes.

Use of archaeological data in retracing diet and growth of extirpated fish populations in the California Delta: An allometric and isotopic approach to Sacramento perch (Archoplites interruptus) historical ecology

Sacramento perch (Archoplites interruptus), ubiquitous in the archaeological record throughout Central California, is now extirpated from the California Delta. Descriptions of Sacramento perch ecology, biology, and behaviour are either from relocated or declining populations. Archaeological specimens have the potential to provide insight on Sacramento perch demographics and feeding behaviour in their native range prior to large scale damming and the introduction of invasive species. We develop regression formulae to predict live length for three skeletal elements (vomer, dentary, and atlas). Formulae were applied to archaeological specimens (n = 182) from CA-CCO-647 (cal CE 1230–1440), Contra Costa County, California. Archaeological samples were then compared to length data from six contemporary relocated populations. Bulk collagen samples of specimens of varying lengths (n = 12) were run for δ13C and δ15N. Archaeological specimens averaged 196 mm in standard length, and attained longer average and maximum lengths than relocated perch populations. Length distributions showed a high proportion of newly sexually mature individuals, suggesting that Sacramento perch were targeted while spawning nearshore. Nitrogen values correlated positively with standard length, suggesting that within the California Delta, Sacramento perch feeding behaviour changed as individuals grew, likely marking a shift to more piscivorous diets with age. Data highlight the potential of archaeological assemblages in reconstructing past length distributions and feeding behaviour for extirpated fish populations in their endemic ranges.

Stable isotopes demonstrate the importance of freshwater fisheries in Late Holocene native Californian diets in the California Delta

Estimating paleodiet from macroscopic faunal and floral remains alone is difficult. Taphonomic biases make direct quantitative comparisons of different categories, such as fish bone, ungulate bone, and charred seeds challenging. Stable isotope data can help in this regard. To highlight this process, we present new bone collagen stable isotope data (δ13C, δ15N, and δ34S) from a series of animal and human remains from a Late Holocene (ca. 1000–300 cal BP) archaeological site in the California Delta. We contrast stable isotope data from humans with that from canid (Canis sp.), deer (Odocoileus sp.), elk (Cervus sp.), pronghorn (Antilocapra americana), and Sacramento perch (Archoplites interruptus) remains from the site. Most of these species are endangered or extirpated locally, making archaeological sites a primary source of paleoecological data. Of fourteen human individuals, twelve show isotope values consistent with heavy exploitation of freshwater wetland resources, which we interpret as a “local” dietary signature. By contrast, two individuals display a pattern more similar to precontact humans in other parts of interior California, which we interpret as recent immigrants to the site. Three subadults display elevated δ15N values relative to adults, consistent with these individuals still consuming significant amounts of breast milk near the time of death. A linear mixing model provides a quantitative estimate the role of different food groups in local diets. Together, we estimate that local adults gained over 60% of their protein from freshwater fishes. This heavy reliance on local fisheries is consistent with large numbers of fish bone from the site.

The pitfalls associated with more intensive engagement in collaborative forums: The role of behavioral spillovers and cognitive load

Polycentric governance systems feature numerous decision-making venues (“forums”) where policy actors repeatedly interact to address a subset of policy problems. Previous studies find that forums where actors dedicate greater time and cognitive resources tend to be perceived as more effective. Drawing on behavioral game theory and the Ecology of Games, we argue that the improvements afforded to any one forum vis-à-vis more intensive participation may come at a cost: lower levels of perceived effectiveness in linked forums. We use survey data collected in the Tampa Bay (FL) and California Delta (CA) water governance systems to examine our contention. Using a series of spatial Durbin models, we find that perceived effectiveness of a given forum is directly impacted by the intensiveness by which actors participate in that forum (positive association). However, there are also behavioral spillovers: the intensity with which actors participate in other forums in the system has indirect negative consequences for perceived forum effectiveness.

Herbicide treatment alters the effects of water hyacinth on larval mosquito abundance.

Invasive aquatic weeds are managed with herbicides to reduce their negative impacts on waterways in many areas, including the California Delta Region. Herbicides create a dynamic environment of living and decomposing plant matter that could affect larval mosquitoes and other invertebrates, such as their predators and competitors. Our objective was to compare the number of larval mosquitoes in water or water hyacinth, before and after an herbicide treatment. We created replicated pond mesocosms with water hyacinth, water hyacinth treated with glyphosate and an oil adjuvant, open water, and water with glyphosate plus adjuvant. We sampled for larval mosquitoes and other aquatic invertebrates. Before herbicide addition, there was a trend for more larval mosquitoes in open water tanks than in tanks with water hyacinth. Herbicide application resulted in an immediate decrease of larval mosquitoes. As decay progressed, larval mosquitoes became most abundant in mesocosms with herbicide-treated hyacinth and very few larval mosquitoes were found in other habitat treatments. Although the numbers of predatory and competitor insects had some variation between treatments, no clear pattern emerged. This information on how invasive weed management with herbicides affects larval mosquitoes will allow control practices for larval mosquitoes and invasive weeds to be better integrated.

Socio-cultural perceptions of flood risk and management of a levee system: Applying the Q methodology in the California Delta

The Sacramento-San Joaquin Delta is an agricultural, recreational, historical, and cultural center and the hub of the state's water supply system. For decades the region has been ripe with political controversies stemming from conflicting interests over its natural resources which all depend on the protection of approximately 1800 km of earthen levees that surround over 60 islands, some of which are below sea level and two-thirds of which are privately owned. This study uses the Q methodology to explore the discourses of the broad range of stakeholders, including farmers, land- and water-based recreation enthusiasts, water exporters, utilities, environmentalists, and government agencies, about flood risk and flood management in the Delta. The results of this study reveal five distinct views regarding the risk of submersion of one or more islands due to either overtopping during high waters or structural levee failures. The findings of this study also elucidate nuanced narratives on the viability of anticipatory climate change adaptation in the Delta. Proximity, sense of vulnerability, values, trust, and views of climate change are the underlying factors in these perspectives. The perspectives identified suggest that resolving decades of distrust among stakeholder groups will remain difficult; however, taking a cultural approach to understanding perspectives may provide an opportunity to open up the conversations to adaptation approaches, and thus fulfill the legal mandate to protect the Delta as an evolving place.

First record of vertical movements of the totoaba (Totoaba macdonaldi) as evidenced by pop-up satellite tags in the Upper Gulf of California

AbstractThe description of the movements and habitat preference of marine fishes is essential to understand their biology and in the evaluation of commercially exploited species and the conservation of endangered ones. In this regard, little is known about the movements of the totoaba (Totoaba macdonaldi), despite its being listed as critically endangered and having been a relevant fishery resource in the past century in Mexico. Totoaba is a fish species endemic to the Gulf of California characterized by late maturation, prolonged life and annual reproduction. Totoaba has maintained its known historical distribution range, although its movements and habitat occupancy in the water column have remained poorly understood. The present study describes, for the first time and at a daily fine scale, the vertical movements and habitat preferences of the totoaba in the Upper Gulf of California. Pop-up satellite archival tags (PSATs) were used to record depth and temperature at 4-minute intervals. Ten individuals were caught and tagged in May 2016 in the Upper Gulf of California and Colorado River Delta Biosphere Reserve. All PSATs were either prematurely released or lost. Data derived from two recovered tags that saved data for 43 and 75 tracking days, respectively, were analysed. The results showed that tagged fishes moved southward to the vicinity of Angel de la Guarda Island; these are consistent with spatial displacement patterns reported in the literature, with a linear displacement of 223 km from deployment to pop-up sites. Fish spent 47% of the time within a depth range of 25–35 m. Depth increased to 70 m for one fish in early summer (late June). The preferred temperature of fishes ranged between 21–23°C. A generalized linear model revealed that vertical movement was influenced by temperature. The vertical displacement of the totoaba shows a diurnal variation that may be associated with the distribution of its prey. Further work is needed to test this hypothesis with a larger number of organisms.

Revisiting the Central California Meganos Intrusion with New Stable Isotope and Radiocarbon Analyses at El Sobrante (CA-CCO-151)

ABSTRACTJames Bennyhoff proposed a “Meganos intrusion” of people from the California Delta into the San Francisco Bay Area. Using new radiocarbon and stable isotope data, we re-examine stratigraphic and mortuary patterns at CA-CCO-151, the El Sobrante Mound. Which contains both a pre-Meganos (or Berkeley) and Meganos component. Results show that the transition to Meganos was gradual, occurring over a 200-year window between 1,400 and 1,210 cal B.P., with mortuary traits accumulating in piecemeal fashion. This is less consistent with an intrusion, and more in line with a slow diffusion of Meganos culture into the Bay Area. We propose a new model, wherein patrilocal Meganos populations had higher intrinsic growth rates than matrilocal Berkeley populations. Meganos males were able to marry into matrilocal Bay Area communities, and once there, passed on certain aspects of Meganos culture to their children. By virtue of higher Meganos out-migration, Bay Area communities slowly transitioned over roughly eight generations.

Effects of Drought and the Emergency Drought Barrier on the Ecosystem of the California Delta

In 2015, the fourth year of the recent drought, the California Department of Water Resources installed a rock barrier across False River west of Franks Tract to limit salt intrusion into the Delta at minimal cost in freshwater. This Barrier blocked flow in False River, greatly reducing landward salt transport by decreasing tidal dispersion in Franks Tract. We investigated some ecological consequences of the Barrier, examining its effects on water circulation and exchange, on distributions of submerged aquatic vegetation (SAV) and bivalves, and on phytoplankton and zooplankton. The Barrier allowed SAV to spread to areas of Franks Tract that previously had been clear. The distributions of bivalves (Potamocorbula and Corbicula) responded to the changes in salinity at time–scales of months for newly settled individuals, to 1 or more years for adults, but the Barrier’s effect was confounded with that of the drought. Nutrients, phytoplankton biomass, and a Microcystis abundance index showed little response to the Barrier. Transport of copepods — determined using output from a particle-tracking model — indicated some intermediate-scale reduction with the Barrier in place, but monitoring data did not show a larger-scale response in abundance. These studies were conducted separately and synthesized after the fact, and relied on reference conditions that were not always suitable for identifying the Barrier’s effects. If barriers are considered in the future, we rcommend a modest program of investigation to replicate study elements, and to ensure suitable reference conditions are available to allow barrier effects to be distinguished unambiguously from other sources of variability.

The Role of Forum Membership Diversity on Institutional Externalities in Resource Governance Systems

In many resource governance systems, representatives of resource-related organizations gather in forums to discuss and develop solutions to policy problems. Forums often deal with interdependent policy problems, giving rise to institutional externalities: instances where decisions made in one forum either decrease (negative institutional externality) or increase (positive institutional externality) the rate by which current policy outputs in other forums resolve their prescribed policy problems. In this article we argue that forum-specific factors can impact the direction of such externalities. We theorize that forums with more diverse memberships in terms of both the issues that participants care about and types of organizations represented are better equipped to incorporate more holistic, ecosystem-based perspectives, which promote the generation of positive institutional externalities. Our study utilizes survey data collected from forum participants in the California Delta. Results from a series of cross-nested regressions demonstrate a positive association between forum diversity and positive externalities.

Does More Storage Give California More Water?

AbstractIncreasing reservoir storage is commonly proposed to mitigate increasing water demand and provide drought reserves, especially in semiarid regions such as California. This paper examines the value of expanding surface reservoir capacity in California using hydroeconomic modeling for historical conditions, a future warm‐dry climate, and California's recently adopted policy to end groundwater overdraft. Results show expanding surface storage capacity rarely provides sizable economic value in most of California. On average, expanding facilities north of California's Delta provides some benefit in 92% of 82 years modeled under historical conditions and in 61% of years modeled in a warm‐dry climate. South of California's Delta, expanding storage capacity provides no benefits in 14% of years modeled under historical conditions and 99% of years modeled with a warm‐dry climate. Results vary across facilities between and within regions. The limited benefit of surface storage capacity expansion to statewide water supply should be considered in planning California's water infrastructure.

Impact of Insolation Data Source on Remote Sensing Retrievals of Evapotranspiration over the California Delta

The energy delivered to the land surface via insolation is a primary driver of evapotranspiration (ET)—the exchange of water vapor between the land and atmosphere. Spatially distributed ET products are in great demand in the water resource management community for real-time operations and sustainable water use planning. The accuracy and deliverability of these products are determined in part by the characteristics and quality of the insolation data sources used as input to the ET models. This paper investigates the practical utility of three different insolation datasets within the context of a satellite-based remote sensing framework for mapping ET at high spatiotemporal resolution, in an application over the Sacramento–San Joaquin Delta region in California. The datasets tested included one reanalysis product: The Climate System Forecast Reanalysis (CFSR) at 0.25° spatial resolution, and two remote sensing insolation products generated with geostationary satellite imagery: a product for the continental United States at 0.2°, developed by the University of Wisconsin Space Sciences and Engineering Center (SSEC) and a coarser resolution (1°) global Clouds and the Earth’s Radiant Energy System (CERES) product. The three insolation data sources were compared to pyranometer data collected at flux towers within the Delta region to establish relative accuracy. The satellite products significantly outperformed CFSR, with root-mean square errors (RMSE) of 2.7, 1.5, and 1.4 MJ·m−2·d−1 for CFSR, CERES, and SSEC, respectively, at daily timesteps. The satellite-based products provided more accurate estimates of cloud occurrence and radiation transmission, while the reanalysis tended to underestimate solar radiation under cloudy-sky conditions. However, this difference in insolation performance did not translate into comparable improvement in the ET retrieval accuracy, where the RMSE in daily ET was 0.98 and 0.94 mm d−1 using the CFSR and SSEC insolation data sources, respectively, for all the flux sites combined. The lack of a notable impact on the aggregate ET performance may be due in part to the predominantly clear-sky conditions prevalent in central California, under which the reanalysis and satellite-based insolation data sources have comparable accuracy. While satellite-based insolation data could improve ET retrieval in more humid regions with greater cloud-cover frequency, over the California Delta and climatologically similar regions in the western U.S., the CFSR data may suffice for real-time ET modeling efforts.

New Radiocarbon Dates from CA-CCO-138 (Hotchkiss Mound) and CA-CCO-139 (Simone Mound) and Insights into Mounds, Settlement Patterns, and Culture History in the California Delta

ABSTRACTWe report 91 new AMS radiocarbon dates on human bone collagen from two important central California sites: CA-CCO-138 (Hotchkiss Mound; n = 46) and CA-CCO-139 (Simone Mound; n = 45). The sites lie within 500 m of one another in the California Delta and have figured prominently in the formulation of culture historical sequences in central California. The new AMS dates show that the two sites are nearly separate in their occupation sequences, with CA-CCO-139 interments dating between 1,190 and 790 cal BP and CA-CCO-138 between 810 and 150 cal BP (median date ranges). We compare the new dates to previous age assignments based on associated artifacts and depth, and discuss implications for understanding ancient settlement patterns, mound occupation sequences, and culture history in the region.

The Impact of Forum Interdependence and Network Structure on Actor Performance in Complex Governance Systems

One of the main assumptions of the Ecology of Games Framework (EGF) is that governance processes are heavily affected by the interactions among policy actors that take place in multiple decision‐making forums, which often function interdependently. In this article, we use data collected in the Tampa Bay and California Delta water governance systems to examine how “biophysical interdependence”—the extent to which forums deal with interconnected policy problems—impacts the costs that actors face when they participate in forums, which in turn can affect their performance in them. Furthermore, we examine how the individual information exchange networks that actors have (i.e., their ego‐networks) can mediate the previous relationship. We find that actors with networks that have more closure are better able to mitigate the costs associated with participating in biophysically interdependent forums, thus leading to better in‐forum performance. Our findings shed new light on the relationship between structure and function in complex ecologies of games.

Reconstructing Early Hydrologic Change in the California Delta and its Watersheds

AbstractRegulatory goals for the California Delta attempt to restore natural ecosystems through various water management efforts. Defining management criteria for restoration is challenging, given that the earliest data describing the hydrology of the region follow many decades of change associated with agricultural development, channel modification, and flood control. This study explores the hydrology of the 1850–1920 period by synthesizing new reconstructed precipitation, basin inflows, land use change, and levee construction time series, in a semidistributed hydrologic model. The model demonstrated that it is impossible to simultaneously reproduce estimated historical flood extents, frequencies, and durations given contemporary topography. Bounding cases were constructed to span potential water budget partitioning and suggest that the state of this region by the 1920s was hydrologically similar to that of the natural regime (i.e., flow experienced was depressed due to drought, but within the bounds of variability of the natural Delta system), partly due to the flow augmentation provided by flood control infrastructure and enhanced channel conveyance. The model suggests that levee construction, rather than land use change, had the greatest impact on Delta hydrology. This and other reconstructions, however, suggest that decreases in annual Delta outflows accelerated after 1920. Future efforts to reconstruct Delta hydrology should focus on improving information about the historical topography and channel geometry of the Central Valley river network, with a view to refining understanding of the natural and historical flood regime.

Restored Wetlands Could Lower Local Surface Temperatures

A 3-year study of wetlands and cropland in a major California delta highlights the need to consider the physical effects of vegetation when planning land use changes.

Institutional externalities and actor performance in polycentric governance systems

AbstractThis article examines the relationship between institutional externalities and an actor's ability to achieve their goals in the decision‐making forums that exist in polycentric governance systems. We argue that an actor's performance is largely a function of the transaction costs associated with participation in a variety of forums. Institutional externalities—instances where the decisions made in one forum impact another forum—may increase or decrease transaction costs in linked forums, subsequently impacting actor performance. Using survey data collected from forum participants in the California Delta and Tampa Bay watershed governance systems, we examine how the strength of perceived externalities generated between linked forums affects an individual's perceived performance in the forum receiving the externality. We find that externalities are prevalent in both systems, but have varying effects on performance. Externalities, on average, negatively impact actor performance in the California Delta, but neither increase nor decrease performance in Tampa Bay. Further analyses reveal that in both systems, the effect of externalities on performance in the externality‐receiving forum is largely conditional on their performance in the externality‐generating forum. Externalities are negatively associated with forum performance when actors exhibit low levels of performance in the externality‐generating forum. The negative effect is mitigated when actors exhibit higher levels of performance in the externality‐generating forum.