California Streams Research Articles

Spatiotemporal trend analysis of metal concentrations in sediments of a residential California stream with toxicity and regulatory implications

ABSTRACTThe objective of this study was to determine if concentrations of arsenic, cadmium, chromium, copper, lead, nickel and zinc measured in the sediments of a residential stream in California (Pleasant Grove Creek) have changed temporally or spatially from 2006 to 2016. Threshold Effect Levels (TELs), conservative ecological effects benchmarks, and exceedances for the seven metals were also evaluated over the 11-year time period to provide insight into potential metal toxicity to resident benthic communities. In addition, the bioavailability of metals in sediments was also determined by calculating Simultaneous Extracted Metal/Acid Volatle Sulfide (SEM/AVS) ratios to allow an additional assessment of toxicity. Regulatory implications of this data set and the role of metal toxicity are also discussed. Stream-wide temporal trend analysis showed no statistically significant trends for any of the metals. However, spatial analysis for several sites located near storm drains did show a significant increase for most metals over the 11-year period. TEL exceedances during the 7 years of sampling, spanning 2006–2016, were reported for all metals with the number of exceedances ranging from 47 for copper and zinc to 1 for lead. A spatial analysis showed that the highest number of TEL exceedances and the highest number of SEM/AVS ratios greater than one with at least one metal exceeding a TEL occurred at upstream sites. The potentially toxic metal concentrations reported in Pleasant Grove Creek should be used in the 303 (d) listing process for impaired water bodies in California.

Classification of California streams using combined deductive and inductive approaches: Setting the foundation for analysis of hydrologic alteration

AbstractRegional classification of streams is an early step in the Ecological Limits of Hydrologic Alteration framework. Many stream classifications are based on an inductive approach using hydrologic data from minimally disturbed basins, but this approach may underrepresent streams from heavily disturbed basins or sparsely gaged arid regions. An alternative is a deductive approach, using watershed climate, land use, and geomorphology to classify streams, but this approach may miss important hydrological characteristics of streams. We classified all stream reaches in California using both approaches. First, we used Bayesian and hierarchical clustering to classify reaches according to watershed characteristics. Streams were clustered into seven classes according to elevation, sedimentary rock, and winter precipitation. Permutation‐based analysis of variance and random forest analyses were used to determine which hydrologic variables best separate streams into their respective classes. Stream typology (i.e., the class that a stream reach is assigned to) is shaped mainly by patterns of high and mean flow behavior within the stream's landscape context. Additionally, random forest was used to determine which hydrologic variables best separate minimally disturbed reference streams from non‐reference streams in each of the seven classes. In contrast to stream typology, deviation from reference conditions is more difficult to detect and is largely defined by changes in low‐flow variables, average daily flow, and duration of flow. Our combined deductive/inductive approach allows us to estimate flow under minimally disturbed conditions based on the deductive analysis and compare to measured flow based on the inductive analysis in order to estimate hydrologic change.

New Freshwater Gomphonemoid Diatoms from Streams in the Sierra Nevada Mountains, California, USA

Light and scanning electron microscopic observations of three new species of freshwater gomphonemoid diatoms are presented from mountain streams in California: Gomphonema californicum sp. nov., Gomphonema sierrianum sp. nov., and Gomphoneis oreophila sp. nov. Two of the species have morphological novelties related to the structure of the areolae, which are discussed in comparison with similar taxa. Gomphonema californicum shows a variety of areolar morphologies (i.e. lineola-like, c-shaped, and circular) within a single uniseriate stria. Unique to Gomphoneis oreophila, a member of the Herculeana subgroup, are the uniform areolae with circular openings without apparent occlusions. All of these species are distributed in remote streams of the Sierra Nevada Mountains of California, suggesting there are still new species to be found in this biodiversity-rich region.

Summer die-off of western pond turtle (Actinemys marmorata) along an intermittent coast range stream in central California

Abstract During late summer and fall 2014, we documented western pond turtle (Actinemys marmorata) mortality, as indicated by the presence of turtle shells, along a 3.7-km reach of Coyote Creek in the Diablo Range of central California. In total, we observed 39 western pond turtle shells scattered irregularly along our study reach. Shells were found in dry reaches adjacent to or close to pools containing live turtles, as well as in or adjacent to dry pools in isolated dry reaches. Ninety percent of shells observed contained no carcass, and several shells showed evidence of predation. Though the cause of mortality is unclear, our observations confirm that western pond turtles may experience high mortality during droughts, which could result in significant population decline. The presence of live turtles in refugial pools emphasizes the importance of protecting and managing permanent pools in the face of intensified drought conditions.

Evidence for Negative Effects of Drought on Baetis sp. (Small Minnow Mayfly) Abundance in a Southern California Stream

Abstract Benthic macroinvertebrate (BMI) sampling was conducted at two sites in Topanga Creek from 2003-2014. During this period, Southern California experienced extreme drought conditions (US Drought Monitor 2014). Examining trends in species composition over this period allows for a relatively long-term analysis of potential effects of drought on BMI communities. The Southern California Coastal Index of Biotic Integrity (SCC-IBI; Ode 2007) was applied to BMI samples from Topanga Creek to measure the effects of drought on quantitative biotic integrity. The following trends regarding the BMI community of Topanga Creek emerged during the course of this study: 1) Wet year rainfall in Topanga Creek Watershed positively correlated to relative and per sq. ft. springtime abundance of Baetis sp., relative abundance of Simulium sp. up to 78.7 cm (31) rain, and negatively correlated to relative abundance of Chironomidae n.d., 2) percent algae cover in April and May positvely correlated to abundance per sq. ft. Ba...

Spatiotemporal Trends Analysis of Pyrethroid Sediment Concentrations Spanning 10 Years in a Residential Creek in California.

The objective of this study was to assess temporal and spatial trends for eight pyrethroids monitored in sediment spanning 10years from 2006 to 2015 in a residential stream in California (Pleasant Grove Creek). The timeframe for this study included sampling 3years during a somewhat normal non-drought period (2006-2008) and 3years during a severe drought period (2013-2015). Regression analysis of pyrethroid concentrations in Pleasant Grove Creek for 2006, 2007, 2008, 2012, 2013, 2014, and 2015 using ½ the detection limit for nondetected concentrations showed statistically significant declining trends for cyfluthrin, cypermethrin, deltamethrin, permethrin, and total pyrethoids. Additional trends analysis of the Pleasant Grove Creek pyrethroid data using only measured concentrations, without nondetected values, showed similar statistically significant declining trends for cyfluthrin, cypermethrin, deltamethrin, esfenvalerate, fenpropathrin, permethrin, and total pyrethroids. Spatial trends analysis for the specific creek sites showed that six of the eight pyrethroids had a greater number of sites with statistically significant declining concentrations. Possible reasons for reduced pyrethroid concentrations in the stream bed in Pleasant Grove Creek during this 10-year period are label changes in 2012 that reduced residential use and lack of precipitation during the later severe drought years of 2013-2015.

Large‐Scale Journal Articles Addressing Pressing Issues

The Journal of the American Water Resources Association (JAWRA) publishes multidisciplinary water resources journal articles reporting research results across a wide range of spatial scales providing critical scientific information on diverse topics. Increasingly, water policy issues dealing with matters such as climate change and coastal eutrophication require a large-scale, integrated research to address these and other pressing problems. JAWRA has a strong tradition of publishing large-scale research articles. A few examples of the variety of large-scale journal articles follow. JAWRA has published numerous articles focused on the water quality of the Chesapeake Bay and its watershed. Recent articles include Linker et al. (2013) who computed atmospheric nutrient loads to the Chesapeake Bay watershed, Shenk and Linder (2013) who describe the development and application of the 2010 Chesapeake Bay Total Maximum Daily Load model, and Weller and Baker (2014) who used statistical models to provide the first empirical estimates of riparian buffer effects on cropland nitrate export to streams throughout the Chesapeake Bay watershed. The SPAtially Referenced Regression on Watershed attributes (SPARROW) models have been used to address the large-scale water quality issues across the United States (U.S.). Recently-published JAWRA journal articles examined the nitrogen and phosphorus export to the Gulf of Mexico (Robertson et al., 2014; McLellan et al., 2015a, b), dissolved solids in the Upper Colorado River (Keum and Kaluarachchi, 2015), and nitrogen (Saleh et al., 2015) and phosphorus (Domagalski and Saleh, 2015) sources and transport to California streams and rivers. JAWRA has published many other types of large-scale water quality or contaminant articles. For example, Flanagan Pritz et al. (2014) analyzed fish samples from remote water bodies in national parks in Alaska and the western U.S. for semivolatile organic compounds. White et al. (2015) used the Soil and Water Assessment Tool (SWAT) to develop nutrient and sediment export coefficients for land-use settings in ecoregions across the U.S. Stets et al. (2015) examined the long-term water quality monitoring data to evaluate the changes instream nitrate across the U.S. and to quantify the relationships of these changes to the land use and other factors. JAWRA articles also examine the large-scale hydrologic processes. Sanford and Selnick (2013) combined a water-balance approach with a climate and land-cover regression equation to estimate the actual evapotranspiration across the conterminous U.S. Patil et al. (2014) used a spatially lumped hydrologic model to predict the daily streamflow of watersheds across the state of Oregon and analyzed the model's performance using the statewide Oregon Hydrologic Landscape Classification (Wigington et al., 2013). Fleming and Barton (2015) conducted a 90-year trend analysis on the annual temperature, precipitation, and streamflow for three major river basins in the southern interior ecoprovince of British Columbia. Evaluation of projected hydrologic responses to climate change is another important topical area for JAWRA. Qiao et al. (2013) used Gravity Recovery And Climate Experiment, streamflow, and groundwater data to reduce the parameter uncertainty for the application of SWAT to the lower Missouri River basin and then used the model (Qiao et al., 2014), along with climate scenarios, to estimate the changes in future streamflow quantity and variability. Using a physically based hydrologic model and an ensemble of statistically downscaled global climate model scenarios, Tohver et al. (2014) examined the projected changes of hydrologic extremes, such as floods and low flows, for numerous river locations in the Pacific Northwest. Johnson et al. (2015) used SWAT to model streamflow, total suspended solids, nitrogen, and phosphorus responses to climate and urban land use change scenarios in large watersheds across the U.S. Water resources issues needing to be addressed at a large spatial scale continue to grow. The number and diversity of JAWRA large-scale journal articles illustrates the commitment of the JAWRA to publish large-scale research. Please feel free to contact me ([email protected]) if you have questions regarding a potential large-scale journal article for JAWRA. Inquiries related to other topics are always welcome as well.

SPARROW Modeling of Nitrogen Sources and Transport in Rivers and Streams of California and Adjacent States, U.S.

AbstractThe SPARROW (SPAtially Referenced Regressions On Watershed attributes) model was used to evaluate the spatial distribution of total nitrogen (TN) sources, loads, watershed yields, and factors affecting transport and decay in the stream network of California and portions of adjacent states for the year 2002. The two major TN sources to local catchments on a mass basis were fertilizers and manure (51.7%) and wastewater discharge (15.9%). Other sources contributed < 12%. Fertilizer use is widespread in the Central Valley region of California, and also important in several other regions because of the diversity of California agriculture. Precipitation, sand content of surficial soils, wetlands, and tile drains were important for TN movement to stream reaches. Median streamflow in the study area is about 0.04 m3/s. Aquatic losses of nitrogen were found to be most important in intermittent and small to medium sized streams (0.2‐14 m3/s), while larger streams showed less loss, and therefore are important for TN transport. Nitrogen loss in reservoirs was found to be insignificant, possibly because most of the larger ones are located upstream of nitrogen sources. The model was used to show loadings, sources, and tributary inputs to several major rivers. The information provided by the SPARROW model is useful for determining both the major sources contributing nitrogen to streams and the specific tributaries that transport the load.

Temporal and spatial trends in sediment contaminants associated with toxicity in California watersheds

California's Stream Pollution Trends program (SPoT) assesses long-term water quality trends, using 100 base-of-the-watershed sampling sites. Annual statewide sediment surveys from 2008 to 2012 identified consistent levels of statewide toxicity (19%), using the freshwater amphipod Hyalella azteca. Significant contaminant trends included a decrease in PCBs, stable concentrations of metals and PAHs, and a statewide increase in detections and concentrations of pyrethroid pesticides. The pyrethroid pesticide bifenthrin was detected in 69% of samples (n = 410). Detection of toxicity increased in a subset of samples tested at a more environmentally relevant test temperature (15 °C), and the magnitude of toxicity was much greater, indicating pyrethroid pesticides as a probable cause. Pyrethroid toxicity thresholds (LC50) were exceeded in 83% of samples with high toxicity. Principal components analysis related pyrethroids, metals and total organic carbon to urban land use.

Natural swimming speed of Dascyllus reticulatus increases with water temperature

Abstract Recent research on the relationship between coral reef water temperature and fish swimming activity has stated that swimming speed is inversely correlated with temperature above a species' optimum temperature (Johansen, J. L., and Jones, G. P. 2011. Increasing ocean temperature reduces the metabolic performance and swimming ability of coral reef damselfishes. Global Change Biology, 17: 2971–2979; Johansen, J. L., Messmer,V., Coker, D. J., Hoey, A. S., and Pratchett, M. S. 2014. Increasing ocean temperatures reduce activity patterns of a large commercially important coral reef fish. Global Change Biology, 20: 1067–1074). For tropical coral reefs, one anticipated consequence of global warming is an increase of ≥3°C in average water temperature in addition to greater thermal fluctuations [IPCC (Intergovernmental Panel on Climate Change). 2007. Summary for policymakers. In Climate Change 2007: The Physical Science Basis. Contribution of Working, Group I to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change. Ed. by S. Solomon, D. Qin, and M. Manning et al. Cambridge University Press, Cambridge, UK; Lough, J. 2007. Climate and climate change on the Great Barrier Reef. In Climate Change and the Great Barrier Reef. Ed. by J. Johnson and P. A. Marshall, pp. 15–50. Great Barrier Reef Marine Park Authority and Australian Greenhouse Office, Townsville, Qld, Australia; Johansen and Jones, 2011]. Evaluating the behaviour of coral reef associated fish species at different temperatures can help to assess their sensitivity to climate change. In this study, the speed of freely swimming fish in a natural setting is investigated as a function of seasonal changes in water temperature, as contrasted with systematic temperature increases in a fish tank. We show that Dascyllus reticulatus swim faster as a function of increased water temperature over the range 20.9–30.3°C. The experiments were carried out using ∼3.6 million fish trajectories observed at the Kenting National Park in Taiwan. Fish speed was computed by detecting and tracking the fish through consecutive video frames, then converting image speeds to scene speeds. Temperatures were grouped into 10 intervals. The data reveal an ∼2 mm s−1 increase in average speed per additional temperature degree over the range of 20.9–30.3°C. The Mann–Kendall test using the mean and median speed for each interval revealed that there is a speed increase trend as temperature increases at the 0.05 significance level, rather than a random increase. Our results complement previous studies that investigated the effect of temperature on the swimming performance of different fish species in the laboratory (Johansen and Jones, 2011; Myrick, C. A. and Cech, J. J. 2000. Swimming performance of four California stream fishes: temperature effects. Environmental Biology of Fishes, 58: 289–295; Ojanguren, A. F. and Braña, F. 2000. Thermal dependence of swimming endurance in juvenile brown trout. Journal of Fish Biology, 56: 1342–1347; Lough 2007; Johansen et al., 2014).

Evaluating the adequacy of a reference-site pool for ecological assessments in environmentally complex regions

Many advances in the field of bioassessment have focused on approaches for objectively selecting the pool of reference sites used to establish expectations for healthy waterbodies, but little emphasis has been placed on ways to evaluate the suitability of the reference-site pool for its intended applications (e.g., compli- ance assessment vs ambient monitoring). These evaluations are critical because an inadequately evaluated ref- erence pool may bias assessments in some settings. We present an approach for evaluating the adequacy of a reference-site pool for supporting biotic-index development in environmentally heterogeneous and pervasively altered regions. We followed common approaches for selecting sites with low levels of anthropogenic stress to screen 1985 candidate stream reaches to create a pool of 590 reference sites for assessing the biological integrity of streams in California, USA. We assessed the resulting pool of reference sites against 2 performance criteria. First, we evaluated how well the reference-site pool represented the range of natural gradients present in the entire population of streams as estimated by sites sampled through probabilistic surveys. Second, we eval- uated the degree to which we were successful in rejecting sites influenced by anthropogenic stress by comparing biological metric scores at reference sites with the most vs fewest potential sources of stress. Using this approach, we established a reference-site pool with low levels of human-associated stress and broad coverage of environmen- tal heterogeneity. This approach should be widely applicable and customizable to particular regional or program- matic needs.

Early Emigration of Juvenile Coho Salmon: Implications for Population Monitoring

AbstractSalmon monitoring programs often measure juvenile production by operating migrant traps downstream of spawning and rearing areas during smolt migration. However, this approach does not account for individuals that move downstream of trapping locations prior to smolt sampling. We used a mark–recapture study with passive integrated transponder tagging to estimate the proportion of Coho Salmon Oncorhynchus kisutch juveniles, tagged in the fall in a Northern California stream, that migrated to rearing habitat downstream of a seasonally operated trap before spring smolt sampling. Emigrants were detected by using the migrant trap, located near the upstream limit of tidal influence, and continuously operated antennas located in tidal wetlands downstream of the trap. For all three cohorts sampled (2010, 2011, 2012), we identified two distinct emigration periods (not including fry emigrants that emigrated in spring at a size too small to tag): a fall–winter period, when early emigrant parr moved into a restored tidal wetland (early emigrants); and a spring period, when smolts emigrated (smolt emigrants). There was little movement in the intervening period. Emigration timing varied depending on the location in the basin where fish were tagged; locations in the lower main stem generally produced more early emigrants, while locations in the upper basin produced more smolt emigrants. Across locations, early emigrants accounted for 2–25% of the fall‐marked juveniles from 2010, 8–29% from 2011, and 7–13% in 2012. Smolt emigrants accounted for 15–49% of the fall‐marked juveniles from 2010, 13–14% from 2011, and 3–35% from 2012. The consistent occurrence of early emigration in this and other recent studies brings into question estimates of smolt abundance and demographic rates (e.g., overwinter and marine survival) that do not account for this life history variant.Received June 19, 2014; accepted October 23, 2014

Ecology of the invasive New Zealand mud snail, Potamopyrgus antipodarum (Hydrobiidae), in a mediterranean-climate stream system

The New Zealand mud snail, Potamopyrgus antipodarum, is a widely distributed non-native species of management concern on four continents. In a southern California stream, P. antipodarum abundance, which ranged from ca. <10 to nearly 150,000 snails m−2, was related to discharge and temperature patterns. Laboratory experiments indicated that P. antipodarum (1) survivorship decreased from 13 to 27°C, but its growth rate was higher at 13 and 20°C than 27°C; (2) grazing rates were similar to those of native algivores in short-term trials; (3) grazing impact was greater than that of a native hydrobiid snail in longer-term trials; (4) ingested different diatom sizes than some other grazers; (5) reduced the abundances of medium-sized and large diatoms, and several filamentous cyanobacteria and chlorophytes, while increasing the relative abundances of tough filamentous chlorophytes (e.g., Cladophora); (6) impact on other grazing invertebrates was species specific, ranging from competition to facilitation; (7) reduced the survivorship of Anaxyrus boreas tadpoles; and (8) was consumed by non-native Procambarus clarkii and naiads of Aeshna and Argia. Ecological effects of introduced P.antipodarum are subtle, occurring primarily at transitory high densities, but flow regulation may enhance their effects by eliminating high flows that reduce their population sizes.

Correspondence of biological condition models of California streams at statewide and regional scales.

We used boosted regression trees (BRT) to model stream biological condition as measured by benthic macroinvertebrate taxonomic completeness, the ratio of observed to expected (O/E) taxa. Models were developed with and without exclusion of rare taxa at a site. BRT models are robust, requiring few assumptions compared with traditional modeling techniques such as multiple linear regression. The BRT models were constructed to provide baseline support to stressor delineation by identifying natural physiographic and human land use gradients affecting stream biological condition statewide and for eight ecological regions within the state, as part of the development of numerical biological objectives for California’s wadeable streams. Regions were defined on the basis of ecological, hydrologic, and jurisdictional factors and roughly corresponded with ecoregions. Physiographic and land use variables were derived from geographic information system coverages. The model for the entire state (n = 1,386) identified a composite measure of anthropogenic disturbance (the sum of urban, agricultural, and unmanaged roadside vegetation land cover) within the local watershed as the most important variable, explaining 56 % of the variance in O/E values. Models for individual regions explained between 51 and 84 % of the variance in O/E values. Measures of human disturbance were important in the three coastal regions. In the South Coast and Coastal Chaparral, local watershed measures of urbanization were the most important variables related to biological condition, while in the North Coast the composite measure of human disturbance at the watershed scale was most important. In the two mountain regions, natural gradients were most important, including slope, precipitation, and temperature. The remaining three regions had relatively small sample sizes (n ≤ 75 sites) and had models that gave mixed results. Understanding the spatial scale at which land use and land cover affect taxonomic completeness is imperative for sound management. Our results suggest that invertebrate taxonomic completeness is affected by human disturbance at the statewide and regional levels, with some differences among regions in the importance of natural gradients and types of human disturbance. The construction and application of models similar to the ones presented here could be useful in the planning and prioritization of actions for protection and conservation of biodiversity in California streams.

Relationship of bifenthrin sediment concentrations to grain size and total organic carbon in California waterbodies: implications for ecological risk.

A summary analysis of data sets from six California waterbodies was conducted to determine the relationship of bifenthrin sediment concentrations to: % sand/gravel; % silt; % clay; % silt/clay and % total organic carbon (TOC). The relationship of TOC to % sand/gravel, % silt, % clay, and % silt/clay was also analyzed. Statistically significant and meaningful direct relationships were reported between bifenthrin and % TOC, % silt, % clay and % silt/clay while a significant and meaningful inverse relationship was reported between bifenthrin and % sand/gravel. A significant and meaningful inverse relationship was reported between % TOC and % sand/gravel, while a significant and meaningful direct relationship was reported between % TOC and % silt, % clay and % silt/clay. Significant bifenthrin sediment concentrations would not be expected in non-depositional (sand/gravel) areas which have been reported to be dominant in various streams in California's Central Valley and are also the preferred habitat for many benthic macroinvertebrate taxa.

100 years of California’s water rights system: patterns, trends and uncertainty

For 100 years, California’s State Water Resources Control Board and its predecessors have been responsible for allocating available water supplies to beneficial uses, but inaccurate and incomplete accounting of water rights has made the state ill-equipped to satisfy growing societal demands for water supply reliability and healthy ecosystems. Here, we present the first comprehensive evaluation of appropriative water rights to identify where, and to what extent, water has been dedicated to human uses relative to natural supplies. The results show that water right allocations total 400 billion cubic meters, approximately five times the state’s mean annual runoff. In the state’s major river basins, water rights account for up to 1000% of natural surface water supplies, with the greatest degree of appropriation observed in tributaries to the Sacramento and San Joaquin Rivers and in coastal streams in southern California. Comparisons with water supplies and estimates of actual use indicate substantial uncertainty in how water rights are exercised. In arid regions such as California, over-allocation of surface water coupled with trends of decreasing supply suggest that new water demands will be met by re-allocation from existing uses. Without improvements to the water rights system, growing human and environmental demands portend an intensification of regional water scarcity and social conflict. California’s legal framework for managing its water resources is largely compatible with needed reforms, but additional public investment is required to enhance the capacity of the state’s water management institutions to effectively track and regulate water rights.

The notion of climate-driven strath-terrace production assessed via dissimilar stream-process response to late Quaternary climate

Previous research results from the Gabilan Mesa are combined with new optically stimulated luminescence (OSL) age estimates and sedimentological analyses with the aim of identifying factors that inhibit climate-driven strath-terrace production, and factors that make possible strath-terrace production independent of climate forcing. The factors are revealed by comparing the morphostratigraphy and OSL age estimates of terraces in the adjacent San Lorenzo Creek and Pancho Rico Creek drainage basins of the central California Coast Ranges. OSL age estimates on San Lorenzo Creek fill-terrace alluvium overlying bedrock at two paleofluvial levels range between 50.5 and 41.3ka and between 33.4 and 18.2ka. These OSL age estimates indicate that although the channel of Pancho Rico Creek was degrading at these times, San Lorenzo Creek aggradation was synchronous with previously documented regional, climatically driven aggradation that elsewhere in southern California led to strath production and alluvial deposition. The regional-scale climate forcing events had different effects on San Lorenzo and Pancho Rico Creeks because of the influences of drainage-basin lithology on bedload size and tectonic tilting direction on base-level fall. The Holocene history of channel denudation and strath production of Pancho Rico Creek is also different from that of San Lorenzo Creek, and different from that of many other streams in southern California. After Pancho Rico Creek captured the upper part of the drainage basin of San Lorenzo Creek sometime after 15.5 to 11.7ka, Pancho Rico Creek has been producing unpaired, erosional strath terraces. The weak, clay rich, fine-grained sedimentary rock underlying Pancho Rico Valley is an ideal substrate in which to form straths. The meandering channel of Pancho Rico Creek produces straths, and weathering resistant, relatively hard bedload introduced by stream capture ensures their preservation as strath terraces.

Exploring Particle Density Effects on Partial Mobility of Steelhead Spawning Gravels

Yellowbank Creek is a small stream in coastal central California being assessed for salmonid habitat limiting factors and restoration potential. Yellowbank flows through low-density marine mudstone bedrock, which is the gravel source for the stream. To assess the potential effects of the low-density substrate on spawning gravels, a tracer stone study comparing the incipient motion of low-density mudstone particles and typical density granitic particles was used to populate a logistic regression particle entrainment model. A model comparison approach was used to test the strength of the model. Results demonstrate partial mobility of both mudstone and granitic particles under boundary shear conditions ranging from 6.9 to 42.2 N m-2. The modelling results quantify the strong negative correlation between particle entrainment and particle density. Mudstone gravel was three times more likely to be entrained than granitic gravel, within the context of the experimental conditions. The effect of density difference on partial mobility was greater in smaller grain size fractions. This work has implications for salmonid spawning success in atypical geologic settings and may assist in prioritization of restoration efforts. Copyright © 2013 John Wiley & Sons, Ltd.

On the patterns and processes of wood in northern California streams

Forest management and stream habitat can be improved by clarifying the primary riparian and geomorphic controls on streams. To this end, we evaluated the recruitment, storage, transport, and the function of wood in 95km of streams (most drainage areas<30km2) in northern California, crossing four coastal to inland regions with different histories of forest management (managed, less-managed, unmanaged). The dominant source of variability in stream wood storage and recruitment is driven by local variation in rates of bank erosion, forest mortality, and mass wasting. These processes are controlled by changes in watershed structure, including the location of canyons, floodplains and tributary confluences; types of geology and topography; and forest types and management history. Average wood storage volumes in coastal streams are 5 to 20 times greater than inland sites primarily from higher riparian forest biomass and growth rates (productivity), with some influence by longer residence time of wood in streams and more wood from landsliding and logging sources. Wood recruitment by mortality (windthrow, disease, senescence) was substantial across all sites (mean 50%) followed by bank erosion (43%) and more locally by mass wasting (7%). The distances to sources of stream wood are controlled by recruitment process and tree height. Ninety percent of wood recruitment occurs within 10 to 35m of channels in managed and less-managed forests and upward of 50m in unmanaged Sequoia and coast redwood forests. Local landsliding extends the source distance. The recruitment of large wood pieces that create jams (mean diameter 0.7m) is primarily by bank erosion in managed forests and by mortality in unmanaged forests. Formation of pools by wood is more frequent in streams with low stream power, indicating the further relevance of environmental context and watershed structure. Forest management influences stream wood dynamics, where smaller trees in managed forests often generate shorter distances to sources of stream wood, lower stream wood storage, and smaller diameter stream wood. These findings can be used to improve riparian protection and inform spatially explicit riparian management.

NOVEL AQUATIC ECOSYSTEMS: THE NEW REALITY FOR STREAMS IN CALIFORNIA AND OTHER MEDITERRANEAN CLIMATE REGIONS

ABSTRACTTemporary streams in California and other Mediterranean climate areas are among the aquatic habitats most altered by human actions and by invasions by alien species. They typically support novel ecosystems, defined as ecosystems dominated by new combinations of organisms in highly altered habitats. Although these new ecosystems have many attributes of the ecosystems they replaced, such as native species, they typically contain many new interactions among species. Managers need to recognize this reality to find ways to direct change towards novel ecosystems with desirable features, including native species. The concept of reconciliation ecology is a practical approach to living with the new reality; it includes actively guiding ecosystem change, as illustrated by Putah Creek, Cosumnes River, Eel River and Six Bit Gulch in California. The first three waterways are all highly altered and managed with varying degrees of success to favour desired aquatic species, whereas Six Bit Gulch experiences such extreme conditions that the original ecosystem is still largely intact. The examples illustrate that most aquatic ecosystems in California are so highly altered that attempting to restore them to an earlier condition or stable state is largely not possible. Where more or less intact systems persist, it is usually because extreme environmental conditions restrict both alien invaders and human use in small watersheds. This pattern appears to be fairly typical of streams in Mediterranean climate areas. Copyright © 2013 John Wiley &amp; Sons, Ltd.