During their life cycle, fish carry out distinct movements within rivers and migrate upstream and downstream to reproduce, to feed, and to shelter in refuge habitats. During downstream movements, they can incur severe injuries that may be lethal directly or indirectly over time when passing through hydropower plants or when being entrained at other water intakes. Horizontal bar rack bypass systems are a state-of-the-art technology to protect and guide downstream moving fish towards a reasonably safe corridor around water intakes. They have been in operation at multiple hydropower plants for more than a decade, but only little is known about the potential fish protection and guidance efficiencies and the fine scale reactions of different fish species when encountering such racks. To resolve this, systematic live fish laboratory tests were conducted under various hydraulic conditions involving a diverse assemblage of riverine fish species differing in their swimming behavior and morphology. Six riverine species, namely spirlin (), barbel (), nase (), brown trout (), Atlantic salmon (), and European eel () were tested with a rack consisting of foil-shaped bars, clear bar spacings of 15 and 20 mm, a horizontal rack angle of 30° to the flow direction, and a full depth open channel bypass. Variations in fish behavior were observed between different species and hydraulic conditions, but the results suggest that the guidance and protection efficiencies primarily depend on the ratio of the fish width to the clear bar spacing. Larger fish were well protected by the horizontal bar rack, while smaller fish frequently passed through the rack. New equations are proposed to estimate the protection and guidance efficiencies as a function of the clear bar spacing and the fish species' biometry, which is highly relevant to assess the effect of horizontal bar racks as fish protection measures prior to installation.

Vegetated buffers and filter strips are a widely used Best Management Practice (BMP) for enhancing streamside ecosystem quality and water quality improvement through nonpoint source pollutant removal. Most existing studies are either site-specific, rely on limited data points, or evaluate buffer width and slope as the only design variables for predicting sediment reduction, not considering other parameters such as soil texture, vegetation types, and runoff loads that can significantly influence the buffer efficiency. In this paper, we carry out a meta-analysis of published studies and fit regression models to explore the sediment removal capacity of riparian buffers. We compiled 905 data points from over 90 studies (including data from an online BMP database) documenting sediment trapping by vegetated buffers and recorded data regarding buffer characteristics such as buffer width, slope, area, vegetation type, sediment loading, water flow rates, and sediment removal efficiency. We found that an exponential regression model describing the relationship between sediment removal efficiency by the buffer and water inflow/outflow volume ratio explained 44% of the variance. Adding the square root of roughness increased the to 0.50. The model performance was compared with other sediment reduction regression models reported in the literature. The results point towards the importance of considering flow parameters in vegetative buffer design. The improved empirical relationships derived here can be used at local scales to understand sediment trapping potential by vegetated buffers for water quality mitigation purposes and can be built into extant hydrologic models for improved watershed-scale assessments.

One of the primary functions of green roofs in urban areas is to moderate rainwater runoff, and one of the major impediments to the survival of plants on an extensive green roof (EGR) is a lack of available water during dry periods. Runoff moderation and water storage are both influenced by the composition of the growing media. Here we present a framework for evaluating the hydrologic performance of EGR growing media and also provide hydrologic attribute data for several commonly used EGR media constituents. In this three-phase study, we: 1) measured hydrologic attributes of individual EGR media constituents, 2) predicted attributes of media mixtures using individual constituent data, and 3) tested the seven top-ranking mixtures to evaluate hydrologic performance. Hydrologic attributes included wet weight and water held at maximum retentive capacity, long-term water retention, and hydraulic conductivity. Because perlite was light in weight yet held the greatest amount of water both at its maximum retentive capacity and in the long term, media mixtures dominated by perlite were predicted to have the best overall hydrologic performance. Mixtures dominated by pumice were also predicted to perform relatively well but were heavier. Despite the slightly greater weight and slightly lower performance, pumice may be a preferred alternative to perlite because perlite is a processed constituent with greater estimated embodied energy. Results indicate that performance of mixtures can be adequately predicted using performance of individual constituents for wet weight, water held, and long-term water retention. Hydraulic conductivity was less predictable because the pore volume in mixtures can be unrelated to the pore volume of the individual constituents. The framework presented here can be used to evaluate the performance of other EGR media, and the media attribute data can be used in formulating EGR media mixtures for specific applications. In addition, the attribute data can serve as a benchmark for evaluating other EGR media. Our results underscore the need for standardization of methods for more effective comparisons of EGR substrates, and also reinforce the need to evaluate EGR components using real-world scenarios.

Restoration and reconnection of floodplain systems provide multiple societal and ecosystem benefits, while providing municipalities the opportunity to attempt alternative approaches to maintain infrastructure protection and function. In some restored floodplains, treated wastewater effluent discharge is redirected over land instead of directly into rivers to allow natural flow and infiltration, to facilitate restoration designs such as levee setback, and to provide additional freshwater to floodplain ecosystems. However, indirect discharge of treated effluent over land may pose risks to surface and groundwater when pollutants like excess nutrients enter the floodplain and undergo transformation. We investigated the consequences for groundwater and surface water quality when effluent was redirected as open water channels over a floodplain surface. In this study, seasonal floodplain nutrient concentrations in groundwater and surface water were observed for more than 5 years as a floodplain and wastewater treatment plant underwent a major restoration project that included river-floodplain reconnection with levee setback and redirection of effluent discharge from a river channel to open flow across the restored floodplain. Nutrient loading to the surrounding floodplain groundwater and surface water was observed, but based on measures of hydrological connectivity, groundwater flow paths, and biogeochemistry, nutrients from the effluent moved within the floodplain with minimal effect to the surrounding floodplain water quality. We did not find evidence of substantial additional processing that could replace advanced nutrient treatment in this system, however we did observe evidence of diverse nutrient processes that may support enhanced retention if treatment channels were designed to enhance these processes. We suggest that indirect discharge of high quality treated effluent in a restored floodplain is a viable alternative to direct discharge into a river when groundwater flow directs that discharge to habitats where minimal nutrient sensitivity is expected.

Despite the valuable ecosystem services provided by mangrove ecosystems they remain threatened around the globe. Urban development has been a primary cause for mangrove destruction and deterioration in south Florida USA for the last several decades. As a result, the restoration of mangrove forests has become an important topic of research. Using field sampling and remote-sensing we assessed the past and present hydrologic conditions of a mangrove creek and its connected mangrove forest and brackish marsh systems located on the coast of Naples Bay in southwest Florida. We concluded that the hydrology of these connected systems had been significantly altered from its natural state due to urban development. We propose here a mangrove creek restoration plan that would extend the existing creek channel 1.1 km inland through the adjacent mangrove forest and up to an adjacent brackish marsh. We then tested the hydrologic implications using a hydraulic model of the mangrove creek calibrated with tidal data from Naples Bay and water levels measured within the creek. The calibrated model was then used to simulate the resulting hydrology of our proposed restoration plan. Simulation results showed that the proposed creek extension would restore a twice-daily flooding regime to a majority of the adjacent mangrove forest and that there would still be minimal tidal influence on the brackish marsh area, keeping its salinity at an acceptable level. This study demonstrates the utility of combining field data and hydraulic modeling to aid in the design of mangrove restoration plans.

Phytoremediation makes use of plants and associated microorganisms to clean up soils and sediments contaminated with inorganic and organic pollutants. In this study, switchgrass () was used to test for its efficiency in improving the removal of three specific polychlorinated biphenyl (PCB) congeners (PCB 52, 77 and 153) in soil microcosms. The congeners were chosen for their ubiquity, toxicity, and recalcitrance. After 24 weeks of incubation, loss of 39.9 ± 0.41% of total PCB molar mass was observed in switchgrass treated soil, significantly higher than in unplanted soil (29.5 ± 3.4%) (p<0.05). The improved PCB removal in switchgrass treated soils could be explained by phytoextraction processes and enhanced microbial activity in the rhizosphere. Bioaugmentation with LB400 was performed to further enhance aerobic PCB degradation. The presence of LB400 was associated with improved degradation of PCB 52, but not PCB 77 or PCB 153. Increased abundances of A (a functional gene that codes for a subunit of PCB-degrading biphenyl dioxygenase in bacteria) and its transcript were observed after bioaugmentation. The highest total PCB removal was observed in switchgrass treated soil with LB400 bioaugmentation (47.3 ± 1.22 %), and the presence of switchgrass facilitated LB400 survival in the soil. Overall, our results suggest the combined use of phytoremediation and bioaugmentation could be an efficient and sustainable strategy to eliminate recalcitrant PCB congeners and remediate PCB-contaminated soil.

The current economic paradigm, which is based on increasing human population, economic development, and standard of living, is no longer compatible with the biophysical limits of the finite Earth. Failure to recover from the economic crash of 2008 is not due just to inadequate fiscal and monetary policies. The continuing global crisis is also due to scarcity of critical resources. Our macroecological studies highlight the role in the economy of energy and natural resources: oil, gas, water, arable land, metals, rare earths, fertilizers, fisheries, and wood. As the modern industrial technological-informational economy expanded in recent decades, it grew by consuming the Earth's natural resources at unsustainable rates. Correlations between per capita GDP and per capita consumption of energy and other resources across nations and over time demonstrate how economic growth and development depend on "nature's capital". Decades-long trends of decreasing per capita consumption of multiple important commodities indicate that overexploitation has created an unsustainable bubble of population and economy.

Theoretically, sequential cycles of dechlorination followed by aerobic bio-oxidation are desirable to achieve complete degradation of a mixture of higher and lower chlorinated PCBs. In this research, soil was artificially contaminated with polychlorinated biphenyls (PCBs) in mixture and as single congeners, aged, and planted with two different plant species. Alternating redox cycles were created in the root zone of plants by flooding and draining the soil. Over 32 weeks, switchgrass () and poplar ( DN34) planted systems that were exposed to alternate cycles of flooding performed better in reducing parent PCBs than planted systems that were not cycled (p<0.05). The cycled systems also had a higher mass of PCB transformation products than the uncycled systems. Multiple cycles were necessary to achieve significant differences between the cycled and uncycled treatments.

Restoration measures of deteriorated river ecosystems generally aim at increasing the spatial heterogeneity and connectivity of these systems in order to increase biodiversity and ecosystem stability. While this is believed to benefit overall ecological integrity, consequences of such restoration projects on biogeochemical processes per se (i.e. ecosystem functioning) in fluvial systems are rarely considered. We address these issues by evaluating the characteristics of surface water connection between side arms and the main river channel in a former braided river section and the role and degree of connectivity (i.e. duration of surface water connection) on the sediment biogeochemistry. We hypothesized that potential respiration and denitrification would be controlled by the degree of hydrological connectivity, which was increased after floodplain restoration. We measured potential microbial respiration (SIR) and denitrification (DEA) and compared a degraded floodplain section of the Danube River with a reconnected and restored floodplain in the same river section. Re-establishing surface water connection altered the controls on sediment microbial respiration and denitrification ultimately impacting potential microbial activities. Meta-variables were created to characterize the effects of hydrology, morphology, and the available carbon and nutrient pools on potential microbial processing. Mantel statistics and path analysis were performed and demonstrate a hierarchy where the effects of hydrology on the available substrates and microbial processing are mediated by the morphology of the floodplain. In addition, these processes are highest in the least connected sites. Surface water connection, mediated by morphology regulates the potential denitrification rate and the ratio of NO to N emissions, demonstrating the effects of restoration in floodplain systems.

Miniaturizing the Earth's biogeochemical cycles to support human life during future space missions is the goal of the NASA research and engineering program in advanced life support. Mission requirements to reduce mass, volume, and power have focused efforts on (1) a maximally simplified agro-ecosystem of humans, food crops, and microbes; and, (2) a design for optimized productivity of food crops with high light levels over long days, with hydroponics, with elevated carbon dioxide and other controlled environmental factors, as well as with genetic selection for desirable crop properties. Mathematical modeling contributes to the goals by establishing trade-offs, by analyzing the growth and development of experimental crops, and by pointing to the possibilities of directed phasic control using modified field crop models to increase the harvest index.

Spring wheat (Triticum aestivum L., cv. Yecora Rojo) was grown in the intensive agricultural biome (IAB) of Biosphere 2 during the l995-l996 winter/spring season. Environmental conditions were characterized by a day/night temperature regime of 27/17 degrees C, relative humidity (RH) levels around 45%, mean atmospheric CO2 concentration of 450 ppmv, and natural light conditions with mean intensities about half of outside levels. Weekly samples of above-ground plant matter were collected throughout the growing season and phenological events recorded. A computer model, CERES-Wheat, previously tested under both field and controlled conditions, was used to simulate the observed crop growth and to help in data analysis. We found that CERES-Wheat simulated the data collected at Biosphere 2 to within 10% of observed, thus suggesting that wheat growth inside the IAB was comparable to that documented in other environments. The model predicts phenological stages and final dry matter (DM) production within l0% of the observed data. Measured DM production rates, normalized for light absorbed by the crop. suggested photosynthetic efficiencies intermediate between those observed under optimal field conditions and those recorded in NASA-Controlled Ecological Life-Support Systems (CELSS). We suggest that such a difference can be explained primarily in terms of low light levels inside the IAB, with additional effects due to elevated CO2 concentrations and diffuse light fractions.

Hyporheic exchange between a river channel and its floodplain region assists in mediating processes such as nutrient removal and temperature regulation. Floodplain restoration in the form of levee setbacks are often carried out to improve the hyporheic exchange. In this study Light Detection and Ranging (LiDAR) data were used along with the head data from observation wells and stage data from rivers to setup and calibrate a groundwater model for 458 km of area within Gap to Gap reach of the Yakima River, WA. This area has witnessed several efforts of floodplain restoration in the form of levee setbacks. The groundwater model was used to quantify hyporheic flow emerging from the Yakima River in steady and transient states during pre-restoration (using LiDAR data of 2008) and post-restoration period (after levee setback using LiDAR data of 2013). The comparison of results from the model runs during pre and post-restoration periods showed that the length of the pathlines increased after levee setback for both steady and transient state model simulations. The largest increase of about 62 m was noticed in the month of September 2014 (pre: 398 m and post: 460 m). The study also showed that the direction of the flow changed following levee setback, expanding the area for hyporheic flux exchange between surface and groundwater. The model run during transient state also suggested that pathlines were longer during drier months compared to wet months. Overall, the study showed that levee setbacks improved the hyporheic connection between surface and groundwater in the Yakima floodplain which demonstrates that levee setback can provide a valuable hydrologic tool to restore ecosystem processes in previously leveed rivers.

A constructed, variable-flow treatment wetland was evaluated for its ability to reduce microbial loads from the Banklick Creek, an impacted recreational waterway in Northern Kentucky. For this study, levels of traditional ( and enterococci measured by culture and molecular techniques) and alternative fecal indicators (infectious somatic and F+ coliphage, spp. and by culture), potential pathogens (molecular signal of spp.) as well as various microbial source tracking (MST) markers (human fecal marker HF183 and avian fecal marker GFD) were monitored during the summer and early fall through five treatment stages within the Banklick Creek Wetland. No difference in concentrations of traditional or alternative fecal indicators were observed in any of the sites monitored. Microbial source tracking markers were employed to identify sources of fecal contamination within the wetland. Human marker HF183 concentrations at beginning stages of treatment were found to be significantly higher ( value range: 0.0016-0.0003) than levels at later stages. Conversely, at later stages of treatment where frequent bird activity was observed, and avian marker (GFD) signals were detected at significantly higher frequencies ( value range: 0.024 to <0.0001), and both signals were strongly correlated ( = 0.0001). Our study suggests constructed wetlands are an effective means for removal of microbial contamination in ambient waters, but reliance on general fecal indicators is not ideal for determining system efficacy or assessing appropriate remediation efforts.