- Analysis of Daily Peaking and Run‐of‐River Operations with
Flow Variability Metrics, Considering Subdaily to Seasonal Time Scales
- Authors: Nicholas A. Haas; Ben L. O'Connor, John W. Hayse, Mark S. Bevelhimer, Theodore A. Endreny
Pages: n/a - n/a
Abstract: Environmental flows are an important consideration in licensing hydropower projects as operational flow releases can result in adverse conditions for downstream ecological communities. Flow variability assessments have typically focused on pre‐ and post‐dam conditions using metrics based on daily averaged flow values. This study used subdaily and daily flow data to assess environmental flow response to changes in hydropower operations from daily peaking to run‐of‐river. An analysis tool was developed to quantify flow variability metrics and was applied to four hydropower projects. Significant differences were observed between operations at the 99% confidence level in the median flow values using hourly averaged flow datasets. Median daily rise and fall rates decreased on average 34.5 and 27.9%, respectively, whereas median hourly rise and fall rates decreased on average 50.1 and 50.6%, respectively. Differences in operational flow regimes were more pronounced in the hourly averaged flow datasets and less pronounced or nonexistent in the daily averaged flow datasets. These outcomes have implications for the development of ecology‐flow relationships that quantify effects of flow on processes such as fish stranding and displacement, along with habitat stability. Results indicate that flow variability statistics should be quantified using subdaily datasets to accurately represent the nature of hydropower operations, especially for daily peaking facilities.
- Evaluating Pre‐ and Post‐Fire Peak Discharge Predictions
across Western U.S. Watersheds
- Authors: Alicia M. Kinoshita; Terri S. Hogue, Carolyn Napper
Pages: n/a - n/a
Abstract: This study reviews five models commonly used in post‐fire hydrologic assessments: the Rowe Countryman and Storey (RCS), United States Geological Survey (USGS) Linear Regression Equations, USDA Windows Technical Release 55 (USDA TR‐55), Wildcat5, and U.S. Army Corps of Engineers (USACE) Hydrologic Modeling System (HEC‐HMS). The models are applied to eight diverse basins in the western United States (U.S.) (Arizona, California, Colorado, Montana, and Washington) affected by wildfires and assessed by input parameters, calibration methods, model constraints, and performance. No one model is versatile enough for application to all study sites. Results show inconsistency between model predictions for events across the sites and less confidence with larger return periods (25‐ and 50‐year events) and post‐fire predictions. The RCS method performs well, but application is limited to southern California. The USGS linear regression model has wider regional application, but performance is less reliable at the large recurrence intervals and post‐fire predictions are reliant on a subjective modifier. Of the three curve number‐based models, Wildcat5 performs best overall without calibration, whereas the calibrated TR‐55 and HEC‐HMS models show significant improvement in pre‐fire predictions. Results from our study provide information and guidance to ultimately improve model selection for post‐fire prediction and encourage uniform parameter acquisition and calibration across the western U.S.
- The Effects of Changing Land Cover on Streamflow Simulation in Puerto Rico
- Authors: Ashley E. Van Beusekom; Lauren E. Hay, Roland J. Viger, William A. Gould, Jaime A. Collazo, Azad Henareh Khalyani
Pages: n/a - n/a
Abstract: This study quantitatively explores whether land cover changes have a substantive impact on simulated streamflow within the tropical island setting of Puerto Rico. The Precipitation Runoff Modeling System (PRMS) was used to compare streamflow simulations based on five static parameterizations of land cover with those based on dynamically varying parameters derived from four land cover scenes for the period 1953‐2012. The PRMS simulations based on static land cover illustrated consistent differences in simulated streamflow across the island. It was determined that the scale of the analysis makes a difference: large regions with localized areas that have undergone dramatic land cover change may show negligible difference in total streamflow, but streamflow simulations using dynamic land cover parameters for a highly altered subwatershed clearly demonstrate the effects of changing land cover on simulated streamflow. Incorporating dynamic parameterization in these highly altered watersheds can reduce the predictive uncertainty in simulations of streamflow using PRMS. Hydrologic models that do not consider the projected changes in land cover may be inadequate for water resource management planning for future conditions.
- Characterizing a Major Urban Stream Restoration Project: Nine Mile Run
(Pittsburgh, Pennsylvania, USA)
- Authors: Daniel J. Bain; Erin M. Copeland, Marion T. Divers, Marijke Hecht, Kristina G. Hopkins, Justin Hynicka, Michael Koryak, Mary Kostalos, Lisa Brown, Emily M. Elliott, Joseph Fedor, Michele Gregorich, Brady Porter, Brenda Smith, Christopher Tracey, Margaret Zak
Pages: n/a - n/a
Abstract: Urban stream restoration continues to be used as an ecological management tool, despite uncertainty about the long‐term sustainability and resilience of restored systems. Evaluations of restoration success often focus on specific instream indicators, with limited attention to the wider basin or parallel hydrologic and geomorphic process. A comprehensive understanding of urban stream restoration progress is particularly important for comparisons with nonurban sites as urban streams can provide substantial secondary benefits to urban residents. Here, we utilize a wide range of indicators to retrospectively examine the restoration of Nine Mile Run, a multi‐million dollar stream restoration project in eastern Pittsburgh (Pennsylvania, USA). Examination of available continuous hydrological data illustrates the high cost of failures to incorporate the data into planning and adaptive management. For example, persistent extreme flows drive geomorphic degradation threatening to reverse hydrologic connections created by the restoration and impact the improved instream biotic communities. In addition, human activities associated with restoration efforts suggest a positive feedback as the stream restoration has focused effort on the basin beyond the reach. Ultimately, urban stream restoration remains a potentially useful management tool, but continued improvements in post‐project assessment should include examination of a wider range of indicators.
- Bedded Sediment Conditions and Macroinvertebrate Responses in New Mexico
Streams: A First Step in Establishing Sediment Criteria
- Authors: Benjamin K. Jessup; Philip R. Kaufmann, Forrest John, Lynette S. Guevara, Seva Joseph
Pages: n/a - n/a
Abstract: Excess fine sediments in streambeds are among the most pervasive causes of degradation in streams of the United States. Simple criteria for acceptable streambed fines are elusive because streambed fines and biotic tolerances vary widely in the absence of human disturbances. In response to the need for sediment benchmarks that are protective of minimum aquatic life uses under the Clean Water Act, we undertook a case study using surveys of sediment, physical habitat, and macroinvertebrates from New Mexico streams. Our approach uses weight of evidence to develop suggested benchmarks for protective levels of surficial bedded sediments
- Freshwater Mussel Population Status and Habitat Quality in the Clinch
River, Virginia and Tennessee, USA: A Featured Collection
- Authors: Carl E. Zipper; Braven Beaty, Gregory C. Johnson, Jess W. Jones, Jennifer Lynn Krstolic, Brett J.K. Ostby, William J. Wolfe, Patricia Donovan
Pages: n/a - n/a
Abstract: The Clinch River of southwestern Virginia and northeastern Tennessee is arguably the most important river for freshwater mussel conservation in the United States. This featured collection presents investigations of mussel population status and habitat quality in the Clinch River. Analyses of historic water‐ and sediment‐quality data suggest that water column ammonia and water column and sediment metals, including Cu and Zn, may have contributed historically to declining densities and extirpations of mussels in the river's Virginia sections. These studies also reveal increasing temporal trends for dissolved solids concentrations throughout much of the river's extent. Current mussel abundance patterns do not correspond spatially with physical habitat quality, but they do correspond with specific conductance, dissolved major ions, and water column metals, suggesting these and/or associated constituents as factors contributing to mussel declines. Mussels are sensitive to metals. Native mussels and hatchery‐raised mussels held in cages in situ accumulated metals in their body tissues in river sections where mussels are declining. Organic compound and bed‐sediment contaminant analyses did not reveal spatial correspondences with mussel status metrics, although potentially toxic levels were found. Collectively, these studies identify major ions and metals as water‐ and sediment‐quality concerns for mussel conservation in the Clinch River.
- Reach‐Scale Comparison of Habitat and Mollusk Assemblages for Select
Sites in the Clinch River with Regional Context
- Authors: Brett J.K. Ostby; Jennifer L. Krstolic, Gregory C. Johnson
Pages: n/a - n/a
Abstract: Several hypotheses, including habitat degradation and variation in fluvial geomorphology, have been posed to explain extreme spatial and temporal variation in Clinch River mollusk assemblages. We examined associations between mollusk assemblage metrics (richness, abundance, recruitment) and physical habitat (geomorphology, streambed composition, fish habitat, and riparian condition) at 10 sites selected to represent the range of current assemblage condition in the Clinch River. We compared similar geomorphological units among reaches, employing semi‐quantitative and quantitative protocols to characterize mollusk assemblages and a mix of visual assessments and empirical measurements to characterize physical habitat. We found little to no evidence that current assemblage condition was associated with 54 analyzed habitat metrics. When compared to other sites in the Upper Tennessee River Basin (UTRB) that once supported or currently support mollusk assemblages, Clinch River sites were more similar to each other, representing a narrower range of conditions than observed across the larger geographic extent of the UTRB. A post‐hoc analysis suggested stream size and average boundary shear stress at bankfull stage may have historically limited species richness in the UTRB (p
- Influences of Water and Sediment Quality and Hydrologic Processes on
Mussels in the Clinch River
- Authors: Gregory C. Johnson; Jennifer L. Krstolic, Brett J.K. Ostby
Pages: n/a - n/a
Abstract: Segments of the Clinch River in Virginia have experienced declining freshwater mussel populations during the past 40 years, while other segments of the river continue to support some of the richest mussel communities in the country. The close proximity of these contrasting reaches provides a study area where differences in climate, hydrology, and historic mussel distribution are minimal. The USGS conducted a study between 2009 and 2011 to evaluate possible causes of the mussel declines. Evaluation of mussel habitat showed no differences in physical habitat quality, leaving water and sediment quality as possible causes for declines. Three years of continuous water‐quality data showed higher turbidity and specific conductance in the reaches with low‐quality mussel assemblages compared to reaches with high‐quality mussel assemblages. Discrete water‐quality samples showed higher major ions and metals concentrations in the low‐quality reach. Base‐flow samples contained high major ion and metal concentrations coincident to low‐quality mussel populations. These results support a conceptual model of dilution and augmentation where increased concentrations of major ions and other dissolved constituents from mined tributaries result in reaches with declining mussel populations. Tributaries from unmined basins provide water with low concentrations of dissolved constituents, diluting reaches of the Clinch River where high‐quality mussel populations occur.
- Water and Sediment Quality in the Clinch River, Virginia and Tennessee,
USA, over Nearly Five Decades
- Authors: Jennifer E. Price; Carl E. Zipper, Jess W. Jones, Christopher T. Franck
Pages: n/a - n/a
Abstract: The Clinch River, in eastern United States, supports a diverse freshwater fauna including endangered mussels. Although mussel populations are stable in the Clinch's northeastern Tennessee segment, long‐term declines have been documented upstream in Virginia. We analyzed water and sediment quality data collected by government agencies from the 1960s through 2013 in an effort to inform current management. The river was divided into sections considering data availability and major tributaries. We tested for spatial differences among river sections and for temporal trends, and compared measured values to potentially protective levels if available. Ammonia concentrations approaching and exceeding protective levels were recorded, most often during the 1970s and 1980s in upstream sections. Sediment metals occurred at levels potentially causing biological effects, mainly during the 1980s and 1990s. In the 2000s, water‐column metals have been well below protective levels for general aquatic life. Dissolved solids (DS) increased in most river sections over the study period but mussel‐specific protective levels are not known. Analysis of water pH, total N, and total P did not generate conservation concern. Enhanced monitoring for sediment metals, water‐column metals, and ionic composition of DS; closer alignment of agency water monitoring practices in the two states; and research to determine biological effects of DS at current and anticipated levels can aid future conservation management.
- Clinch River Freshwater Mussels Upstream of Norris Reservoir, Tennessee
and Virginia: A Quantitative Assessment from 2004 to 2009
- Authors: Jess Jones; Steven Ahlstedt, Brett Ostby, Braven Beaty, Michael Pinder, Nathan Eckert, Robert Butler, Don Hubbs, Craig Walker, Shane Hanlon, John Schmerfeld, Richard Neves
Pages: n/a - n/a
Abstract: The Clinch River is located in northeastern Tennessee (TN) and southwestern Virginia (VA) of the United States, and contains a diverse mussel assemblage of 46 extant species, including 20 species listed as federally endangered. To facilitate quantitative monitoring of the fauna, quadrat data were collected from 2004 to 2009 at 18 sites in the river, including 12 sites in TN and 6 sites in VA. Thirty‐eight mussel species were collected alive in total from quadrat samples taken annually at sites in the TN section of the river. Over the five‐year study period, mussel density averaged 25.5 m−2 at all sites sampled in TN. In contrast, mussel density averaged only 3.1 m−2 at sites sampled in VA. The best historical site in VA was Pendleton Island in Scott County, where mussel density was estimated as high as 25 m−2 in 1979, comparable to current densities recorded in TN. Mussel densities are now
- Application of a Modified Health Belief Model to the
Pro‐Environmental Behavior of Private Well Water Testing
- Authors: Crista L. Straub; Jessica E. Leahy
Pages: n/a - n/a
Abstract: A social cognition model of health behavior, the health belief model, was applied to the pro‐environmental behavior of private well water testing. Conceptualizing environmental behaviors as health behaviors may provide new insight into pro‐environmental behavior change. A groundwater education program was provided to K‐12 children throughout New England. Both child participants and their parents completed surveys pertaining to private well water behavior. Results indicate that perceived barriers and socioeconomic status significantly influenced past well water testing of parent participants. Perceived barriers included: participants' concern related to the cost of treating their water, and how a well water problem would influence their property value. Parent participants also indicated that they would perform future well water testing if they received a reminder cue to action that might include: getting a discount or reminder in the mail, if a well testing program was available, and state or local requirement. Our findings reinforce the need for continued private well water research and parallels to additional environmental behaviors.
- Flexibility in Water Resources Management: Review of Concepts and
Development of Assessment Measures for Flood Management Systems
- Authors: Kara N. DiFrancesco; Desiree D. Tullos
Pages: n/a - n/a
Abstract: Discussions around adapting water management systems to climate change often express the need to increase system flexibility. Yet despite the frequent use of the term flexibility, very little work has examined what exactly it means to have a flexible water management system, what features of a system make it more flexible than another system, or when the costs to implement flexible options outweigh the benefits gained from increased flexibility. To define and operationalize the concept of flexibility in the field of water resources management, this article reviews and analyzes concepts of flexibility from the fields of information technology, manufacturing, management, and adaptive social‐ecological systems. We identify five characteristics of flexible water resources systems, namely: slack, redundancy, connectivity, compatibility/coordination, and adjustability. We then operationalize the assessment of flexibility for flood management systems by proposing original flexibility metrics and discussing their application. We conclude with a discussion on the tradeoffs of increasing flexibility.
- Decoupling Streamflow Responses to Climate Variability and Land Use/Cover
Changes in a Watershed in Northern China
- Authors: Junting Guo; Zhiqiang Zhang, Jie Zhou, Shengping Wang, Peter Strauss
Abstract: Restored annual streamflow (Qr) and measured daily streamflow of the Chaohe watershed located in northern China and associated long-term climate and land use/cover data were used to explore the effects of land use/cover change and climate variability on the streamflow during 1961-2009. There were no significant changes in annual precipitation (P) and potential evapotranspiration, whereas Qr decreased significantly by 0.81 mm/yr (p
- Long-Term Trends of Specific Conductance in Waters Discharged by Coal-Mine
Valley Fills in Central Appalachia, USA
- Authors: Daniel M. Evans; Carl E. Zipper, Patricia F. Donovan, W. Lee Daniels
Abstract: Anthropogenic salinization of freshwaters is a global concern. Coal surface mining causes release of dissolved sulfate, bicarbonate, calcium, magnesium, and other ions to surface waters in central Appalachia, USA, through practices that include mine rock disposal in valley fills (VFs). This region's surface waters naturally have low salinity, with specific conductance (SC, a salinity indicator) generally
- Assessment of Quality for Middle Level and High School Student-Generated
Water Quality Data
- Authors: John M. Peckenham; Sarah K. Peckenham
Abstract: Student scientists have analyzed groundwater used for drinking water in rural areas to understand groundwater quality. This was part of a greater effort to understand risks to drinking water. The data produced by middle level and high school students have not been accepted by experts because of concerns about method and student accuracy. We assessed the inherent errors associated with method accuracy, student precision, and sample variability to establish bounds for attainable trueness in water analyses. Analytical test kits and probes were evaluated for the determination of pH, conductivity, chloride, hardness, iron, total soluble metals, and nitrate. In terms of precision, all methods met or exceeded design specifications. Method trueness was variable and in general ranged from good to poor depending on method. A gage reproducibility and repeatability analysis of instrumental methods (pH and conductivity) partitioned the variances into student error (12-46%), instrumental error (8-21%), and random error (45-68%). Overall, student-generated data met some of the quality objectives consistent with the method limitations. Some methods exhibited a systematic bias and data adjustment may be necessary. Given good management of the student analyst process, it is possible to make precise and accurate measurements consistent with the methods specifications.
- Price Determination and Efficiency in the Market for South Platte Basin
Ditch Company Shares
- Authors: Matthew T. Payne; Mark Griffin Smith, Clay J. Landry
Abstract: Water scarcity presents an obstacle to economic development in the western United States. Water rights markets help improve water allocation, allowing states to derive the highest economic benefit from available resources, and supporting new uses and economic development. However, the implicit (marginal) prices of water rights attributes are uncertain. To address this problem, we apply econometric analysis to a unique dataset to estimate the implicit values that market participants place on the attributes of shares of ditch company water rights in Colorado's South Platte River Basin. Our analysis demonstrates that ditch company share buyers value proximity of water diversion, reliability of water deliveries, and temporal flexibility of water use. To assess reliability we introduce the use of the coefficient of variation to capture, in one variable, the randomness of supply from ditch company shares that are not a single water right, but a portfolio of rights with different appropriation dates. Finally, we test and correct for spatial autocorrelation for the first time in a study of water market prices.
- Estimation of Nonpoint Source Nitrate Concentrations in Indiana Rivers
Based on Agricultural Drainage in the Watershed
- Authors: Yan Jiang; Jane R. Frankenberger, Yinghui Sui, Laura C. Bowling
Abstract: Subsurface tile-drained agricultural fields are known to be important contributors to nitrate in surface water in the Midwest, but the effect of these fields on nitrate at the watershed scale is difficult to quantify. Data for 25 watersheds monitored by the Indiana Department of Environmental Management and located near a U.S. Geological Survey stream gage were used to investigate the relationship between flow-weighted mean concentration (FWMC) of nitrate-N and the subsurface tile-drained area (DA) of the watershed. The tile DA was estimated from soil drainage class, land use, and slope. Nitrate loads from point sources were estimated based on reported flows of major permitted facilities with mean nitrate-N concentrations from published sources. Linear regression models exhibited a statistically significant relationship between annual/monthly nonpoint source (NPS) nitrate-N and DA percentage. The annual model explained 71% of the variation in FWMC of nitrate-N. The annual and monthly models were tested in 10 additional watersheds, most with absolute errors within 1 mg/l in the predicted FWMC. These models can be used to estimate NPS nitrate for unmonitored watersheds in similar areas, especially for drained agricultural areas where model performance was strongest, and to predict the nitrate reduction when various tile drainage management techniques are employed.
- Impacts of 21st-Century Climate Change on Hydrologic Extreme in the
Pacific Northwest Region of North America
- Authors: Ingrid M. Tohver; Alan F. Hamlet, Se-Yeun Lee
Abstract: Climate change projections for the Pacific Northwest (PNW) region of North America include warmer temperatures (T), reduced precipitation (P) in summer months, and increased P during all other seasons. Using a physically based hydrologic model and an ensemble of statistically downscaled global climate model scenarios produced by the Columbia Basin Climate Change Scenarios Project, we examine the nature of changing hydrologic extremes (floods and low flows) under natural conditions for about 300 river locations in the PNW. The combination of warming, and shifts in seasonal P regimes, results in increased flooding and more intense low flows for most of the basins in the PNW. Flood responses depend on average midwinter T and basin type. Mixed rain and snow basins, with average winter temperatures near freezing, typically show the largest increases in flood risk because of the combined effects of warming (increasing contributing basin area) and more winter P. Decreases in low flows are driven by loss of snowpack, drier summers, and increasing evapotranspiration in the simulations. Energy-limited basins on the west side of the Cascades show the strongest declines in low flows, whereas more arid, water-limited basins on the east side of the Cascades show smaller reductions in low flows. A fine-scale analysis of hydrologic extremes over the Olympic Peninsula echoes the results for the larger rivers discussed above, but provides additional detail about topographic gradients.
- Prediction of Annual Streambank Erosion for Sequoia National Forest,
- Authors: Hilda Kwan; Sherman Swanson
Abstract: Many bank erosion models have limitations that restrict their use in wildland settings. Scientists and land managers at the Sequoia National Forest would like to understand the mechanisms and rates of streambank erosion to evaluate management issues and post-wildfire effects. This study uses bank erosion hazard index (BEHI) and near-bank stress (NBS) methods developed in Rosgen (2006 Watershed Assessment of River Stability and Sediment Supply [WARSSS]) for predicting streambank erosion in a geographic area that is dominated by colluvium and in which streambank erosion modeling has not been previously evaluated. BEHI evaluates bank susceptibility to erosion based on bank angle, bank and bankfull height, rooting depth and density, surface protection, and stratification of material within the banks. NBS assesses energy distribution against the bank measured as a ratio of bankfull near-bank maximum depth to mean bankfull depth. We compared BEHI classes and NBS to actual bank erosion measured from 2008 to 2012. This index predicted streambank erosion with clear separation among BEHI ratings with R2 values of 0.76 for extreme, 0.37 for high/very high, 0.49 for moderate, and 0.70 for low BEHI. The relationships between measured erosion and BEHI extend the application of BEHI/NBS to a new region where they can inform management priorities, afforestation, stream/riparian restoration projects, and potentially burned area rehabilitation.
- Large Biases in Regression-Based Constituent Flux Estimates: Causes and
- Authors: Robert M. Hirsch
Abstract: It has been documented in the literature that, in some cases, widely used regression-based models can produce severely biased estimates of long-term mean river fluxes of various constituents. These models, estimated using sample values of concentration, discharge, and date, are used to compute estimated fluxes for a multiyear period at a daily time step. This study compares results of the LOADEST seven-parameter model, LOADEST five-parameter model, and the Weighted Regressions on Time, Discharge, and Season (WRTDS) model using subsampling of six very large datasets to better understand this bias problem. This analysis considers sample datasets for dissolved nitrate and total phosphorus. The results show that LOADEST-7 and LOADEST-5, although they often produce very nearly unbiased results, can produce highly biased results. This study identifies three conditions that can give rise to these severe biases: (1) lack of fit of the log of concentration vs. log discharge relationship, (2) substantial differences in the shape of this relationship across seasons, and (3) severely heteroscedastic residuals. The WRTDS model is more resistant to the bias problem than the LOADEST models but is not immune to them. Understanding the causes of the bias problem is crucial to selecting an appropriate method for flux computations. Diagnostic tools for identifying the potential for bias problems are introduced, and strategies for resolving bias problems are described.
- Featured Collection Introduction: Riparian Ecosystems and Buffers II
- Authors: Paul M. Mayer; Kathleen A. Dwire, Judith A. Okay, Philippe G. Vidon
First page: 529
- Postemergence Control of Microstegium vimineum on Riparian Restoration
Sites with Aquatic-Use Registered Herbicides
- Authors: Karen R. Hall; Jean Spooner, Robert J. Richardson, Steve T. Hoyle, Douglas J. Frederick
First page: 533
Abstract: Microstegium vimineum is an invasive grass introduced from Asia that has spread throughout riparian areas of the eastern United States threatening native riparian vegetation. Postemergence (POST) herbicides registered for aquatic use were evaluated for control of M. vimineum on two riparian restoration sites in the Piedmont and Upper Coastal Plain of North Carolina. This study found that standard and lower than standard rates of diquat, fluridone, flumioxazin, glyphosate, imazamox, and imazapyr reduced weed stem density and biomass at 6 and 30 weeks after treatment (WAT). Both rates of bispyribac and penoxsulam provided less control of M. vimineum. Visual ratings showed both rates of diquat, flumioxazin, imazamox, and imazapyr controlled 63-100% of M. vimineum at 6 WAT and 84-100% at 30 WAT. Fluridone and glyphosate provided slightly less control. Bispyribac and penoxsulam treatments provided less control at 6 and 30 WAT compared to the other treatments. Plots treated with both rates of diquat, flumioxazin, imazamox, and imazapyr were nearly devoid of all vegetation at 30 WAT. Recommendations include POST application of lower than standard rates of diquat, flumioxazin, fluridone, glyphosate, imazamox, and imazapyr on riparian restoration sites infested with M. vimineum. Immediate vegetation management measures including temporary and permanent plant cover should be employed on treated sites where weeds are completely eradicated to prevent erosion.
- Does Riparian Forest Restoration Thinning Enhance Biodiversity' The
Ecological Importance of Large Wood
- Authors: Michael M. Pollock; Timothy J. Beechie
First page: 543
Abstract: Intact riparian ecosystems are rich in biological diversity, but throughout the world, many have been degraded. Biodiversity declines, particularly of vertebrates, have led to experimental efforts to restore riparian forests by thinning young stands to accelerate creation of large diameter live trees. However, many vertebrates depend on large diameter deadwood that is standing as snags or fallen to the forest floor or fallen into streams. Therefore, we reviewed the sizes of deadwood and live trees used by different vertebrate species to understand which species are likely to benefit from different thinning treatments. We then examined how riparian thinning affects the long-term development of both large diameter live trees and deadwood. To this end, we used a forest growth model to examine how different forest thinning intensities might affect the long-term production and abundance of live trees and deadwood. Our results suggest that there are long-term habitat tradeoffs associated with different thinning intensities. Species that utilize large diameter live trees will benefit most from heavy thinning, whereas species that utilize large diameter deadwood will benefit most from light or no thinning. Because far more vertebrate species utilize large deadwood rather than large live trees, allowing riparian forests to naturally develop may result in the most rapid and sustained development of structural features important to most terrestrial and aquatic vertebrates.
- Streamside Forest Buffer Width Needed to Protect Stream Water Quality,
Habitat, and Organisms: A Literature Review
- Authors: Bernard W. Sweeney; J. Denis Newbold
First page: 560
Abstract: This literature review addresses how wide a streamside forest buffer needs to be to protect water quality, habitat, and biota for small streams (≤~100 km2 or ~5th order watershed) with a focus on eight functions: (1) subsurface nitrate removal varied inversely with subsurface water flux and for sites with water flux>50 l/m/day (~40% avg base flow to Chesapeake Bay) median removal efficiency was 55% (26-64%) for buffers 40 m wide; (2) sediment trapping was ~65 and ~85% for a 10- and 30-m buffer, respectively, based on streamside field or experimentally loaded sites; (3) stream channel width was significantly wider when bordered by ~25-m buffer (relative to no forest) with no additional widening for buffers ≥25 m; (4) channel meandering and bank erosion were lower in forest but more studies are needed to determine the effect of buffer width; (5) temperature remained within 2°C of levels in a fully forested watershed with a buffer ≥20 m but full protection against thermal change requires buffers ≥30 m; (6) large woody debris (LWD) has been poorly studied but we infer a buffer width equal to the height of mature streamside trees (~30 m) can provide natural input levels; (7, 8) macroinvertebrate and fish communities, and their instream habitat, remain near a natural or semi-natural state when buffered by ≥30 m of forest. Overall, buffers ≥30 m wide are needed to protect the physical, chemical, and biological integrity of small streams.
- Land Use and Climate Variability Amplify Carbon, Nutrient, and Contaminant
Pulses: A Review with Management Implications
- Authors: Sujay S. Kaushal; Paul M. Mayer, Philippe G. Vidon, Rose M. Smith, Michael J. Pennino, Tamara A. Newcomer, Shuiwang Duan, Claire Welty, Kenneth T. Belt
First page: 585
Abstract: Nonpoint source pollution from agriculture and urbanization is increasing globally at the same time climate extremes have increased in frequency and intensity. We review>200 studies of hydrologic and gaseous fluxes and show how the interaction between land use and climate variability alters magnitude and frequency of carbon, nutrient, and greenhouse gas pulses in watersheds. Agricultural and urban watersheds respond similarly to climate variability due to headwater alteration and loss of ecosystem services to buffer runoff and temperature changes. Organic carbon concentrations/exports increase and organic carbon quality changes with runoff. Nitrogen and phosphorus exports increase during floods (sometimes by an order of magnitude) and decrease during droughts. Relationships between annual runoff and nitrogen and phosphorus exports differ across land use. CH4 and N2O pulses in riparian zones/floodplains predominantly increase with: flooding, warming, low oxygen, nutrient enrichment, and organic carbon. CH4, N2O, and CO2 pulses in streams/rivers increase due to similar factors but effects of floods are less known compared to base flow/droughts. Emerging questions include: (1) What factors influence lag times of contaminant pulses in response to extreme events' (2) What drives resistance/resilience to hydrologic and gaseous pulses' We conclude with eight recommendations for managing watershed pulses in response to interactive effects of land use and climate change.
- Instream Large Wood: Denitrification Hotspots with Low N2O Production
- Authors: Julia G. Lazar; Arthur J. Gold, Kelly Addy, Paul M. Mayer, Kenneth J. Forshay, Peter M. Groffman
First page: 615
Abstract: We examined the effect of instream large wood on denitrification capacity in two contrasting, lower order streams — one that drains an agricultural watershed with no riparian forest and minimal stores of instream large wood and another that drains a forested watershed with an extensive riparian forest and abundant instream large wood. We incubated two types of wood substrates (fresh wood blocks and extant streambed wood) and an artificial stone substrate for nine weeks in each stream. After in situ incubation, we collected the substrates and their attached biofilms and established laboratory-based mesocosm assays with stream water amended with 15N-labeled nitrate-N. Wood substrates at the forested site had significantly higher denitrification than wood substrates from the agricultural site and artificial stone substrates from either site. Nitrate-N removal rates were markedly higher on woody substrates compared to artificial stones at both sites. Nitrate-N removal rates were significantly correlated with biofilm biomass. Denitrification capacity accounted for only a portion of nitrate-N removal observed within the mesocosms in both the wood controls and instream substrates. N2 accounted for 99.7% of total denitrification. Restoration practices that generate large wood in streams should be encouraged for N removal and do not appear to generate high risks of instream N2O generation.
- Influence of Restoration Age and Riparian Vegetation on Reach-Scale
Nutrient Retention in Restored Urban Streams
- Authors: Sara K. McMillan; Alea K. Tuttle, Gregory D. Jennings, Angela Gardner
First page: 626
Abstract: In urban watersheds, stormwater inputs largely bypass the buffering capacity of riparian zones through direct inputs of drainage pipes and lowered groundwater tables. However, vegetation near the stream can still influence instream nutrient transformations via maintenance of streambank stability, input of woody debris, modulation of organic matter sources, and temperature regulation. Stream restoration seeks to mimic many of these functions by engineering channel complexity, grading stream banks to reconnect incised channels, and replanting lost riparian vegetation. The goal of this study was to quantify these effects by measuring nitrate and phosphate uptake in five restored streams in Charlotte and Raleigh, North Carolina, with a range of restoration ages. Using nutrient spiraling methods, uptake velocity of nitrate (0.02-3.56 mm/min) and phosphate (0.14-19.1 mm/min) was similar to other urban restored streams and higher than unimpacted forested streams with variability influenced by restoration age and geomorphology. Using a multiple linear regression approach, reach-scale phosphate uptake was greater in newly restored sites, which was attributed to assimilation by algal biofilms, whereas nitrate uptake was highest in older sites potentially due to greater channel stability and establishment of microbial communities. The patterns we observed highlight the influence of riparian vegetation on energy inputs (e.g., heat, organic matter) and thereby on nutrient retention.
- Hydrobiogeochemical Controls on Riparian Nutrient and Greenhouse Gas
Dynamics: 10 Years Post-Restoration
- Authors: Philippe Vidon; Pierre-Andre Jacinthe, Xiaoqiang Liu, Katelin Fisher, Matthew Baker
First page: 639
Abstract: Little is known about the impact of agricultural legacy on subsurface biogeochemical processes in the years following restoration of riparian wetlands (WLs). More knowledge is also needed on the relative importance of seasons, precipitation events, and inputs of water and nutrients driving nitrogen (N), phosphorus (P), sulfur (S), and greenhouse gas (GHG) (N2O, CO2, CH4) dynamics in these systems. This investigation of a riparian zone comprising a restored WL area and a nonrestored well-drained alluvium (AL) area in the United States Midwest revealed that despite successful hydrological restoration a decade earlier, biogeochemical conditions in the WL area remained less anoxic than in natural WLs, and not significantly different from those in the AL area. No significant differences in N, P, S, and C compound concentrations or fluxes were observed between the AL and WL areas. Over the duration of the study, nitrate (NO3−) and soluble reactive phosphorus appeared to be primarily driven by hillslope contributions. Ammonium (NH4+), sulfate (SO42−), and CO2 responded strongly to seasonal changes in biogeochemical conditions in the riparian zone, while N2O and CH4 fluxes were most influenced by large rewetting events. Overall, our results challenge overly simplistic assumptions derived from direct interpretation of redox thermodynamics, and show complex patterns of solutes and GHGs at the riparian zone scale.
- Groundwater Nitrate Concentration Reductions in a Riparian Buffer Enrolled
in the NC Conservation Reserve Enhancement Program
- Authors: Jacob D. Wiseman; Michael R. Burchell, Garry L. Grabow, Deanna L. Osmond, T.L. Messer
First page: 653
Abstract: Riparian buffers have been used for many years as a best management practice to decrease the effects of nonpoint pollution from watersheds. The NC Conservation Reserve Enhancement Program (NC CREP) has established buffers to treat groundwater nitrate-nitrogen (NO3−-N) from agricultural sources in multiple river basins. A maturing 46 m wide riparian buffer enrolled in NC CREP was studied to determine its effectiveness in reducing groundwater NO3−-N concentrations from a cattle pasture fertilized with poultry litter. Three monitoring blocks that included groundwater quality wells, water table wells, and soil redox probes, were established in the buffer. NO3−-N concentrations decreased significantly across the buffer in all of the monitoring blocks with mean reductions of 76-92%. Many biological processes, including denitrification and plant uptake, may have been responsible for the observed NO3−-N reductions but could not be differentiated in this study. However, mean reductions in Cl− concentrations ranged from 48-65% through the blocks, which indicated that dilution was an important factor in observed NO3−-N reductions. These findings should be carefully considered for future buffer enrollments when assigning nitrogen removal credits.
- Field Testing the Riparian Ecosystem Management Model on a Riparian Buffer
in the North Carolina
Upper Coastal Plain
- Authors: Amey S. Tilak; Michael R. Burchell, Mohamed A. Youssef, Richard R. Lowrance, Randy G. Williams
First page: 665
Abstract: The riparian ecosystem management model (REMM) was field tested using five years (2005-2009) of measured hydrologic and water quality data on a riparian buffer located in the Tar-Pamlico River Basin, North Carolina. The buffer site received NO3-N loading from an agricultural field that was fertilized with inorganic fertilizer. Field results showed the buffer reduced groundwater NO3-N concentration moving to the stream over a five-year period. REMM was calibrated hydrologically using daily field-measured water table depths (WTDs), and with monthly NO3-N concentrations in groundwater wells. Results showed simulated WTDs and NO3-N concentrations in good agreement with measured values. The mean absolute error and Willmott's index of agreement for WTDs varied from 13-45 cm and 0.72-0.92, respectively, while the root mean square error and Willmott's index of agreement for NO3-N concentrations ranged from 1.04-5.92 mg/l and 0.1-0.86, respectively, over the five-year period. REMM predicted plant nitrogen (N) uptake and denitrification were within ranges reported in other riparian buffer field studies. The calibrated and validated REMM was used to simulate 33 years of buffer performance at the site. Results showed that on average the buffer reduced NO3-N concentrations from 12 mg/l at the field edge to 0.7 mg/l at the stream edge over the simulation period, while the total N and NO3-N load reductions from the field edge to the stream were 77 and 82%, respectively.
- A General Equilibrium Model of Ecosystem Services in a River Basin
- Authors: Travis Warziniack
First page: 683
Abstract: This study builds a general equilibrium model of ecosystem services, with sectors of the economy competing for use of the environment. The model recognizes that production processes in the real world require a combination of natural and human inputs, and understanding the value of these inputs and their competing uses is necessary when considering policies of resource conservation. We demonstrate the model with a numerical example of the Mississippi-Atchafalaya river basin, in which grain production in the upper basin causes hypoxia that causes damages to the downstream fishing industry. We show that the size of damages is dependent on both environmental and economic shocks. While the potential damages to fishing are large, most of the damage occurs from economic forces rather than a more intensive use of nitrogen fertilizers. We show that these damages are exacerbated by increases in rainfall, which will likely get worse with climate change. We discuss welfare effects from a tax on nitrogen fertilizers and investments in riparian buffers. A 3% nitrogen tax would reduce the size of the hypoxic zone by 11% at a cost of 2% of Iowa's corn output. In comparison, riparian buffers are likely to be less costly and more popular politically.
- Cropland Riparian Buffers throughout Chesapeake Bay Watershed: Spatial
Patterns and Effects on Nitrate Loads Delivered to Streams
- Authors: Donald E. Weller; Matthew E. Baker
First page: 696
Abstract: We used statistical models to provide the first empirical estimates of riparian buffer effects on the cropland nitrate load to streams throughout the Chesapeake Bay watershed. For each of 1,964 subbasins, we quantified the 1990 prevalence of cropland and riparian buffers. Cropland was considered buffered if the topographic flow path connecting it to a stream traversed a streamside forest or wetland. We applied a model that predicts stream nitrate concentration based on physiographic province and the watershed proportions of unbuffered and buffered cropland. We used another model to predict annual streamflow based on precipitation and temperature, and then multiplied the predicted flows and concentrations to estimate 1990 annual nitrate loads. Across the entire Chesapeake watershed, croplands released 92.3 Gg of nitrate nitrogen, but 19.8 Gg of that was removed by riparian buffers. At most, 29.4 Gg more might have been removed if buffer gaps were restored so that all cropland was buffered. The other 43.1 Gg of cropland load cannot be addressed with riparian buffers. The Coastal Plain physiographic province provided 52% of the existing buffer reduction of Bay-wide nitrate loads and 36% of potential additional removal from buffer restoration in cropland buffer gaps. Existing and restorable nitrate removal in buffers were lower in the other three major provinces because of less cropland, lower buffer prevalence, and lower average buffer nitrate removal efficiency.
- Contested Waters: An Environmental History of the Colorado River, A.R.
Summitt. University Press of Colorado, 5589 Arapahoe Ave., Ste. 2066,
Boulder, Colorado 80303. 2013. 286 pages. $35. ISBN 978-1-60732-201-6.
- Authors: Cindy Dyballa
First page: 805
- Long-Term High-Resolution Radar Rainfall Fields for Urban Hydrology
- Authors: Daniel B. Wright; James A. Smith, Gabriele Villarini, Mary Lynn Baeck
First page: 713
Abstract: Accurate records of high-resolution rainfall fields are essential in urban hydrology, and are lacking in many areas. We develop a high-resolution (15 min, 1 km2) radar rainfall data set for Charlotte, North Carolina during the 2001-2010 period using the Hydro-NEXRAD system with radar reflectivity from the National Weather Service Weather Surveillance Radar 1988 Doppler weather radar located in Greer, South Carolina. A dense network of 71 rain gages is used for estimating and correcting radar rainfall biases. Radar rainfall estimates with daily mean field bias (MFB) correction accurately capture the spatial and temporal structure of extreme rainfall, but bias correction at finer timescales can improve cold-season and tropical cyclone rainfall estimates. Approximately 25 rain gages are sufficient to estimate daily MFB over an area of at least 2,500 km2, suggesting that robust bias correction is feasible in many urban areas. Conditional (rain-rate dependent) bias can be removed, but at the expense of other performance criteria such as mean square error. Hydro-NEXRAD radar rainfall estimates are also compared with the coarser resolution (hourly, 16 km2) Stage IV operational rainfall product. Stage IV is adequate for flood water balance studies but is insufficient for applications such as urban flood modeling, in which the temporal and spatial scales of relevant hydrologic processes are short. We recommend the increased use of high-resolution radar rainfall fields in urban hydrology.
- Upstream Sediment-Control Dams: Five Decades of Experience in the Rapidly
Eroding Dahan River Basin, Taiwan
- Authors: Hsiao-Wen Wang; G. Mathias Kondolf
First page: 735
Abstract: Sedimentation is emerging as a key issue in sustainable reservoir management. One approach to controlling reservoir sedimentation is to trap sediment in hydraulic structures upstream of the reservoir. In the 1,163-km2 catchment of the Dahan River (Taiwan) over 120 “sabo” dams were built to reduce sediment yield to Shihmen Reservoir. Built in 1963 for water supply, Shihmen has lost over 40% of its 290-Mm3 storage capacity to sedimentation. Most of these upstream structures were small, but three had capacities>9 Mm3. Field measurements and historical data from the Water Resources Agency show most smaller dams had filled with sediment by 1976. The three largest were full or nearly so by 2007, when one (Barlin Dam) failed, releasing a pulse of 7.5 Mm3, most of its 10.4 Mm3 stored sediment downstream. The Central Range of Taiwan is rapidly eroding (denudation rates 3-6 mm/yr), so geologically high loads make sediment problems manifest sooner. Even in other environments, however, eventually small dams built upstream of large reservoirs are likely to fill themselves, creating multiple small sediment-filled reservoirs, some located in sites inaccessible to mechanical removal. Our analysis suggests sabo dams do not offer a long-term basis for controlling reservoir sedimentation in such a high-sediment yield environment. Sustainable solutions must somehow pass sediment downstream, as would be accomplished by a sediment bypass around Shihmen Reservoir, as now being studied.
- Geospatial and Temporal Analysis of a 20-Year Record of Landsat-Based
Water Clarity in Minnesota's 10,000 Lakes
- Authors: Leif G. Olmanson; Patrick L. Brezonik, Marvin E. Bauer
First page: 748
Abstract: A large 20-year database on water clarity for all Minnesota lakes ≥8 ha was analyzed statistically for spatial distributions, temporal trends, and relationships with in-lake and watershed factors that potentially affect lake clarity. The database includes Landsat-based water clarity estimates expressed in terms of Secchi depth (SDLandsat), an integrative measure of water quality, for more than 10,500 lakes for time periods centered around 1985, 1990, 1995, 2000, and 2005. Minnesota lake clarity is lower (more turbid) in the south and southwest and clearer in the north and northeast; this pattern is evident at the levels of individual lakes and ecoregions. Temporal trends in clarity were detected in ~11% of the lakes: 4.6% had improving clarity and 6.2% had decreasing clarity. Ecoregions in southern and western Minnesota, where agriculture is the predominant land use, had higher percentages of lakes with decreasing clarity than the rest of the state, and small and shallow lakes had higher percentages of decreasing clarity trends than large and deep lakes. The mean SDLandsat statewide remained stable from 1985 to 2005 but decreased in ecoregions dominated by agricultural land use. Deep lakes had higher clarity than shallow lakes statewide and for lakes grouped by land cover. SDLandsat decreased as the percentage of agriculture and/or urban area increased at county and catchment levels and it increased with increasing forested land.
- Use of Hydrologic Landscape Classification to Diagnose Streamflow
Predictability in Oregon
- Authors: Sopan D. Patil; Parker J. Wigington, Scott G. Leibowitz, Randy L. Comeleo
First page: 762
Abstract: We implement a spatially lumped hydrologic model to predict daily streamflow at 88 catchments within the state of Oregon and analyze its performance using the Oregon Hydrologic Landscape (OHL) classification. OHL is used to identify the physio-climatic conditions that favor high (or low) streamflow predictability. High prediction catchments (Nash-Sutcliffe efficiency of Q (NS) > 0.75) are mainly classified as rain dominated with very wet climate, low aquifer permeability, and low to medium soil permeability. Most of them are located west of the Cascade Mountain Range. Conversely, most low prediction catchments (NS
- A Cooperative Approach to Reduce Water Pollution Abatement Cost in an
Interjurisdictional Lake Basin
- Authors: Laijun Zhao; Wei Huang, H. Oliver Gao, Jian Xue, Changmin Li, Yue Hu
First page: 777
Abstract: A cooperative approach via transfer fee was developed to improve the cost-effectiveness of water pollution control in interjurisdictional lake basin management in China. Different from the existing literature that studies water quality trading and pollution reduction at micro levels (i.e., focusing on enterprises and firms), this article explores cooperative pollution reduction strategies from a macro level, targeting multiple jurisdictional regions. The merits of this new approach include: (1) improving the cost-effectiveness of pollution reduction by making use of the cost differentiation in pollution reduction between industries and municipal sewage plants, and between different administrative areas; (2) managing payments for ecosystem services by horizontal transfer payment; and (3) incorporating the concepts of game, cooperation, coordination, and watershed-based management in implementation. For empirical demonstration, a bilevel optimization model was built and calibrated using the 2005 data of the Lake Tai basin to work out the optimal solutions for cooperative chemical oxygen demand (COD) reduction. Results show that policies based on this new approach can significantly reduce the overall COD abatement costs for the basin as well as the individual jurisdictional regions compared to the current practice.
- Load Estimation Method Using Distributions with Covariates: A Comparison
with Commonly Used Estimation Methods
- Authors: Sébastien Raymond; Alain Mailhot, Guillaume Talbot, Patrick Gagnon, Alain N. Rousseau, Florentina Moatar
First page: 791
Abstract: Load estimates obtained using an approach based on statistical distributions with parameters expressed as a function of covariates (e.g., streamflow) (distribution with covariates hereafter called DC method) were compared to four load estimation methods: (1) flow-weighted mean concentration; (2) integral regression; (3) segmented regression (the last two with Ferguson's correction factor); and (4) hydrograph separation methods. A total of 25 datasets (from 19 stations) of daily concentrations of total dissolved solids, nutrients, or suspended particulate matter were used. The selected stations represented a wide range of hydrological conditions. Annual flux errors were determined by randomly generating 50 monthly sample series from daily series. Annual and interannual biases and dispersions were evaluated and compared. The impact of sampling frequency was investigated through the generation of bimonthly and weekly surveys. Interannual uncertainty analysis showed that the performance of the DC method was comparable with those of the other methods, except for stations showing high hydrological variability. In this case, the DC method performed better, with annual biases lower than those characterizing the other methods. Results show that the DC method generated the smallest pollutant load errors when considering a monthly sampling frequency for rivers showing high variability in hydrological conditions and contaminant concentrations.