- 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.
- Hydrologic Controls on Nitrogen and Phosphorous Dynamics in Relict Oxbow
Wetlands Adjacent to an Urban Restored Stream
- Authors: Melanie D. Harrison; Andrew J. Miller, Peter M. Groffman, Paul M. Mayer, Sujay S. Kaushal
Abstract: Although wetlands are known to be sinks for nitrogen (N) and phosphorus (P), their function in urban watersheds remains unclear. We analyzed water and nitrate (NO3−) and phosphate (PO43−) dynamics during precipitation events in two oxbow wetlands that were created during geomorphic stream restoration in Baltimore County, Maryland that varied in the nature and extent of connectivity to the adjacent stream. Oxbow 1 (Ox1) received 1.6-4.2% and Oxbow 2 (Ox2) received 4.2-7.4% of cumulative streamflow during storm events from subsurface seepage (Ox1) and surface flow (Ox2). The retention time of incoming stormwater ranged from 0.2 to 6.7 days in Ox1 and 1.8 to 4.3 days in Ox2. Retention rates in the wetlands ranged from 0.25 to 2.74 g N/m2/day in Ox1 and 0.29 to 1.94 g N/m2/day in Ox2. Percent retention of the NO3−-N load that entered the wetlands during the storm events ranged from 64 to 87% and 23 to 26%, in Ox1 and Ox2, respectively. During all four storm events, Ox1 and Ox2 were a small net source of dissolved PO43− to the adjacent stream (i.e., more P exited than entered the wetland), releasing P at a rate of 0.23-20.83 mg P/m2/day and 3.43-24.84 mg P/m2/day, respectively. N and P removal efficiency of the oxbows were regulated by hydrologic connectivity, hydraulic loading, and retention time. Incidental oxbow wetlands have potential to receive urban stream and storm flow and to be significant N sinks, but they may be sources of P in urban watersheds.
- Daily Bank Erosion Rates in the Lower Yellow River before and after Dam
- Authors: Junqiang Xia; Tao Li, Xiaojuan Li, Xiaolei Zhang, Quanli Zong
Abstract: During the period of water impoundment and sediment detention of the Sanmenxia Reservoir, riverbank erosion processes played a key role in the channel evolution of the Lower Yellow River (LYR). However, research into bank erosion rates of the LYR has been neglected due to the lack of direct field monitoring. In this study, an indirect method is proposed to determine bank erosion rates at daily time scales by outlining a detailed calculation procedure using measured hydrological data. A total of 810 data points of daily bank erosion rates before and after the construction of Sanmenxia Dam was calculated at seven hydrometric sections along the LYR, with the corresponding values of the bank stability coefficient and the width-to-depth ratio also being calculated. Empirical relations were then developed to estimate the daily bank erosion rates, using these parameters at the sections. Temporal and spatial variability in daily bank erosion rates in the LYR before and after dam construction were also investigated, revealing that: (1) the bank erosion rates had a mean value of 16.7-29.1 m/day in the braided reach, with a maximum value of 290.0 m/day, while they were relatively low in the meandering reach, with a mean value of 2.5 m/day; (2) the erosion rates before dam construction were slightly greater than those after dam construction, with the difference reaching 5-10 m/day in the braided reach, decreasing in the transitional reach gradually, and being slight in the meandering reach.
- Potential Impacts of Climate Change on the Reliability of Water and
Hydropower Supply from a Multipurpose Dam in South Korea
- Authors: Jong Y. Park; Seong J. Kim
Abstract: Future climate change is a source of growing concerns for the supply of energy and resources, and it may have significant impacts on industry and the economy. Major effects are likely to arise from changes to the freshwater resources system, due to the connection of energy generation to these water systems. Using future climate data downscaled by a stochastic weather generator, this study investigates the potential impacts of climate change on long-term reservoir operations at the Chungju multipurpose dam in South Korea, specifically considering the reliability of the supply of water and hydropower. A reservoir model, Hydrologic Engineering Center-Reservoir System Simulation (HEC-ResSim), was used to simulate the ability of the dam to supply water and hydropower under different conditions. The hydrologic model Soil and Water Assessment Tool was used to determine the HEC-ResSim boundary conditions, including daily dam inflow from the 6,642 km2 watershed into the 2.75 Gm3 capacity reservoir. Projections of the future climate indicate that temperature and precipitation during 2070-2099 (2080s) show an increase of +4.1°C and 19.4%, respectively, based on the baseline (1990-2009). The results from the models suggest that, in the 2080s, the average annual water supply and hydropower production would change by +19.8 to +56.5% and by +33.9 to 92.3%, respectively. Model simulations suggest that under the new climatic conditions, the reliability of water and hydropower supply would be generally improved, as a consequence of increased dam inflow.
- A 576-Year Weber River Streamflow Reconstruction from Tree Rings for Water
Resource Risk Assessment in the Wasatch Front, Utah
- Authors: Matthew F. Bekker; R. Justin DeRose, Brendan M. Buckley, Roger K. Kjelgren, Nathan S. Gill
Abstract: We present a 576-year tree-ring-based reconstruction of streamflow for northern Utah's Weber River that exhibits considerable interannual and decadal-scale variability. While the 20th Century instrumental period includes several extreme individual dry years, it was the century with the fewest such years of the entire reconstruction. Extended droughts were more severe in duration, magnitude, and intensity prior to the instrumental record, including the most protracted drought of the record, which spanned 16 years from 1703 to 1718. Extreme wet years and periods are also a regular feature of the reconstruction. A strong early 17th Century pluvial exceeds the early 20th Century pluvial in magnitude, duration, and intensity, and dwarfs the 1980s wet period that caused significant flooding along the Wasatch Front. The long-term hydroclimatology of northern Utah is marked by considerable uncertainty; hence, our reconstruction provides water managers with a more complete record of water resource variability for assessment of the risk of droughts and floods for one of the largest and most rapidly growing population centers in the Intermountain West.
- GIS-Based Stream Classification in a Mountain Watershed for Jurisdictional
- Authors: Brian S. Caruso
Abstract: This study analyzed stream characteristics in a mountain watershed in southwestern Colorado and developed a three-level hierarchical classification scheme using national datasets to demonstrate jurisdictional evaluation as “waters of the United States (U.S.)” under U.S. Clean Water Act Section 404 at the watershed scale. The National Hydrography Dataset and USGS StreamStats were used with field observations to classify streams in the 53 km2 Cement Creek Watershed based on flow duration (Level 1), stream order (Level 2), and other biophysical metrics (Level 3). Kruskal-Wallis tests and discriminant analysis showed significant differences among Level 2 classes. Level 3 classification used cluster analysis for stream length, distance to the downstream traditional navigable water (TNW), and the ratio of mean annual flow from the source stream to the TNW. Results showed all perennial and intermittent streams are jurisdictional relatively permanent waters (RPWs), which include over a third of all streams, 64% are intermittent or ephemeral, and almost half are ephemeral first order. All ephemeral reaches are non-RPWs requiring significant nexus evaluation to determine jurisdiction. These ephemeral first-order streams can contribute 5% of the annual flow to the TNW at the confluence, while the Cement Creek main stem contributes 21% of the TNW flow. The study demonstrated that the classification provides key biophysical and regulatory information to aid jurisdictional evaluations in mountain watersheds.
- Water Appropriation Systems for Adapting to Water Shortages in Iraq
- Authors: Dina A. Salman; Saud A. Amer, Frank A. Ward
Abstract: Climate variability and population growth have intensified the search internationally for measures to adapt to fluctuations in water supplies. An example can be found in the lower part of the transboundary Tigris-Euphrates Basin where water shortages in 2008-2009 resulted in high economic costs to irrigation farmers. Losses to irrigators in the lower basin have made a compelling case to identify flexible methods to adapt to water shortage. Few published studies have systematically examined ways to enhance the flexibility of water appropriation systems to adapt to water shortage. This article addresses an ongoing challenge in water governance by examining how profitability at both the farm and basin levels is affected by various water appropriation systems. Four water appropriation systems are compared for impacts on farm income under each of three water supply scenarios. Results show that a (1) proportional sharing of water shortages among provinces and (2) unrestricted water trading rank as the top two appropriation systems. The shadow price of water for irrigation rises from zero at a full water supply level to US$93/1,000 m3 when supply falls to 20% of full levels. Similar methods could be used to analyze challenges facing the design or implementation of water appropriation systems in the world's irrigated regions.
- Hydrologic Impact Assessment of Land Cover Change and Stormwater
Management Using the Hydrologic Footprint Residence
- Authors: M.H. Giacomoni; R. Gomez, E.Z. Berglund
Abstract: Urbanization impacts the stormwater regime through increased runoff volumes and velocities. Detention ponds and low impact development (LID) strategies may be implemented to control stormwater runoff. Typically, mitigation strategies are designed to maintain postdevelopment peak flows at predevelopment levels for a set of design storms. Peak flow does not capture the extent of changes to the hydrologic flow regime, and the hydrologic footprint residence (HFR) was developed to calculate the area and duration of inundated land during a storm. This study couples a cellular automata land cover change model with a hydrologic and hydraulic framework to generate spatial projections of future development on the fringe of a rapidly urbanizing metropolitan area. The hydrologic flow regime is characterized for existing and projected land cover patterns under detention pond and LID-based control, using the HFR and peak flow values. Results demonstrate that for less intense and frequent rainfall events, LID solutions are better with respect to HFR; for larger storms, detention pond strategies perform better with respect to HFR and peak flow.
- Multiscale Analysis of Hydrology in a Mountaintop Mine-Impacted Watershed
- Authors: Nicolas P. Zegre; Andrew J. Miller, Aaron Maxwell, Samuel J. Lamont
Abstract: In the Appalachian region of the eastern United States, mountaintop removal mining (MTM) is a dominant driver of land-cover change, impacting 6.8% of the largely forested 4.86 million ha coal fields region. Recent catastrophic flooding and documented biological impairment downstream of MTM has drawn sharp criticism to this practice. Despite its extent, scale, and use since the 1970s, the impact of MTM on hydrology is poorly understood. Therefore, the goal of this study was a multiscale evaluation to establish the nature of hydrologic impacts associated with MTM. To quantify the extent of MTM, land-cover change over the lifetime of this practice is estimated for a mesoscale watershed in southern West Virginia. To assess hydrologic impacts, we conducted long-term trend analyses to evaluate for systematic changes in hydrology at the mesoscale, and conducted hydrometric and response time modeling to characterize storm-scale responses of a MTM-impacted headwater catchment. Results show a general trend in the conversion of forests to mines, and significant decreases in maximum streamflow and variability, and increases in base-flow ratio attributed to valley fills and deep mine drainage. Decreases in variability are shown across spatial and temporal scales having important implications for water quantity and quality. However, considerable research is necessary to understand how MTM impacts hydrology. In an effort to inform future research, we identify existing knowledge gaps and limitations of our study.
- A Recourse-Based Interval Fuzzy Programming Model for Point-Nonpoint
Source Effluent Trading under Uncertainty
- Authors: Y.P. Li; G.H. Huang, H.Z. Li, J. Liu
Abstract: In this study, a recourse-based interval fuzzy programming (RIFP) model is developed for tackling uncertainties expressed as fuzzy, interval, and/or probabilistic forms in an effluent trading program. It can incorporate preregulated water-pollution control policies directly into its optimization process, such that an effective linkage between environmental regulations and economic implications (i.e., penalties) caused by improper policies due to uncertainty existence can be provided. The RIFP model is applied to point-nonpoint source effluent trading of the Xiangxi River in China. The efficiency of trading efforts between water quality improvement and net system benefit under different degrees of satisfying discharge limits is analyzed. The results are able to help support (1) formulation of water-pollution control strategies under various economic objectives and system-reliability constraints, (2) selection of the desired effluent trading pattern for point and nonpoint sources, and (3) generation of tradeoffs among system benefit, satisfaction degree, and pollutant mitigation under multiple uncertainties. Compared with the traditional regulatory approaches, the results demonstrate that the water-pollution control program can be performed more cost-effectively through trading than nontrading.
- Linking Landscape Characteristics and High Stream Nitrogen in the Oregon
Coast Range: Red Alder Complicates Use of Nutrient Criteria
- Authors: Effie A. Greathouse; Jana E. Compton, John Van Sickle
Abstract: Red alder (Alnus rubra), a nitrogen(N)-fixing deciduous broadleaf tree, can strongly influence N concentrations in western Oregon and Washington. We compiled a database of stream N and GIS-derived landscape characteristics in order to examine geographic variation in N across the Oregon Coast Range. Basal area of alder, expressed as a percent of watershed area, accounted for 37% and 38% of the variation in summer nitrate and total N (TN) concentrations, respectively. Relationships between alder and nitrate were strongest in winter when streamflow and landscape connections are highest. Distance to the coast and latitude, potential surrogates for sea salt inputs, and watershed area were also related to nitrate concentrations in an all-subsets regression analysis, which accounted for 46% of the variation in summer nitrate concentrations. The model with the lowest Akaike's Information Criterion did not include developed or agricultural land cover, probably because few watersheds in our database had substantial levels of these land cover classes. Our results provide evidence, at a regional scale, that background sources and processes cause many Coast Range streams to exceed proposed nutrient criteria, and that the prevalence of a single tree species (N-fixing red alder) exerts a dominant control over stream N concentrations across this region.
- Quantifying the Impact of Renewable Energy Futures on Cooling Water Use
- Authors: Jonathan Baker; Kenneth Strzepek, William Farmer, C. Adam Schlosser
Abstract: This article presents an empirically based model, WiCTS (Withdrawal and Consumption for Thermoelectric Systems), to estimate regional water withdrawals and consumption implied by any electricity generation portfolio. WiTCS uses water use rates, developed at the substate level, to predict water use by scaling the rates with predicted energy generation. The capability of WiCTS is demonstrated by assessing the impact of renewable electricity generation scenarios on water use in the United States (U.S.) through 2050. The energy generation scenarios are taken from the Renewable Energy Futures Study performed by the U.S. National Renewable Energy Laboratory of the U.S. Department of Energy. Results indicate reductions in water use are achieved under these renewable energy scenarios. The analysis further explores the impact of two modifications to the modeling framework. The first modification presumes geothermal and concentrated solar power generation technologies employ water-intensive cooling systems vs. cooling technology that requires no water. The second modification presumes all water-intensive cooling technologies use closed cycle cooling (as opposed to once-through cooling) technologies by 2050. Results based on one of the renewable generation scenarios indicate water use increases by over 20% under the first modification, and water consumption increases by approximately 40% while water withdrawals decrease by over 85% under the second modification.
- Instream Restoration to Improve the Ecohydrologic Function of a Subalpine
Meadow: Pre-implementation Modeling with HEC-RAS
- Authors: Courtney E. Moore; Steven P. Loheide, Christopher S. Lowry, Jessica D. Lundquist
Abstract: Vegetation in subalpine meadows in the Sierra Nevada Mountains is particularly vulnerable to lowering of groundwater levels because wet meadow vegetation is reliant upon shallow groundwater during the dry summer growing season. These ecosystems are especially vulnerable to channel incision as meadow aquifers are hydrologically connected to tributaries, and many have not yet recovered from previous anthropogenic influences. While instream restoration projects have become a common approach, lack of postrestoration monitoring and communication often result in a trial-and-error approach. In this study we demonstrate that preimplementation modeling of possible instream restoration solutions, chosen to raise stream stage and subsequently groundwater levels, is a useful tool for evaluating and comparing potential channel modifications. Modeling allows us to identify strategic locations and specific methods. Results show additional sediment depth and roughness on tributaries along with introduced woody debris (simulated by high roughness) on the Tuolumne River are the most effective means of raising stream stage. Results demonstrate that restoration efforts are most efficient in tributary streams. Managers and planners can more efficiently direct resources while minimizing the potential for negative impacts or failed restoration projects by modeling the possible effects of multiple restoration scenarios before implementation.
- 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.