- Effects of Climate and Land Cover on Hydrology in the Southeastern U.S.:
Potential Impacts on Watershed Planning
- Authors: Jacob H. LaFontaine; Lauren E. Hay, Roland J. Viger, R. Steve Regan, Steven L. Markstrom
Abstract: The hydrologic response to statistically downscaled general circulation model simulations of daily surface climate and land cover through 2099 was assessed for the Apalachicola‐Chattahoochee‐Flint River Basin located in the southeastern United States. Projections of climate, urbanization, vegetation, and surface‐depression storage capacity were used as inputs to the Precipitation‐Runoff Modeling System to simulate projected impacts on hydrologic response. Surface runoff substantially increased when land cover change was applied. However, once the surface depression storage was added to mitigate the land cover change and increases of surface runoff (due to urbanization), the groundwater flow component then increased. For hydrologic studies that include projections of land cover change (urbanization in particular), any analysis of runoff beyond the change in total runoff should include effects of stormwater management practices as these features affect flow timing and magnitude and may be useful in mitigating land cover change impacts on streamflow. Potential changes in water availability and how biota may respond to changes in flow regime in response to climate and land cover change may prove challenging for managers attempting to balance the needs of future development and the environment. However, these models are still useful for assessing the relative impacts of climate and land cover change and for evaluating tradeoffs when managing to mitigate different stressors.
- Accuracy Assessment of NOAA Gridded Daily Reference Evapotranspiration for
the Texas High Plains
- Authors: Jerry Moorhead; Prasanna Gowda, Mike Hobbins, Gabriel Senay, George Paul, Thomas Marek, Dana Porter
Abstract: The National Oceanic and Atmospheric Administration (NOAA) provides daily reference evapotranspiration (ETref) maps for the contiguous United States using climatic data from North American Land Data Assimilation System (NLDAS). This data provides large‐scale spatial representation of ETref, which is essential for regional scale water resources management. Data used in the development of NOAA daily ETref maps are derived from observations over surfaces that are different from short (grass — ETos) or tall (alfalfa — ETrs) reference crops, often in nonagricultural settings, which carries an unknown discrepancy between assumed and actual conditions. In this study, NOAA daily ETos and ETrs maps were evaluated for accuracy, using observed data from the Texas High Plains Evapotranspiration (TXHPET) network. Daily ETos, ETrs and the climatic data (air temperature, wind speed, and solar radiation) used for calculating ETref were extracted from the NOAA maps for TXHPET locations and compared against ground measurements on reference grass surfaces. NOAA ETref maps generally overestimated the TXHPET observations (1.4 and 2.2 mm/day ETos and ETrs, respectively), which may be attributed to errors in the NLDAS modeled air temperature and wind speed, to which reference ETref is most sensitive. Therefore, a bias correction to NLDAS modeled air temperature and wind speed data, or adjustment to the resulting NOAA ETref, may be needed to improve the accuracy of NOAA ETref maps.
- A Cost‐Effective Laser Scanning Method for Mapping Stream Channel
Geometry and Roughness
- Authors: Norris Lam; Marcus Nathanson, Niclas Lundgren, Robin Rehnström, Steve W. Lyon
Abstract: This brief pilot study implements a camera‐based laser scanning system that potentially offers a viable, cost‐effective alternative to traditional terrestrial laser scanning (TLS) and LiDAR equipment. We adapted a low‐cost laser ranging system (SICK LSM111) to acquire area scans of the channel and bed for a temporarily diverted stream. The 5 m × 2 m study area was scanned at a 4 mm point spacing which resulted in a point cloud density of 5,600 points/m2. A local maxima search algorithm was applied to the point cloud and a grain size distribution of the stream bed was extracted. The 84th and 90th percentiles of this distribution, which are commonly used to characterize channel roughness, were 90 mm and 109 mm, respectively. Our example shows the system can resolve both large‐scale geometry (e.g., bed slope and channel width) and small‐scale roughness elements (e.g., grain sizes between about 30 and 255 mm) in an exposed stream channel thereby providing a resolution adequate for the estimation of ecohydraulic roughness parameters such as Manning's n. While more work is necessary to refine our specific field‐deployable system's design, these initial results are promising in particular for those working on a limited or fixed budget. This opens up a realm of laser scanning applications and monitoring strategies for water resources that may not have been possible previously due to cost limitations associated with traditional TLS systems.
- Considering Climate Change in the Estimation of Long‐Term Flood
Risks of Devils Lake in North Dakota
- Authors: Gehendra Kharel; Andrei Kirilenko
Abstract: Terminal lakes are impacted by regional changes in climate. Devils Lake (DL), North Dakota, United States (U.S.), is a case in which a prolonged shift in the precipitation pattern resulted in a 10‐m water‐level rise over the past two decades, which cost over one billion U.S. dollars in mitigation. Currently, DL is 1.5 m from an uncontrolled overspill to the nearby Sheyenne River, which could lead to unprecedented environmental, social, and economic costs. Water outlets recently implemented in the lake to slow the water‐level rise and prevent an uncontrolled overspill are subject to significant concerns over the introduction of invasive species and downstream water quality. We developed a hydrological model of the DL basin using the soil and water assessment tool and analyzed DL's overspill probability using an ensemble of statistically downscaled General Circulation Model (GCM) projections of the future climate. The results indicate a significant likelihood (7.3‐20.0%) of overspill in the next few decades in the absence of outlets; some members of the GCM integration ensemble suggest an exceedance probability of over 85.0 and 95.0% for the 2020s and 2050s, respectively. Full‐capacity outlets radically reduce the probability of DL overspill and are able to partially mitigate the problem by decreasing the average lake level by approximately 1.9 and 1.5 m in the 2020s and 2050s, respectively.
- Calibration and Uncertainty Analysis Using the Sparrow Model for
Dissolved‐Solids Transport in the Upper Colorado River Basin
- Authors: Jongho Keum; Jagath J. Kaluarachchi
Abstract: Salinity in the Upper Colorado River Basin (UCRB) is due to both natural sources and processes, and anthropogenic activities. Given economic damage due to salinity of $295 million in 2010, understanding salinity sources and production together with transport are of great importance. SPAtially Referenced Regressions On Watershed (SPARROW) is a nonlinear regression water quality model that simulates sources and transport of contaminants such as dissolved‐solids. However, SPARROW simulations of dissolved‐solids in the UCRB only represent conditions through 1998 due to limited data availability. More importantly, prior simulations focused on a single year calibration and its transferability to other years, and the validity of this approach is questionable, given the changing hydrologic and climatic conditions. This study presents different calibration approaches to assess the best approach for reducing model uncertainty. This study conducted simulations from 1999 to 2011, and the results showed good model accuracy. However, the number of monitoring stations decreased significantly in recent years resulting in higher model uncertainty. The uncertainty analysis was conducted using SPARROW results and bootstrapping. The results suggest that the watershed rankings based on salinity yields changed due to the uncertainty analysis and therefore, uncertainty consideration should be an important part of the management strategy.
- A Review of the United States' Past and Projected Water Use
- Authors: Debra Perrone; George Hornberger, Oscar Vliet, Marijn Velde
Abstract: Good information and data on water demands are needed to perform good analyses, yet collecting and compiling spatially and temporally consistent water demand data are challenges. The objective of our work was to understand the limitations associated with water‐use estimates and projections. We performed a comprehensive literature review of national and regional United States (U.S.) water‐use estimates and projections. We explored trends in past regional projections of freshwater withdrawals and compared these values to regional estimates of freshwater withdrawals made by the U.S. Geological Survey. Our results suggest a suite of limitations exist that have the potential for influencing analyses aiming to extract explanatory variables from the data or using the data to make projections and forecasts. As we explored regional projections, we paid special attention to the two largest water demand‐side sectors — thermoelectric energy and irrigation — and found thermoelectric projections are more spread out than irrigation projections. All data related to water use have limitations, and there is no alternative to making the best use that we can of the available data; our article provides a comprehensive review of these limitations so that water managers can be more informed.
- Agricultural BMP Effectiveness and Dominant Hydrological Flow Paths:
Concepts and a Review
- Authors: Rebecca A. Rittenburg; Audrey L. Squires, Jan Boll, Erin S. Brooks, Zachary M. Easton, Tammo S. Steenhuis
Abstract: We present a conceptual framework that relates agricultural best management practice (BMP) effectiveness with dominant hydrological flow paths to improve nonpoint source (NPS) pollution management. We use the framework to analyze plot, field and watershed scale published studies on BMP effectiveness to develop transferable recommendations for BMP selection and placement at the watershed scale. The framework is based on the location of the restrictive layer in the soil profile and distinguishes three hydrologic land types. Hydrologic land type A has the restrictive layer at the surface and BMPs that increase infiltration are effective. In land type B1, the surface soil has an infiltration rate greater than the prevailing precipitation intensity, but there is a shallow restrictive layer causing lateral flow and saturation excess overland flow. Few structural practices are effective for these land types, but pollutant source management plans can significantly reduce pollutant loading. Hydrologic land type B2 has deep, well‐draining soils without restrictive layers that transport pollutants to groundwater via percolation. Practices that increased pollutant residence time in the mixing layer or increased plant water uptake were found as the most effective BMPs in B2 land types. Matching BMPs to the appropriate land type allows for better targeting of hydrologically sensitive areas within a watershed, and potentially more significant reductions of NPS pollutant loading.
- Variable Source Area Hydrology Modeling with the Water Erosion Prediction
- Authors: Jan Boll; Erin S. Brooks, Brian Crabtree, Shuhui Dun, Tammo S. Steenhuis
Abstract: In nondegraded watersheds of humid climates, subsurface flow patterns determine where the soil saturates and where surface runoff is occurring. Most models necessarily use infiltration‐excess (i.e., Hortonian) runoff for predicting runoff and associated constituents because subsurface flow algorithms are not included in the model. In this article, we modify the Water Erosion Prediction Project (WEPP) model to simulate subsurface flow correctly and to predict the spatial and temporal location of saturation, the associated lateral flow and surface runoff, and the location where the water can re‐infiltrate. The modified model, called WEPP‐UI, correctly simulated the hillslope drainage data from the Coweeta Hydrologic Laboratory hillslope plot. We applied WEPP‐UI to convex, concave, and S‐shaped hillslope profiles, and found that multiple overland flow elements are needed to simulate distributed lateral flow and runoff well. Concave slopes had the greatest runoff, while convex slopes had the least. Our findings concur with observations in watersheds with saturation‐excess overland flow that most surface runoff is generated on lower concave slopes, whereas on convex slopes runoff infiltrates before reaching the stream. Since the WEPP model is capable of simulating both saturation‐excess and infiltration‐excess runoff, we expect that this model will be a powerful tool in the future for managing water quality.
- Assessing BMP Effectiveness and Guiding BMP Planning Using
- Authors: E.S. Brooks; S.M. Saia, J. Boll, L. Wetzel, Z.M. Easton, T.S. Steenhuis
Abstract: There is an increasing need for improved process‐based planning tools to assist watershed managers in the selection and placement of effective best management practices (BMPs). In this article, we present an approach, based on the Water Erosion Prediction Project model and a pesticide transport model, to identify dominant hydrologic flow paths and critical source areas for a variety of pollutant types. We use this approach to compare the relative impacts of BMPs on hydrology, erosion, sediment, and pollutant delivery within different landscapes. Specifically, we focus on using this approach to understand what factors promoted and/or hindered BMP effectiveness at three Conservation Effects Assessment Project watersheds: Paradise Creek Watershed in Idaho, Walnut Creek Watershed in Iowa, and Goodwater Creek Experimental Watershed in Missouri. These watersheds were first broken down into unique land types based on soil and topographic characteristics. We used the model to assess BMP effectiveness in each of these land types. This simple process‐based modeling approach provided valuable insights that are not generally available to planners when selecting and locating BMPs and helped explain fundamental reasons why long‐term improvement in water quality of these three watersheds has yet to be completely realized.
- Featured Collection Introduction: Synthesis and Analysis of Conservation
Effects Assessment Projects for Improved Water Quality
- Authors: Jan Boll; Tammo S. Steenhuis, Erin S. Brooks, Lyubov A. Kurkalova, Rebecca A. Rittenburg, Audrey L. Squires, George Vellidis, Zachary M. Easton, J.D. Wulfhorst
- Cost‐Effective Placement of Best Management Practices in a
Watershed: Lessons Learned from Conservation Effects Assessment Project
- Authors: Lyubov A. Kurkalova
Abstract: This article reviews the key, cross‐cutting findings concerning watershed‐scale cost‐effective placement of best management practices (BMPs) emerging from the National Institute of Food and Agriculture Conservation Effects Assessment Project (CEAP) competitive grants watershed studies. The synthesis focuses on two fundamental aspects of the cost‐effectiveness problem: (1) how to assess the location‐ and farmer‐specific costs of BMP implementation, and (2) how to decide on which BMPs need to be implemented and where within a given watershed. Major lessons learned are that (1) data availability remains a significant limiting factor in capturing within‐watershed BMP cost variability; (2) strong watershed community connections help overcome the cost estimation challenges; (3) detailing cost components facilitates the transferability of estimates to alternative locations and/or economic conditions; and (4) implicit costs vary significantly across space and farmers. Furthermore, CEAP studies showed that (5) evolutionary algorithms provide workable ways to identify cost‐effective BMP placements; (6) tradeoffs between total conservation costs and watershed‐scale cost‐effective water quality improvements are commonly large; (7) quality baseline information is essential to solving cost‐effectiveness problem; and (8) systemic and modeling uncertainties alter cost‐effective BMP placements considerably.
- Robust Prioritization of Climate Change Adaptation Strategies Using the
VIKOR Method with Objective Weights
- Authors: Yeonjoo Kim; Eun‐Sung Chung
Abstract: This study proposes a robust prioritization framework for climate change adaptation strategies under uncertain climate change scenarios, using the VIseKriterijumska Optimizacija I Kompromisno Resenje (VIKOR) method, a multi‐criteria decision‐making approach, together with the Shannon entropy‐based weights. The VIKOR method allows us to find a compromise solution between two decision strategies of maximizing group utility and minimizing individual regret, and the Shannon entropy is used to determine objective weights among multiple climate change scenarios. The proposed methodology was applied to the problem of selecting locations of subwatersheds for reusing treated wastewater (TWW) in a Korean urban watershed. Selected based on the sustainability concept, hydro‐environmental and socioeconomic indicators were used to evaluate the sustainability of TWW reuse under multiple climate change scenarios, using the hydrologic simulation model results and statistical data. Finally, sustainability scores under multiple scenarios were aggregated using the VIKOR together with the Shannon entropy‐based weights for the robust prioritization of adaptation strategies. According to the different levels of regret aversion or affinity, our results for water quality showed different sets of adaptation strategies as the best options, suggesting that our framework would help stakeholders seeking the robust options considering both the utility and regret.
- Introducing a Low‐Head Dam Fatality Database and Internet
- Authors: Edward W. Kern; Rollin H. Hotchkiss, Daniel P. Ames
Abstract: Low‐head dams can cause dangerous currents near the downstream face of the structure. Fatalities at low‐head dams with such currents, often referred to as “drowning machines,” are poorly documented. This technical note presents a new database of fatalities at low‐head dams in the United States together with an interactive map and web‐based user interface. The primary purpose of the system is to raise awareness, generate interest, and educate the general public and decision makers regarding these dangerous structures and the need for remediation. The database was designed as a normalized relational database of event dates, severity, location, reporter, and other circumstances. The open‐access user interface allows the general public to browse fatal incidents by geographic location and to read incident circumstances. The system allows submission of new contributions from users including all metadata needed to characterize the incident. The database is structured to include documentation verifying each entry. The site can be viewed at http://dams.byu.edu/.
- Temporal Changes in Streamflow and Attribution of Changes to Climate and
Landuse in Wisconsin Watersheds
- Authors: Rabi Gyawali; Steve Greb, Paul Block
Abstract: Previous historic trends analyses on 21st Century hydrologic data in the United States generally focus on annual flow statistics and have continued to use USGS hydro‐climatic data network (HCDN) stations, although post‐1988 diversions and runoff regulations are not reflected in the HCDN. Using a more recent dataset, Geospatial Attributes of Gages for Evaluating Streamflow, version II (GAGES II), compiled by Falcone (2012), which includes more watersheds with reference conditions, a comprehensive analysis of changes in seasonal, and annual streamflow in Wisconsin watersheds is demonstrated. Given the pronounced influence of seasonal hydrology in Wisconsin watersheds, the objective of this study is to elucidate the nature of temporal (annual, seasonal, and monthly) changes in runoff. Considerable temporal and regional variability was found in annual and seasonal streamflow changes between the two historic periods 1951‐1980 and 1981‐2010 considered in the study. For example, the northern watersheds show relatively small changes in streamflow discharge ranging from −6.0 to 4.2%, while the southern watersheds show relatively large increases in streamflow discharge ranging from 13.1 to 18.2%. To apportion streamflow changes to climate and nonclimatic factors, a method based on potential evapotranspiration changes is demonstrated. Results show that nonclimatic factors account for more than 60% of changes in annual runoff in Wisconsin watersheds considered in the study.
- Book Reviews
- Authors: Daniel Moscovici; Robert M. Hordon, Cindy Dyballa, Xuan Yu
- Streamside Management Zones Compromised by Stream Crossings, Legacy
Gullies, and Over‐Harvest in the Piedmont
- Authors: A.J. Lang; W.M. Aust, M.C. Bolding, S.M. Barrett, K.J. McGuire, W.A. Lakel
Abstract: Streamside management zone (SMZ) breakthroughs were identified and characterized to determine frequency and potential causes, in order to provide enhanced guidance for future water quality protection. Ten kilometers of SMZs were carefully examined for partial or complete breakthroughs. With partial breakthroughs the SMZ trapped sediment before it reached the stream, while complete breakthroughs appeared to have allowed sediment to have passed through with minimal restriction. A total of 41 breakthroughs occurred (33 complete, 8 partial) across 16 sites, averaging 1 complete breakthrough per 0.3 km of SMZ length. The most common complete breakthroughs were caused by stream crossings (42%), reactivation of legacy agricultural gullies (27%), and harvest related soil disturbances near/within SMZs (24%). Pearson correlations of site characteristics at breakthroughs indicated no strong relationships between breakthrough sites, representing the variable nature of these unique circumstances. Stream crossings are an intentional breakthrough for access purposes, but resulting environmental impacts can be reduced with best management practice implementation. Current recommendations for SMZs tend to work in most situations, yet further research is needed to identify causal factors and quantify breakthrough severity.
- Drainage Impacts on Surficial Water Retention Capacity of a Prairie
- Authors: Andrew C. Kessler; Satish C. Gupta
Abstract: Wetland restoration has been proposed as a tool to mitigate excess runoff and associated nonpoint source pollution in the Upper Midwestern United States. This study quantified the surficial water retention capacity of existing and drained wetlands for the Greater Blue Earth River Basin (GBERB), an intensively drained agricultural watershed. Using airborne light detection and ranging, the historic depressional storage was determined to be 152 mm. Individual depression analysis suggested that the restoration of most drained areas would have little impact on the storage capacity of the GBERB because the majority (53%) of retention capacity was in large depressions (>40 ha) which comprised only a small proportion (40 ha) depressions.
- Assessment of Flood Vulnerability Based on CMIP5 Climate Projections in
- Authors: Jihoon Park; Moon Seong Kang, Inhong Song
Abstract: The objective of this article was to assess flood vulnerability based on the representative concentration pathways (RCP) scenarios at city and county levels. A quantile mapping method was adopted to correct bias that is inherent in climate change scenarios. A series of proxy variables related to climate exposure, sensitivity, and adaptive capacity were chosen to assess flood vulnerability. Proxy variables were standardized using the Z‐score method. Principal component analysis was carried out to calculate the weighting of proxy variables. The study area was the Korean peninsula. The spatial resolution was on a city and county basis and the temporal resolution was 1990s, 2025s, 2055s, and 2085s (divided into 1976‐2005, 2011‐2040, 2041‐2070, and 2071‐2100). In the spatial comparison, we found that the areas with high‐level flood vulnerability increased over time in the central region, including metropolitan areas, and near the southern coast. In the temporal comparison, we found that the RCP4.5 scenario showed a tendency to increase steadily and the RCP8.5 scenario showed a tendency to decrease in the 2055s slightly and increase again in the 2085s. The study findings may provide useful data for the determination of priority for countermeasure development, though robustness of these findings with additional future projections should be established.
- Interpolating SRTM Elevation Data to Higher Resolution to Improve
- Authors: Younggu Her; Conrad D. Heatwole, Moon S. Kang
Abstract: The Shuttle Radar Topography Mission (SRTM) digital elevation model (DEM) has been a valuable resource for hydrological analysis, providing elevation data at a consistent resolution on a near‐global scale. However, its resolution (three arc‐second or 90 m) is sometimes too low to obtain the desired level of accuracy and precision for hydrologic analysis. We evaluated the performance of several methods for interpolating SRTM three arc‐second data to a 30‐m resolution grid to better represent topography and derive terrain characteristics of the landscape. STRM data were interpolated to 30‐m DEMs on a common grid using spline, inverse distance weighting (IDW), kriging (KR), natural neighbor methods, and cubic convolution (CC) resampling. Accuracy of the methods was assessed by comparing interpolated and resampled 30‐m grids with the reference data. Slope, aspect, sinks, and stream networks were derived for the 30‐m grids and compared on a cell‐by‐cell basis to evaluate their performance in reproducing the derivatives. The comparisons identify spline and KR as the most accurate interpolation methods, of which spline is preferred because of its relative simplicity. IDW provided the greatest bias in all methods with artifacts evident in slope and aspect maps. The performance of CC projection directly to a 30‐m resolution was comparable to spline interpolation, thus is recommended as the most convenient method for interpolating SRTM to a higher resolution.
- Development and Evaluation of Bankfull Hydraulic Geometry Relationships
for the Physiographic Regions of the United States
- Authors: Katrin Bieger; Hendrik Rathjens, Peter M. Allen, Jeffrey G. Arnold
Abstract: Bankfull hydraulic geometry relationships are used to estimate channel dimensions for streamflow simulation models, which require channel geometry data as input parameters. Often, one nationwide curve is used across the entire United States (U.S.) (e.g., in Soil and Water Assessment Tool), even though studies have shown that the use of regional curves can improve the reliability of predictions considerably. In this study, regional regression equations predicting bankfull width, depth, and cross‐sectional area as a function of drainage area are developed for the Physiographic Divisions and Provinces of the U.S. and compared to a nationwide equation. Results show that the regional curves at division level are more reliable than the nationwide curve. Reliability of the curves depends largely on the number of observations per region and how well the sample represents the population. Regional regression equations at province level yield even better results than the division‐level models, but because of small sample sizes, the development of meaningful regression models is not possible in some provinces. Results also show that drainage area is a less reliable predictor of bankfull channel dimensions than bankfull discharge. It is likely that the regional curves can be improved using multiple regression models to incorporate additional explanatory variables.
- The Mass and Energy Exchange of a Tibetan Glacier: Distributed Modeling
and Climate Sensitivity
- Authors: Binquan Li; Kumud Acharya, Zhongbo Yu, Zhongmin Liang, Fengge Su
Abstract: Most glaciers in the Tibetan Plateau (TP) are not closely monitored for mass balance (MB) due to their inaccessibility, which makes it difficult to better understand the dynamics of glacial advancement or retreat. Surface energy budget, MB, and the resulting melt runoff were calculated for Zhadang glacier (5,710 m above sea level) of the central TP. Energy balance was calculated on 30‐m square grids for the summers of 2007 and 2008. On average, net radiation dominated the total energy source (66%) while the residual was supplied by sensible heat flux. More than 67% of the energy sink was available for melting on the glacier. Thus, less than 33% of the total energy was consumed by latent heat flux. A large and a slightly negative summer MB were calculated for the 2007 and 2008 summers, respectively. The high sensitivity of the glacier to air temperature may indicate that the lower than average seasonal temperature was more important than the increased precipitation for the slightly negative MB in the summer of 2008. Comparisons of glacial melt runoff indicated that rainfall and snowmelt were the dominant contribution to total runoff in the glacierized basin and the ice melting is also very important. Glacial melt calculation provides a basis for quantifying glacial melt‐runoff contribution to the river streamflow in the TP.
- Calibrating a Basin‐Scale Groundwater Model to Remotely Sensed
Estimates of Groundwater Evapotranspiration
- Authors: Rosemary W.H. Carroll; Greg M. Pohll, Charles G. Morton, Justin L. Huntington
Abstract: Remotely sensed vegetation indices correspond to canopy vigor and cover and have been successfully used to estimate groundwater evapotranspiration (ETg) over large spatial and temporal scales. However, these data do not provide information on depth to groundwater (dtgw) necessary for groundwater models (GWM) to calculate ETg. An iterative approach is provided that calibrates GWM to ETg derived from Landsat estimates of the Enhanced Vegetation Index (EVI). The approach is applied to different vegetation groups in Mason Valley, Nevada over an 11‐year time span. An uncertainty analysis is done to estimate the resulting mean and 90% confidence intervals in ETg to dtgw relationships to quantify errors associated with plant physiologic complexity, species variability, and parameter smoothing to the 100 m GWM‐grid, temporal variability in soil moisture and nonuniqueness in the solution. Additionally, a first‐order second moment analysis shows ETg to dtgw relationships are almost exclusively sensitive to estimated land surface, or maximum, ETg despite relatively large uncertainty in extinction depths and hydraulic conductivity. The EVI method of estimating ETg appears to bias ETg during years with exceptionally wet spring/summer conditions. Excluding these years improves model performance significantly but highlights the need to develop a methodology that accounts not only on quantity but timing of annual precipitation on phreatophyte greenness.
- A Hierarchical Model for Estimating Long‐Term Trend of Atrazine
Concentration in the Surface Water of the Contiguous U.S.
- Authors: Jian Yun; Song S. Qian
Abstract: Atrazine is a herbicide frequently detected in both surface and groundwater in the United States (U.S.), but its spatiotemporal distribution and concentration trends have only been analyzed recently at regional or local scales. We employed a Bayesian hierarchical modeling approach to assess spatial and seasonal variation in atrazine concentration trends between 1990 and 2010 for the contiguous U.S. A Markov chain Monte Carlo simulation algorithm was used to address the problem of left‐censored data (i.e., atrazine concentration values below method reporting levels). We observed opposing temporal trends in the northern (flat or decreasing) and southern (increasing) regions of the U.S. This spatial variation in temporal trends can be partially explained by the relative amount of cropland in the region. Flat or decreasing trends in the north are more likely in regions with high cropland coverage while positive trends in the south are more likely in regions with low cropland coverage.
- The Impact of Dynamic Environmental Flow Releases on Hydropower Production
in the Zambezi River Basin
- Authors: F.F. Nyatsanza; S. Graas, P. Zaag
Abstract: Incorporation of environmental flow releases from reservoirs has proven to be challenging due to fear of losses to existing water uses. Moreover environmental flow requirements (EFR) have not often been operationalized. This study compares the possibility of implementing dynamic EFR based on natural flows lagged against an upstream unregulated gauging point with static EFR. It simulates different scenarios with a high flow release in the wet season and analyses its impacts on hydropower production. This method accounts fully for the natural variability of environmental flows, implying less pressure on existing water uses during relatively dry years. Joint operation of two cascading dams vs. individual operation for EFR was also explored. These approaches were tested for the Zambezi River basin in Southern Africa using a water resources model, WAFLEX. Historic data on reservoir water levels, releases and power generation of the hydropower schemes were synthesized. Combining these yielded a validated series of monthly flow data for a 28 year period (1982‐2010). The results show that Kariba and Cahora Bassa reservoirs face a reduction in power produced when they would annually release an environmental flow. However, the dynamic EFR method entails smaller hydropower losses. Joint environmental flow operations will reduce overall basin power production more than if Cahora Bassa alone would release an environmental flow. However, such joint operation would be more beneficial to the ecosystem.
- Climate Trends but Little Net Water Supply Shift in One of Canada's Most
Water‐Stressed Regions over the Last Century
- Authors: S.W. Fleming; M. Barton
Abstract: The southern interior ecoprovince (SIE) of British Columbia, Canada represents the northernmost extent of the great western North American deserts, it is experiencing some of the nation's fastest economic and population growth making it one of Canada's most water‐stressed regions, and it includes two headwater basins of the transboundary (Canada‐US) Columbia River. Statistical trend analyses were performed on 90‐year regional indicator time series for annual conditions in observed temperature, precipitation, and streamflow reflecting the three major SIE river basins: the Thompson, and transboundary Okanagan and Similkameen. Results suggest that regional climate has grown warmer and wetter, but with little net impact on total water supply availability. The outcome might reflect mutual cancellation of increases in precipitation inputs vs. evapotranspiration losses. Conclusions appeared largely insensitive to low‐pass data filtering, Pacific Decadal Oscillation effects, or solar output variability. Ensemble historical global climate model runs over the same time interval support this absence of appreciable trend in regionally integrated annual runoff volume, but a possible mismatch in precipitation results suggests a direction for further study. Overall, while important changes in hydrologic timing and extremes are likely occurring here, there is limited evidence for a net change in overall water supply availability over the last century.
- Geomorphic and Ecological Consequences of Riprap Placement in River
- Authors: David Reid; Michael Church
Abstract: Riprap, consisting of large boulders or concrete blocks, is extensively used to stabilize streambanks and to inhibit lateral erosion of rivers, yet its effect on river morphology and its ecological consequences have been relatively little studied. In this paper, we review the available information, most of it culled from the “grey” literature. We use a simple one‐dimensional morphodynamic model as a conceptual tool to illustrate potential morphological effects of riprap placement in a gravel‐bed river, which include inhibition of local sediment supply to the channel and consequent channel bed scour and substrate coarsening, and downstream erosion. Riprap placement also tends to sever organic material input from the riparian zone, with loss of shade, wood input, and input of finer organic material. Available information on the consequences for the aquatic ecosystem mainly concerns effects on commercially and recreationally important fishes. The preponderance of studies report unfavorable effects on local numbers, but habitat niches created by openings in riprap can favorably affect invertebrates and some small fishes. There is a need for much more research on both morphological and ecosystem effects of riprap placement.
- Empirical Estimation of Stream Discharge Using Channel Geometry in
Low‐Gradient, Sand‐Bed Streams of the Southeastern Plains
- Authors: Stephen A. Sefick; Latif Kalin, Ely Kosnicki, Brad P. Schneid, Miller S. Jarrell, Chris J. Anderson, Michael H. Paller, Jack W. Feminella
Abstract: Manning's equation is used widely to predict stream discharge (Q) from hydraulic variables when logistics constrain empirical measurements of in‐bank flow events. Uncertainty in Manning's roughness (nM) is the major source of error in natural channels, and sand‐bed streams pose difficulties because flow resistance is affected by flow‐dependent bed configuration. Our study was designed to develop and validate models for estimating Q from channel geometry easily derived from cross‐sectional surveys and available GIS data. A database was compiled consisting of 484 Q measurements from 75 sand‐bed streams in Alabama, Georgia, South Carolina, North Carolina (Southeastern Plains), and Florida (Southern Coastal Plain), with six New Zealand streams included to develop statistical models to predict Q from hydraulic variables. Model error characteristics were estimated with leave‐one‐site‐out jackknifing. Independent data of 317 Q measurements from 55 Southeastern Plains streams indicated the model (Q = AcRH0.6906S0.1216; where Ac is the channel area, RH is the hydraulic radius, and S is the bed slope) best predicted Q, based on Akaike's information criterion and root mean square error. Models also were developed from smaller Q range subsets to explore if subsets increased predictive ability, but error fit statistics suggested that these were not reasonable alternatives to the above equation. Thus, we recommend the above equation for predicting in‐bank Q of unbraided, sandy streams of the Southeastern Plains.
- Calibration and Verification of SWMM for Low Impact Development
- Authors: David J. Rosa; John C. Clausen, Michael E. Dietz
Abstract: The Storm Water Management Model was used to simulate runoff and nutrient export from a low impact development (LID) watershed and a watershed using traditional runoff controls. Predictions were compared to observed values. Uncalibrated simulations underpredicted weekly runoff volume and average peak flow rates from the multiple subcatchment LID watershed by over 80%; the single subcatchment traditional watershed had better predictions. Saturated hydraulic conductivity, Manning's n for swales, and initial soil moisture deficit were sensitive parameters. After calibration, prediction of total weekly runoff volume for the LID and traditional watersheds improved to within 12 and 5% of observed values, respectively. For the validation period, predicted total weekly runoff volumes for the LID and traditional watersheds were within 6 and 2% of observed values, respectively. Water quality simulation was less successful, Nash–Sutcliffe coefficients >0.5 for both calibration and validation periods were only achieved for prediction of total nitrogen export from the LID watershed. Simulation of a 100‐year, 24‐h storm resulted in a runoff coefficient of 0.46 for the LID watershed and 0.59 for the traditional watershed. Results suggest either calibration is needed to improve predictions for LID watersheds or expanded look‐up tables for Green–Ampt infiltration parameter values that account for compaction of urban soil and antecedent conditions are needed.
- Climate Change Impacts and Uncertainties on Spring Flooding of Lake
Champlain and the Richelieu River
- Authors: Philippe Riboust; François Brissette
Abstract: The source of the Richelieu River is Lake Champlain, located between the states of New York, Vermont, and Québec. In 2011, the lake and the Richelieu River reached historical flood levels, raising questions about the influence of climate change on the watershed. The objectives of this work are to model the hydrology of the watershed, construct a reservoir model for the lake and to analyze flooding trends using climate simulations. The basin was modeled using the HSAMI lumped conceptual model from Hydro‐Québec with a semi‐distributed approach in order to estimate the inflows into Lake Champlain. The discharge at the Richelieu River was computed by using a mass balance equation between the inputs and outputs of Lake Champlain. Future trends were estimated over the 2041‐2070 and 2071‐2100 periods using a large number of outputs from general circulation models and regional climate models downscaled with constant scaling and daily translation methods. While there is a certain amount of uncertainty as to future trends, there is a decreasing tendency in the magnitude of the mean spring flood. A flood frequency analysis showed most climate projections indicate the severity of most extreme spring floods may be reduced over the two future periods although results are subject to a much larger uncertainty than for the mean spring flood. On the other hand, results indicate summer‐fall extreme events such as caused by hurricane Irene in August 2011 may become more frequent in the future.
- Identifying and Evaluating a Suitable Index for Agricultural Drought
Monitoring in the Texas High Plains
- Authors: Jerry E. Moorhead; Prasanna H. Gowda, Vijay P. Singh, Dana O. Porter, Thomas H. Marek, Terry A. Howell, B.A. Stewart
Abstract: Drought is a complex and highly destructive natural phenomenon that affects portions of the United States almost every year, and severe water deficiencies can often become catastrophic for agricultural production. Evapotranspiration (ET) by crops is an important component in the agricultural water budget; thus, it is advantageous to include ET in agricultural drought monitoring. The main objectives of this study were to (1) conduct a literature review of drought indices with a focus to identify a simple but simultaneously adequate drought index for monitoring agricultural drought in a semiarid region and (2) using the identified drought index method, develop and evaluate time series of that drought index for the Texas High Plains. Based on the literature review, the Standardized Precipitation‐Evapotranspiration Index (SPEI) was found to satisfy identified constraints for assessing agricultural drought. However, the SPEI was revised by replacing reference ET with potential crop ET to better represent actual water demand. Data from the Texas High Plains Evapotranspiration network was used to calculate SPEIs for the major irrigated crops. Trends and magnitudes of crop‐specific, time‐series SPEIs followed crop water demand patterns for summer crops. Such an observation suggests that a modified SPEI is an appropriate index to monitor agricultural drought for summer crops, but it was found to not account for soil water stored during the summer fallow period for winter wheat.
- Analysis of Meteorological Drought Pattern During Different Climatic and
Cropping Seasons in Bangladesh
- Authors: Mahiuddin Alamgir; Shamsuddin Shahid, Manzul Kumar Hazarika, Syams Nashrrullah, Sobri Bin Harun, Supiah Shamsudin
Abstract: Drought is one of the most frequent natural disasters in Bangladesh which severely affect agro‐based economy and people's livelihood in almost every year. Characterization of droughts in a systematic way is therefore critical in order to take necessary actions toward drought mitigation and sustainable development. In this study, standardized precipitation index is used to understand the spatial distribution of meteorological droughts during various climatic seasons such as premonsoon, monsoon, and winter seasons as well as cropping seasons such as Pre‐Kharif (March‐May), Kharif (May‐October), and Rabi (December‐February). Rainfall data collected from 29 rainfall gauge stations located in different parts of the country were used for a period of 50 years (1961‐2010). The study reveals that the spatial characteristics of droughts vary widely according to season. Premonsoon droughts are more frequent in the northwest, monsoon droughts mainly occur in the west and northwest, winter droughts in the west, and the Rabi and Kharif droughts are more frequent in the north and northwest of Bangladesh. It is expected that the findings of the study will support drought monitoring and mitigation activities in Bangladesh.
- Seeking, Thinking, Acting: Understanding Suburban Resident Perceptions and
Behaviors Related to Stream Quality
- Authors: Kristina M. Slagle; Robyn S. Wilson, Alexander Heeren
Abstract: Theories in risk, psychology, and communication suggest aiming to inform the public about basic ecological facts may not be enough to influence knowledge of risks or behaviors to mitigate water quality risks. The risk information‐seeking and processing model and the theory of planned behavior suggest several additional variables that are likely to influence risk‐mitigating behaviors. We used data from a survey of watershed residents in Ohio to explore a model of behavioral intentions to positively impact stream health. Residents' informational norms, or the perceived pressure to know about local stream health, strongly predicted their information‐seeking behaviors. Active‐seeking behaviors predicted positive attitudes toward behaviors impacting stream health, which predicted intentions to positively impact stream health. Implications for outreach include couching communication in terms of risk found important to the local community, here wildlife were seen as negatively influenced by water quality, as opposed to plain reports typically provided by utility companies. Increasing social pressure to feel informed by emphasizing the existing knowledge of stream ecology among residents could change the norm for the less informed. A low response rate limits the generalizability of findings here, but leveraging these findings in outreach efforts could prove more successful in engaging the public to improve stream health and support policies to improve stream health.
- Development of Sediment and Nutrient Export Coefficients for U.S.
- Authors: Michael White; Daren Harmel, Haw Yen, Jeff Arnold, Marilyn Gambone, Richard Haney
Abstract: Water quality impairment due to excessive nutrients and sediment is a major problem in the United States (U.S.). An important step in the mitigation of impairment in any given water body is determination of pollutant sources and amount. The sheer number of impaired waters and limited resources makes simplistic load estimation methods such as export coefficient (EC) methods attractive. Unfortunately ECs are typically based on small watershed monitoring data, which are very limited and/or often based on data collected from distant watersheds with drastically different conditions. In this research, we seek to improve the accuracy of these nutrient export estimation methods by developing a national database of localized EC for each ecoregion in the U.S. A stochastic sampling methodology loosely based on the Monte‐Carlo technique was used to construct a database of 45 million Soil and Water Assessment Tool (SWAT) simulations. These simulations consider a variety of climate, topography, soils, weather, land use, management, and conservation implementation conditions. SWAT model simulations were successfully validated with edge‐of‐field monitoring data. Simulated nutrient ECs compared favorably with previously published studies. These ECs may be used to rapidly estimate nutrient loading for any small catchment in the U.S. provided the location, area, and land‐use distribution are known.
- The Nature of Multidisciplinary Water Resources Journal Articles
- Authors: Parker J. Wigington
Pages: 301 - 301
- Using Public Participation Geographic Information Systems to Identify
Places of Watershed Service Provisioning
- Authors: Cody Cox; Wayde Morse, Christopher Anderson, Luke Marzen
Abstract: In this study, we used public participation geographic information systems methods to collect spatial data identifying places that stakeholders in Mobile Bay, Alabama think are important providers of watershed services. These methods allowed us to spatially analyze participatory data from general public respondents and directly compare them with other scientific data in a geographic information systems database. This study identified which places in the region participants believe are important providers of specific watershed services, including fish nurseries, storm protection, flood protection, and water quality protection, which would likely have public support for conservation. Additionally, we assessed the accuracy of participant watershed service identification using land cover data to identify inconsistencies and participant knowledge gaps. This information can be used to target outreach education efforts. We found that the accuracy with which participants correctly identified places with the necessary land cover to provide each service varied considerably. We believe this to be a useful tool for managers to elicit stakeholder input and to identify knowledge gaps regarding the provisioning of watershed services.
- Characterizing Geomorphic Change from Anthropogenic Disturbances to Inform
Restoration in the Upper Cache River, Illinois
- Authors: Kristen L. Bouska; Timothy J. Stoebner
Abstract: Over the past century, channelization, agricultural tiling, and land use changes have resulted in significant stream channel degradation of the Cache River in southern Illinois. With the increasing interest in restoration of the watershed's bottomland forests and swamps, we sought to characterize geomorphic change over the past 110 years to inform restoration and management. A previously surveyed stretch of river was resurveyed in the fall of 2011, following a record flood in the spring of that year. Results suggest that the slope of the channel in this section of the river has increased 345% between 1903 and 1972 (p
- Boater Perceptions of Environmental Issues Affecting Lakes in Northern
- Authors: Ben Beardmore
Abstract: Understanding public perceptions of the importance of environmental issues is crucial for gauging support for management activities. I present a novel methodological approach to assess the importance boaters placed on 16 water issues in a lake‐rich region of northern Wisconsin. A latent class maximum difference conjoint model was used to examine the relationships between environmental concern and engagement with lake resources. Boaters were grouped to maximize observed heterogeneity in prioritizing issues of concern. Socio‐demographic characteristics, recreation specialization, place attachment, and attitudes concerning aquatic stewardship and invasive species management were then used to predict class membership. This modeling approach identified five groups whose perceptions of issues pertaining to lakes are influenced by their interactions with the lake environment. While anglers were most concerned about fishing quality, sightseers identified lakeshore development and loss of natural habitat. Groups also differed in their socio‐demographic and attitudinal characteristics. The priorities of each group were substantially different from those of the overall sample. Accounting for differences in stakeholders' environmental concerns may improve public involvement in water management initiatives by allowing managers to identify common concerns and prioritize important issues among multiple groups.
- Variable Irrigation District Action in Water Trading
- Authors: Narishwar Ghimire; Ronald C. Griffin
Abstract: Irrigation districts (IDs) in the American west are highly diverse in their economic attributes and local water scarcity circumstances. This diversity may affect reallocative action via water transactions as scarcity rises. The institutional background defining and constraining IDs is described here. For a Texas study region the progress of permanent water right transfers involving IDs is documented and examined. An econometric analysis of multiple decades of ID water transfer activities in the Lower Rio Grande Valley finds that IDs with larger initial water right holdings and higher populations in nearby cities are more likely to participate in agricultural‐to‐municipal water transfer activities. The findings suggest that consolidation of smaller water right holding IDs may be an avenue for quickening the pace of reallocation, especially in more populated areas.
- Seasonal and Regional Patterns in Performance for a Baltic Sea Drainage
Basin Hydrologic Model
- Authors: Steve W. Lyon; Roya Meidani, Ype Velde, Helen E. Dahlke, Dennis P. Swaney, Carl‐Magnus Mörth, Christoph Humborg
Abstract: This study evaluates the ability of the Catchment SIMulation (CSIM) hydrologic model to describe seasonal and regional variations in river discharge over the entire Baltic Sea drainage basin (BSDB) based on 31 years of monthly simulation from 1970 through 2000. To date, the model has been successfully applied to simulate annual fluxes of water from the catchments draining into the Baltic Sea. Here, we consider spatiotemporal bias in the distribution of monthly modeling errors across the BSDB since it could potentially reduce the fidelity of predictions and negatively affect the design and implementation of land‐management strategies. Within the period considered, the CSIM model accurately reproduced the annual flows across the BSDB; however, it tended to underpredict the proportion of discharge during high‐flow periods (i.e., spring months) and overpredict during the summer low flow periods. While the general overpredictions during summer periods are spread across all the subbasins of the BSDB, the underprediction during spring periods is seen largely in the northern regions. By implementing a genetic algorithm calibration procedure and/or seasonal parameterization of subsurface water flows for a subset of the catchments modeled, we demonstrate that it is possible to improve the model performance albeit at the cost of increased parameterization and potential loss of parsimony.
- Authors: Francesco D'Asaro; Giovanni Grillone
Abstract: Epps et al. (2013) derived Curve Number (CN) values for two forested headwater watersheds in the Lower Coastal Plain of South Carolina during the 2008‐2011 period from rainfall‐runoff data, resulting in 23 events for the Upper Debidue Creek (UDC) watershed and in 20 events for Watershed 80 (WS80). D'Asaro and Grillone analyzed the P, CN data of the UDC watershed finding an evident “complacent” behavior, characterized by a declining CN with increasing P but without approaching a stable value at large storms. In this case, the traditional runoff CN equation does not fit well with the rainfall‐runoff data that indicate a partial source area watershed behavior and are more aptly modeled by the equation introduced by D'Asaro and Grillone (2012), who introduced a C parameter in the well‐known runoff CN formula. The C value, that represents the source area (fraction of drainage area) of the basin that produces runoff with a fixed CN
- A Modeling System to Assess Land Cover Land Use Change Effects on SAV
Habitat in the Mobile Bay Estuary
- Authors: Maurice G. Estes; Mohammad Z. Al‐Hamdan, Jean T. Ellis, Chaeli Judd, Dana Woodruff, Ronald M. Thom, Dale Quattrochi, Brian Watson, Hugo Rodriguez, Hoyt Johnson, Tom Herder
Abstract: Estuarine ecosystems are largely influenced by watersheds directly connected to them. In the Mobile Bay, Alabama watersheds we examined the effect of land cover and land use (LCLU) changes on discharge rate, water properties, and submerged aquatic vegetation, including freshwater macrophytes and seagrasses, throughout the estuary. LCLU scenarios from 1948, 1992, 2001, and 2030 were used to influence watershed and hydrodynamic models and evaluate the impact of LCLU change on shallow aquatic ecosystems. Overall, our modeling results found that LCLU changes increased freshwater flows into Mobile Bay altering temperature, salinity, and total suspended sediments (TSS). Increased urban land uses coupled with decreased agricultural/pasture lands reduced TSS in the water column. However, increased urbanization or agricultural/pasture land coupled with decreased forest land resulted in higher TSS concentrations. Higher sediment loads were usually strongly correlated with higher TSS levels, except in areas where a large extent of wetlands retained sediment discharged during rainfall events. The modeling results indicated improved water clarity in the shallow aquatic regions of Mississippi Sound and degraded water clarity in the Wolf Bay estuary. This integrated modeling approach will provide new knowledge and tools for coastal resource managers to manage shallow aquatic habitats that provide critical ecosystem services.
- Development and Operational Testing of a Super‐Ensemble Artificial
Intelligence Flood‐Forecast Model for a Pacific Northwest River
- Authors: Sean W. Fleming; Dominique R. Bourdin, Dave Campbell, Roland B. Stull, Tobi Gardner
Abstract: Coastal catchments in British Columbia, Canada, experience a complex mixture of rainfall‐ and snowmelt‐driven contributions to flood events. Few operational flood‐forecast models are available in the region. Here, we integrated a number of proven technologies in a novel way to produce a super‐ensemble forecast system for the Englishman River, a flood‐prone stream on Vancouver Island. This three‐day‐ahead modeling system utilizes up to 42 numerical weather prediction model outputs from the North American Ensemble Forecast System, combined with six artificial neural network‐based streamflow models representing various slightly different system conceptualizations, all of which were trained exclusively on historical high‐flow data. As such, the system combines relatively low model development times and costs with the generation of fully probabilistic forecasts reflecting uncertainty in the simulation of both atmospheric and terrestrial hydrologic dynamics. Results from operational testing by British Columbia's flood forecasting agency during the 2013‐2014 storm season suggest that the prediction system is operationally useful and robust.
- Associations between Water Physicochemistry and Prymnesium parvum
Presence, Abundance, and Toxicity in West Texas Reservoirs
- Authors: Matthew M. VanLandeghem; Mukhtar Farooqi, Greg M. Southard, Reynaldo Patiño
Abstract: Toxic blooms of golden alga (Prymnesium parvum) have caused substantial ecological and economic harm in freshwater and marine systems throughout the world. In North America, toxic blooms have impacted freshwater systems including large reservoirs. Management of water chemistry is one proposed option for golden alga control in these systems. The main objective of this study was to assess physicochemical characteristics of water that influence golden alga presence, abundance, and toxicity in the Upper Colorado River basin (UCR) in Texas. The UCR contains reservoirs that have experienced repeated blooms and other reservoirs where golden alga is present but has not been toxic. We quantified golden alga abundance (hemocytometer counts), ichthyotoxicity (bioassay), and water chemistry (surface grab samples) at three impacted reservoirs on the Colorado River; two reference reservoirs on the Concho River; and three sites at the confluence of these rivers. Sampling occurred monthly from January 2010 to July 2011. Impacted sites were characterized by higher specific conductance, calcium and magnesium hardness, and fluoride than reference and confluence sites. At impacted sites, golden alga abundance and toxicity were positively associated with salinity‐related variables and blooms peaked at ~10°C and generally did not occur above 20°C. Overall, these findings suggest management of land and water use to reduce hardness or salinity could produce unfavorable conditions for golden alga.
- Spatiotemporal Associations of Reservoir Nutrient Characteristics and the
Invasive, Harmful Alga Prymnesium parvum in West Texas
- Authors: Matthew M. VanLandeghem; Mukhtar Farooqi, Greg M. Southard, Reynaldo Patiño
Abstract: Golden alga (Prymnesium parvum) is a harmful alga that has caused ecological and economic harm in freshwater and marine systems worldwide. In inland systems of North America, toxic blooms have nearly eliminated fish populations in some systems. Modifying nutrient profiles through alterations to land or water use may be a viable alternative for golden alga control in reservoirs. The main objective of this study was to improve our understanding of the nutrient dynamics that influence golden alga bloom formation and toxicity in west Texas reservoirs. We examined eight sites in the Upper Colorado River basin, Texas: three impacted reservoirs that have experienced repeated golden alga blooms; two reference reservoirs where golden alga is present but nontoxic; and three confluence sites downstream of the impacted and reference sites. Total, inorganic, and organic nitrogen and phosphorus and their ratios were quantified monthly along with golden alga abundance and ichthyotoxicity between December 2010 and July 2011. Blooms persisted for several months at the impacted sites, which were characterized by high organic nitrogen and low inorganic nitrogen. At impacted sites, abundance was positively associated with inorganic phosphorus and bloom termination coincided with increases in inorganic nitrogen and decreases in inorganic phosphorus in late spring. Management of both inorganic and organic forms of nutrients may create conditions in reservoirs unfavorable to golden alga.
- Authors: Steven E. Pells; William L. Peirson
- Reply to Discussion
- Authors: Hilda Kwan; Sherman Swanson
- Authors: David L. Rosgen
- Hydrologic Sensitivity to Climate and Land Use Changes in the Santiam
River Basin, Oregon
- Authors: Cristina Mateus; Desiree D. Tullos, Christopher G. Surfleet
Abstract: Future changes in water supply are likely to vary across catchments due to a river basin's sensitivity to climate and land use changes. In the Santiam River Basin (SRB), Oregon, we examined the role elevation, intensity of water demands, and apparent intensity of groundwater interactions, as characteristics that influence sensitivity to climate and land use changes, on the future availability of water resources. In the context of water scarcity, we compared the relative impacts of changes in water supply resulting from climate and land use changes to the impacts of spatially distributed but steady water demand. Results highlight how seasonal runoff responses to climate and land use changes vary across subbasins with differences in hydrogeology, land use, and elevation. Across the entire SRB, water demand exerts the strongest influence on basin sensitivity to water scarcity, regardless of hydrogeology, with the highest demand located in the lower reaches dominated by agricultural and urban land uses. Results also indicate that our catchment with mixed rain‐snow hydrology and with mixed surface‐groundwater may be more sensitive to climate and land use changes, relative to the catchment with snowmelt‐dominated runoff and substantial groundwater interactions. Results highlight the importance of evaluating basin sensitivity to change in planning for planning water resources storage and allocation across basins in variable hydrogeologic settings.
- Evaluating Alternative Temporal Survey Designs for Monitoring Wetland Area
and Detecting Changes over Time in California
- Authors: Leila G. Lackey; Eric D. Stein
Abstract: Evaluation of wetland extent and changes in extent is a foundation of many wetland monitoring and assessment programs. Probabilistic sampling and mapping provides a cost‐effective alternative to comprehensive mapping for large geographic areas. One unresolved challenge for probabilistic or design‐based approaches is how best to monitor both status (e.g., extent at a single point in time) and trends (e.g., changes in extent over time) within a single monitoring program. Existing wetland status and trends (S&T) monitoring programs employ fixed sampling locations; however, theoretical evaluation and limited implementation in other landscape monitoring areas suggest that alternative designs could increase statistical efficiency and overall accuracy. In particular, designs that employ both fixed and nonfixed sampling locations (alternately termed permanent and temporary samples), termed sampling with partial replacement (SPR), are considered to efficiently and effectively balance monitoring current status with detection of trends. This study utilized simulated sampling to assess the performance of fixed sampling locations, SPR, and strictly nonfixed designs for monitoring wetland S&T over time. Modeled changes in wetland density over time were used as inputs for sampling simulations. In contrast to previous evaluations of SPR, the results of this study support the use of a fixed sampling design and show that SPR may underestimate both S&T.
- Model‐Based Nitrogen and Phosphorus (Nutrient) Criteria for Large
Temperate Rivers: 2. Criteria Derivation
- Authors: Michael W. Suplee; Kyle F. Flynn, Steven C. Chapra
Abstract: Nitrogen and phosphorus criteria were developed for 233 km of the Yellowstone River, one of the first cases where a mechanistic model has been used to derive large river numeric nutrient criteria. A water quality model and a companion model which simulates lateral algal biomass across transects were used to simulate effects of increasing nutrients on five variables (dissolved oxygen, total organic carbon, total dissolved gas, pH, and benthic algal biomass in depths ≤1 m). Incremental increases in nutrients were evaluated relative to their impact on predefined thresholds for each variable; the first variable to exceed a threshold set the nutrient criteria. Simulations were made at a low flow, the 14Q5 (lowest average 14 consecutive day flow, July‐September, recurring one in five years), which was derived using benthic algae growth curves and EPA guidance on excursion frequency. An extant climate dataset with an annual recurrence was used, and tributary water quality and flows were coincident with the river's 10 lowest flow years. The river had different sensitivities to nutrients longitudinally, pH being the most sensitive variable in the upstream reach and algal biomass in the lower. Model‐based criteria for the Yellowstone River are as follows: between the Bighorn and Powder river confluences, 55 μg TP/l and 655 μg TN/l; from the Powder River confluence to Montana state line, 95 μg TP/l and 815 μg TN/l. Pros and cons of using steady‐state models to derive river nutrient criteria are discussed.
- Model‐Based Nitrogen and Phosphorus (Nutrient) Criteria for Large
Temperate Rivers: 1. Model Development and Application
- Authors: Kyle F. Flynn; Michael W. Suplee, Steven C. Chapra, Hua Tao
Abstract: An initial inquiry into model‐based numeric nitrogen and phosphorus (nutrient) criteria for large rivers is presented. Field data collection and associated modeling were conducted on a segment of the lower Yellowstone River in the northwestern United States to assess the feasibility of deriving numeric nutrient criteria using mechanistic water‐quality models. The steady‐state one‐dimensional model QUAL2K and a transect‐based companion model AT2K were calibrated and confirmed against low‐flow conditions at a time when river loadings, water column chemistry, and diurnal indicators were approximately steady state. Predictive simulation was then implemented via nutrient perturbation to evaluate the steady‐state and diurnal response of the river to incremental nutrient additions. In this first part of a two‐part series, we detail our modeling approach, model selection, calibration and confirmation, sensitivity analysis, model outcomes, and associated uncertainty. In the second part (Suplee et al., 2014) we describe the criteria development process using the tools described herein. Both articles provide a fundamental understanding of the process required to develop site‐specific numeric nutrient criteria using models in applied regulatory settings.
- Can Rapid Assessment Protocols Be Used to Judge Sediment Impairment in
Gravel‐Bed Streams? A Commentary
- Authors: Thomas E. Lisle; John M. Buffington, Peter R. Wilcock, Kristin Bunte
Abstract: Land management agencies commonly use rapid assessments to evaluate the impairment of gravel‐bed streams by sediment inputs from anthropogenic sources. We question whether rapid assessment can be used to reliably judge sediment impairment at a site or in a region. Beyond the challenges of repeatable and accurate sampling, we argue that a single metric or protocol is unlikely to reveal causative relations because channel condition can result from multiple pathways, processes, and background controls. To address these concerns, a contextual analysis is needed to link affected resources, causal factors, and site history to reliably identify human influences. Contextual analysis is equivalent in principle to cumulative effects and watershed analyses and has a rich history, but has gradually been replaced by rapid assessment methods. Although the approaches differ, rapid assessment and contextual analysis are complementary and can be implemented in a two‐tiered approach in which rapid assessment provides a coarse (first‐tier) analysis to identify sites that deserve deeper contextual assessment (second‐tier). Contextual analysis is particularly appropriate for site‐specific studies that should be tailored to local conditions. A balance between rapid assessment and contextual analysis is needed to provide the most effective information for management decisions.