- Nitrogen Subsidies from Hillslope Alder Stands to Streamside Wetlands and
Headwater Streams, Kenai Peninsula, Alaska
- Authors: Michael K. Callahan; Dennis F. Whigham, Mark C. Rains, Kai C. Rains, Ryan S. King, Coowe M. Walker, Jasmine R. Maurer, Steven J. Baird
Abstract: We examined nitrogen transport and wetland primary production along hydrologic flow paths that link nitrogen-fixing alder (Alnus spp.) stands to downslope wetlands and streams in the Kenai Lowlands, Alaska. We expected that nitrate concentrations in surface water and groundwater would be higher on flow paths below alder. We further expected that nitrate concentrations would be higher in surface water and groundwater at the base of short flow paths with alder and that streamside wetlands at the base of alder-near flow paths would be less nitrogen limited than wetlands at the base of long flow paths with alder. Our results showed that groundwater nitrate-N concentrations were significantly higher at alder-near sites than at no-alder sites, but did not differ significantly between alder-far sites and no-alder sites or between alder-far sites and alder-near sites. A survey of 15N stable isotope signatures in soils and foliage in alder-near and no-alder flow paths indicated the alder-derived nitrogen evident in soils below alder is quickly integrated downslope. Additionally, there was a significant difference in the relative increase in plant biomass after nitrogen fertilization, with the greatest increase occurring in the no-alder sites. This study demonstrates that streamside wetlands and streams are connected to the surrounding landscapes through hydrologic flow paths, and flow paths with alder stands are potential “hot spots” for nitrogen subsidies at the hillslope scale.
- Measuring Urban Water Conservation Policies: Toward a Comprehensive Index
- Authors: David J. Hess; Christopher A. Wold, Scott C. Worland, George M. Hornberger
Abstract: This article (1) discusses existing efforts to measure water conservation policies (WCPs) in the United States (U.S.); (2) suggests general methodological guidelines for creating robust water conservation indices (WCIs); (3) presents a comprehensive template for coding WCPs; (4) introduces a summary index, the Vanderbilt Water Conservation Index (VWCI), which is derived from 79 WCP observations for 197 cities for the year 2015; and (5) compares the VWCI to WCP data extracted from the 2010 American Water Works Association (AWWA) Water and Wastewater Rates survey. Existing approaches to measuring urban WCPs in U.S. cities are limited because they consider only a portion of WCPs or they are restricted geographically. The VWCI consists of a more comprehensive set of 79 observations classified as residential, commercial/industrial, billing structure, drought plan, or general. Our comparison of the VWCI and AWWA survey responses indicate reasonable agreement (ρ = 0.76) between the two WCIs for 98 cities where the data overlap. The correlation suggests the AWWA survey responses can provide fairly robust longitudinal WCP information, but we argue the measurement of WCPs is still in its infancy, and our approach suggests strategies for improving existing methods.
- Revealing the Diversity of Natural Hydrologic Regimes in California with
Relevance for Environmental Flows Applications
- Authors: Belize A. Lane; Helen E. Dahlke, Gregory B. Pasternack, Samuel Sandoval-Solis
Abstract: Alterations to flow regimes for water management objectives have degraded river ecosystems worldwide. These alterations are particularly profound in Mediterranean climate regions such as California with strong climatic variability and riverine species highly adapted to the resulting flooding and drought disturbances. However, defining environmental flow targets for Mediterranean rivers is complicated by extreme hydrologic variability and often intensive water management legacies. Improved understanding of the diversity of natural streamflow patterns and their spatial arrangement across Mediterranean regions is needed to support the future development of effective flow targets at appropriate scales for management applications with minimal resource and data requirements. Our study addresses this need through the development of a spatially explicit reach-scale hydrologic classification for California. Dominant hydrologic regimes and their physio-climatic controls are revealed, using available unimpaired and naturalized streamflow time-series and generally publicly available geospatial datasets. This methodology identifies eight natural flow classes representing distinct flow sources, hydrologic characteristics, and catchment controls over rainfall-runoff response. The study provides a broad-scale hydrologic framework upon which flow-ecology relationships could subsequently be established towards reach-scale environmental flows applications in a complex, highly altered Mediterranean region.
- Hydraulics Near Unscreened Diversion Pipes in Open Channels: Large Flume
- Authors: Ali Ercan; M. Levent Kavvas, Kara Carr, Zachary Hockett, Hossein Bandeh, Timothy D. Mussen, Dennis Cocherell, Jamilynn B. Poletto, Joseph J. Cech, Nann A. Fangue
Abstract: Most of the water diversions on the Sacramento and San Joaquin Rivers (California, United States) and their tributaries are currently unscreened. These unscreened diversions are commonly used for irrigation and are potentially harmful to migrating and resident fishes. A large flume (test section: 18.29 m long, 3.05 m wide and 3.20 m high) was used to investigate the hydraulic fields near an unscreened water diversion under ecologically and hydraulically relevant diversion rates and channel flow characteristics. We investigated all combinations of three diversion rates (0.28, 0.42, and 0.57 m3/s) and three sweeping velocities (0.15, 0.38, and 0.61 m/s), with one additional test at 0.71 m3/s and 0.15 m/s. We measured the three-dimensional velocity field at seven cross sections near a diversion pipe and constructed regression equations of the observed maximum velocities near the pipe. Because the velocity components in three directions (longitudinal, transverse, and vertical) were significantly greater near the diversion pipe inlet compared with those farther from it, they cannot be neglected in the modeling and design of fish guidance and protection devices for diversion pipes. Our results should be of great value in quantifying the hydraulic fields that are formed around fish guidance devices to design more effective protection for fishes from entrainment into unscreened water-diversion pipes.
- SWATMOD-Prep: Graphical User Interface for Preparing Coupled SWAT-MODFLOW
- Authors: Ryan Bailey; Hendrik Rathjens, Katrin Bieger, Indrajeet Chaubey, Jeffrey Arnold
Abstract: This article presents SWATMOD-Prep, a graphical user interface that couples a SWAT watershed model with a MODFLOW groundwater flow model. The interface is based on a recently published SWAT-MODFLOW code that couples the models via mapping schemes. The spatial layout of SWATMOD-Prep guides the user through the process of importing shape files (sub-basins, hydrologic response units [HRUs], river network) from an existing SWAT model, creating a grid, performing necessary geo-processing operations to link the models, writing out SWAT-MODFLOW files, and running the simulation. The option of creating a new single-layer MODFLOW model for near-surface alluvial aquifers is available, with the user prompted to provide groundwater surface elevation (through a digital elevation model), aquifer thickness, and necessary aquifer parameter values. The option of simulating nitrate transport in the aquifer also is available, using the reactive transport model RT3D. The interface is in the public domain. It is programmed in Python, with various software packages used for geo-processing operations (e.g., selection, intersection of rasters) and inputting/outputting data, and is written for Windows. The use of SWATMOD-Prep is demonstrated for the Little River Experimental Watershed, Georgia. SWATMOD-Prep and SWAT-MODFLOW executables are available with an accompanying user's manual at: http://swat.tamu.edu/software/swat-modflow/. The user's manual also accompanies this article as Supporting Information.
- Issue Information
- PubDate: 2017-02-02T08:13:14.443126-05:
- Effects of Impervious Area and BMP Implementation and Design on Storm
Runoff and Water Quality in Eight Small Watersheds
- Authors: Brent T. Aulenbach; Mark N. Landers, Jonathan W. Musser, Jaime A. Painter
Abstract: The effects of increases in effective impervious area (EIA) and the implementation of water quality protection designed detention pond best management practices (BMPs) on storm runoff and stormwater quality were assessed in Gwinnett County, Georgia, for the period 2001-2008. Trends among eight small watersheds were compared, using a time trend study design. Significant trends were detected in three storm hydrologic metrics and in five water quality constituents that were adjusted for variability in storm characteristics and climate. Trends in EIA ranged from 0.10 to 1.35, and changes in EIA treated by BMPs ranged from 0.19 to 1.32; both expressed in units of percentage of drainage area per year. Trend relations indicated that for every 1% increase in watershed EIA, about 2.6, 1.1, and 1.5% increases in EIA treated by BMPs would be required to counteract the effects of EIA added to the watersheds on peak streamflow, stormwater yield, and storm streamflow runoff, respectively. Relations between trends in EIA, BMP implementation, and water quality were counterintuitive. This may be the result of (1) changes in constituent inputs in the watersheds, especially downstream of areas treated by BMPs; (2) BMPs may have increased the duration of stormflow that results in downstream channel erosion; and/or (3) spurious relationships between increases in EIA, BMP implementation, and constituent inputs with development rates.
- Probabilistic Flood Inundation Forecasting Using Rating Curve Libraries
- Authors: Caleb A. Buahin; Nikhil Sangwan, Cassandra Fagan, David R. Maidment, Jeffery S. Horsburgh, E. James Nelson, Venkatesh Merwade, Curtis Rae
Abstract: One approach for performing uncertainty assessment in flood inundation modeling is to use an ensemble of models with different conceptualizations, parameters, and initial and boundary conditions that capture the factors contributing to uncertainty. However, the high computational expense of many hydraulic models renders their use impractical for ensemble forecasting. To address this challenge, we developed a rating curve library method for flood inundation forecasting. This method involves pre-running a hydraulic model using multiple inflows and extracting rating curves, which prescribe a relation between streamflow and stage at various cross sections along a river reach. For a given streamflow, flood stage at each cross section is interpolated from the pre-computed rating curve library to delineate flood inundation depths and extents at a lower computational cost. In this article, we describe the workflow for our rating curve library method and the Rating Curve based Automatic Flood Forecasting (RCAFF) software that automates this workflow. We also investigate the feasibility of using this method to transform ensemble streamflow forecasts into local, probabilistic flood inundation delineations for the Onion and Shoal Creeks in Austin, Texas. While our results show water surface elevations from RCAFF are comparable to those from the hydraulic models, the ensemble streamflow forecasts used as inputs to RCAFF are the largest source of uncertainty in predicting observed floods.
- Comparing Costs of Onsite Best Management Practices to Nutrient Credits
for Stormwater Management: A Case Study in Virginia
- Authors: Alicia L. Nobles; Jonathan L. Goodall, G. Michael Fitch
Abstract: Best management practices (BMPs) are widely used to mitigate impacts of increased impervious surfaces on stormwater runoff. However, there is limited detailed and up-to-date information available on the cost of designing, constructing, and maintaining BMPs over their lifetime. The objective of this study is to analyze BMPs recently constructed by the Virginia Department of Transportation (VDOT) to quantify their total cost per pound of phosphorus removed annually. A motivating factor for the study is recent changes to regulatory guidelines in Virginia which allow for full or partial substitution of purchased nutrient credits in lieu of constructing onsite BMPs to achieve compliance with stormwater quality regulations. Results of the analysis of nine BMPs found their cost ranged from $20,100 to $74,900, in 2014 dollars, per pound ($44,313-$165,126 per kg) of phosphorus removed. Based on these results and assuming current credit prices procured by VDOT, purchasing nutrient credits is a cost-effective option for the agency, especially when factoring in the cost of additional right of way for the BMP. Based on this finding, we expect compliance with stormwater quality regulations through credit purchases to become more widely used in Virginia. Moving forward, we suggest more direct tracking of BMP costs to support comparisons between BMP costs across a range of types and conditions to credit purchases for meeting stormwater regulations.
- The Watershed Flow and Allocation Model: An NHDPlus-Based Watershed
Modeling Approach for Multiple Scales and Conditions
- Authors: Michele C. Eddy; Fekadu G. Moreda, Robert M. Dykes, Brandon Bergenroth, Aaron Parks, James Rineer
Abstract: The Watershed Flow and Allocation model (WaterFALL®) provides segment-specific, daily streamflow at both gaged and ungaged locations to generate the hydrologic foundation for a variety of water resources management applications. The model is designed to apply across the spatially explicit and enhanced National Hydrography Dataset (NHDPlus) stream and catchment network. To facilitate modeling at the NHDPlus catchment scale, we use an intermediate-level rainfall-runoff model rather than a complex process-based model. The hydrologic model within WaterFALL simulates rainfall-runoff processes for each catchment within a watershed and routes streamflow between catchments, while accounting for withdrawals, discharges, and onstream reservoirs within the network. The model is therefore distributed among each NHDPlus catchment within the larger selected watershed. Input parameters including climate, land use, soils, and water withdrawals and discharges are georeferenced to each catchment. The WaterFALL system includes a centralized database and server-based environment for storing all model code, input parameters, and results in a single instance for all simulations allowing for rapid comparison between multiple scenarios. We demonstrate and validate WaterFALL within North Carolina at a variety of scales using observed streamflows to inform quantitative and qualitative measures, including hydrologic flow metrics relevant to the study of ecological flow management decisions.
- Fish and Invertebrate Flow-Biology Relationships to Support the
Determination of Ecological Flows for North Carolina
- Authors: Jennifer Phelan; Tom Cuffney, Lauren Patterson, Michele Eddy, Robert Dykes, Sam Pearsall, Chris Goudreau, Jim Mead, Fred Tarver
Abstract: A method was developed to characterize fish and invertebrate responses to flow alteration in the state of North Carolina. This method involved using 80th percentile linear quantile regressions to relate six flow metrics to the diversity of riffle-run fish and benthic Ephemeroptera, Plecoptera, and Trichoptera (EPT) richness. All twelve flow-biology relationships were found to be significant, with both benthos and fish showing negative responses to ecodeficits and reductions in flow. The responses of benthic richness to reduced flows were consistent and generally greater than that of fish diversity. However, the riffle-run fish guild showed the greatest reductions in diversity in response to summer ecodeficits. The directional consistency and differential seasonal sensitivities of fish and invertebrates to reductions in flow highlight the need to consider seasonality when managing flows. In addition, all relationships were linear, and therefore do not provide clear thresholds to support ecological flow determinations and flow prescriptions to prevent the degradation of fish and invertebrate communities in North Carolina rivers and streams. A method of setting ecological flows based on the magnitude of change in biological condition that is acceptable to society is explored.
- Flow-Biology Relationships Based on Fish Habitat Guilds in North Carolina
- Authors: Lauren Patterson; Jennifer Phelan, Chris Goudreau, Robert Dykes
Abstract: The health of freshwater biota is dependent on streamflow, yet identification of the flow regimes required to maintain ecological integrity remains challenging to states in the United States seeking to establish ecological flows. We tested the relationship between decreases in streamflow and Shannon-Weaver diversity index of fish species for four flow-based habitat guilds: riffle, riffle-run, pool-run, and pool in North Carolina. We found species that prefer shallow habitats, such as riffles and riffle-runs were the most sensitive to decreases in streamflow; whereas no significant relationships were found for pool or pool-run species. The sensitivity to decreases in streamflow was greatest during summer and fall, when streams are naturally lower. When all fish habitat guilds were included in the assessment of flow-biology relationships, there were no significant relationships to decreases in streamflow. As the sensitivity of fish to reductions in streamflow is not constant across habitat guilds, combining all fish species together for flow-biology analyses may greatly underestimate the response of fish species to decreases in flow and should be acknowledged when establishing ecological flows.
- Evaluating Flow Metric-Based Stream Classification Systems to Support the
Determination of Ecological Flows in North Carolina
- Authors: Michele C. Eddy; Jennifer Phelan, Lauren Patterson, Jessie Allen, Sam Pearsall
Abstract: Hydroecological classification systems are typically based on an assemblage of streamflow metrics and seek to divide streams into ecologically relevant classes. Assignment of streams to classes is suggested as an initial step in the process of establishing ecological flow standards. We used two distinct hydroecological river classification systems available within North Carolina to evaluate the ability of a hydrologic model to assign the same classes as those determined by observed streamflows and to assess the transferability of such systems to ungaged streams. Class assignments were examined by rate of overall matches, rate of class matches, spatial variability in matches, and time period used in class assignment. The findings of this study indicate assignments of stream class: (1) are inconsistent among different classification systems; (2) differ between observed and modeled data; and (3) are sensitive to the period of record within observed data. One clear source of inconsistency/sensitivity in class assignments lies with the use of threshold values for metrics that distinguish stream classes, such that even small changes in metric values can result in different class assignments. Because these two hydroecological classification systems are representative of other classification systems that rely on quantitative decision thresholds, it can be surmised that the use of such systems based on stream flow metrics is not a reliable approach for guiding ecological flow determinations.
- Featured Collection Introduction: North Carolina Ecological Flows
- Authors: Sam Pearsall; Michele Eddy, Jennifer Phelan
- Estimating Root Zone Soil Moisture at Continental Scale Using Neural
- Authors: Xiaojun Pan; Kurt C. Kornelsen, Paulin Coulibaly
Abstract: This study investigates the feasibility of artificial neural networks (ANNs) to retrieve root zone soil moisture (RZSM) at the depths of 20 cm (SM20) and 50 cm (SM50) at a continental scale, using surface information. To train the ANNs to capture interactions between land surface and various climatic patterns, data of 557 stations over the continental United States were collected. A sensitivity analysis revealed that the ANNs were able to identify input variables that directly affect the water and energy balance in root zone. The data important for RZSM retrieval in a large area included soil texture, surface soil moisture, and the cumulative values of air temperature, surface soil temperature, rainfall, and snowfall. The results showed that the ANNs had high skill in retrieving SM20 with a correlation coefficient above 0.7 in most cases, but were less effective at estimating SM50. The comparison of the ANNs showed that using soil texture data improved the model performance, especially for the estimation of SM50. It was demonstrated that the ANNs had high flexibility for applications in different climatic regions. The method was used to generate RZSM in North America using Soil Moisture and Ocean Salinity (SMOS) soil moisture data, and achieved a spatial soil moisture pattern comparable to that of Global Land Data Assimilation System Noah model with comparable performance to the SMOS surface soil moisture retrievals. The models can be efficient alternatives to assimilate remote sensing soil moisture data for shallow RZSM retrieval.
- Editor-in-Chief Search
- Pages: 1 - 2
- Book Reviews
- Authors: Richard H. McCuen
- Does Including Soil Moisture Observations Improve Operational Streamflow
Forecasts in Snow-Dominated Watersheds?
- Authors: Adrian A. Harpold; Kent Sutcliffe, Jordan Clayton, Angus Goodbody, Shareily Vazquez
Abstract: Changing climate and growing water demand are increasing the need for robust streamflow forecasts. Historically, operational streamflow forecasts made by the Natural Resources Conservation Service have relied on precipitation and snow water equivalent observations from Snow Telemetry (SNOTEL) sites. We investigate whether also including SNOTEL soil moisture observations improve April-July streamflow volume forecast accuracy at 0, 1, 2, and 3-month lead times at 12 watersheds in Utah and California. We found statistically significant improvement in 0 and 3-month lead time accuracy in 8 of 12 watersheds and 10 of 12 watersheds for 1 and 2-month lead times. Surprisingly, these improvements were insensitive to soil moisture metrics derived from soil physical properties. Forecasts were made with volumetric water content (VWC) averaged from October 1 to the forecast date. By including VWC at the 0-month lead time the forecasts explained 7.3% more variability and increased the streamflow volume accuracy by 8.4% on average compared to standard forecasts that already explained an average 77% of the variability. At 1 to 3-month lead times, the inclusion of soil moisture explained 12.3-26.3% more variability than the standard forecast on average. Our findings indicate including soil moisture observations increased statistical streamflow forecast accuracy and thus, could potentially improve water supply reliability in regions affected by changing snowpacks.
- Estimation of Catchment Nutrient Loads in New Zealand Using Monthly Water
Quality Monitoring Data
- Authors: T.H. Snelder; R.W. McDowell, C.E. Fraser
Abstract: Causes of variation between loads estimated using alternative calculation methods and their repeatability were investigated using 20 years of daily flow and monthly concentration samples for 77 rivers in New Zealand. Loads of dissolved and total nitrogen and phosphorus were calculated using the Ratio, L5, and L7 methods. Estimates of loads and their precision associated with short-term records of 5, 10, and 15 years were simulated by subsampling. The representativeness of the short-term loads was quantified as the standard deviation of the 20 realizations. The L7 method generally produced more realistic loads with the highest precision and representativeness. Differences between load estimates were shown to be associated with poor agreement between the data and the underlying model. The best method was shown to depend on the match between the model and functional and distributional characteristics of the data, rather than on the contaminant. Short-term load estimates poorly represented the long-term load estimate, and deviations frequently exceeded estimated imprecision. The results highlight there is no single preferred load calculation method, the inadvisability of “unsupervised” load estimation and the importance of inspecting concentration-flow, unit load-flow plots and regression residuals. Regulatory authorities should be aware that the precision of loads estimated from monthly data are likely to be “optimistic” with respect to the actual repeatability of load estimates.
- Numerical and Qualitative Contrasts of Two Statistical Models for Water
Quality Change in Tidal Waters
- Authors: Marcus W. Beck; Rebecca R. Murphy
Abstract: Two statistical approaches, weighted regression on time, discharge, and season and generalized additive models, have recently been used to evaluate water quality trends in estuaries. Both models have been used in similar contexts despite differences in statistical foundations and products. This study provided an empirical and qualitative comparison of both models using 29 years of data for two discrete time series of chlorophyll-a (chl-a) in the Patuxent River estuary. Empirical descriptions of each model were based on predictive performance against the observed data, ability to reproduce flow-normalized trends with simulated data, and comparisons of performance with validation datasets. Between-model differences were apparent but minor and both models had comparable abilities to remove flow effects from simulated time series. Both models similarly predicted observations for missing data with different characteristics. Trends from each model revealed distinct mainstem influences of the Chesapeake Bay with both models predicting a roughly 65% increase in chl-a over time in the lower estuary, whereas flow-normalized predictions for the upper estuary showed a more dynamic pattern, with a nearly 100% increase in chl-a in the last 10 years. Qualitative comparisons highlighted important differences in the statistical structure, available products, and characteristics of the data and desired analysis.
- PRISM vs. CFSR Precipitation Data Effects on Calibration and Validation of
- Authors: D.E. Radcliffe; R. Mukundan
Abstract: Precipitation is one of the most important drivers in watershed models. Our objective was to compare two sources of interpolated precipitation data in terms of their effect on calibration and validation of two Soil and Water Assessment Tool (SWAT) models. One model was a suburban watershed in metropolitan Atlanta, Georgia. The precipitation sources were Parameter-elevation Relationships on Independent Slopes Model (PRISM) data on a 4-km grid and climate forecast system reanalysis (CFSR) data on a 38-km grid. The PRISM data resulted in a better fit to the calibration data (Nash Sutcliffe efficiency [NSE] = 0.64, Kling-Gupta efficiency [KGE] = 0.74, p-factor = 0.84, and r-factor = 0.43) than the CFSR data (NSE = 0.47, KGE = 0.53, p-factor = 0.67, and r-factor = 0.39). Validation results were similar. Sensitive parameters were similar in both the PRISM and CFSR models, but fitted values indicated more rapid groundwater flow to the streams with the PRISM data. The same comparison was made in the Big Creek watershed located approximately 1,000 km away, in central Louisiana. Results were similar with a more responsive groundwater system indicating PRISM data may produce better predictions of streamflow because of a more accurate estimate of rainfall within a watershed or because of a denser grid. Our study implies PRISM is providing a better estimate than CFSR of precipitation within a watershed when rain gauge data are not available, resulting in more accurate simulations of streamflows at the watershed outlet. Editor's note: This paper is part of the featured series on SWAT Applications for Emerging Hydrologic and Water Quality Challenges. See the February 2017 issue for the introduction and background to the series.
- Modes of Variability of Annual and Seasonal Rainfall in Mexico
- Authors: Gabriela Alvarez-Olguin; Carlos Escalante-Sandoval
Abstract: The aim of this study is to identify temporal and spatial variability patterns of annual and seasonal rainfall in Mexico. A set of 769 weather stations located in Mexico was examined. The country was divided into 12 homogeneous rainfall regions via principal component analysis. A Pettitt test was conducted to perform a homogeneity analysis for detecting abrupt changes in mean rainfall levels, and a Mann-Kendall test was conducted to examine the presence of monotonically increasing/decreasing patterns in the data. In total, 14.4% of the annual series was deemed nonstationary. Fourteen percent of the samples were nonstationary in the winter and summer, and 9% were nonstationary in the spring and autumn. According to the results, the nonstationarity of some seasonal rainfall series may be associated with the presence of atmospheric phenomena (e.g., El Niño/Southern Oscillation, Pacific Decadal Oscillation, Atlantic Multidecadal Oscillation, and North Atlantic Oscillation). A rainfall frequency analysis was performed for the nonstationary annual series, and significant differences in the return levels x^T can be expected for the scenarios analyzed. The identification of areas that are more susceptible to changes in rainfall levels will improve water resource management plans in the country, and it is expected that these plans will take into account nonstationary theory.
- Featured Series Introduction: SWAT Applications for Emerging Hydrologic
and Water Quality Challenges
- Authors: Venkatesh Merwade; Claire Baffaut, Katrin Bieger, Laurie Boithias, Hendrik Rathjens
- Testing of the Modified Streambank Erosion and Instream Phosphorus
Routines for the SWAT Model
- Authors: A.R. Mittelstet; D.E. Storm, G.A. Fox
Abstract: In some watersheds, streambanks are a source of two major pollutants, phosphorus (P) and sediment. P originating from both uplands and streambanks can be transported and stored indefinitely on floodplains, streambanks, and in closed depressions near the stream. The objectives of this study were to (1) test the modified streambank erosion and instream P routines for the Soil and Water Assessment Tool (SWAT) model in the Barren Fork Creek watershed in northeast Oklahoma, (2) predict P in the watershed with and without streambank-derived P, and (3) determine the significance of streambank erosion P relative to overland P sources. Measured streambank and channel parameters were incorporated into a flow-calibrated SWAT model and used to estimate streambank erosion and P for the Barren Fork Creek using modified streambank erosion and instream P routines. The predicted reach-weighted streambank erosion was 40 kg/m vs. the measured 42 kg/m. Streambank erosion contributed 47% of the total P to the Barren Fork Creek and improved P predictions compared to observed data, especially during the high-flow events. Of the total P entering the stream system, approximately 65% was removed via the watershed outlet and 35% was stored in the floodplain and stream system. This study successfully applied the SWAT model's modified streambank erosion and instream P routines and demonstrated that streambank-derived P can improve P modeling at the watershed scale. Editor's note: This paper is part of the featured series on SWAT Applications for Emerging Hydrologic and Water Quality Challenges. See the February 2017 issue for the introduction and background to the series.
- Spatial and Temporal Evaluation of Hydrological Response to Climate and
Land Use Change in Three South Dakota Watersheds
- Authors: Manashi Paul; Mohammad Adnan Rajib, Laurent Ahiablame
Abstract: This study analyzed changes in hydrology between two recent decades (1980s and 2010s) with the Soil and Water Assessment Tool (SWAT) in three representative watersheds in South Dakota: Bad River, Skunk Creek, and Upper Big Sioux River watersheds. Two SWAT models were created over two discrete time periods (1981-1990 and 2005-2014) for each watershed. National Land Cover Datasets 1992 and 2011 were, respectively, ingested into 1981-1990 and 2005-2014 models, along with corresponding weather data, to enable comparison of annual and seasonal runoff, soil water content, evapotranspiration (ET), water yield, and percolation between these two decades. Simulation results based on the calibrated models showed that surface runoff, soil water content, water yield, and percolation increased in all three watersheds. Elevated ET was also apparent, except in Skunk Creek watershed. Differences in annual water balance components appeared to follow changes in land use more closely than variation in precipitation amounts, although seasonal variation in precipitation was reflected in seasonal surface runoff. Subbasin-scale spatial analyses revealed noticeable increases in water balance components mostly in downstream parts of Bad River and Skunk Creek watersheds, and the western part of Upper Big Sioux River watershed. Results presented in this study provide some insight into recent changes in hydrological processes in South Dakota watersheds. Editor's note: This paper is part of the featured series on SWAT Applications for Emerging Hydrologic and Water Quality Challenges. See the February 2017 issue for the introduction and background to the series.
- Introduction to SWAT+, A Completely Restructured Version of the Soil and
Water Assessment Tool
- Authors: Katrin Bieger; Jeffrey G. Arnold, Hendrik Rathjens, Michael J. White, David D. Bosch, Peter M. Allen, Martin Volk, Raghavan Srinivasan
Abstract: SWAT+ is a completely restructured version of the Soil and Water Assessment Tool (SWAT) that was developed to face present and future challenges in water resources modeling and management and to meet the needs of the worldwide user community. It is expected to improve code development and maintenance; support data availability, analysis, and visualization; and enhance the model's capabilities in terms of the spatial representation of elements and processes within watersheds. The most important change is the implementation of landscape units and flow and pollutant routing across the landscape. Also, SWAT+ offers more flexibility than SWAT in defining management schedules, routing constituents, and connecting managed flow systems to the natural stream network. To test the basic hydrologic function of SWAT+, it was applied to the Little River Experimental Watershed (Georgia) without enhanced overland routing and compared with previous models. SWAT+ gave similar results and inaccuracies as these models did for streamflow and water balance. Taking full advantage of the new capabilities of SWAT+ regarding watershed discretization and landscape and river interactions is expected to improve simulations in future studies. While many capabilities of SWAT have already been enhanced in SWAT+ and new capabilities have been added, the model will continue to evolve in response to advancements in scientific knowledge and the demands of the growing worldwide user community. Editor's note: This paper is part of the featured series on SWAT Applications for Emerging Hydrologic and Water Quality Challenges. See the February 2017 issue for the introduction and background to the series.
- Impacts of Human Behavioral Heterogeneity on the Benefits of Probabilistic
Flood Warnings: An Agent-Based Modeling Framework
- Authors: Erhu Du; Samuel Rivera, Ximing Cai, Laura Myers, Andrew Ernest, Barbara Minsker
Abstract: Flood forecasts and warnings are intended to reduce flood-related property damages and loss of human life. Considerable research has improved flood forecasting accuracy (e.g., more accurate prediction of the occurrence of flood events) and lead time. However, the delivery of improved forecast information alone is not necessarily sufficient to reduce flood damage and loss of life, as people have varying responses and reactions to flood warnings. This study develops an agent-based modeling framework that evaluates the impacts of heterogeneity in human behaviors (i.e., variation in behaviors in response to flood warnings), as well as residential density, on the benefits of flood warnings. The framework is coupled with a traffic model to simulate evacuation processes within a road network under various flood warning scenarios. The results show the marginal benefit associated with providing better flood warnings is significantly constrained if people behave in a more risk-tolerant manner, especially in high-density residential areas. The results also show significant impacts of human behavioral heterogeneity on the benefits of flood warnings, and thus stress the importance of considering human behavioral heterogeneity in simulating flood warning-response systems. Further study is suggested to more accurately model human responses and behavioral heterogeneity, as well as to include more attributes of residential areas to estimate and improve the benefits of flood warnings.
- AutoRAPID: A Model for Prompt Streamflow Estimation and Flood Inundation
Mapping over Regional to Continental Extents
- Authors: Michael L. Follum; Ahmad A. Tavakoly, Jeffrey D. Niemann, Alan D. Snow
Abstract: This article couples two existing models to quickly generate flow and flood-inundation estimates at high resolutions over large spatial extents for use in emergency response situations. Input data are gridded runoff values from a climate model, which are used by the Routing Application for Parallel computatIon of Discharge (RAPID) model to simulate flow rates within a vector river network. Peak flows in each river reach are then supplied to the AutoRoute model, which produces raster flood inundation maps. The coupled tool (AutoRAPID) is tested for the June 2008 floods in the Midwest and the April-June 2011 floods in the Mississippi Delta. RAPID was implemented from 2005 to 2014 for the entire Mississippi River Basin (1.2 million river reaches) in approximately 45 min. Discretizing a 230,000-km2 area in the Midwest and a 109,500-km2 area in the Mississippi Delta into thirty-nine 1° by 1° tiles, AutoRoute simulated a high-resolution (~10 m) flood inundation map in 20 min for each tile. The hydrographs simulated by RAPID are found to perform better in reaches without influences from unrepresented dams and without backwater effects. Flood inundation maps using the RAPID peak flows vary in accuracy with F-statistic values between 38.1 and 90.9%. Better performance is observed in regions with more accurate peak flows from RAPID and moderate to high topographic relief.
- Conceptual Framework for the National Flood Interoperability Experiment
- Authors: David R. Maidment
Abstract: The National Flood Interoperability Experiment is a research collaboration among academia, National Oceanic and Atmospheric Administration National Weather Service, and government and commercial partners to advance the application of the National Water Model for flood forecasting. In preparation for a Summer Institute at the National Water Center in June-July 2015, a demonstration version of a near real-time, high spatial resolution flood forecasting model was developed for the continental United States. The river and stream network was divided into 2.7 million reaches using the National Hydrography Dataset Plus geospatial dataset and it was demonstrated that the runoff into these stream reaches and the discharge within them could be computed in 10 min at the Texas Advanced Computing Center. This study presents a conceptual framework to connect information from high-resolution flood forecasting with real-time observations and flood inundation mapping and planning for local flood emergency response.
- A Comprehensive Python Toolkit for Accessing High‐Throughput Computing
to Support Large Hydrologic Modeling Tasks
- Authors: Scott D. Christensen; Nathan R. Swain, Norman L. Jones, E. James Nelson, Alan D. Snow, Herman G. Dolder
Abstract: The National Flood Interoperability Experiment (NFIE) was an undertaking that initiated a transformation in national hydrologic forecasting by providing streamflow forecasts at high spatial resolution over the whole country. This type of large‐scale, high‐resolution hydrologic modeling requires flexible and scalable tools to handle the resulting computational loads. While high‐throughput computing (HTC) and cloud computing provide an ideal resource for large‐scale modeling because they are cost‐effective and highly scalable, nevertheless, using these tools requires specialized training that is not always common for hydrologists and engineers. In an effort to facilitate the use of HTC resources the National Science Foundation (NSF) funded project, CI‐WATER, has developed a set of Python tools that can automate the tasks of provisioning and configuring an HTC environment in the cloud, and creating and submitting jobs to that environment. These tools are packaged into two Python libraries: CondorPy and TethysCluster. Together these libraries provide a comprehensive toolkit for accessing HTC to support hydrologic modeling. Two use cases are described to demonstrate the use of the toolkit, including a web app that was used to support the NFIE national‐scale modeling.
- Continental‐Scale River Flow Modeling of the Mississippi River Basin
Using High‐Resolution NHDPlus Dataset
- Authors: Ahmad A. Tavakoly; Alan D. Snow, Cédric H. David, Michael L. Follum, David R. Maidment, Zong‐Liang Yang
Abstract: As a key component of the National Flood Interoperability Experiment (NFIE), this article presents the continental scale river flow modeling of the Mississippi River Basin (MRB), using high‐resolution river data from NHDPlus. The Routing Application for Parallel computatIon of Discharge (RAPID) was applied to the MRB with more than 1.2 million river reaches for a 10‐year study (2005‐2014). Runoff data from the Variable Infiltration Capacity (VIC) model was used as input to RAPID. This article investigates the effect of topography on RAPID performance, the differences between the VIC‐RAPID streamflow simulations in the HUC‐2 regions of the MRB, and the impact of major dams on the streamflow simulations. The model performance improved when initial parameter values, especially the Muskingum K parameter, were estimated by taking topography into account. The statistical summary indicates the RAPID model performs better in the Ohio and Tennessee Regions and the Upper and Lower Mississippi River Regions in comparison to the western part of the MRB, due to the better performance of the VIC model. The model accuracy also increases when lakes and reservoirs are considered in the modeling framework. In general, results show the VIC‐RAPID streamflow simulation is satisfactory at the continental scale of the MRB.