Showing papers in "Journal of The American Water Resources Association in 2015"

Calibration and Verification of SWMM for Low Impact Development

Abstract: The Storm Water Management Model was used to simulate runoff and nutrient export from a lowimpact development (LID) watershed and a watershed using traditional runoff controls. Predictions werecompared to observed values. Uncalibrated simulations underpredicted weekly runoff volume and average peakflow rates from the multiple subcatchment LID watershed by over 80%; the single subcatchment traditionalwatershed had better predictions. Saturated hydraulic conductivity, Manning’s n for swales, and initial soilmoisture deficit were sensitive parameters. After calibration, prediction of total weekly runoff volume for theLID and traditional watersheds improved to within 12 and 5% of observed values, respectively. For the valida-tion 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 >0.5for both calibration and validation periods were only achieved for prediction of total nitrogen export from theLID watershed. Simulation of a 100-year, 24-h storm resulted in a runoff coefficient of 0.46 for the LIDwatershed and 0.59 for the traditional watershed. Results suggest either calibration is needed to improve predic-tions for LID watersheds or expanded look-up tables for Green–Ampt infiltration parameter values that accountfor compaction of urban soil and antecedent conditions are needed.(KEY TERMS: SWMM; low impact development; modeling; simulation; calibration; runoff; infiltration; nutri-ents.)Rosa, David J., John C. Clausen, and Michael E. Dietz, 2015. Calibration and Verification of SWMM for LowImpact Development. Journal of the American Water Resources Association (JAWRA) 1-12. DOI: 10.1111/jawr.12272INTRODUCTIONThe Storm Water Management Model (SWMM) isa widely used rainfall-runoff simulation model whoselatest version has the ability to model low impactdevelopment (LID) techniques (Rossman, 2009). Thegoal of LID is to maintain the pre-developmenthydrology of a site, thereby reducing negative effectson receiving waters (Prince George’s County, 1999a).Example LID practices include cluster development,bioretention areas, permeable pavement, and grassedswales that serve to reduce imperviousness and man-age stormwater runoff through storage, infiltration,evapotranspiration, and retention. LID practices usedat a watershed level have been demonstrated tosignificantly reduce stormwater runoff volume, peakflow and the mass exports of several pollutants instormwater compared with traditional development(Dietz and Clausen, 2008; Bedan and Clausen, 2009).LID design has traditionally been aimed at cap-turing and treating storms with return periods less

Analysis of Meteorological Drought Pattern During Different Climatic and Cropping Seasons in Bangladesh

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 andnorthwest of Bangladesh It is expected that the findings of the study will support drought monitoring and mitigation activities in Bangladesh

Reducing nitrogen export from the corn belt to the Gulf of Mexico: agricultural strategies for remediating hypoxia.

Abstract: SPAtially Referenced Regression on Watershed models developed for the Upper Midwest were used to help evaluate the nitrogen-load reductions likely to be achieved by a variety of agricultural conservation practices in the Upper Mississippi-Ohio River Basin (UMORB) and to compare these reductions to the 45% nitrogen-load reduction proposed to remediate hypoxia in the Gulf of Mexico (GoM). Our results indicate that nitrogen-management practices (improved fertilizer management and cover crops) fall short of achieving this goal, even if adopted on all cropland in the region. The goal of a 45% decrease in loads to the GoM can only be achieved through the coupling of nitrogen-management practices with innovative nitrogen-removal practices such as tile-drainage treatment wetlands, drainage–ditch enhancements, stream-channel restoration, and floodplain reconnection. Combining nitrogen-management practices with nitrogen-removal practices can dramatically reduce nutrient export from agricultural landscapes while minimizing impacts to agricultural production. With this approach, it may be possible to meet the 45% nutrient reduction goal while converting less than 1% of cropland in the UMORB to nitrogen-removal practices. Conservationists, policy makers, and agricultural producers seeking a workable strategy to reduce nitrogen export from the Corn Belt will need to consider a combination of nitrogen-management practices at the field scale and diverse nitrogen-removal practices at the landscape scale.

Comparing Green and Grey Infrastructure Using Life Cycle Cost and Environmental Impact: A Rain Garden Case Study in Cincinnati, OH

Abstract: Green infrastructure (GI) is quickly gaining ground as a less costly, greener alternative to traditional methods of stormwater management. One popular form of GI is the use of rain gardens to capture and treat stormwater. We used life cycle assessment (LCA) to compare environmental impacts of residential rain gardens constructed in the Shepherd's Creek watershed of Cincinnati, Ohio to those from a typical detain and treat system. LCA is an internationally standardized framework for analyzing the potential environmental performance of a product or service by including all stages in its life cycle, including material extraction, manufacturing, use, and disposal. Complementary to the life cycle environmental impact assessment, the life cycle costing approach was adopted to compare the equivalent annual costs of each of these systems. These analyses were supplemented by modeling alternative scenarios to capture the variability in implementing a GI strategy. Our LCA models suggest rain garden costs and impacts are determined by labor requirement; the traditional alternative's impacts are determined largely by the efficiency of wastewater treatment, while costs are determined by the expense of tunnel construction. Gardens were found to be the favorable option, both financially (~42% cost reduction) and environmentally (62-98% impact reduction). Wastewater utilities may find significant life cycle cost and environmental impact reductions in implementing a rain garden plan.

The Influence of Two‐Stage Ditches with Constructed Floodplains on Water Column Nutrients and Sediments in Agricultural Streams

Abstract: The two-stage ditch is a novel management practice originally implemented to increase bank stability through floodplain restoration in channelized agricultural streams To determine the effects of two-stage construction on sediment and nutrient loads, we monitored turbidity, and also measured total suspended solids (TSS), dissolved inorganic nitrogen (N) species, and phosphorus (P) after two-stage ditch construction in reference and manipulated reaches of four streams Turbidity decreased during floodplain inundation at all sites, but TSS and P, soluble reactive phosphorus (SRP) and total phosphorus (TP) decreased only in the two-stage ditches with longer duration of inundation Both TSS and TP were positively correlated within individual streams, but neither were correlated with turbidity Phosphorus was elevated in the stream to which manure was applied adjacent to the two-stage reach, but not the reference reach, suggesting that landscape nutrient management plans could restrict nutrient transport to the stream, ultimately determining the efficacy of instream management practices In addition, ammonium and nitrate decreased in two-stage reaches with lower initial N concentrations Overall, results suggest that turbidity, TSS, and TP were reduced during floodplain inundation, but the two-stage alone may not be effective for managing high inorganic N loads

Development and Evaluation of Bankfull Hydraulic Geometry Relationships for the Physiographic Regions of the United States

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.

Two-Stage Ditch Floodplains Enhance N-Removal Capacity and Reduce Turbidity and Dissolved P in Agricultural Streams

Abstract: Two-stage ditches represent an emerging management strategy in artificially drained agricultural landscapes that mimics natural floodplains and has the potential to improve water quality. We assessed the potential for the two-stage ditch to reduce sediment and nutrient export by measuring water column turbidity, nitrate (NO3−), ammonium (NH4+), and soluble reactive phosphorus (SRP) concentrations, and denitrification rates. During 2009-2010, we compared reaches with two-stage floodplains to upstream reaches with conventional trapezoid design in six agricultural streams. At base flow, these short two-stage reaches (<600 m) reduced SRP concentrations by 3-53%, but did not significantly reduce NO3− concentrations due to very high NO3− loads. The two-stage also decreased turbidity by 15-82%, suggesting reduced suspended sediment export during floodplain inundation. Reach-scale N-removal increased 3-24 fold during inundation due to increased bioreactive surface area with high floodplain denitrification rates. Inundation frequency varied with bench height, with lower benches being flooded more frequently, resulting in higher annual N-removal. We also found both soil organic matter and denitrification rates were higher on older floodplains. Finally, influence of the two-stage varied among streams and years due to variation in stream discharge, nutrient loads, and denitrification rates, which should be considered during implementation to optimize potential water quality benefits.

Long-Term Trends of Nutrients and Sediment from the Nontidal Chesapeake Watershed: An Assessment of Progress by River and Season

Abstract: To assess historical loads of nitrogen (N), phosphorus (P), and suspended sediment (SS) from the nontidal Chesapeake Bay watershed (NTCBW), we analyzed decadal seasonal trends of flow-normalized loads at the fall-line of nine major rivers that account for >90% of NTCBW flow. Evaluations of loads by season revealed N, P, and SS load magnitudes have been highest in January-March and lowest in July-September, but the temporal trends have followed similar decadal-scale patterns in all seasons, with notable exceptions. Generally, total N (TN) load has dropped since the late 1980s, but particulate nutrients and SS have risen since the mid-1990s. The majority of these rises were from Susquehanna River and relate to diminished net trapping at the Conowingo Reservoir. Substantial rises in SS were also observed, however, in other rivers. Moreover, the summed rise in particulate P load from other rivers is of similar magnitude as from Susquehanna. Dissolved nutrient loads have dropped in the upland (Piedmont and above) rivers, but risen in two small rivers in the Coastal Plain affected by lagged groundwater input. In addition, analysis of fractional contributions revealed consistent N trends across the upland watersheds. Finally, total N:total P ratios have declined in most rivers, suggesting the potential for changes in nutrient limitation. Overall, this integrated study of historical data highlights the value of maintaining long-term monitoring at multiple watershed locations.

Salinity as a Limiting Factor for Biological Condition in Mining‐Influenced Central Appalachian Headwater Streams

Abstract: Recent studies have found that Appalachian coal mining causes increased surface water salinity, and that benthic macroinvertebrate communities in salinized mining-influenced streams differ from communities in streams draining unmined areas. Understanding the role of salinity in shaping these communities is challenging because such streams are often influenced by a variety of stressors in addition to salinity. We characterized associations of salinity with biotic condition while isolating salinity from other stressors through rigorous site selection. We used a multimetric index of biotic condition to characterize benthic macroinvertebrate communities in headwater streams in the Central Appalachian Ecoregion of Virginia across a gradient of sulfate-dominated salinity. We found strong negative seasonal correlations between biotic condition and three salinity measures (specific conductance, total dissolved solids, and SO42− concentration). We found no evidence to suggest stressors other than salinity as significant influences on biotic condition in these streams. Our results confirm negative associations of salinity with benthic macroinvertebrate community condition, as observed in other studies. Thus, our findings demonstrate that elevated salinity is an important limiting factor for biological condition in Central Appalachian headwater streams.

Hydrologic Effects of Surface Coal Mining in Appalachia (U.S.)

Abstract: Surface coal mining operations alter landscapes of the Appalachian Mountains, United States, by replacing bedrock with mine spoil, altering topography, removing native vegetation, and constructing mine soils with hydrologic properties that differ from those of native soils. Research has demonstrated hydrologic effects of mining and reclamation on Appalachian landscapes include increased peakflows at newly mined and reclaimed watersheds in response to strong storm events, increased subsurface void space, and increased base flows. We review these investigations with a focus on identifying changes to hydrologic flow paths caused by surface mining for coal in the Appalachian Mountains. We introduce two conceptual control points that govern hydrologic flow paths on mined lands, including the soil surface that partitions infiltration vs. surface runoff and a potential subsurface zone that partitions subsurface storm flow vs. deeper percolation. Investigations to improve knowledge of hydrologic pathways on reclaimed Appalachian mine sites are needed to identify effects of mining on hydrologic processes, aid development of reclamation methods to reduce hydrologic impacts, and direct environmental mitigation and public policy.

The Aging of America's Reservoirs: In-Reservoir and Downstream Physical Changes and Habitat Implications

Abstract: Reservoirs are important for various purposes including flood control, water supply, power generation, and recreation. The aging of America's reservoirs and progressive loss of water storage capacity resulting from ongoing sedimentation, coupled with increasing societal needs, will cause the social, economic, environmental, and political importance of reservoirs to continually increase. The short- and medium-term ( 50 years) environmental changes as reservoirs enter “old” age are less understood. Additional research is needed to help guide the future management of aging reservoir systems and support the difficult decisions that will have to be made. Important research directions include assessment of climate change effects on aging and determination of ecosystem response to ongoing aging and various management actions that may be taken with the intent of minimizing or reversing the physical effects of aging.

Agricultural BMP Effectiveness and Dominant Hydrological Flow Paths: Concepts and a Review

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.

Hydrological Responses to Climate and Land-Use Changes along the North American East Coast: A 110-Year Historical Reconstruction†

Abstract: The North American east coast (NAEC) region experienced significant climate and land-use changes in the past century. To explore how these changes have affected land water cycling, the Dynamic Land Ecosystem Model (DLEM 2.0) was used to investigate the spatial and temporal variability of runoff and river discharge during 1901-2010 in the study area. Annual runoff over the NAEC was 420 ± 61 mm/yr (average ± standard deviation). Runoff increased in parts of the northern NAEC but decreased in some areas of the southern NAEC. Annual freshwater discharge from the study area was 378 ± 61 km3/yr (average ± standard deviation). Factorial simulation experiments suggested that climate change and variability explained 97.5% of the interannual variability of runoff and also resulted in the opposite changes in runoff in northern and southern regions of the NAEC. Land-use change reduced runoff by 5-22 mm/yr from 1931 to 2010, but the impacts were divergent over the Piedmont region and Coastal Plain areas of the southern NAEC. Land-use change impacts were more significant at local and watershed spatial scales rather than at regional scales. Different responses of runoff to changing climate and land-use should be noted in future water resource management. Hydrological impacts of afforestation and deforestation as well as urbanization should also be noted by land-use policy makers.

Characterizing and Contextualizing the Water Challenges of Megacities

Abstract: We characterize and compare water challenges confronting the 28 megacities of the world in 2014. Relying on existing literature and diverse primary data sources, we present a unique portrait at a global scale of the water implications of the rapid growth in megacities. We find that differentiating and analyzing the complexity of megacities' water problems based on geographic contexts, historical development trajectories, urban population growth rates, and forms of urban expansion helps explain the nature of the various water management problems they confront. Two governance features also shed light on megacity water challenges: fragmentation resulting from forms of megacity urban expansion; and, urban dualism resulting from contradictions between historical and cultural legacies and the rise of global engineering and technological norms for water management. The increasing vulnerability of megacities to climate change poses risks as well as opportunities for a more collective response to address this global phenomenon. Our analysis raises important questions and offers guidance about the future trajectories of many more large cities around the world that are on their way to becoming megacities.

A National Assessment of the Potential Linkage between Soil, and Surface and Groundwater Concentrations of Phosphorus†

Abstract: A meta-analysis of three national databases determined the potential linkage between soil and surface and groundwater enrichment with phosphorus (P). Soil P was enriched especially under dairying commensurate with an increase in cow numbers and the tonnage of P-fertilizers sold. Median P concentrations were enriched in surface waters receiving runoff from industrial and dairy land uses, and in groundwater beneath dairying especially in those aquifers with gravel or sand lithology, irrespective of groundwater redox status. After geographically pairing surface and groundwater sites to maximize the chance of connectivity, a subset of sites dominated by aquifers with gravel and sand lithology showed increasing P concentrations with as little as 10 years data. These data raise the possibility that groundwater could contribute much P to surface water if: there is good connectivity between surface and groundwater, intensive land use occurs on soils prone to leaching, and leached-P is not attenuated through aquifers. While strategies are available to mitigate P loss from intensive farming systems in the short-term, factors such as enriched soils and slow groundwater may mean that despite their use, there will be a long-term input (viz. legacy), that may sustain surface water P enrichment. To avoid poor surface water quality, management and planning may need to consider the connectivity and characteristics of P in soil-groundwater-surface water systems.

Modeling Streamflow and Water Quality Sensitivity to Climate Change and Urban Development in 20 U.S. Watersheds

Abstract: Watershed modeling in 20 large, United States (U.S.) watersheds addresses gaps in our knowledge of streamflow, nutrient (nitrogen and phosphorus), and sediment loading sensitivity to mid-21st Century climate change and urban/residential development scenarios. Use of a consistent methodology facilitates regional scale comparisons across the study watersheds. Simulations use the Soil and Water Assessment Tool. Climate change scenarios are from the North American Regional Climate Change Assessment Program dynamically downscaled climate model output. Urban and residential development scenarios are from U.S. Environmental Protection Agency's Integrated Climate and Land Use Scenarios project. Simulations provide a plausible set of streamflow and water quality responses to mid-21st Century climate change across the U.S. Simulated changes show a general pattern of decreasing streamflow volume in the central Rockies and Southwest, and increases on the East Coast and Northern Plains. Changes in pollutant loads follow a similar pattern but with increased variability. Ensemble mean results suggest that by the mid-21st Century, statistically significant changes in streamflow and total suspended solids loads (relative to baseline conditions) are possible in roughly 30-40% of study watersheds. These proportions increase to around 60% for total phosphorus and total nitrogen loads. Projected urban/residential development, and watershed responses to development, are small at the large spatial scale of modeling in this study.

Spatial Optimization of Six Conservation Practices Using Swat in Tile‐Drained Agricultural Watersheds

Abstract: Targeting of agricultural conservation practices to the most effective locations in a watershed can promote wise use of conservation funds to protect surface waters from agricultural nonpoint source pollution. A spatial optimization procedure using the Soil and Water Assessment Tool was used to target six widely used conservation practices, namely no-tillage, cereal rye cover crops (CC), filter strips (FS), grassed waterways (GW), created wetlands, and restored prairie habitats, in two west-central Indiana watersheds. These watersheds were small, fairly flat, extensively agricultural, and heavily subsurface tile-drained. The targeting approach was also used to evaluate the model's representation of conservation practices in cost and water quality improvement, defined as export of total nitrogen, total phosphorus, and sediment from cropped fields. FS, GW, and habitats were the most effective at improving water quality, while CC and wetlands made the greatest water quality improvement in lands with multiple existing conservation practices. Spatial optimization resulted in similar cost-environmental benefit tradeoff curves for each watershed, with the greatest possible water quality improvement being a reduction in total pollutant loads by approximately 60%, with nitrogen reduced by 20-30%, phosphorus by 70%, and sediment by 80-90%.

Evaluating Geomorphic Change in Constructed Two‐Stage Ditches

Abstract: Straight, trapezoidal-shaped surface drainage channels efficiently drain the soil profile, but their deviations from natural fluvial conditions drive the need for frequent maintenance. Ecological and socioeconomic impacts of drainage ditch maintenance activities can be significant, leading to harmful algal blooms and increased sedimentation. We developed a two-stage ditch design that is more consistent with fluvial form and process. The approach has potential to enhance ecological services while meeting drainage needs essential for agricultural production. We studied geomorphic change of the inset channel, benches and banks of seven two-stage ditches in Ohio, Indiana, and Michigan. Three to 10 years after construction, inset channel changes reflected natural adjustments, but not all ditches had reached their quasi-equilibrium state. Ditches had experienced both degradation and aggradation on the benches at a rate of 0.5-13 mm/yr. Aggradation on the benches was not likely to threaten tile drain outlets. Localized scour was observed on the banks at some sites, but at all but one site changes were not statistically significant. Except for the removal of woody vegetation, none of the ditches required routine maintenance since construction. Two-stage ditches can be a stable, viable option for drainage ditch management if designed and installed properly on the landscape.

Identifying and evaluating a suitable index for agricultural drought monitoring in the texas high plains

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.

Regional and Temporal Differences in Nitrate Trends Discerned from Long‐Term Water Quality Monitoring Data

Abstract: Riverine nitrate (NO3) is a well-documented driver of eutrophication and hypoxia in coastal areas. The development of the elevated river NO3 concentration is linked to anthropogenic inputs from municipal, agricultural, and atmospheric sources. The intensity of these sources has varied regionally, through time, and in response to multiple causes such as economic drivers and policy responses. This study uses long-term water quality, land use, and other ancillary data to further describe the evolution of river NO3 concentrations at 22 monitoring stations in the United States (U.S.). The stations were selected for long-term data availability and to represent a range of climate and land-use conditions. We examined NO3 at the monitoring stations, using a flow-weighting scheme meant to account for interannual flow variability allowing greater focus on river chemical conditions. River NO3 concentration increased strongly during 1945-1980 at most of the stations and have remained elevated, but stopped increasing during 1981-2008. NO3 increased to a greater extent at monitoring stations in the Midwest U.S. and less so at those in the Eastern and Western U.S. We discuss 20th Century agricultural development in the U.S. and demonstrate that regional differences in NO3 concentration patterns were strongly related to an agricultural index developed using principal components analysis. This unique century-scale dataset adds to our understanding of long-term NO3 patterns in the U.S.

Effects of Climate and Land Cover on Hydrology in the Southeastern U.S.: Potential Impacts on Watershed Planning

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.

Development of Sediment and Nutrient Export Coefficients for U.S. Ecoregions

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.

Beijing's Water Resources: Challenges and Solutions

Abstract: Beijing's local water resources have been overexploited and the ecological and environmental pressures exceed the carrying capacity of this densely populated megacity This article examines the current status of Beijing's water resources with respect to its industrial, residential, and eco-environmental water usage and the challenges it may face in the near future The article describes the context of water uses, the steps taken by Beijing to alleviate the water shortage problems, and challenges to Beijing's abilities to meet its urgent and future water needs A multipronged strategy is proposed that aims at both the present problems and the anticipated future challenges In particular, engineering and institutional approaches for Beijing's successful transition from overexploitation to sustainable utilization of water resources are explained Actions include reasonable water utilization, water conservation, reclaimed wastewater, and importing water from neighboring areas We conclude that Beijing must take additional steps in water resource management to ensure its sustainable development that involves continued urbanization sprawls and population growth Future water resource management strategies should focus on strengthening water demand management through water conservation, efficient interbasin water transfers, use of nontraditional water resources, strategically reserving water supply, and promoting rehabilitation of the eco-environments

Development and Operational Testing of a Super‐Ensemble Artificial Intelligence Flood‐Forecast Model for a Pacific Northwest River

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.

Trust in Sources of Soil and Water Quality Information: Implications for Environmental Outreach and Education†

Abstract: Public trust in organizations focused on improving environmental quality is important for increasing awareness and changing behaviors that have water quality implications. Few studies have addressed trust in soil and water quality information sources, particularly for both agricultural and nonagricultural respondents of the same watersheds. Surveys in 19 watersheds across five states in the Midwest assessed trust in, and familiarity with, soil and water quality information sources. Overall, respondents most trusted University Extension, Soil and Water Conservation Districts, and the Natural Resource Conservation Service, while lawn care companies, environmental groups, and land trusts were less trusted. Significant differences in trusted sources were found between watersheds, and between agricultural and nonagricultural respondents across and within watersheds. Among agricultural respondents, a clear relationship exists between familiarity and trust; as familiarity with an organization increases, so too does level of trust. This relationship is less clear-cut for nonagricultural respondents in this region. We highlight implications of these findings for soil and water quality outreach efforts.

Geomorphic and Ecological Consequences of Riprap Placement in River Systems

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.

A Faster and Economical Approach to Floodplain Mapping Using Soil Information

Abstract: Flood inundation maps play a key role in assessment and mitigation of potential flood hazards. However, owing to high costs associated with the conventional flood mapping methods, many communities in the United States lack flood inundation maps. The objective of this study is to develop and examine an economical alternative approach to floodplain mapping using widely available soil survey geographic (SSURGO) database. In this study, floodplain maps are developed for the entire state of Indiana, and some counties in Minnesota, Wisconsin, and Washington states by identifying flood-prone soil map units based on their attributes. For validation, the flood extents obtained from SSURGO database are compared with the extents from other floodplain maps such as the Federal Emergency Management Agency issued flood insurance rate maps (FIRMs), flood extents observed during past floods, and flood maps derived using digital elevation models. In general, SSURGO-based floodplain maps (SFMs) are largely in agreement with other flood inundation maps. Specifically, the floodplain extents from SFMs cover 78-95% area compared to FIRMs and observed flood extents. Thus, albeit with a slight loss in accuracy, the SSURGO approach offers an economical and fast alternative for floodplain mapping. In particular, it has potentially high utility in areas where no detailed flood studies have been conducted.

A Comparison of Bayesian Methods for Uncertainty Analysis in Hydraulic and Hydrodynamic Modeling

Abstract: We evaluate and compare the performance of Bayesian Monte Carlo (BMC), Markov chain Monte Carlo (MCMC), and the Generalized Likelihood Uncertainty Estimation (GLUE) for uncertainty analysis in hydraulic and hydrodynamic modeling (HHM) studies. The methods are evaluated in a synthetic 1D wave routing exercise based on the diffusion wave model, and in a multidimensional hydrodynamic study based on the Environmental Fluid Dynamics Code to simulate estuarine circulation processes in Weeks Bay, Alabama. Results show that BMC and MCMC provide similar estimates of uncertainty. The posterior parameter densities computed by both methods are highly consistent, as well as the calibrated parameter estimates and uncertainty bounds. Although some studies suggest that MCMC is more efficient than BMC, our results did not show a clear difference between the performance of the two methods. This seems to be due to the low number of model parameters typically involved in HHM studies, and the use of the same likelihood function. In fact, for these studies, the implementation of BMC results simpler and provides similar results to MCMC. The results of GLUE are, on the other hand, less consistent to the results of BMC and MCMC in both applications. The posterior probability densities tend to be flat and similar to the uniform priors, which can result in calibrated parameter estimates centered in the parametric space.

An Analysis of the Effects of Land Use and Land Cover on Flood Losses along the Gulf of Mexico Coast from 1999 to 2009

Abstract: Major coastal flooding events over the last decade have led decision makers in the United States to favor structural engineering solutions as a means to protect vulnerable coastal communities from the adverse impacts of future storms. While a resistance-based approach to flood mitigation involving large-scale construction works may be a central component of a regional flood risk reduction strategy, it is equally important to consider the role of land use and land cover (LULC) patterns in protecting communities from floods. To date, little observational research has been conducted to quantify the effects of various LULC configurations on the amount of property damage occurring across coastal regions over time. In response, we statistically examine the impacts of LULC on observed flood damage across 2,692 watersheds bordering the Gulf of Mexico. Specifically, we analyze statistical linear regression models to isolate the influence of multiple LULC categories on over 372,000 insured flood losses claimed under the National Flood Insurance Program per year from 2001 to 2008. Results indicate that percent increase in palustrine wetlands is the equivalent to, on average, a $13,975 reduction in insured flood losses per year, per watershed. These and other results provide important insights to policy makers on how protecting specific types of LULC can help reduce adverse impacts to local communities.

Integrated Modeling of Water Supply and Demand under Management Options and Climate Change Scenarios in Chifeng City, China

Abstract: Water resource management is becoming increasingly challenging in northern China because of the rapid increase in water demand and decline in water supply due to climate change. We provide a case study demonstrating the importance of integrated watershed management in sustaining water resources in Chifeng City, northern China. We examine the consequences of various climate change scenarios and adaptive management options on water supply by integrating the Soil and Water Assessment Tool and Water Evaluation and Planning models. We show how integrated modeling is useful in projecting the likely effects of management options using limited information. Our study indicates that constructing more reservoirs can alleviate the current water shortage and groundwater depletion problems. However, this option is not necessarily the most effective measure to solve water supply problems; instead, improving irrigation efficiency and changing cropping structure may be more effective. Furthermore, measures to increase water supply have limited effects on water availability under a continuous drought and a dry-and-warm climate scenario. We conclude that the combined measure of reducing water demand and increasing supply is the most effective and practical solution for the water shortage problems in the study area.