- A Geospatial Methodology to Identify Locations of Concentrated Runoff from
- Authors: Gregory Hancock; Stuart E. Hamilton, Monica Stone, Jim Kaste, John Lovette
Abstract: A geospatial methodology has been developed that utilizes high resolution lidar‐derived DEMs to help track runoff from agricultural fields and identify areas of potential concentrated flow through vegetated riparian areas in the Coastal Plain of Virginia. Points of concentrated flow are identified across 74 agricultural fields within the Virginia portion of the Chesapeake Bay watershed. On average, 70% of the surface area of the agricultural fields analyzed drains through less than 20 m of the field margin, and on average 81% of the field surface area drains through 1% or less of the field margin. Within the riparian buffer, locations that were predicted by the geospatial model to have high levels of concentrated flow were found to exhibit evidence of channelization. Results indicate that flow concentration and channelized flow through vegetated riparian areas may be common along the margin of agricultural fields, resulting in vegetated riparian areas that are less effective at sediment trapping than assumed. Additional results suggest that the regulations governing the location and width of vegetated riparian may not be sufficient to achieve goals for reducing sediment and nutrient runoff from nonpoint agricultural sources. Combined with the increasing availability of lidar‐derived DEMs, the geospatial model presented has the potential to advance management practices aimed at reducing nonpoint source pollution leaving agricultural fields.
- Regional Blue and Green Water Balances and Use by Selected Crops in the
- Authors: Michael White; Marilyn Gambone, Haw Yen, Jeff Arnold, Daren Harmel, Chinnasamy Santhi, Richard Haney
Abstract: The availability of freshwater is a prerequisite for municipal development and agricultural production, especially in the arid and semiarid portions of the western United States (U.S.). Agriculture is the leading user of water in the U.S. Agricultural water use can be partitioned into green (derived from rainfall) and blue water (irrigation). Blue water can be further subdivided by source. In this research, we develop a hydrologic balance by 8‐Digit Hydrologic Unit Code using a combination of Soil and Water Assessment Tool simulations and available human water use estimates. These data are used to partition agricultural groundwater usage by sustainability and surface water usage by local source or importation. These predictions coupled with reported agricultural yield data are used to predict the virtual water contained in each ton of corn, wheat, sorghum, and soybeans produced and its source. We estimate that these four crops consume 480 km3 of green water annually and 23 km3 of blue water, 12 km3 of which is from groundwater withdrawal. Regional trends in blue water use from groundwater depletion highlight heavy usage in the High Plains, and small pockets throughout the western U.S. This information is presented to inform water resources debate by estimating the cost of agricultural production in terms of water regionally. This research illustrates the variable water content of the crops we consume and export, and the source of that water.
- Using GIS to Delineate Headwater Stream Origins in the Appalachian
Coalfields of Kentucky
- Authors: Jonathan A. Villines; Carmen T. Agouridis, Richard C. Warner, Christopher D. Barton
Abstract: Headwater streams have a significant nexus or physical, chemical, and/or biological connection to downstream reaches. Generally, defined as 1st‐3rd order with ephemeral, intermittent, or perennial flow regimes, these streams account for a substantial portion of the total stream network particularly in mountainous terrain. Due to their often remote locations, small size, and large numbers, conducting field inventories of headwater streams is challenging. A means of estimating headwater stream location and extent according to flow regime type using publicly available spatial data is needed to simplify this complex process. Using field‐collected headwater point of origin data from three control watersheds, streams were characterized according to a set of spatial parameters related to topography, geology, and soils. These parameters were (1) compared to field‐collected point of origin data listed in three nearby Jurisdictional Determinations, (2) used to develop a geographic information system (GIS)‐based stream network for identifying ephemeral, intermittent, and perennial streams, and (3) applied to a larger watershed and compared to values obtained using the high‐resolution National Hydrography Dataset (NHD). The parameters drainage area and local valley slope were the most reliable predictors of flow regime type. Results showed the high‐resolution NHD identified no ephemeral streams and 9 and 65% fewer intermittent and perennial streams, respectively, than the GIS model.
- Using Fly Ash as a Marker to Quantify Culturally‐Accelerated
Sediment Accumulation in Playa Wetlands
- Authors: Zhenghong Tang; Yue Gu, Jeff Drahota, Ted LaGrange, Andy Bishop, Mark S. Kuzila
Abstract: Wetlands in the Rainwater Basin in Nebraska are vulnerable to sediment accumulation from the surrounding watershed. Sediment accumulation has a negative impact on wetland quality by decreasing the depth and volume of water stored, and the plant community species composition and density growing in the wetland. The objective of this study was to determine the amount of sediment that has accumulated in five selected wetlands in the Rainwater Basin in Nebraska. Soil cores were taken at five or six locations along transects across each wetland. This study used the fly ash, which is generated by coal‐burning locomotives that were present generally in the late 1800s and early 1900s, as a marker to quantify the sediment deposition rates. The cores were divided into 5 cm sections and the soils were analyzed using a fly ash extraction and identification technique. Results indicate that the average depth of sediment ranged from 23.00 to 38.00 cm. The annual average depth of sediment accumulation ranged from 0.18 cm/yr to 0.29 cm/yr. The annual sediment accumulation rate from both wind erosion and water erosion in these five sampling wetlands was between 1.946 and 3.225 kg/m2/yr. The results of this research can be used to develop restoration plans for wetlands. The fly ash testing technology can also be applied to other areas with the railroads across the United States.
- Long‐Term Trends of Nutrients and Sediment from the Nontidal
Chesapeake Watershed: An Assessment of Progress by River and Season
- Authors: Qian Zhang; Damian C. Brady, Walter R. Boynton, William P. Ball
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.
- Landowner Motivations for Civic Engagement in Water Resource Protection
- Authors: Amit K. Pradhananga; Mae Davenport, Bjorn Olson
Abstract: Scholars and water resource professionals recognize citizens must get involved in water resource issues to protect water resources. Yet questions persist on how to motivate community members to get and stay civically involved in nonpoint source pollution issues, given that problems are often ill‐defined. To be successful, interventions intended to engage individuals in collective action must be based on an understanding of the determinants of public‐sphere behavior. The purpose of this study is to explore the psycho‐social factors which influence landowner civic engagement in water resource protection. Data were collected using a self‐administered mail survey of landowners in the Cannon River Watershed and analyzed using structural equation modeling. Study findings suggest landowners are more likely to be civically engaged in water resource issues if they feel a personal obligation to take civic action and perceive they have the ability to protect water resources. Landowners who believe water resource protection is a local responsibility, perceive important others expect them to protect water resources, and believe they have the ability to protect water resources are more likely to feel a sense of obligation to take civic action. A combination of strategies including civic engagement programs addressing barriers to landowner engagement will be most effective for promoting civic engagement in water resource protection.
- Getting to the First Handshake: Enhancing Security by Initiating
Cooperation in Transboundary River Basins
- Abstract: How does transboundary water cooperation begin at the initial stages, and how can third parties help to foster said cooperation? Many nations with transboundary waters do not cooperate or have ceased cooperation. Yet cooperation often prevails, resulting in 688 water‐related treaties signed from 1820 to 2007. We address the following: by which practices can development partners best design and implement cooperative projects at the state level to enhance basin water security in the earliest stages? This article identifies strategies for initiating cooperation and lessons drawn from reviewing select cases. We compiled from the Oregon State University Transboundary Freshwater Dispute Database all transboundary water resources projects over the last decade with multinational participation. We selected 10 case studies that enhance water security that fit the following filtering criteria: (1) Funding exclusively/primarily from outside sources, (2) Including nonofficial stakeholders in project design/implementation, (3) Absence of formal relations around water resources between or among the riparian nations before the project was discussed, (4) Project design possibly enhancing hydropolitical relations. Findings suggest that to enhance water security, project designs should respect participating riparians' autonomies, create basin‐wide networks of scientists, allow for each partner to garner responsibility for project activities, and consult a diverse group of stakeholders.
- Trust in Sources of Soil and Water Quality Information: Implications for
Environmental Outreach and Education
- Authors: Amber Saylor Mase; Nicholas L. Babin, Linda Stalker Prokopy, Kenneth D. Genskow
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.
- Mediated Modeling in Water Resource Dialogues Connecting Multiple Scales
- Authors: Marjan Belt; Daniella Blake
Abstract: We observe a paradigm shift toward collaborative, multi‐level (from local to global) water management and suggestions for scale‐related design principles in the literature. Decision‐support tools are needed that can help achieve scale design principles. Mediated modeling (MM) refers to model building with people, rather than for people. This tool belongs to a family of participatory, systems oriented tools. This article explores their suitability for addressing challenges and principles that arise at multiple‐scales. MM can promote the understanding of cross‐level and cross‐scale links, creating salient, credible, and legitimate knowledge and encouraging boundary functions. Prerequisites for successful MM processes include an openness and willingness to collaborative learning. As new “meso‐level” institutions emerge to address complex challenges in water management collaboratively, tools like MM may play an important role in structuring dialogues, developing adaptive management capacity and advance an ecosystem services approach.
- Two‐Stage Ditch Floodplains Enhance N‐Removal Capacity and
Reduce Turbidity and Dissolved P in Agricultural Streams
- Authors: Ursula H. Mahl; Jennifer L. Tank, Sarah S. Roley, Robert T. Davis
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 (
- Implementing Innovative Drainage Management Practices in the Mississippi
River Basin to Enhance Nutrient Reductions
- Abstract: In the Mississippi River Basin (MRB), practices that enhance drainage (e.g., channelization, tile drainage) are necessary management tools in order to maintain optimal agricultural production in modern farming systems. However, these practices facilitate, and may speed the delivery of excess nutrients and sediments to downstream water bodies via agricultural streams and ditches. These nonpoint sources contribute to elevated nutrient loading in the Gulf of Mexico, which has been linked to widespread hypoxia and associated ecological and economic problems. Research suggests agricultural drainage ditches are important links between farm fields and downstream ecosystems, and application of new management practices may play an important role in the mitigation of water quality impairments from agricultural watersheds. In this article, we describe how researchers and producers in the MRB are implementing and validating novel best management practices (BMPs) that if used in tandem could provide producers with continued cropping success combined with improved environmental protection. We discuss three BMPs — low‐grade weirs, slotted inlet pipes, and the two‐stage ditch. While these new BMPs have improved the quality of water leaving agricultural landscapes, they have been validated solely in isolation, at opposite ends of the MRB. These BMPs have similar function and would greatly benefit from stacked incorporation across the MRB to the benefit of the basin as a whole.
- Quantifying Tradeoffs Associated with Hydrologic Environmental Flow
- Authors: S. Kyle McKay
Abstract: Freshwater management requires balancing and tradingoff multiple objectives, many of which may be competing. Ecological needs for freshwater are often described in terms of environmental flow recommendations (e.g., minimum flows), and there are many techniques for developing these recommendations, which range from hydrologic rules to multidisciplinary analyses supported by large teams of subject matter experts. Although hydrologic rules are well acknowledged as overly simplified, these techniques remain the state‐of‐the‐practice in many locations. This article seeks to add complexity to the application of these techniques by studying the emergent properties of hydrologic environmental flow methodologies. Two hydrologic rules are applied: minimum flow criteria and sustainability boundaries. Objectives and metrics associated with withdrawal rate and similarity to natural flow regimes are used to tradeoff economic and environmental needs, respectively, over a range of flow thresholds and value judgments. A case study of hypothetical water withdrawals on the Middle Oconee River near Athens, Georgia is applied to demonstrate these techniques. For this case study, sustainability boundaries emerge as preferable relative to both environmental and economic outcomes. Methods applied here provide a mechanism for examining the role of stakeholder values and tradeoffs in application of hydrologic rules for environmental flows.
- Sources and Transport of Phosphorus to Rivers in California and Adjacent
States, U.S., as Determined by SPARROW Modeling
- Authors: Joseph Domagalski; Dina Saleh
Abstract: The SPARROW (SPAtially Referenced Regression on Watershed attributes) model was used to simulate annual phosphorus loads and concentrations in unmonitored stream reaches in California, U.S., and portions of Nevada and Oregon. The model was calibrated using de‐trended streamflow and phosphorus concentration data at 80 locations. The model explained 91% of the variability in loads and 51% of the variability in yields for a base year of 2002. Point sources, geological background, and cultivated land were significant sources. Variables used to explain delivery of phosphorus from land to water were precipitation and soil clay content. Aquatic loss of phosphorus was significant in streams of all sizes, with the greatest decay predicted in small‐ and intermediate‐sized streams. Geological sources, including volcanic rocks and shales, were the principal control on concentrations and loads in many regions. Some localized formations such as the Monterey shale of southern California are important sources of phosphorus and may contribute to elevated stream concentrations. Many of the larger point source facilities were located in downstream areas, near the ocean, and do not affect inland streams except for a few locations. Large areas of cultivated land result in phosphorus load increases, but do not necessarily increase the loads above those of geological background in some cases because of local hydrology, which limits the potential of phosphorus transport from land to streams.
- SPARROW Modeling of Nitrogen Sources and Transport in Rivers and Streams
of California and Adjacent States, U.S.
- Authors: Dina Saleh; Joseph Domagalski
Abstract: The SPARROW (SPAtially Referenced Regressions On Watershed attributes) model was used to evaluate the spatial distribution of total nitrogen (TN) sources, loads, watershed yields, and factors affecting transport and decay in the stream network of California and portions of adjacent states for the year 2002. The two major TN sources to local catchments on a mass basis were fertilizers and manure (51.7%) and wastewater discharge (15.9%). Other sources contributed
- Reducing Fertilizer‐Nitrogen Losses from Rowcrop Landscapes:
Insights and Implications from a Spatially Explicit Watershed Model
- Authors: Eileen McLellan; Keith Schilling, Dale Robertson
Abstract: We present conceptual and quantitative models that predict changes in fertilizer‐derived nitrogen delivery from rowcrop landscapes caused by agricultural conservation efforts implemented to reduce nutrient inputs and transport and increase nutrient retention in the landscape. To evaluate the relative importance of changes in the sources, transport, and sinks of fertilizer‐derived nitrogen across a region, we use the spatially explicit SPAtially Referenced Regression On Watershed attributes watershed model to map the distribution, at the small watershed scale within the Upper Mississippi‐Ohio River Basin (UMORB), of: (1) fertilizer inputs; (2) nutrient attenuation during delivery of those inputs to the UMORB outlet; and (3) nitrogen export from the UMORB outlet. Comparing these spatial distributions suggests that the amount of fertilizer input and degree of nutrient attenuation are both important in determining the extent of nitrogen export. From a management perspective, this means that agricultural conservation efforts to reduce nitrogen export would benefit by: (1) expanding their focus to include activities that restore and enhance nutrient processing in these highly altered landscapes; and (2) targeting specific types of best management practices to watersheds where they will be most valuable. Doing so successfully may result in a shift in current approaches to conservation planning, outreach, and funding.
- Instream Bacteria Influences from Bird Habitation of Bridges
- Authors: David Pendergrass; Anne McFarland, Larry Hauck
Abstract: The representativeness of ambient water samples collected from bridge crossings has occasionally been challenged because critics contend birds nesting on bridges elevate fecal indicator bacteria concentrations over samples collected from river reaches not spanned by bridges. This study was designed to evaluate the influence, if any, of bridge‐dwelling bird colonies on instream bacteria concentrations. Three bridges in central Texas were sampled under dry‐weather conditions for instream Escherichia coli. Two bridges were inhabited by migratory cliff swallows and one was devoid of birds. Numerous samples were collected from locations upstream, at the upstream bridgeface, and downstream of each bridge to determine whether significant increases in E. coli occurred in a downstream direction when birds were present. E. coli values increased significantly at bridgeface and downstream locations compared to upstream locations throughout the nesting season. During peak bird activity in May, bacteria geometric mean concentrations at bridgeface and downstream locations jumped from background levels 190 colony forming units (CFU)/100 mL, well above the state geometric mean criterion of 126 CFU/100 mL for primary contact recreation use. Results confirmed that under dry‐weather conditions bird colonies can have a significant impact on bacteria concentrations in the vicinity of the bridges they inhabit and therefore, to avoid this impact, monitoring should occur upstream of bridges.
- An Analysis of the Effects of Land Use and Land Cover on Flood Losses
along the Gulf of Mexico Coast from 1999 to 2009
- Authors: Samuel D. Brody; Wesley E. Highfield, Russell Blessing
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.
- Bankfull Regional Curves for the Alleghany Plateau/Valley and Ridge,
Piedmont, and Coastal Plain Regions of Maryland
- Authors: Tamara L. McCandless; Richard R. Starr, William A. Harman
Abstract: Regional curves are empirical relationships that can help identify the bankfull stage in ungaged watersheds and aid in designing the riffle dimension in stream restoration projects. Bankfull regional curves were developed from gage stations with drainage areas less than 102 mi2 (264.2 km2) for the Alleghany Plateau/Valley and Ridge (AP/VR), Piedmont, and Coastal Plain regions of Maryland. The AP/VR regions were combined into one region for this project. These curves relate bankfull discharge, cross‐sectional area, width, and mean depth to drainage area within the same hydro‐physiographic region (region with similar rainfall/runoff relationship). The bankfull discharge curve for the Coastal Plain region was further subdivided into the Western Coastal Plain (WCP) and Eastern Coastal Plain (ECP) region due to differences in topography and runoff. Results show that the Maryland Piedmont yields the highest bankfull discharge rate per unit drainage area, followed by the AP/VR, WCP, and ECP. Likewise, the Coastal Plain and AP/VR streams have less bankfull cross‐sectional area per unit drainage area than the Piedmont. The average bankfull discharge return interval across the three hydro‐physiographic regions was 1.4 years. The Maryland regional curves were compared to other curves in the eastern United States. The average bankfull discharge return interval for the other studies ranged from 1.1 to 1.8 years.
- Evaluating Geomorphic Change in Constructed Two‐Stage Ditches
- Authors: Jessica L. D'Ambrosio; Andrew D. Ward, Jonathan D. Witter
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.
- Influence of Riparian Seepage Zones on Nitrate Variability in Two
Agricultural Headwater Streams
- Authors: Mark R. Williams; Anthony R. Buda, Herschel A. Elliott, Kamini Singha, James Hamlett
Abstract: Riparian seeps have been recognized for their contributions to stream flow in headwater catchments, but there is limited data on how seeps affect stream water quality. The objective of this study was to examine the effect of seeps on the variability of stream NO3‐N concentrations in FD36 and RS, two agricultural catchments in Pennsylvania. Stream samples were collected at 10‐m intervals over reaches of 550 (FD36) and 490 m (RS) on 21 occasions between April 2009 and January 2012. Semi‐variogram analysis was used to quantify longitudinal patterns in stream NO3‐N concentration. Seep water was collected at 14 sites in FD36 and 7 in RS, but the number of flowing seeps depended on antecedent conditions. Seep NO3‐N concentrations were variable (0.1‐29.5 mg/l) and were often greater downslope of cropped fields compared to other land uses. During base flow, longitudinal variability in stream NO3‐N concentrations increased as the number of flowing seeps increased. The influence of seeps on the variability of stream NO3‐N concentrations was less during storm flow compared to the variability of base flow NO3‐N concentrations. However, 24 h after a storm in FD36, an increase in the number of flowing seeps and decreasing streamflow resulted in the greatest longitudinal variability in stream NO3‐N concentrations recorded. Results indicate seeps are important areas of NO3‐N delivery to streams where targeted adoption of mitigation measures may substantially improve stream water quality.
- Adaptive Targeting: Engaging Farmers to Improve Targeting and Adoption of
Agricultural Conservation Practices
- Authors: Margaret M. Kalcic; Jane Frankenberger, Indrajeet Chaubey, Linda Prokopy, Laura Bowling
Abstract: Targeting of agricultural conservation practices to cost‐effective locations has long been of interest to watershed managers, yet its implementation cannot succeed without meaningful engagement of agricultural producers who are decision makers on the lands they farm. In this study, we engaged 14 west‐central Indiana producers and landowners in an adaptive targeting experiment. Interviews carried out prior to targeting provided rich spatial information on existing conservation practices as well as producers' preferences for future conservation projects. We targeted six of the most accepted conservation practices using the Soil and Water Assessment Tool and spatial optimization using a genetic algorithm approach. Fairly optimal conservation scenarios were possible with even the most limiting constraints of farmer‐accepted practices. We presented in follow‐up interviews a total of 176 conservation practice recommendations on 103 farm fields to 10 farmers whose lands were targeted for conservation. Primary findings indicated producers were interested in the project, were open to hearing recommendations about their lands, and expressed a high likelihood of adopting 35% of targeted recommendations. Farmers generally viewed the interview process and presentation of results quite favorably, and the interviews were found to build trust and make the targeting process more acceptable to them.
- Spatial Optimization of Six Conservation Practices Using Swat
in Tile‐Drained Agricultural Watersheds
- Authors: Margaret M. Kalcic; Jane Frankenberger, Indrajeet Chaubey
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%.
- A National Assessment of the Potential Linkage between Soil, and Surface
and Groundwater Concentrations of Phosphorus
- Authors: R.W. McDowell; N. Cox, C.J. Daughney, D. Wheeler, M. Moreau
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.
- Restoration of Riparian Buffer Function in Reclaimed Surface Mine Soils
- Authors: Nathan H. Rahe; Karl W.J. Williard, Jon E. Schoonover
Abstract: Ecosystem processes such as water infiltration and denitrification largely determine how riparian buffers function to protect surface water quality. Reclaimed mine areas offer a unique opportunity to study the restoration of riparian function without the confounding influence of past land use. Between 1980 and 2000 in southern Illinois, agricultural fields with forest buffers were established along three restored stream reaches in reclaimed mine land. Our research objective was to compare common indicators of soil quality (infiltration, soil C and N, bulk density, and soil moisture) between forest and cultivated riparian zones to determine if riparian function was being restored. Soil bulk density was significantly lower in the forest buffers compared to the agricultural fields. The forest buffers had greater soil total C, total N, and moisture levels than agricultural fields likely due to greater organic matter inputs. Soil total C and N levels in forest buffers were positively related to age of restoration, indicating soil quality is gradually being restored in the buffers. Restoration success of riparian buffers should not be estimated by the return of structure alone; it also includes reestablishment of functions such as nutrient cycling and water retention that largely determine water quality benefits. Watershed planning efforts can expect a lag time on the order of decades between riparian restoration activities and surface water quality improvement.
- The Influence of Two‐Stage Ditches with Constructed Floodplains on
Water Column Nutrients and Sediments in Agricultural Streams
- Authors: Robert T. Davis; Jennifer L. Tank, Ursula H. Mahl, Sarah G. Winikoff, Sarah S. Roley
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.
- Featured Collection Introduction: Agricultural Hydrology and Water Quality
- Authors: Anthony R. Buda; Karl W.J. Williard, Jon E. Schoonover, M.S. Srinivasan
- Comparing Green and Grey Infrastructure Using Life Cycle Cost and
Environmental Impact: A Rain Garden Case Study in Cincinnati, OH
- Authors: Donald Vineyard; Wesley W. Ingwersen, Troy R. Hawkins, Xiaobo Xue, Bayou Demeke, William Shuster
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.
- Projected Changes in Discharge in an Agricultural Watershed in Iowa
- Authors: Gabriele Villarini; Enrico Scoccimarro, Kathleen D. White, Jeffrey R. Arnold, Keith E. Schilling, Joyee Ghosh
Abstract: Our improved capability to adapt to the future changes in discharge is linked to our capability to predict the magnitude or at least the direction of these changes. For the agricultural United States Midwest, too much or too little water has severe socioeconomic impacts. Here, we focus on the Raccoon River at Van Meter, Iowa, and use a statistical approach to examine projected changes in discharge. We build on statistical models using rainfall and harvested corn and soybean acreage to explain the observed discharge variability. We then use projections of these two predictors to examine the projected discharge response. Results are based on seven global climate models part of the Coupled Model Intercomparison Project Phase 5 and two representative concentration pathways (RCPs 4.5 and 8.5). There is not a strong signal of change in the discharge projections under the RCP 4.5. However, the results for the RCP 8.5 point to a stronger changing signal related to larger projected increases in rainfall, resulting in increased trends, in particular, in the upper part of the discharge distribution (i.e., 60th percentile and above). Examination of two hypothetical agricultural scenarios indicates that these increasing trends could be alleviated by decreasing the extent of the agricultural production. We also discuss how the methodology presented in this study represents a viable approach to move forward with the concept of return period for engineering design and management in a nonstationary world.
- Stream Temperature Patterns over 35 Years in a Managed Forest of Western
- Authors: Maryanne Reiter; Robert E. Bilby, Storm Beech, John Heffner
Abstract: Stream temperature changes as a result of forest practices have been a concern in the Pacific Northwest for several decades. As a result of this concern, stream protection requirements for forest lands were first adopted in the early 1970s and have become progressively more stringent. While there have been multiple studies examining the effects of stream protection buffers on water temperature, there are few studies examining temperature patterns over long periods on intensively managed forests. Water temperature in the upper Deschutes River watershed, Washington has been monitored since 1975 and represents one of the longest studies of water quality on managed forests in the Pacific Northwest. This data record, collected from basins of varying sizes, has enabled us to examine the combined effects of hydro‐climatic patterns and forest management on stream temperature. Effects of harvest conducted prior to buffer regulations were clearly identifiable and most pronounced on smaller streams. We were not able to detect any response on larger channels to more recent timber harvest where riparian buffers were required. This analysis also emphasizes that it is critical to account for changing climate when examining long‐term temperature patterns. We found that in many cases the temperature improvements associated with more stringent buffer requirements implemented over the last 35 years in the Deschutes watershed have been offset by warming climatic conditions.
- 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.
- Regional and Temporal Differences in Nitrate Trends Discerned from
Long‐Term Water Quality Monitoring Data
- Authors: E.G. Stets; V.J. Kelly, C.G. Crawford
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.
- Hydrologic Effects of Surface Coal Mining in Appalachia (U.S.)
- Authors: Daniel M. Evans; Carl E. Zipper, Erich T. Hester, Stephen H. Schoenholtz
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.
- Combination of Biological and Habitat Indices for Assessment of Idaho
- Authors: Benjamin Jessup; Jason Pappani
Abstract: States and tribes are encouraged to use multiple biological assemblages in assessment of water bodies. An assessment index for each assemblage provides information on aspects of the aquatic resource that may be unique in terms of stressor sensitivity, stressor type, or ecological scale. However, assessment results relative to impairment thresholds can disagree among indices for an individual water body, leading to uncertain overall water‐body assessments. We explored options for combining stream indices for macroinvertebrates, fish, and habitat in ways that would yield the most consistent and sensitive results relative to established disturbance categories. Methods varied in the scoring or rating scales used to standardize each index value, the thresholds used to define impairment of aquatic life uses, and the ways of synthesizing multiple indices. The index compositing method that scores each index on a continuous scale and averages the scores after standardizing had superior accuracy, sensitivity, and precision. In addition, using the 25th quantile of reference sites instead of the 10th quantile resulted in a more balanced error rate among reference and degraded site categories.
- Improved Weather Generator Algorithm for Multisite Simulation
of Precipitation and Temperature
- Authors: Leanna M. King; A. Ian McLeod, Slobodan P. Simonovic
Abstract: The KnnCAD Version 4 weather generator algorithm for nonparametric, multisite simulations of temperature and precipitation data is presented. The K‐nearest neighbor weather generator essentially reshuffles the historical data, with replacement. In KnnCAD Version 4, a block resampling scheme is introduced to preserve the temporal correlation structure in temperature data. Perturbation of the reshuffled variable data is also added to enhance the generation of extreme values. The Upper Thames River Basin in Ontario, Canada is used as a case study and the model is shown to simulate effectively the historical characteristics at the site. The KnnCAD Version 4 approach is shown to improve on the previous versions of the model and offers a major advantage over many parametric and semiparametric weather generators in that multisite use can be easily achieved without making statistical assumptions dealing with the spatial correlations and probability distributions of each variable.
- A Level‐of‐Service Concept for Planning Future Water Supply
Projects under Probabilistic Demand and Supply Framework
- Authors: Tirusew Asefa; Alison Adams, Nisai Wanakule
Abstract: One of the most challenging tasks of water supply utilities is planning the timing and quantity of new water supply sources as demand for water consumption grows. Many water supply utilities target on meeting 100% of their customers' needs based on scenario‐based deterministic demand projections numbers even though there are uncertainties in both supply and demand values. This may result in under or overly conservative approach in assessing future needs. In this article, a level‐of‐service concept is introduced to capture a utility's willingness to accept a given level of risk, plan for it, and invoke a management strategy during extreme events than build a facility to accommodate those in planning for new water supply sources. Accounting for uncertainties in both supply and demand help quantify reliability by achieving a prescribed level of service. The major benefit of such an approach for planning future water supply is that it allows policy makers to evaluate the use of adaptive water management strategies and develop supply in an incremental fashion as demand warrants it. For example, if a given level of service cannot be reliably met with the existing system at a future time t, an incremental water supply project would come online to bring the required reliability level up but no more.
- A Faster and Economical Approach to Floodplain Mapping Using Soil
- Authors: Nikhil Sangwan; Venkatesh Merwade
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.
- Modeling Streamflow and Water Quality Sensitivity to Climate Change and
Urban Development in 20 U.S. Watersheds
- Authors: T. Johnson; J. Butcher, D. Deb, M. Faizullabhoy, P. Hummel, J. Kittle, S. McGinnis, L.O. Mearns, D. Nover, A. Parker, S. Sarkar, R. Srinivasan, P. Tuppad, M. Warren, C. Weaver, J. Witt
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.
- 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
- 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.
- Robust Prioritization of Climate Change Adaptation Strategies Using the
VIKOR Method with Objective Weights
- 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.
- 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.
- 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.
- 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.
- 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.