Search

Land resources are central to understanding the relationship between humans and their environment. We broadly define land resources to include all the ecological resources of climate, water, soil, landforms, flora, and fauna and all the socioeconomic systems that interact with agriculture, forestry, and other land uses within some system boundary. Understanding the vulnerability of land resources to changes in land management or climate forcing is critical to developing sustainable land management strategies. Vulnerability assessments are complex, given the multiple uses of the assessments, the multidisciplinary nature of the problem, limited understanding, the dynamic structure of vulnerability, scale issues, and problems with identifying effective vulnerability indicators. Here, we propose a novel conceptual framework for vulnerability assessments of land resources that combines the driver-pressure-state-impact-response (DPSIR) framework adopted by the European Environment Agency to describe interactions between society and the environment, and the exposure-sensitivity-adaptive capacity (ESA) framework used by the Intergovernmental Panel on Climate Change to assess impacts of climate change. The DPSIR-ESA Vulnerability Assessment (DEVA) framework operationalizes the process of assessing the vulnerability of a target system to external stressors. The DEVA framework includes seven steps: (1) definition of the target system (land resource), (2) description of internal characteristics of the target system (state), (3) description of target system vulnerability indicators (adaptive capacity, sensitivity), (4) description of stressor characteristics (drivers, pressures), (5) description of stressor vulnerability indicators (exposure), (6) description of target system response to stressors (impacts), and (7) description of modifications to target system or stressors (responses). In stating that they have applied the DEVA framework, analysts acknowledge that they (1) have considered the full breadth of each DEVA element, (2) have made conscious decisions to limit the scope and complexity of certain elements, and (3) can communicate both the rationale for these decisions and the impact of these decisions on the vulnerability assessment results and recommendations. The DEVA framework was refined during invited presentations and follow-up discussions at a series of special sessions with leading experts at two successive ASABE Annual International Meetings. Six case studies drawn from the sessions elaborate on the DEVA framework and provide examples of the key concepts. The DEVA framework gives engineers, planners, and analysts a flexible new approach to apply a broad array of useful tools for vulnerability assessment of land resource systems. [ABSTRACT FROM AUTHOR]

This article highlights current research into land and water resources, agroecosystems, and agricultural production systems published by the Natural Resources and Environmental Systems (NRES) community of ASABE journals (Transactions of the ASABE and Applied Engineering in Agriculture) in 2017. Context, scope, and key results of the published articles are reviewed and perhaps more importantly areas for increased research attention are recommended. This article describes experimental and modeling advances in hydrology, agroecosystems, climate change effects, soil erosion, agricultural irrigation, agricultural drainage, forest resource management, livestock systems, natural treatment systems, international water issues, and water quality topic areas. Three special collections were published (International Watershed Technology, Crop Modeling and Decision Support for Optimizing Use of Limited Water, and Advances in Drainage). Other focal areas included 14 articles relating to livestock waste management, 13 concerning irrigated agricultural systems, 8 addressing climate change effects on land, water, and agroecosystems, and 16 on various aspects of soil erosion measurement and modeling. Building on the articles reviewed from 2017 and toward a vision of future agroecosystems research, the NRES community of ASABE journals strives to expand its role in making new knowledge accessible to sustain agricultural and natural systems in a changing world. With this goal in mind, recommendations for future research needs are proposed with an emphasis on increased application of remote sensing data to agroecosystems research, improved assessment of agroecosystem resiliency and vulnerability to land and climate change, development of integrated models of agroecosystem services, meeting stubborn water management challenges in agricultural production systems, and focusing on publishing fully reproducible model results. [ABSTRACT FROM AUTHOR]

The objective of this article is to introduce a collection of articles that explore current research and scientific thought on wetland ecosystem resilience. The collection contains articles on wetland resilience to climate change, agricultural land use-driven change, and recreational land use, along with evaluations of wetland resilience through high-resolution monitoring and modeling tools. Wetland settings in the U.S. span tidal marshes and coastal plain non-riverine wetlands in North Carolina, prairie potholes in Iowa, Appalachian floodplain wetlands, and floating treatment wetlands in the Midwest. The studies in this collection found vertical accretion rates of 0.7 to 4.0 mm year-1 in a tidal marsh, a wide range of potential wetland hydroperiod responses to climate change, substantial decreases in inundation period, crop yield, and surface-water nitrate (but increases in phosphorus) in artificially drained potholes, and nitrate removal in carbon-amended floating treatment wetlands. Further work is needed to better understand how to design and enhance wetland systems in agricultural regions, better preserve wetland ecosystem services in areas affected by land use and climate change, and provide technical standards for the wide range of designs currently used for wetland treatment systems. [ABSTRACT FROM AUTHOR]

Complete, accurate water stage data are often essential for timely, informed water resource analysis, management, and planning. Periods of missing data in long-term water-monitoring programs are inevitable and must be addressed. This study addressed the concern that missing daily stage data have led to miscalculation of the stage-based nutrient criterion in a Florida Everglades marsh and canal system by assessing two models to replace the missing data: a new daily water-balance-based model (WB) and the well-documented gap-fill model (GF) that estimates daily stage based on statistical relationships to selected reference gages. Both models were assessed for data gaps of 1, 7, and 14 days by comparing daily stage estimates to measured stage for every possible 1-day, 7-day, and 14-day data gap over the January 1999 through April 2015 period of record. Both models resulted in smaller overall errors for back-filling marsh gage data than for canal gage data. The WB model was best for filling data gaps up to 14 days at the marsh gages in all seasons. The WB model also outperformed the GF model for the canal gage in all months except June and, to a lesser degree, May and August. Although each model provided a systematic method to replace missing stage data, thereby reducing the bias inherent in calculating the nutrient criterion for cases with missing data, the physical-process-based WB model outperformed the empirical-based GF model and minimized the need for manual error-screening methods to offset errors during periods of poor model performance. [ABSTRACT FROM AUTHOR]

The increasing use of hydrologic and water quality (H/WQ) models for technical, policy, and legal decision making calls for greater transparency in communicating the methods used and decisions made when using H/WQ models. The objectives of this article are to: (1) provide guidelines to properly document H/WQ model calibration, validation, and use, and (2) raise issues about how to improve model documentation and reproducibility, and encourage open discussion of these topics in the H/WQ modeling community. First, eight recommended elements of model documentation and reporting are identified and described, and good examples are provided for each. Next, steps to move the H/WQ modeling community toward a culture of full model reproducibility are discussed. The use by model practitioners of the consistent and comprehensive elements described herein for documentation and reporting of H/WQ model calibration, validation, and use will allow better interpretation of published modeling studies, improve the utility of modeling studies, and allow more systematic advancement of H/WQ models. [ABSTRACT FROM AUTHOR]

Hydrologic and water quality (H/WQ) models are widely used to support site-specific environmental assessment, design, planning, and decision making. Calibration and validation (C/V) are fundamental processes used to demonstrate that an H/WQ model can produce suitable results in a particular application. However, the lack of comprehensive guidelines has led to the use of ad hoc, inconsistent, and incomplete C/V processes, which have made it difficult to interpret the myriad of published modeling studies, reduced the utility of many modeling applications, and slowed the advancement of H/WQ modeling. The objective of this article is to provide a generalized structure and process to assist modelers in developing a C/V strategy for H/WQ modeling applications. These best practice recommendations were developed based on an expansive review of the modeling literature, including a special collection of articles on H/WQ model calibration, validation, and use, as well as extensive discussion and debate among the authors. The model C/V recommendations include careful consideration, execution, and documentation of the following elements: (1) goals of model use, (2) data and parameters used in C/V, and (3) model C/V processes. Considerations in element 3 include the warm-up period, C/V strategy complexity, C/V process staging, spatiotemporal allocation of C/V comparison data, manual vs. automatic C/V, and additional diagnostics. Notable examples from the literature are provided for each strategy element. The comprehensive C/V strategy described herein will allow for better interpretation of future modeling studies, improved utility of modeling applications, and more systematic advancement of H/WQ models. [ABSTRACT FROM AUTHOR]

As a continuation of efforts to provide a common background and platform for development of calibration and validation (C/V) guidelines for hydrologic and water quality (H/WQ) modeling, ASABE members worked to determine critical topics related to model C/V, perform a synthesis of a previously published special collection of articles and other relevant literature, and provide topic-specific recommendations based on the synthesis as well as personal modeling expertise. This article introduces a special collection of nine research articles covering key topics related to calibration and validation of H/WQ models. The topics include: terminology, hydrologic processes and model representation, spatial and temporal scales, model parameterization, C/V strategies, sensitivity, uncertainty, performance measures and criteria, and documentation and reporting. The main objective of this introductory article is to introduce and summarize key aspects of these topics, including recommendations. Individually, the articles provide model practitioners with detailed topic-specific recommendations related to model calibration, validation, and use. Collectively, the articles present recommendations to enhance H/WQ modeling. [ABSTRACT FROM AUTHOR]

Wetlands and coastal systems are unique, highly productive, and often threatened landscapes that provide a host of services to both humans and the environment. This article introduces a five-article Wetlands and Coastal Systems Special Collection that evolved from a featured session at the 2015 ASABE Annual International Meeting in New Orleans, Louisiana. The Collection provides perspectives on tools and techniques for enhancing the protection and restoration of wetlands and coastal systems with emphasis on vegetation, hydrology, water quality, and planning. Topics span the Florida Everglades (two articles) and Virginia floodplain (one article) wetland systems and include remote sensing (one article) and geographic information system-based (one article) modeling tools developed to address wetland planning and analysis issues. The Special Collection provides valuable information to engineers, scientists, planners, and other specialists working on large-scale and small-scale wetlands and coastal systems. [ABSTRACT FROM AUTHOR]

This article introduces a collection of papers from the third biennial ASABE 21st Century Watershed Technology Conference and Workshop: Improving Water Quality and the Environment, held in Bari, Italy, on 26-31 May 2012. This Special Collection consists of seven articles (plus one published previously) selected from the 59 meeting papers. The technical presentations at the conference focused on solving spatial and temporal water quality and quantity problems and addressed topics such as watershed management in developing countries, water quality standards, agricultural best management practice (BMP) effectiveness, emerging problems, impact of extreme weather conditions, biological monitoring, increasing stakeholder involvement, political and economic implications, watershed implementation planning, forest and rangeland water quality issues, and water resources education. At first glance, these topics seem quite diverse. However, a growing trend in cutting-edge hydrological science research, and a thread that emerged from these papers, is that of "data mining." In this article, we make an editorial statement that briefly introduces the basic principles of data mining and uses this concept as an organizing theme to feature eight articles of this Special Collection. [ABSTRACT FROM AUTHOR]

Ephemeral gullies (EGs) are incised channels resulting from concentrated overland flow that often form in a similar location every year. These erosional features add to producers" management efforts and costs. Locating EGs and predicting their length is crucial for estimating sediment load and planning conservation strategies. Since topography plays an important role in the formation of EGs, this study investigated the prediction of EG location and length in two agricultural areas (S1 and S2) in two different physiographic regions using four topographic index models: compound topographic index (CTI), slope area (SA), wetness topographic index (WTI), and slope area power (SAP). The impacts of digital elevation model (DEM) resolution, agricultural land use mask data source, and topographic model critical thresholds were also evaluated. Automated geospatial models were developed to locate and derive EG length. Results show that the SA model predicted EG occurrence and length better than other models tested. The SA and CTI model predictions had similar patterns in terms of locating EG trajectory; however, the CTI model had greater discontinuity along the trajectory. The method developed to derive length in this study was sensitive to discontinuity, so the performance of the CTI model was poor. Finer-resolution DEMs (2 m)predicted EG location and lengths better than coarser-resolution DEMs (10 m or greater). Use of actual field-level reconnaissance data instead of NASS data for agricultural land use masking decreased false negative classification by 16% or more for all models. Detailed calibration of the SA model yielded different optimal thresholds for the two study regions: TSA = 30 for S1 and TSA= 50 for S2. Topographic index models were found to be useful in locating EGs and estimating expected lengths, but site-specific calibration of the topographic index model threshold was required, which might limit the general utility of these methods. [ABSTRACT FROM AUTHOR]

Soil erosion by the environmental agents of water and wind is a continuing global menace that threatens the agricultural base that sustains our civilization. For over 70 years, ASABE members have been at the forefront of research to understand erosion processes, measure erosion and related processes, and model very complex sediment detachment, transport, and deposition. The ASABE Erosion Control Group (SW-22) and Erosion Control Research (SW-223) committees periodically sponsor international symposia to provide an avenue for exchange of ideas and information by engineers, scientists, and students from around the world. The two most recent symposia were the Soil Erosion Research for the 21st Century Symposium hem in January 2001 in Honolulu, Hawaii, and the International Symposium on Erosion and Landscape Evolution (ISELE) held in September 2011 in Anchorage, Alaska. This article describes these two events, provides a description of major outcomes, and introduces a collection of papers that were presented as part of the 2011 1SELE in Alaska. The 1SELE sessions focused on seven themes: water erosion process research; aeolian erosion and fugitive dust emission; highly disturbed, urban, and arid lands; erosion measurement and assessment; prevention and control of upland and in-stream erosion; soil erosion modeling; and impacts of global change on erosion and landscape evolution. More than 120 people from 16 countries attended the ISELE and gave 112 oral and poster presentations. From those presentations, 24 papers were accepted for publication in Transactions of the ASABE (22 papers, this issue) and Applied Engineering in Agriculture (two papers, next issue). The results .from these symposia and in these papers show active and vibrant research to address soil erosion problems, particularly in the face of global environmental changes. [ABSTRACT FROM AUTHOR]

Forests are an integral component of the landscape, and maintaining their functional integrity is fundamental for the sustainability of ecosystems and societies alike. Tools, innovations, and practices, analogous to those developed to improve agricultural production and quantify environmental impacts, are needed to ensure the sustainability of these forested landscapes as well as the ecosystem goods and services they produce. This article introduces ten technical articles on critical ecohydrologic processes, protection and restoration, and the effects of management practices on the hydrology and water quality of forests and forested wetlands, using both monitoring and modeling approaches. Prepared by experts in forest science, forest and agricultural hydrology, and water management, the studies reported in this special collection are concentrated in the Atlantic Coastal plain and focus on forests with shallow water tables. Experimental studies describe the effects of riparian vegetation harvest, human disturbance, and future climatic change on groundwater, the significance of emergent vegetation after harvest, and long-term hydrologic water balance of a managed pine forest. Modeling studies use the SWAT model to predict streamflow dynamics of a less disturbed, coastal forested watershed, and DRAINMOD to determine the impacts of minor silvicultural drainage on wetland hydrology and to improve wetland restoration. Finally, a study describes potential uncertainties associated with infrequent water sampling of nutrient loads from drained forested watersheds. This introductory article summarizes these studies of shallow water table forests and relates them to the broader field of forest hydrology, including its challenges and opportunities, while identifying pressing issues of land use and climate change. The results from these studies should help guide management and restoration of forest wetland ecosystems and direct future forest hydrologic research, including research in large prior converted agricultural landscapes. [ABSTRACT FROM AUTHOR]

Climate change impacts watershed hydrology and contributes to alteration of hydrologic regimes in streams. However, global climate models (GCMs) operate, at spatial and temporal scales that are too large to capture important watershed-scale hydrologic shifts. A method of disaggregating monthly ensemble GCM data into temperature and precipitation data series for daily, watershed-specific hydrologic simulations with SWAT was developed and assessed in the Soldier Creek watershed in northeast Kansas. A stochastic weather generator (WINDS) was employed to produce a baseline scenario (no changes from late 20th century conditions) and two scenarios based on ensemble means of 15 GCMs representing future conditions (A2 storyline) referred to as the 2050 and 2100 scenarios. Future hydrologic regimes exhibited non-linear annual and monthly responses in hydrologic budget components, such as surface runoff, baseflow, and soil moisture, to temperature and precipitation changes. For the 2050 scenario, the combination of higher temperatures along with decreased annual precipitation and increased spring precipitation resulted in higher surface runoff, baseflow, and streamflow in May and June with a longer drought season later in summer. The significant decrease in streamflow, runoff, and baseflow for the 2100 scenario reflected an increase in monthly and annual temperature rather than a direct result of precipitation decline. The 2100 scenario also produced a reduction in low-flow duration, an increase in the number of drought occurrences, and a decrease in flood frequency and duration. In retrospect, use of the stochastic weather generator to temporally downscale monthly GCM results while incorporating site-specific climate variability (such as occurs with convective storms often missed in coarse-resolution GCM data) produced more meaningful analysis of hydrological impacts, which is critical to predicting and understanding the impacts of climate change. Although this method allowed simulation of future-climate shifts based on GCM-simulated monthly shifts, it could not simulate potential shifts in climate patterns within a month, such as changes in transitional probabilities that govern the intensity and distribution of storms with months, by future work, translation of regional climate model responses into WINDS stochastic parameter adjustments will allow more accurate and efficient simulation. The severity of the increased drought and decreased flood responses simulated in this study would not be anticipated by review of precipitation trends alone nor by analysis of annual hydrologic responses alone. Similarly, many critical hydrologic responses reflected interactions between climate variables (e.g., precipitation and temperature) at sub-annual temporal scales, which highlights the need to consider climatic interactions in future studies of climate change impacts. [ABSTRACT FROM AUTHOR]

This article introduces a special collection of nine articles that address a wide range of topics all related to improving the application of watershed management planning. The articles are grouped into two broadly defined categories: modeling applications, and monitoring and assessment. The modeling application articles focus on one of two widely used watershed-scale water quality modeling packages: HSPF or SWAT. The HSPF article assesses tire model's robustness when applied to watersheds across a range of topographic settings and climatic conditions, by the SWAT-related articles, researchers used tire model to inform watershed management efforts in a variety of ways, including subwatershed prioritization in the context of achieving broader watershed management goals, examining the utility of applying SWAT in a watershed receiving groundwater inputs from outside the topographic watershed boundaries, and estimating the uncertainty and risk associated with meeting TMDL target loads. The monitoring and assessment articles cover such diverse topics as an examination of how best management practice effectiveness is assessed, examination of estimated nutrient loads to a reservoir where a nutrient TMDL has been developed, examination of the sources of fecal indicator bacteria in an urban watershed, and detailed accounting of issues related to flow measurements in small watersheds. The articles in this collection contribute to the body of literature that seeks to inform and advance sound watershed management planning and execution. [ABSTRACT FROM AUTHOR]

This article introduces a special collection of 16 research articles on new developments and applications of the Soil and Water Assessment Tool (SWAT) to address various environmental issues at a range of geographic and temporal scales. Highlights include addition of a subdaily erosion and sediment transport algorithm, a biozone module, and a new algorithm for shallow water table depth. Model applications include climate change impact assessments, model adaptation to regional environmental conditions, watershed-scale soil erosion assessments, and linkages to other models. A summary of reported model performance indicates that 85% of daily flow calibration statistics reported in this collection were satisfactory or better, with very good performance in four of the 20 calibration results and in three of the 19 validation results. Details of reported model parameters for calibration of flow and water quality constituents are provided for other SWAT modelers. This collection builds upon a previous ASABE 2010 SWAT Special Collection, demonstrating continued developments to enhance SWAT's capabilities and highlighting SWAT's continued expansion in international applications, especially in Asia. [ABSTRACT FROM AUTHOR]

Uncertainty is considered the major barrier that limits water quality trading (WQT) programs. One aspect of WQT uncertainty is caused by differences between point source (PS) and nonpoint source (NPS) timing and processes. A method that could separate NPS pollutant and environmental process uncertainties from other WQT program structure and market uncertainties would improve the design of a WQT program and provide a consistent procedure for other applications, such as achieving total maximum daily load (TMDL) targets, that require site-specific quantification of source loads and reductions. The objectives of this study were to develop and demonstrate a method to explicitly define an environmental trading ratio (eTR) that quantifies the environmental equivalence of PS to NPS effluent trades with statistical analysis of watershed modeling results. A pilot study modeled five selected scenarios with the SWAT watershed model and 36 years historical climate data in the Lower Kansas watershed in northeastern Kansas. Minimum tillage, surface fertilizer application, and no edge-of-field vegetative filter strips (VFS) produced greater total N loads, whereas no-till with surface fertilizer application and no edge-of-field VFS produced greater total P loads. The potential pollutant load reductions for a given shift in scenarios varied by subbasin. The eTR values of potential pollutant load reductions showed similar trends, indicating that the best alternative scenario might change from one subbasin to another. The eTR values in this study reflected significant total N and total P load reductions at a known confidence level and were substantially less than the programmatic trading ratios typically fixed at 2 to 1. These analyses show solid evidence that using a site-specific eTR system can address the uncertainty of environmental equivalence of source loads in a WQT program. [ABSTRACT FROM AUTHOR]

This study compared the utility and results of four watershed models that include water quality elements: Spreadsheet Tool for Estimating Pollutant Load (STEPL), a GIS-based model to calculate pollutant loads for watersheds (PLOAD), Long-term Hydrologic Impact Assessment (L-THIA), and ArcGIS Soil and Water Assessment Tool (ArcSWAT). These models are different in their levels of complexity, data requirements, time step, and simulation techniques. Therefore, different scenarios were conducted to test some of the standard applications of each model based on data quality and model capabilities. Climatological, land use, and soil datasets as well as flow rates, sediment, nitrate, and total P concentrations were collected for the Pomona Lake watershed in Kansas over 30 years. Stakeholders' information was integrated into the models to the extent possible. Using results obtained from STEPL, L-THIA, PLOAD, and uncalibrated ArcSWAT for estimating long-term (30 years) average pollution loads in a watershed can result in incorrect load estimation. In addition, the STEPL, L-THIA, and PLOAD models may not be the most reliable in identifying pollutant source areas in a watershed. Therefore, in the context of effective resource allocation, use of simple models (such as STEPL, L-THIA, and PLOAD) is not suggested for critical source area targeting for watershed planning if the nature of the problem is complex. However, the simple models can still be used to evaluate relative contribution of different land uses to overall pollution loads. [ABSTRACT FROM AUTHOR]

Cropland best management practice recommendations often combine tillage and nutrient application improvements to reduce nutrient losses with surface runoff. This study used the Soil and Water Assessment Tool (SWAT) model to evaluate nutrient runoff yields from conventional-till and no-till management practices with surface and deep-banded fertilizer application in a sorghum-soybean rotation. The model was calibrated for three field plots (0.39 to 1.46 ha) with different combinations of practices and validated for three field plots (0.40 to 0.56 ha) during 2001 to 2004. Daily performance of the calibrated SWAT model in simulating total N for all treatments was satisfactory for median-based Nash-Sutcliffe model efficiency (Ef* of 0.54 to 0.64), good to very good for percent bias (PBIAS of 31% to 7%), and satisfactory to good for median-based root mean square error to observations standard deviation ratio (RSR* of 0.72 to 0.62). Performance was slightly lower and more variable for total P calibration (Ef* of 0.42 to 0.62, PBIAS of-48% to 2%, and RSR* of 0.76 to 0.62). Monthly statistics improved for total P runoff yield compared to daily performance, but changed little for total N runoff yields, probably due to the stronger influence of outliers in the N data. Based on validation results, SWAT was more robust in simulating total N runoff yields from the treatment with less soil disturbance (NT/SB) and total P for the two treatments with more soil disturbance (NT/DB and TILL). A major concern was that SWAT predicted greater annual average total N runoff yields for no-till treatments than for tilled treatments, which was contrary to measured values at the study site. This reinforces a fundamental research issue that tillage system effects on nutrient losses are still very much uncertain and thus may not be properly modeled. The SWAT model generally underpredicted monthly total N yields for all treatments in the higher-precipitation months of May and June and overpredicted total N and total P yields from September through November. Calibration for N and P resulted in identical calibration parameters for NPERCO (1.0), RSDCO (0.05), BIOMIX (0.2), PPERCO (10), PHOSKD (175), and UBP (50) regardless of tillage practice or fertilizer application method. Together with results that calibrated parameters for runoff (CN, Ksat, AWC) and erosion (Cmin) differed among the treatments, this study found that differences in nutrient yields among tillage and fertilizer management may be adequately modeled with SWAT by calibrating runoff and sediment yields only, and that further calibration of nutrient parameters may not improve model results. [ABSTRACT FROM AUTHOR]

Prediction accuracy of physically based hydrologic models largely depends on how well the models and input data represent the real world in terms of precipitation, topography, soils, land use/land cover, and land management. Precipitation is, by far, the largest source of uncertainty; misestimating it by a small percentage leads to inadequate soil-moisture accounting and subsequent inaccuracy in runoff and streamflow estimation. The objectives of this study were (1) to determine the optimum local bias adjustment factor (BAF) threshold limits (TLs) by using SWAT-modeled streamflow values and frequency distributions with NEXRAD or raingauge precipitation inputs, and (2) to assess the impact of BAF TLs derived from 40 raingauges in and around a large watershed in west central Kansas on hydrologic response of the SWAT model. NEXRAD overestimated precipitation depths (45% to 184%) in warm months including April to September and underestimated depths (33% to 64%) in cold months including December to February; the remaining months had fairly close estimates (within ± 20%). Assessment of bias-adjusted NEXRAD data based on daily raingauge comparisons found the best model efficiency (Ef) using 0.15 lower TL, whereas the lowest bias was for 0.33 lower TL, both with 2.0 upper TL. However, assessment of NEXRAD data based on predicted versus observed daily streamflow found the best Ef using O. 15 lower TL and the lowest bias using 0.25 lower TL. NEXRAD data bias-adjusted using TLs of 2.0 (upper) combined with 0.15 (lower) produced satisfactory streamflow results, similar to the default nearest-raingauge method used in SWAT. This result is encouraging considering the substantial seasonal bias evident in the Stage III NEXRAD data and it indicates the potential for future improvements in streamflow simulation accuracy as NEXRAD accuracy increases. This study demonstrated that TLs are needed in bias-adjustment of NEXRAD data for reasonable hydrologic simulation, and that better streamflow simulation accuracy is obtained if the optimum TLs are based on streamflow assessment rather than assessment of the precipitation data. [ABSTRACT FROM AUTHOR]

This article introduces a special collection of 20 research articles that present current developments and applications of the Soil and Water Assessment Tool (SWAT). The first objective is to review and introduce the research addressed within this special collection. The second objective is to summarize and synthesize the model performance statistics and parameters published in these articles to provide a succinct guide to complement a previous SWAT model summary. Recent SWAT developments in landscape representation, stream routing, and soil P dynamics are presented in this collection. Numerous critical applications of the SWAT model were conducted across a variety of landscape scales, climatic and physiographic regions, and pollutant sources. In this article, model performance in terms of coefficient of determination, Nash-Sutcliffe efficiency, and percent bias across all the studies is summarized and found to be satisfactory or better in all cases. These results are then compiled with a previous synthesis of results to generate a comprehensive assessment of SWAT. Model parameters used to calibrate the model for streamflow, sediment, N, and P in numerous studies are also summarized. This collection demonstrates that research in development and application of the SWAT model and associated tools continues to grow internationally in a wide range of settings and applications. [ABSTRACT FROM AUTHOR]

The spatial resolution of input rainfall data affects hydrologic model response and accuracy. The objective of this study was to evaluate the effects of spatial rainfall aggregation on predicted streamflow at five streamgage sites in the 6,316 km² Smoky Hill River/Kanopolis Lake watershed in central Kansas. NEXRAD Stage III hourly rainfall estimates were accumulated for 24 h periods for 1995 through 2002. The original NEXRAD grid cells, approximately 4 x 4 km, were aggregated with incrementally coarser spatial scale resolutions of 8, 16, 32, 64, 128, and 256 km. These data along with interpolated ground-based raingage data were used to evaluate the influence of rainfall input type and spatial scale on streamflow modeled with the Soil and Water Assessment Tool (SWAT) model (2000 version). Interpolated ground-based rainfall data improved daily streamflow simulation compared to the SWAT default method of assigning subwatershed rainfall from the nearest raingage. Streamflow simulation improved further when NEXRAD-derived rainfall data were input for most of the aggregated grid-cell resolutions. However, the best model performance was not for the finest (4 km) grid resolution, but rather at resolutions ranging from 32 km to 128 km, depending on the location of streamflow measurement within the watershed. Greater variability in model performance was observed among the five streamgage sites within the watershed than among model runs using a range of aggregated grid-cell resolutions. These results indicate that greater rainfall spatial resolution for interpolated raingage data or, to a greater extent, aggregated NEXRAD precipitation data has the potential to improve SWAT simulation results compared to the typical use of nearest gage data. [ABSTRACT FROM AUTHOR]

The Soil and Water Assessment Tool (SWAT) version 2005 includes a microbial sub-model to simulate fecal bacteria transport at the watershed scale. The objectives of this study were to demonstrate methods to characterize fecal coliform bacteria (FCB) source loads and to assess the model sensitivity to five user-defined model parameters (BACTKDQ bacteria soil partition coefficient in surface runoff, TBA CT: temperature adjustment factor, WDLPQ: less-persistent bacteria die-off in solution phase, WDLPS: less-persistent bacteria die-off in sorbed phase, and BACTKKDB: bacteria partition coefficient in manure) and one input parameter (BACTLPDB: FCB concentration in manure). Fecal bacterial source loads were described and applied spatially for confined livestock, seasonal grazing livestock, failing human septic systems, and indigenous large mammal, small mammal, and avian wildlife. The relative sensitivity index (S) was tested using the independent parameter perturbation (IPP) method. Validation results for an uncalibrated SWAT model using nine runoff events from Rock Creek watershed (77 km² were considered adequate to proceed with sensitivity analyses. Flow simulation resulted in good coefficient of determination (R² of 0.67 and Nash-Sutcliffe Efficiency Index (E) of 0.55, and FCB source load characterization methods were sufficiently precise to result in fair correlation (R² = 0.29) and reasonable measured vs. predicted response slope (0.69). Within the ranges recommended for use in SWAT, BACTKDQ had moderate sensitivity (S < 2.67) within -99.5% from 175 (baseline value), BACTLPDB had low sensitivity (S < 0.25) within -90% from 3.29 x 107 cfu 100 mL-1 BACTKKDB had low sensitivity (S < 0.12) within -89% from 0.9, TBACT had low sensitivity (S < 0.36) +20% from 1.07, WDLPQ had low sensitivity (S < 0.25) ±50% from 0.23, and WDLPS had no sensitivity (S < 0.06) ±50% from 0.023 when compared with all surface runoff events. This study recommends that SWAT could adopt default values of 0.23 for WDLPQ and 0.023 for WDLPS without adversely affecting results. Moderate sensitivity for BACTKDQ indicates that users should select these with caution considering locally relevant data. The sensitivity of BACTKDQ was found high when compared with nine measured surface runoff events. [ABSTRACT FROM AUTHOR]

Students are known to be motivated by course activities that are relevant to their careers. Design projects offer this type of real-life experience and have the potential to provide a rich environment for learning engineering design skills. The objective of this study was to assess student learning of the design process resulting from a first-semester course organized around a team design project. Biological and agricultural engineering (BAE) and agricultural technology management (ATM) students prepared a functional layout design for one of eight BAE/ATM student spaces within Seaton Hall. The development of the layout design followed a design process, culminating in a presentation to the client (department head) and other constituents. Students were assessed using multiple instruments: self-assessment, assessment of the presentation, and a short-answer exam. Results were classified according to seven elements of the design process: (1) teamwork, (2) information gathering, (3) problem definition, (4) idea generation, (5) evaluation and decision making, (6) implementation, and (7) communication. Students appeared to learn in proportion to their perceived level of class emphasis in the problem-definition element and the teamwork element. Students both learned the problem-definition element and recognized this progress, which was considered a critical advance for first-semester engineers. Higher levels of understanding were demonstrated in the communication element and the information-gathering element despite a perceived lesser class emphasis. Further work is needed to control for student prior knowledge of the design process elements and to train students in self-assessment. [ABSTRACT FROM AUTHOR]

This article introduces the five papers in the "International Watershed Technology" collection. These papers were selected from 60 technical presentations at the fifth biennial ASABE 21st Century Watershed Technology Conference and Workshop: Improving the Quality of Water Resources at Local, Basin, and Regional Scales, held in Quito, Ecuador, on 3-9 December 2016. The conference focused on solving spatial and temporal water quality and quantity problems and addressed topics such as watershed management in developing countries, aquatic ecology and ecohydrology, ecosystem services, climate change mitigation strategies, flood forecasting, remote sensing, and water resource policy and management. While diverse, the presentation topics reflected the continuing evolution of the "data mining" and "big data" themes of past conferences related to geospatial data applications, with increasing emphasis on practical solutions. The papers selected for this collection represent applications of spatial data analyses toward practical ends with a theme of "tools and techniques for sustainability." The papers address a range of topics, including the matching of crops with water availability, and assessing the environmental impacts of agricultural production. The papers identify some of the latest tools and techniques for improving sustainability in watershed resource management that are relevant to both developing and developed countries. [ABSTRACT FROM AUTHOR]

This article introduces a collection of papers from the fourth biennial ASABE 21st Century Watershed Technology Conference and Workshop: Improving Water Quality and the Environment, held in Hamilton, New Zealand, on November 3-6, 2014. This Special Collection consists of three articles selected from the 47 meeting papers. The technical presentations at the conference focused on solving spatial and temporal water quality and quantity problems and addressed topics such as watershed management in developing countries, water quality standards, agricultural best management practice (BMP) effectiveness, emerging problems, impact of extreme weather conditions, biological monitoring, increasing stakeholder involvement, political and economic implications, watershed implementation planning, forest and rangeland water quality issues, and water resources education. At first glance, these topics seem quite diverse. A more detailed look suggested that the "big data" and data mining themes of the last conference in Bari, Italy, continued to develop. [ABSTRACT FROM AUTHOR]