Single-event Wind Erosion Evaluation Program Research Articles

Agricultural activities lead to sediment infilling of wetlandscapes in the Canadian Prairies: Assessment of contributions by tillage, water and wind erosion

Soil erosion and sediment delivery models have been increasingly employed in studies of catchment sediment dynamics in current years. These models are also used to represent the spatial interaction of soil erosion and sediment transport processes, thereby providing spatially-distributed predictions of soil redistribution rates for agricultural landscapes. It has been widely recognized that individual soil erosion processes and their interactions contribute towards total soil erosion; however, quantifying the rates and patterns of soil erosion processes and their interactions within topographically complex landscapes is challenging. Therefore, the objective of this research was to estimate and model the relative contributions of tillage, water and wind erosion towards total soil erosion in the Canadian Prairie provinces of Manitoba and Alberta using 137Cs, a fallout radionuclide tracer, and three well-established models: (i) Tillage Erosion Model (TillEM); (ii) Revised Universal Soil Loss Equation, version 2 (RUSLE2); and (iii) Single-event Wind Erosion Evaluation Program (SWEEP). The findings indicate that the patterns of 137Cs-estimated soil erosion were closely matched with the erosion pattern predicted by TillEM and suggests that tillage erosion dominates the pattern of total soil erosion on the knolls of hummocky landscapes. Additionally, soil particle size variation within the wetland catchments reflected the modeled patterns of water and tillage erosion. Furthermore, our findings confirmed that colour coefficients are useful in identifying spatial heterogeneity of soil within wetland catchments and reflect the patterns of soil loss and gains. These results indicate that water and tillage erosion, and also their interactions, are main erosion processes in the Canadian Prairie Pothole Region (PPR), but that soil movement by tillage practices has been the predominant redistribution process.

Applying Wind Erosion and Air Dispersion Models to Characterize Dust Hazard to Highway Safety at Lordsburg Playa, New Mexico, USA

Lordsburg Playa, a dry lakebed in the Chihuahuan Desert of southwestern New Mexico (USA), is crossed by Interstate Highway 10 (I-10). Dust from the playa threatens highway safety and has caused dozens of fatal accidents. Two numerical models—the U.S. Department of Agriculture’s Single-Event Wind Erosion Evaluation Program (SWEEP) and the American Meteorological Society and U.S. Environmental Protection Agency Regulatory Model (AERMOD)—were used to simulate and predict the generation and dispersion of windblown soil, dust, and PM10 from playa hotspots and estimate PM10 concentrations downwind. SWEEP simulates soil loss and particulate matter emissions from the playa surface, and AERMOD predicts the concentration of transported dust. The modeling was informed by field and laboratory data on Lordsburg Playa’s properties, soil and land use/land cover databases, and weather data from meteorological stations. The integrated models predicted that dust plumes originating on the playa—including a large, highly emissive area away from the highway and a smaller, less emissive site directly upwind of the interstate—can lead to hourly average PM10 concentrations of tens, to hundreds of thousands, of micrograms per cubic meter. Modeling results were consistent with observations from webcam photos and visibility records from the meteorological sites. Lordsburg Playa sediment contains metals, as will its dust, but human exposures will be short-term and infrequent. This study was the first to successfully combine the SWEEP wind erosion model and the AERMOD air dispersion model to evaluate PM10 dispersion by wind erosion in a playa environment. With this information, land managers will be able to understand the potential levels of dust and PM10 exposure along the highway, and better manage human health and safety during conditions of blowing dust and sand at Lordsburg Playa.

Performance of the single‐event wind erosion evaluation program (SWEEP) model in assessing the impact of crop rotation, green manure, fertilizer, and tillage on wind erosion

AbstractAgricultural land management strategies have been applied to minimize wind erosion in the inland Pacific Northwest (iPNW) due to their profound influence on various soil properties and crop residue characteristics. However, simulating soil loss in response to these treatment strategies remains a challenge. The objective of this study was to test the performance of the single‐event wind erosion evaluation program (SWEEP) in simulating soil loss from agricultural land under contrasting tillage, crop rotation, fertilizer, and green manure treatments in the iPNW. These management strategies appeared to impact residue characteristics but had little or no impact on soil properties except tillage treatments in the short term (<2 years). Tillage appeared to have a greater impact on soil properties and residue characteristics than other treatments. As a result, the performance of SWEEP varied among disk‐tillage (DT), undercutter‐tillage (UT), and NT (no‐tillage/zero‐tillage) treatments. No or little difference was found in the performance of SWEEP between winter wheat‐summer fallow (WW‐SF) and WW‐oilseed‐SF (WW‐O‐SF) crop rotations and synthetic and biosolids fertilizer treatments. In addition, the performance of SWEEP was acceptable for both crop rotation and fertilizer treatments. In contrast, poor agreement between simulated and measured erosion was found for manure treatments in which SWEEP over‐estimated erosion by 313 and 210% for no manure and manure treatments, respectively. The over‐estimation of SWEEP may be due to the over‐estimation of abrasion flux from the fully crusted soil surface. Our results suggest that SWEEP can be used to identify control measures for windblown soil loss in the iPNW.

Consequences of chemical pretreatments in particle size analysis for modelling wind erosion

The particle size distribution (PSD) of soil plays a vital role in wind erosion prediction. However, the impact of different pretreatments to remove binding agents for PSD and consequences for wind erosion modelling have not been tested. We collected 90 topsoil samples of Chernozems and Kastanozems from different test sites in Kazakhstan. Soil samples covered typical land-use types and farming methods with calcium carbonate contents reaching from 2.2 to 117.3 g kg−1 and soil organic carbon content from 11.2 to 48.7 g kg−1. Prior to particle size analysis by laser diffraction, samples were chemically pretreated separately and successively with 10% hydrochloric acid (HCl), to dissolve carbonates and 30% hydrogen peroxide (H2O2), to oxidise organic binding material. The HCl pretreatment resulted in incomplete dispersion or even aggregation due to calcium ions released by the dissolution of carbonates, while removing organic matter with H2O2 caused complete sample dispersion. The associated changes in PSD were overall minor, and only a few of our samples were assigned to a different texture class. Obtained PSD data was used to calculate texture-based properties, such as the geometric mean diameter (GMD), with a pedotransfer function. Calculated and measured input data were applied to the Single–event Wind Erosion Evaluation Program (SWEEP) to estimate potential soil losses. As a result, SWEEP's simulations showed substantial variations if the GMD is calculated based on PSD under the influence of different pretreatments. At the same time, there was no variation if the GMD was independently measured. We suggest that for standard particle size analysis of calcareous soils, pretreatment with HCl should be avoided because it might cause misleading results. Considering the variation induced by PSD analysis and resulting potential soil losses, pretreatments for laser diffraction analysis can be omitted for the investigated, silt-dominated Chernozems and Kastanozems if additional texture-based parameters are measured.

Influence of physical crust cover on the wind erodibility of soils in the inland Pacific Northwest, USA

AbstractSoil crusts are especially important for agricultural fields in the inland Pacific Northwest where there is a high wind erosion risk due to exposure of fine erodible soils in fallow croplands. The objective of this study was therefore to evaluate the effect of physical soil crust cover on wind erosion and identify critical soil crust cover amounts to control wind erosion. The effect of crust cover of five loessial soils on wind erosion was tested in a wind tunnel. The results indicated that crust cover appeared to have little influence on soil loss until crust cover was > 30%. Soil loss at this percentage of crust cover was 55.04% to 68.08% lower as compared with a soil surface devoid of crust cover for the five soil types. The relationship between soil loss and crust cover appeared to be nearly a linear function, although an exponential function also provided a good fit to the data. With progressive development of a crust cover, the rate of change in soil loss varied among soil types. From 0 to 100% crust cover, the rate of change in soil loss ranged from −312.8 g m−2 for Palouse silt loam to −1449.1 g m−2 for Warden sandy loam. The rate was not only associated with intrinsic soil erodibility, but also crust stability and abrasion flux. Due to the lower intrinsic soil erodibility and greater crust stability, Palouse silt loam crust was characterized by lower flaking potential and limited abrasion flux relative to the other tested soil types. The Single‐event Wind Erosion Evaluation Program (SWEEP) was used to simulate and identify the effect of crust cover on erosion processes. Differences between simulated and measured soil loss suggest that cracks in soil crusts may affect soil loss and should be incorporated into the SWEEP to expand the model capability for representing crusted soils.

Predicting soil wind erosion potential under different corn residue management scenarios in the central Great Plains

Various models and simplified equations are available to predict wind erosion potential. However, their performance can be often site-specific, depending on soil characteristics and agronomic practices, warranting site-specific model validations. Thus, in this study, we 1) validated the wind erodible fraction (WEF) predictive equations by Fryrear et al. (1994) and López et al. (2007) and 2) estimated the total soil loss with the Single-event Wind Erosion Evaluation Program (SWEEP) using 3-yr measured data from six experiments located across a precipitation gradient in the central Great Plains. Each site had three corn (Zea mays L.) residue removal treatments: control (no removal), grazed, and baled. The measured and predicted WEF were significantly correlated. While the Fryrear et al. (1994) equation performed better than the López et al. (2007) equation, it underestimated WEF with 59% uncertainty across site-years. To reduce this underestimation and uncertainty, we developed a new statistical equation (WEF% = 84.3 + 2.64 × % silt-0.30 × % clay-7.43 × % organic matter-0.15 × % residue cover; r2 = 0.56). The predictive ability of the new equation was, however, no better than that of the existing predictive equations, suggesting the need for further refinement of WEF equations for the region. Simulated total soil loss by wind using the SWEEP model indicated that corn residue baling may increase soil loss if residue cover drops below 20% in the study region. Overall, the existing WEF equations could under- or over-estimate WEF based on site-specific residue management, warranting further model refinement and site-specific validation, whereas the SWEEP estimated soil loss corroborates the critical importance of maintaining sufficient residue cover (>20%) to reduce wind erosion.

Threshold Friction Velocity Influenced by the Crust Cover of Soils in the Columbia Plateau

Core Ideas Particulate emissions from agricultural lands threaten air quality. Soil crusts reduce emissions by increasing threshold friction velocity. Threshold friction velocity was determined from temporal variations in particle concentrations inside a wind tunnel. Crust cover increased threshold friction velocity, particularly under 60 and 100% crust cover. Soil crusts provide stability and protection against wind erosion from semiarid and arid lands. Although erosion is initiated when the friction velocity (U*) exceeds the threshold friction velocity (U*t) of soils, there is little information available on the effect of soil crust cover on U*t. The objective of this study was therefore to evaluate the effect of soil crust cover on the U*t of five loessial soils of the Columbia Plateau, United States. Soil samples were sieved and the erodible fraction was placed in 1 by 0.2 by 0.015 m trays. Water drops 4.5 mm in diameter were applied to the soil surface at a known density, which, after drying, created various percentages of crust cover. The trays were placed inside a wind tunnel to assess U*t. which was determined by systematically wind speed until an increase was observed in total suspended particulate concentration inside the tunnel. No significant differences in U*t were found among 0, 15, and 30% cover but significant differences in U*t were found between 60 and 100% cover. The U*t of 100% crust cover was about twice that of 0% cover. Crust crushing energy, which influences abrasion, did not vary across crust cover treatments. The Single‐event Wind Erosion Evaluation Program (SWEEP) revealed the similar influence of crust cover on U*t. The SWEEP adequately simulated U*t for 0, 15, and 30% crust cover but overestimated U*t for 60 and 100% cover. These results suggest that crusts effectively protect the soil from wind erosion by increasing U*t.

Crop residue harvest impacts wind erodibility and simulated soil loss in the Central Great Plains

AbstractCrop residue removal can affect the susceptibility to soil wind erosion in climates such as those of the Central Great Plains, United States. Six on‐farm trials were conducted in Kansas from 2011 to 2013 to determine the effects of winter wheat (Triticum aestivum L.), corn (Zea mays L.), and grain sorghum (Sorghum bicolor (L.) Moench), residue removal at 0, 25, 50, 75, and 100% of initial height on soil wind erosion parameters. Those parameters include soil surface random roughness (RR), and wind erodible fraction (EF; aggregates <0.84 mm), geometric mean diameter (GMD) and geometric standard deviation (GSD), stability of dry aggregates (DAS). Complete (100%) residue removal decreased the surface RR, increased EF, and decreased GMD. Overwinter EF values increased for five of six sites from fall 2011 to spring of 2012, particularly for the uppermost removal height (≥75%). Measured EF, GMD, GSD, DAS, and RR were also input into the Single‐event Wind Erosion Evaluation Program (SWEEP) to determine the effect of these parameters on simulated soil loss. The SWEEP simulated the wind velocity needed to initiate wind erosion as well as soil loss under each residue removal height at a wind velocity of 13 m s−1 for three hours. Threshold wind velocity required to initiate wind erosion generally decreased with increasing crop residue removal height, particularly for >75% removal. Total estimated soil loss over the three‐hour event ranged from ≈2 to 25 Mg ha−1, depending on EF, GMD, GSD, RR, and percent crop residue cover. Removing 75% residue increased simulated wind erosion at three of six sites while removing 50% appears sustainable at all six study sites. Findings reinforce the need for site‐by‐site consideration of the potential amount of crop residue that may be harvested while mitigating wind erosion. Study results indicate the value of maintaining residue at >75% of original height.

Evaluation of the RWEQ and SWEEP in simulating soil and PM10 loss from a portable wind tunnel

Wind erosion threatens sustainable agriculture and environmental quality in the US Pacific Northwest. Wind erosion models such as the Revised Wind Erosion Equation (RWEQ) and Wind Erosion Prediction System (WEPS) have been developed as tools for identifying practices that control windblown soil loss. Models, however, must be tested under a range of crop, soil, and weather conditions. The objective of this study was to test the performance of the RWEQ and WEPS erosion submodel (Single-event Wind Erosion Evaluation Program or SWEEP) in simulating soil and/or PM10 (particulate matter ≤10μm in diameter) loss from a portable wind tunnel. A wind tunnel, which allows simulations to be conducted under known conditions, was used to assess wind erosion from four tillage treatments imposed during the fallow phase of a winter wheat – summer fallow rotation near Lind, WA. There was good agreement between the measured and simulated soil loss using the SWEEP for conventional and reduced tillage. However, the SWEEP inadequately simulated soil loss for minimum and no tillage and PM10 loss from all tillage treatments. The performance of the SWEEP improved when the SWEEP threshold friction velocity algorithm was replaced with the Lu and Shao algorithm. The RWEQ adequately simulated soil loss, but only for minimum tillage. Model performance can be improved to a certain extent by modifying parameters or perhaps by calibration, but poorly simulating wind erosion under the known surface conditions in this study suggests the models inadequately define the complexity of erosion processes in the field.

Application of the WEPS and SWEEP models to non-agricultural disturbed lands

Wind erosion not only affects agricultural productivity but also soil, air, and water quality. Dust and specifically particulate matter ≤10 μm (PM-10) has adverse effects on respiratory health and also reduces visibility along roadways, resulting in auto accidents. The Wind Erosion Prediction System (WEPS) was developed by the USDA-Agricultural Research Service to simulate wind erosion and provide for conservation planning on cultivated agricultural lands. A companion product, known as the Single-Event Wind Erosion Evaluation Program (SWEEP), has also been developed which consists of the stand-alone WEPS erosion submodel combined with a graphical interface to simulate soil loss from single (i.e., daily) wind storm events. In addition to agricultural lands, wind driven dust emissions also occur from other anthropogenic sources such as construction sites, mined and reclaimed areas, landfills, and other disturbed lands. Although developed for agricultural fields, WEPS and SWEEP are useful tools for simulating erosion by wind for non-agricultural lands where typical agricultural practices are not employed. On disturbed lands, WEPS can be applied for simulating long-term (i.e., multi-year) erosion control strategies. SWEEP on the other hand was developed specifically for disturbed lands and can simulate potential soil loss for site- and date-specific planned surface conditions and control practices. This paper presents novel applications of WEPS and SWEEP for developing erosion control strategies on non-agricultural disturbed lands. Erosion control planning with WEPS and SWEEP using water and other dust suppressants, wind barriers, straw mulch, re-vegetation, and other management practices is demonstrated herein through the use of comparative simulation scenarios. The scenarios confirm the efficacy of the WEPS and SWEEP models as valuable tools for supporting the design of erosion control plans for disturbed lands that are not only cost-effective but also incorporate a science-based approach to risk assessment.

Comparison of wind erosion based on measurements and SWEEP simulation: A case study in Kangbao County, Hebei Province, China

Farmland especially dry farmland managed in traditional ways has high wind erosion risk and contributes mainly to dust emission in arid area. Modeling predicting provides a general view to soil erosion susceptibility, and is very helpful for the understanding of potential spatial source of wind erosion. This study applied the Single-event Wind Erosion Evaluation Program (SWEEP) to predict soil wind erosion of farmland in the study area. SWEEP is a standalone version of the erosion sub-model from the Wind Erosion Prediction System (WEPS). It needs fewer calculation parameters than WEPS and is often used for single erosion events of limited size. The objective of this study was to test the feasibility of using SWEEP to estimate annual wind erosion of farmland over large areas (downwind distance >1600m) with limited wind data (2005–2011) from weather stations. We validated the simulation results by comparing them with field measurements and wind tunnel data for the same soils. The soil material eroded by wind included PM10, suspension, saltation, and creep particles. Suspension particles were the main component involved in the soil loss (averaged 61.8%). However, saltation and creep particles dominate the particle clouds for fields with a downwind length of less than 550m (averaged 56.6%), and the mass flux dominated by suspension particles stabilizes when this length is longer than 1000m (averaged 83.4%). PM 10 always has very low proportion (<2.3%). Our validation results suggest that it is feasible to use SWEEP for large areas with limited wind data. However, SWEEP could not simulate the small soil losses that occur especially at low wind velocities well. Many factors contribute to this problem, but the main one is overestimation of the threshold wind velocity. Previous research suggest that it will be difficult to replace SWEEP’s calculation algorithms for the threshold wind velocity, but both these algorithms and some SWEEP parameters must be improved to provide accurate predictions of soil erosion.

Impacts of Corn Residue Grazing and Baling on Wind Erosion Potential in a Semiarid Environment

Core Ideas Corn residue baling increased the wind‐erodible fraction relative to no baling. Cattle grazing of corn residues had smaller effects on wind erosion than baling. As residue cover decreased, the wind‐erodible fraction increased. Soil erodibility decreased as particulate organic matter increased. Simulated soil loss showed that baling increased the wind erosion potential. Implications of corn (Zea mays L.) residue grazing and baling on wind erosion in integrated crop–livestock systems are not well understood. This study (i) determined soil properties affecting wind erosion potential including dry aggregate‐size distribution, geometric mean diameter (GMD), geometric standard deviation of dry aggregates, and wind‐erodible fraction (WEF), (ii) correlated these properties with soil organic C (SOC) and particulate organic matter (POM), and (iii) simulated soil loss using the Single‐event Wind Erosion Evaluation Program (SWEEP) model after 7 and 8 yr of irrigated no‐till corn residue management in a semiarid region in west‐central Nebraska. Residue treatments were: control (no residue removal), light grazing (2.5 animal unit months [AUM] ha−1), heavy grazing (5.0 AUM ha−1), and baling. We simulated soil loss for a 3‐h windstorm with a wind velocity of 13 m s−1. Soil properties differed in spring but not in fall. Baling reduced 6.3‐ to 45‐mm macroaggregates by 37% and GMD by 80% and increased WEF by 25% relative to the control. Light and heavy grazing, after 8 yr, significantly reduced 6.3‐ to 14‐mm macroaggregates 43% compared with the control and tended to reduce GMD and increase WEF, although not statistically significant. As residue cover decreased, GMD decreased and WEF increased. Residue removal did not reduce SOC and POM concentrations, but soil erodibility decreased as POM increased. Simulation showed that soil erodibility increased as residue cover decreased in spring, and baling increased the wind erosion potential. Overall, residue baling increases the wind erosion potential but residue grazing has smaller effects in this semiarid environment.

Validation of SWEEP for creep, saltation, and suspension in a desert–oasis ecotone

Abstract Wind erosion in the desert–oasis ecotone can accelerate desertification, but little is known about the susceptibility of the ecotone to wind erosion in the Tarim Basin despite being a major source of windblown dust in China. The objective of this study was to test the performance of the Single-event Wind Erosion Evaluation Program (SWEEP) in simulating soil loss as creep, saltation, and suspension in a desert–oasis ecotone. Creep, saltation, and suspension were measured and simulated in a desert–oasis ecotone of the Tarim Basin during discrete periods of high winds in spring 2012 and 2013. The model appeared to adequately simulate total soil loss (ranged from 23 to 2272 g m−2 across sample periods) according to the high index of agreement (d = 0.76). The adequate agreement of the SWEEP in simulating total soil loss was due to the good performance of the model (d = 0.71) in simulating creep plus saltation. The SWEEP model, however, inadequately simulated suspension based upon a low d (⩽0.43). The slope estimates of the regression between simulated and measured suspension and difference of mean suggested that the SWEEP underestimated suspension. The adequate simulation of creep plus saltation thus provides reasonable estimates of total soil loss using SWEEP in a desert–oasis environment.

Performance of the SWEEP Model Affected by Estimates of Threshold Friction Velocity

Abstract. The Wind Erosion Prediction System (WEPS) is a process-based model and needs to be verified under a broad range of climates, soils, and land management practices. Occasional poor performance of the WEPS erosion submodel (Single-event Wind Erosion Evaluation Program, or SWEEP) in simulating small amounts of erosion of loessial soils, which contribute to poor air quality in the Columbia Plateau region of the U.S. Pacific Northwest, has been partly attributed to overestimation of threshold friction velocity (u*t). Few studies have been conducted to improve the poor performance of the SWEEP in this region. Therefore, the objective of this study was to test the performance of the SWEEP in simulating the occurrence of erosion when the simulated u*t (SWEEP u*t) was replaced with measured values of u*t or with estimates of u*t derived from algorithms used in the Lu and Shao model, Shao model, Texas Tech Erosion Analysis Model (TEAM), and Wind Erosion on European Light Soils (WEELS) model. The occurrence of erosion from agricultural lands was better estimated by the SWEEP when SWEEP u*t was replaced with the u*t algorithm used in the Lu and Shao model. However, soil loss was better estimated by the SWEEP when using SWEEP u*t rather than the measured u*t or other u*t algorithms. Since prediction of both the occurrence and magnitude of wind erosion is important to overall model performance, there is a need to further improve the SWEEP in the Columbia Plateau and other regions where small amounts of erosion can impact soil resources and environmental quality.

Validation of SWEEP for Contrasting Agricultural Land Use Types in the Tarim Basin

The Tarim Basin is a major source of windblown dust in China. Land management and use can greatly impact windblown dust, thus, models such as the Wind Erosion Prediction System (WEPS) are important for identifying management practices that reduce the emission of dust. The objective of this study was to test the performance of the WEPS erosion submodel (the Single-event Wind Erosion Evaluation Program (SWEEP)) under contrasting agricultural land use types in the Tarim Basin of northwest China. Wind erosion of a sandy soil was measured and simulated in a cotton (Gossypium hirsutum L.) field and red date (Ziziphus jujuba L.) orchard during the spring of 2012 and 2013. The SWEEP did not simulate differences in soil loss for contrasting agricultural land use types, although measured soil loss was typically smaller than that considered to be of consequence (>100 g m) in the original design of the SWEEP. In fact, the model simulated no erosion for all six high wind events in which we observed erosion in the cotton field and red date orchard. The insensitivity of SWEEP to simulate erosion was caused by the simulated friction velocity being consistently lower than the threshold friction velocity for the loess soil at the cotton field and red date orchard. Because SWEEP is being used to assess wind erodibility of lands and simulate regional air quality in China, SWEEP must be improved for application to lands that emit large and small amounts of windblown dust.

Comparison of Measured and Simulated Friction Velocity and Threshold Friction Velocity Using SWEEP

Adequately simulating the occurrence and magnitude of erosion using the Wind Erosion Prediction System is critical for resource conservation and improving environmental quality in the United States and other regions of the world. Past observations indicate an insensitivity of the Wind Erosion Prediction System erosion submodel (Single-event Wind Erosion Evaluation Program (SWEEP)) to simulate the occurrence of wind erosion from loess soils during intensifying winds in the Pacific Northwest United States. This insensitivity is attributed to either underestimation of friction velocity (u*) or overestimation of threshold friction velocity (u*t), but no definitive work has been conducted to validate u* and u*t in the SWEEP. The objective of this study was to compare measured u* and u*t with those simulated by the SWEEP. The SWEEP begins to simulate erosion when u* exceeds u*t, thus we compared measured and simulated u* and u*t of agricultural fields during wind erosion events in eastern Washington. No evidence indicated that the SWEEP consistently overestimated or underestimated u*. The SWEEP was very sensitive to the stem area index, and estimation of u* was better when the SWEEP was used at field sites characterized by a lower rather than a higher stem area index. Our results, however, indicate that the SWEEP overestimated u*t during all observed erosion events. Therefore, simulating the occurrence of wind erosion of loess soils in the Pacific Northwest and other arid and semiarid regions of the world may be improved through better estimation of u*t in the SWEEP.

Tillage and straw management affect PM10 emission potential in subarctic Alaska

Emission of windblown dust and PM10 (particulates ≤10μm in diameter regulated by many nations as an air pollutant) from agricultural soils can impact regional air quality. Little information exists that describes the potential for PM10 and airborne dust emissions from subarctic soils or agricultural soils subject to different tillage and residue management. This study documents the influence of tillage and residue management on fine particulate emissions from a subarctic soil in Interior Alaska. Surface characteristics and properties of a silt loam soil subject to conventional, spring disk, autumn chisel plow, and no tillage, with stubble and loose straw retained or removed from the soil surface after harvest of continuous barley (Hordeum vulgare L.), was measured twenty years after establishing treatments. These soil characteristics and properties were used to simulate PM10 emission potential and soil loss from tillage and residue treatments using the Single-event Wind Erosion Evaluation Program (SWEEP). Primary particle size analysis indicated no statistical difference in the size of primary soil particles among tillage or residue treatments. Aggregate size distribution analysis showed that tillage affected the freely-available PM10 content of the soil in the field. No tillage resulted in the lowest freely-available PM10 content as compared with other tillage treatments. Simulations made with SWEEP suggest that PM10 emissions and soil loss are potentially highest for conventional tillage and lowest for no tillage while emissions and soil loss were lower from spring disk than autumn chisel plow. Tillage practices can therefore affect air quality and long range transport of fine particulates emitted into the atmosphere during high wind events in subarctic Alaska.

Comparison of measured wind tunnel and SWEEP simulated soil losses

Wind erosion estimates from the Single-event Wind Erosion Evaluation Program (SWEEP) model of the Wind Erosion Prediction System (WEPS) were compared to wind tunnel experiments. The influences of wind speed and soil texture were investigated. From a previous study, soil losses were measured directly in a wind tunnel using three soil types (sandy loam, loamy sand, and sand), each under three free-stream wind speed conditions (10, 18, and 26ms−1). A different sand soil from another experiment was also tested under five wind speeds from 10 to 18ms−1 over intervals of 2ms−1 using a sediment trap and a flux profile estimating method. The comparison of measured and estimated agricultural soil losses under non-extreme winds (less than 18ms−1 in the wind tunnel) was good. The loamy sand comparison had an error less than 6% while the sandy loam soil had an error of about 35%. SWEEP underestimated the amount of erosion with the sand soil. However, because the estimating equations used in SWEEP to predict soil parameters for agricultural soils are not directly applicable to pure sand surfaces, this was expected. When conducting SWEEP simulations, it is recommended to use the actual aggregate size distribution (ASD) data, if available, rather than relying on SWEEP's ASD parameter values being estimated from other soil properties.

Evaluation of the SWEEP model during high winds on the Columbia Plateau

AbstractA standalone version of the Wind Erosion Prediction System (WEPS) erosion submodel, the Single‐event Wind Erosion Evaluation Program (SWEEP), was released in 2007. A limited number of studies exist that have evaluated SWEEP in simulating soil loss subject to different tillage systems under high winds. The objective of this study was to test SWEEP under contrasting tillage systems employed during the summer fallow phase of a winter wheat–summer fallow rotation within eastern Washington. Soil and PM10 (particulate matter ≤10 µm in diameter) loss and soil and crop residue characteristics were measured in adjacent fields managed using conventional and undercutter tillage during summer fallow in 2005 and 2006. While differences in soil surface conditions resulted in measured differences in soil and PM10 loss between the tillage treatments, SWEEP failed to simulate any difference in soil or PM10 loss between conventional and undercutter tillage. In fact, the model simulated zero erosion for all high wind events observed over the two years. The reason for the lack of simulated erosion is complex owing to the number of parameters and interaction of these parameters on erosion processes. A possible reason might be overestimation of the threshold friction velocity in SWEEP since friction velocity must exceed the threshold to initiate erosion. Although many input parameters are involved in the estimation of threshold velocity, internal empirical coefficients and equations may affect the simulation. Calibration methods might be useful in adjusting the internal coefficients and empirical equations. Additionally, the lack of uncertainty analysis is an important gap in providing reliable output from this model. Published in 2009 by John Wiley &amp; Sons, Ltd.