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1.
No-till (NT) is a soil management system designed to protect soil resources from water erosion and provide numerous benefits compared to conventional tillage through the increase of organic matter inputs into the soil. However, NT in isolation is not sufficient to control erosion processes caused by an excessive production of surface runoff. This study evaluated soil losses on agricultural hillslopes under no-till characterized by contrasted water, soil, and crop management conditions. To this end, water and soil losses were monitored between 2014 and 2018 at two scales, including four macroplots (0.6 ha; 27 events) and two paired zero-order catchments (2.4 ha; 63 events). The resulting dataset covered a wide range of rainfall conditions that occurred in contrasted soil, crop, and runoff management conditions. Hyetographs, hydrographs, and sedigraphs were constructed, and these data were used to evaluate the impact of management on sediment yields, including that of terraces, scarification, and phytomass on sediment yield. The installation of terraces reduced sediment yield by 58.7%, mainly through surface runoff control. Crop management including an increased phytomass input efficiently controlled soil losses (63%), although it did not reduce runoff volume and peak flow. In contrast, scarification had no impact on runoff and soil losses. The current research demonstrated the need to combine the installation of terraces and leaving a high amount of phytomass on the soil to control surface runoff and erosion and reduce sediment yield. The current research therefore reinforces the relevance of the monitoring strategy conducted at the scale of macroplots and zero-order catchments to evaluate the impact of contrasted water, soil, and crop management methods and select the most effective conservation agriculture practices.  相似文献   

2.
Obtaining good quality soil loss data from plots requires knowledge of the factors that affect natural and measurement data variability and of the erosion processes that occur on plots of different sizes. Data variability was investigated in southern Italy by collecting runoff and soil loss from four universal soil‐loss equation (USLE) plots of 176 m2, 20 ‘large’ microplots (0·16 m2) and 40 ‘small’ microplots (0·04 m2). For the four most erosive events (event erosivity index, Re ≥ 139 MJ mm ha?1 h?1), mean soil loss from the USLE plots was significantly correlated with Re. Variability of soil loss measurements from microplots was five to ten times greater than that of runoff measurements. Doubling the linear size of the microplots reduced mean runoff and soil loss measurements by a factor of 2·6–2·8 and increased data variability. Using sieved soil instead of natural soil increased runoff and soil loss by a factor of 1·3–1·5. Interrill erosion was a minor part (0·1–7·1%) of rill plus interrill erosion. The developed analysis showed that the USLE scheme was usable to predict mean soil loss at plot scale in Mediterranean areas. A microplot of 0·04 m2 could be used in practice to obtain field measurements of interrill soil erodibility in areas having steep slopes. Copyright © 2003 John Wiley & Sons, Ltd.  相似文献   

3.
The Brazilian savanna (cerrado) is a large and important economic and environmental region that is experiencing significant loss of its natural landscapes due to pressures of food and energy production, which in turn has caused large increases in soil erosion. However the magnitude of the soil erosion increases in this region is not well understood, in part because scientific studies of surface runoff and soil erosion are scarce or nonexistent in the cerrado as well as in other savannahs of the world. To understand the effects of deforestation we assessed natural rainfall‐driven rates of runoff and soil erosion on an undisturbed tropical woodland classified as ‘cerrado sensu stricto denso’ and bare soil. Results were evaluated and quantified in the context of the cover and management factor (C‐factor) of the Universal Soil Loss Equation (USLE). Replicated data on precipitation, runoff, and soil loss on plots (5 × 20 m) under undisturbed cerrado and bare soil were collected for 77 erosive storms that occurred over 3 years (2012 through 2014). C‐factor was computed annually using values of rainfall erosivity and soil loss rate. We found an average runoff coefficient of ~20% for the plots under bare soil and less than 1% under undisturbed cerrado. The mean annual soil losses in the plots under bare soil and cerrado were 12.4 t ha‐1 yr‐1 and 0.1 t ha‐1 yr‐1, respectively. The erosivity‐weighted C‐factor for the undisturbed cerrado was 0.013. Surface runoff, soil loss and C‐factor were greatest in the summer and fall. Our results suggest that shifts in land use from the native to cultivated vegetation result in orders of magnitude increases in soil loss rates. These results provide benchmark values that will be useful to evaluate past and future land use changes using soil erosion models and have significance for undisturbed savanna regions worldwide. Copyright © 2015 John Wiley & Sons, Ltd.  相似文献   

4.
Studies of soil erosion on small plots present upscaling problems. The results in the literature on the effect of slope length (i.e. scale) on runoff and soil erosion are contradictory. Furthermore, most studies that examine scale effects measured through erosion plots have been conducted in Mediterranean environments. The objective of this study was to assess the effects of plot size on runoff and soil loss in a subtropical environment. Other measurements were taken to appraise the topsoil property changes inside the plots. The soil was ploughed twice, the surface was leveled with a hoe and it was kept bare during the experiment. Data were collected from 10 paired plots, five plots measuring 10 m × 1 m and five plots measuring 1 m × 1 m, installed in the same pedo‐geomorphologic unit. Measurements were carried out from November 2008 to November 2009. During this period, 97 natural storms were registered. The results indicate that the small plots tended to have higher runoff (30% higher) compared to larger plots, especially during periods of greater rainfall volume, duration and intensity. The soil loss was similar in both the 1 m2 plots (6·33 kg/m2) and the 10 m2 plots (6·26 kg/m2). Moreover, the dynamics of the soil loss during the experiment was relatively similar across both plot sizes. The large plots tended to have a greater internal complexity. In these plots, the steps retreat were higher, the overland flow scars were more frequent, and points of rill initiation and protochannels emerged in several parts of the plots. The results of the small plots were comparable to the results obtained on the large plots, especially in relation to soil loss. These plots were useful for short‐term assessments of soil erosion. Copyright © 2011 John Wiley & Sons, Ltd.  相似文献   

5.
Runoff and erosion processes can increase after wildfire and post-fire salvage logging, but little is known about the specific effects of soil compaction and surface cover after post-fire salvage logging activities on these processes. We carried out rainfall simulations after a high-severity wildfire and post-fire salvage logging to assess the effect of compaction (uncompacted or compacted by skid traffic during post-fire salvage logging) and surface cover (bare or covered with logging slash). Runoff after 71 mm of rainfall across two 30-min simulations was similar for the bare plots regardless of the compaction status (mean 33 mm). In comparison, runoff in the slash-covered plots averaged only 22 mm. Rainsplash in the downslope direction averaged 30 g for the bare plots across compaction levels and decreased significantly by 70% on the slash-covered plots. Sediment yield totalled 460 and 818 g m−2 for the uncompacted and compacted bare plots, respectively, and slash significantly reduced these amounts by an average rate of 71%. Our results showed that soil erosion was still high two years after the high severity burning and the effect of soil compaction nearly doubled soil erosion via nonsignificant increases in runoff and sediment concentration. Antecedent soil moisture (dry or wet) was the dominant factor controlling runoff, while surface cover was the dominant factor for rainsplash and sediment yield. Saturated hydraulic conductivity and interrill erodibility calculated from these rainfall simulations confirmed previous laboratory research and will support hydrologic and erosion modelling efforts related to wildfire and post-fire salvage logging. Covering the soil with slash mitigated runoff and significantly reduced soil erosion, demonstrating the potential of this practise to reduce sediment yield and soil degradation from burned and logged areas.  相似文献   

6.
Catchments have highly variable yields of runoff and soil erosion. The size, land use and the surface cover play a significant role and influence the catchment response and parameter values of simulation models. Two experimental basins—the Cariri basins—were equipped in a semi-arid region of Brazil, for obtaining runoff and sediment yield at different catchment scales, as well as, to evaluate the influence of the land use and surface cover. In the first basin, located in the municipality of Sumé, the field studies were carried out at two different scales: four micro-catchments with an area of around 0.5 ha and nine standard Wischmeier-type erosion plots of 100 m2. The experimental units had varied vegetation and management. They were subjected only to natural rainfall events, and were monitored from 1982 to 1991. The total runoff and total sediment yield were determined for each of the events. The installations in the second basin, in the municipality of São João do Cariri, from 1999, include two erosion plots, three micro-catchments, and two sub-catchments of a small basin. These basins are still being monitored for runoff and sediment production. Among the micro-catchments two are nested to detect any scale effect at the micro-catchment level. Nearly 600 events of precipitation, that produced runoff in at least one of the experimental units, have been registered. These data have been used to evaluate the influence of various factors, including cultivation practices and to calibrate hydrological models for plots and micro-catchments. Parameters have been tested by means of cross validations among micro-catchments and sub-catchments. The data sets are made available to all the catchment hydrology researchers and others at https://doi.org/10.5281/zenodo.4690886 .  相似文献   

7.
Soil and nutrient loss play a vital role in eutrophication of water bodies. Several simulated rainfall experiments have been conducted to investigate the effects of a single controlling factor on soil and nutrient loss. However, the role of precipitation and vegetation coverage in quantifying soil and nutrient loss is still unclear. We monitored runoff, soil loss, and soil nutrient loss under natural rainfall conditions from 2004 to 2015 for 50–100 m2 runoff plots around Beijing. Results showed that soil erosion was significantly reduced when vegetation coverage reached 20% and 60%. At levels below 30%, nutrient loss did not differ among different vegetation cover levels. Minimum soil N and P losses were observed at cover levels above 60%. Irrespective of the management measure, soil nutrient losses were higher at high-intensity rainfall (Imax30>15 mm/h) events compared to low-intensity events (p < 0.05). We applied structural equation modelling (SEM) to systematically analyze the relative effects of rainfall characteristics and environmental factors on runoff, soil loss, and soil nutrient loss. At high-intensity rainfall events, neither vegetation cover nor antecedent soil moisture content (ASMC) affected runoff and soil loss. After log-transformation, soil nutrient loss was significantly linearly correlated with runoff and soil loss (p < 0.01). In addition, we identified the direct and indirect relationships among the influencing factors of soil nutrient loss on runoff plots and constructed a structural diagram of these relationships. The factors positively impacting soil nutrient loss were runoff (44%–48%), maximum rainfall intensity over a 30-min period (18%–29%), rainfall depth (20%–27%), and soil loss (10%–14%). Studying the effects of rainfall and vegetation coverage factors on runoff, soil loss, and nutrient loss can improve our understanding of the underlying mechanism of slope non-point source pollution.  相似文献   

8.
The hydrology and contrasting erosional responses of two snowmelt events on arable farmland in Fife, Scotland, are compared. Snowmelt-generated runoff in January 1993 caused widespread soil erosion across eastern Scotland. Gullying was exemplified by three sites in Fife, where thaw of a drifted snowpack was augmented by rainfall to produce a larger erosive response than meteorological data alone would have predicted. Up to 127 m3 of soil was lost from individual gullies in fields sown to winter cereals. In February 1996 snowfall of comparable depth again covered the field area, but a more uniform snowpack, slower thaw, greater crop cover and lower rainfall during the thaw phase combined to lessen the impact of erosion. These case studies demonstrate the complexity of the erosion/runoff relationship for rain on snow events, in which erosional severity depends not just on snow depth but on snow distribution, thaw rate and the amount and timing of rainfall during the thaw phase. © 1998 John Wiley & Sons, Ltd.  相似文献   

9.
1 INTRODUCTION Soil crusting, or soil sealing, is one of the common phenomena in agricultural lands or semi-arid and arid soils. Due to the breakdown of soil aggregates by raindrops, soil surface develops a very thin, often less than a few millimeters, dense layer. Many studies indicated that such a thin layer significantly reduces infiltration capacity and increases surface runoff (i.e. McIntyre, 1958; Edward and Larson, 1969; Agassi et al., 1985; Bradford et al., 1986; Romkens et al.,…  相似文献   

10.
The degradation of grasslands is a common problem across semi‐arid areas worldwide. Over the last 150 years, much of the south‐western United States has experienced significant land degradation, with desert grasslands becoming dominated by shrubs and concurrent changes in runoff and erosion which are thought to propagate further the process of degradation. Plot‐based experiments to determine how spatio‐temporal characteristics of soil moisture, runoff and erosion change over a transition from grassland to shrubland were carried out at four sites over a transition from black grama (Bouteloua eriopoda) grassland to creosotebush (Larrea tridentata) shrubland at the Sevilleta NWR LTER site in New Mexico. Each site consisted of a 10 × 30 m bounded runoff plot and adjacent characterization plots with nested sampling points where soil moisture content was measured. Results show distinct spatio‐temporal variations in soil moisture content, which are due to the net effect of processes operating at multiple spatial and temporal scales, such as plant uptake of water at local scales versus the redistribution of water during runoff events at the hillslope scale. There is an overall increase in runoff and erosion over the transition from grassland to shrubland, which is likely to be associated with an increase in connectivity of bare, runoff‐generating areas, although these increases do not appear to follow a linear trajectory. Erosion rates increased over the transition from grassland to shrubland, likely related in part to changes in runoff characteristics and the increased capacity of the runoff to detach, entrain and transport sediment. Over all plots, fine material was preferentially eroded which has potential implications for nutrient cycling since nutrients tend to be associated with fine sediment. Copyright © 2009 John Wiley & Sons, Ltd.  相似文献   

11.
Soil erosion by water is a pressing environmental problem caused and suffered by agriculture in Mediterranean environments. Soil conservation practices can contribute to alleviating this problem. The aim of this study is to gain more profound knowledge of the effects of conservation practices on soil losses by linking crop management and soil status to runoff and sediment losses measured at the outlet of a catchment during seven years. The catchment has 27.42 ha and is located in a commercial farm in southern Spain, where a package of soil conservation practices is an essential component of the farming system. The catchment is devoted to irrigated annual crops with maize–cotton–wheat as the primary rotation. Mean annual rainfall‐induced runoff coefficient was 0.14 and mean annual soil loss was 2.4 Mg ha?1 y?1. Irrigation contributed to 40% of the crop water supply, but the amount of runoff and sediment yield that it generated was negligible. A Principal Components Analysis showed that total soil loss is determined by the magnitude of the event (rainfall and runoff depths, duration) and by factors related to the aggressiveness of the events (rainfall intensity and preceding soil moisture). A third component showed the importance of crop coverage to reduce sediment losses. Cover crops grown during autumn and early winter and crop residues protecting the soil surface enhanced soil conservation notably. The role of irrigation to facilitate growing cover crops in Mediterranean environments is discussed. Copyright © 2016 John Wiley & Sons, Ltd.  相似文献   

12.
The Tabernas desert, an extensive badlands area in Almeria province (south‐east Spain), is characterized by a high variability in soil surface cover and soil properties along with important topographical contrasts giving rise to a wide range of hydrological behaviour. A double approach through field monitoring and modelling has been used to ascertain the influence of soil‐surface variability on the overall hydrological response. Small plots were monitored for 3 years to assess runoff from the different surface types. Data provided by the long‐term monitoring of three small catchments formed by different soil surfaces were used to find out the specific contribution of each soil surface to the catchment runoff. A simple spatially distributed model was built to predict runoff generation based on the infiltration rate of each soil‐surface type (defined as terrain units with the same cover, the same soil type and on the same landform). Plot results prove that the soil surface units within the study area behave differently in terms of hydrological response to natural rainfall. These responses are explained by the types of cover, topographical characteristics and soil properties. When runoff events are simple (with one or two runoff peaks), the modelled hydrographs reproduce the hydrographs observed reasonably well, but in complex events (with several runoff peaks) the adjustment is not as good. The model also shows the influence of the spatial distribution of soil surfaces on the overall runoff, aiding exploration of the spatial hydrological relationships among different landscape units. Copyright © 2002 John Wiley & Sons, Ltd.  相似文献   

13.
Eight runoff plots, located within a small catchment within the Walnut Gulch Experimental Watershed, southern Arizona, were constructed to test the argument that sediment yield (kg m?2) decreases as plot length increases. The plots ranged in length from 2 m to 27·78 m. Runoff and sediment loss from these plots were obtained for ten natural storm events. The pattern of sediment yield from these plots conforms to the case in which sediment yield first increases as plot length increases, but then subsequently decreases. Data from the present experiment indicate that maximum sediment yield would occur from a plot 7 m long. Analysis of both runoff and sediment yield from the plots indicates that the relationship of sediment yield to plot length derives both from the limited travel distance of individual entrained particles and from a decline in runoff coefficient as plot length increases. Particle‐size analysis of eroded sediment confirms the role of travel distance in controlling sediment yield. Whether in response to the finite travel distance of entrained particles or the relationship of runoff coefficient to plot length, the experiment clearly demonstrates that the erosion rates for hillslopes and catchments cannot be simply extrapolated from plot measurements, and that alternative methods for estimating large‐area erosion rates are required. Copyright © 2006 John Wiley & Sons, Ltd.  相似文献   

14.
Cryptogams are communities of non-vascular plants that live on the soil surface. Numerous functions have been attributed to these crusts, including changes in soil fertility and nutrient status, soil hydrology and soil erosion. Most significant for this paper is the reported benefit of cryptogams in reducing soil erosion by water in semi-arid areas. However, to date there have been few attempts to understand the soil conservation value of cryptogams in subsistence agricultural systems or in humid mountain environments. This paper investigates the potential of cryptogams in soil erosion by water on agricultural hillslope terraces (bariland) in the Nepal Middle Hills of the southern monsoonal Himalaya. The research is significant because the loss of fertile topsoil is considered by some to be the biggest threat to the livelihoods of subsistence farmers in the area in the medium and long term. The current study was conducted in the field between two of the weeding events that take place under maize cover, grown in the traditional manner. Three groundcover types which represented (i) maize only (types A), (ii) maize and weed cover (types B), and (iii) maize and cryptogam cover (types C) were monitored utilizing multiple microerosion plots. Measurements of runoff and soil loss data were collected sequentially on a storm-by-storm basis throughout the monitored period from 24 July 1997 to 29 August 1997. Measurements of infiltration rates were also taken on each of the groundcover types at selected times. Results collected from the erosion plots demonstrate that runoff and soil losses over distances of <2 m can be significantly reduced by up to 50 per cent with cryptogam cover, compared to maize-only canopies. Mean runoff for all storm events sampled from plot types A, B and C were 3·4 l m−2, 1·6 l m−2 and 1·5 l m−2 respectively. For soil loss, the results were 21·7 g m−2, 11·3 g m−2 and 10·2 g m−2 respectively. Therefore, cryptogams would appear to offer a similar degree of protection to the soil surface from runoff and raindrop erosion, to that afforded by weed cover. Weed and cryptogam covers protect the soil surface from rainfall kinetic energies and work to preserve surface microtopographies, depressional storage and surface water detention. Terminal infiltration rates taken at the end of the monitored period showed that well developed maize- and cryptogam-covered soil surfaces (types C) have a mean terminal infiltration rate of 35·0 mm h−1 compared to 44·5 mm h−1 for comparable maize- and weed-covered soil surfaces (types B), and 15·5 mm h−1 for maize-only soil surfaces (types A). These results show that cryptogams and weeds also have relatively higher infiltration rates than comparable maize-only covered plots, devoid of groundcover. The findings in this study may have implications for traditional weed management practices used by local hill farmers, which often destroy cryptogam soil coatings two to three times during the maize growing period. However, further work needs to be done to ascertain farmers' understandings of cryptogams. It is hoped that conservationists will benefit from incorporating cryptogams into the design of future soil erosion studies relating to development programmes. Copyright © 2001 John Wiley & Sons, Ltd.  相似文献   

15.
Based on observations of runoff plots and field investigations of gully cross-sections, impacts of various soil and water conservation measures on runoff and sediment yield are analyzed for different rainfall conditions. The results show that antecedent rainfall and rainfall intensity are the main factors affecting the runoff and soil erosion processes. Rainfall events with antecedent rainfall can produce high runoff and sediment yield. Large differences in the characteristics of two rainfall events will result in greater variations of total runoff and sediment yield from the same runoff plot. Under the same soil control measure and rainfall condition, soil and water conservation measures can reduce the impacts of antecedent rainfall and rainfall intensity on runoff and soil erosion. Among various measures, level terrace seems to be the greatest for soil conservation purposes. Combining with engineering measures,Vegetation measures is also effective in controlling runoff and soil erosion. In the initial stage of vegetation enclosure measures, engineering measure is necessary to improve the environment for ecological recovery. Gully head protection can control gully erosion effectively, but the effectiveness of gully head protection would be reduced when rainfall intensity increases. Therefore, the design of a gully head protection structure must be based on local hydrological conditions.  相似文献   

16.
Surface runoff and soil erosion under eucalyptus and oak canopy   总被引：1，自引：0，他引：1       下载免费PDF全文
To assess potential differences in stormwater runoff and sediment yield between plots of blue gum eucalyptus (Eucalyptus globulus) and coast live oak (Quercus agrifolia), we measured runoff, sediment yield, water repellency and soil moisture at eight paired sites. Eucalyptus has been associated in many studies worldwide with elevated soil water repellency and increased runoff, a likely contributor to soil erosion. To better understand these connections and their relationship to land cover, there is a need for studies employing either rainfall simulators or natural rainfall. Our research employs the latter, and was subject to contrasting hydrologic conditions in the two years of the study. Fieldwork was conducted from October 2006 to February 2008 in the San Francisco Bay Area of central California. During the 2006–2007 winter wet season, runoff was significantly higher under eucalypts than at paired oak sites, and in the early phases of the season was connected with elevated water repellency. However, sediment yield at all sites during the 2006–2007 hydrologic year was below the detection limit of the Gerlach sediment collection traps, possibly due to a limited wet season, and only appeared as suspended sediment captured in overflow buckets. Intensive rainfall events in January 2008 however created substantial runoff of sediment and litter with significantly greater yield at oak sites compared to paired eucalyptus sites. Water repellency likely had little effect on runoff during these events, and the primary cause of greater erosion under oaks is the thinner cover of leaf litter in comparison to eucalyptus. Our study is limited to undisturbed sites with intact litter cover that have not experienced recent wildfires; if disturbed, we would expect a different picture given the propensity for crown fires of eucalypts, enhancement of rainsplash erosion, and the likely greater potential for stream‐connected sediment yield from post‐disturbance soil erosion events.  相似文献   

17.
In arid and semi‐arid rangeland environments, an accurate understanding of runoff generation and sediment transport processes is key to developing effective management actions and addressing ecosystem response to changes. Yet, many primary processes (namely sheet and splash and concentrated flow erosion, as well as deposition) are still poorly understood due to a historic lack of measurement techniques capable of parsing total soil loss into these primary processes. Current knowledge gaps can be addressed by combining traditional erosion and runoff measurement techniques with image‐based three‐dimensional (3D) soil surface reconstructions. In this study, data (hydrology, erosion and high‐resolution surface microtopography changes) from rainfall simulation experiments on 24 plots in saline rangelands communities of the Upper Colorado River Basin were used to improve understanding on various sediment transport processes. A series of surface change metrics were developed to quantify and characterize various erosion and transport processes (e.g. plot‐wide versus concentrated flow detachment and deposition) and were related to hydrology and biotic and abiotic land surface characteristics. In general, erosivity controlled detachment and transport processes while factors modulating surface roughness such as vegetation controlled deposition. The extent of the channel network was a positive function of slope, discharge and vegetation. Vegetation may deflect runoff in many flow paths but promoted deposition. From a management perspective, this study suggests that effective runoff soil and salt load reduction strategies should aim to promote deposition of transported sediments rather than reducing detachment which might not be feasible in these resource‐limited environments. Copyright © 2016 John Wiley & Sons, Ltd.  相似文献   

18.
Effects of hedgerows on sediment erosion in Three Gorges Dam Area, China   总被引：9，自引：2，他引：7  
The Three Gorges Dam Area refers to the river section from Chongqing to Yichang on the Yangtze River, which has a drainage area of 75,098 km^2, and involves 19 cities and counties. Contour hedgerows have been used in this area to control soil erosion and to improve hillslope stability in the catchment of this river section. Five experimental hedgerow plots were established in 1994 in order to study the effects of hedgerows on erosion control. During the period of 1994-1997, runoff and soil loss data were collected on these test plots, including the chemical and physical properties of soil and related topographical data. The results indicate that： （1） after 4 years of cultivation and crop planting, soil fertility increased dramatically in the hedgerow plots. Soil organic matter, total nitrogen, and total phosphorus contents in the hedgerow plots were 5-9 times higher than that in the control plot. In each of the hedgerow plots, soil structure became more stable, the quantity of granules larger than 0.02 mm increased and those finer than 0.02 mm decreased; （2） All hedgerow plots showed a major effect on reducing soil loss and surface runoff; （3） Overland flow velocity along the upper portion of the hedgerow plots was greatly reduced due to hedgerow resistance, which explains the significant decrease in soil losses in hedgerow plots, despite the fact that the hedgerow plots and the control plots had the same total runoff.  相似文献   

19.
Water runoff and sediment transport from agricultural uplands are substantial threats to water quality and sustained crop production. To improve soil and water resources, farmers, conservationists, and policy‐makers must understand how landforms, soil types, farming practices, and rainfall interact with water runoff and soil erosion processes. To that end, the Iowa Daily Erosion Project (IDEP) was designed and implemented in 2003 to inventory these factors across Iowa in the United States. IDEP utilized the Water Erosion Prediction Project (WEPP) soil erosion model along with radar‐derived precipitation data and government‐provided slope, soil, and management information to produce daily estimates of soil erosion and runoff at the township scale (93 km2 [36 mi2]). Improved national databases and evolving remote sensing technology now permit the derivation of slope, soil, and field‐level management inputs for WEPP. These remotely sensed parameters, along with more detailed meteorological data, now drive daily WEPP hillslope soil erosion and water runoff estimates at the small watershed scale, approximately 90 km2 (35 mi2), across sections of multiple Midwest states. The revisions constitute a substantial improvement as more realistic field conditions are reflected, more detailed weather data are utilized, hill slope sampling density is an order of magnitude greater, and results are aggregated based on surface hydrology enabling further watershed research and analysis. Considering these improvements and the expansion of the project beyond Iowa it was renamed the Daily Erosion Project (DEP). Statistical and comparative evaluations of soil erosion simulations indicate that the sampling density is adequate and the results are defendable. The modeling framework developed is readily adaptable to other regions given suitable inputs. © 2017 The Authors. Earth Surface Processes and Landforms published by John Wiley & Sons Ltd.  相似文献   

20.
《水文科学杂志》2013,58(4):883-892
Abstract

Contour benches are earthen structures constructed across cultivated slopes, at intervals down the slope, largely used in semi-arid zones. The results of an experiment to monitor water and sediment balance inside a contour bench terrace system are presented. The study site, located in the El-Gouazine watershed (central Tunisia), includes two terraced plots of approximately 3000 m2, one of which was left fallow for several years, while the other was tilled. The characteristics of rainfall—runoff processes and erosion inside both terraced plots during a two-year period (2004–2006) are described. Ploughing reduced runoff by 75%. Erosion was monitored following runoff episodes that produced observable deposits in the bench channel. After ploughing, erosion was reduced by 44% between July 2004 and July 2005 and by 50% between October 2005 and July 2006. However, erosion per millimetre of runoff was about twice as great on the tilled soil as on the fallow. Even though ploughing weakens the soil, it seems to reduce erosion by increasing infiltration. For the studied rain events, ploughing used in combination with contour bench terraces seems to have limited erosion and enhanced the effectiveness of contour bench terrace management.  相似文献   

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