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1.
Solute concentrations and fluxes in rainfall, throughfall and stemflow in two forest types, and stream flow in a 90 ha catchment in southern Chile (39°44′S, 73°10′W) were measured. Bulk precipitation pH was 6·1 and conductivity was low. Cation concentrations in rainfall were low (0·58 mg Ca2+ l?1, 0·13 mg K+ l?1, 0·11 mg Mg2+ l?1 and <0·08 mg NH4–N l?1), except for sodium (1·10 mg l?1). Unexpected high levels of nitrate deposition in rainfall (mean concentration 0·38 mg NO3–N l?1, total flux 6·3 kg NO3–N ha?1) were measured. Concentrations of soluble phosphorous in bulk precipitation and stream flow were below detection limits (<0·09 mg l?1) for all events. Stream‐flow pH was 6·3 and conductivity was 28·3 μs. Stream‐water chemistry was also dominated by sodium (2·70 mg l?1) followed by Ca, Mg and K (1·31, 0·70 and 0·36 mg l?1). The solute budget indicated a net loss of 3·8 kg Na+ ha?1 year?1, 5·4 kg Mg2+ ha?1 year?1, 1·5 kg Ca2+ ha?1 year?1 and 0·9 kg K+ ha?1 year?1, while 4·9 kg NO3–N ha?1 year?1 was retained by the ecosystem. Stream water is not suitable for domestic use owing to high manganese and, especially, iron concentrations. Throughfall and stemflow chemistry at a pine stand (Pinus radiata D. Don) and a native forest site (Siempreverde type), both located within the catchment, were compared. Nitrate fluxes within both forest sites were similar (1·3 kg NO3–N ha?1 year?1 as throughfall). Cation fluxes in net rainfall (throughfall plus stemflow) at the pine stand generally were higher (34·8 kg Na+ ha?1 year?1, 21·5 kg K+ ha?1 year?1, 5·1 kg Mg2+ ha?1 year?1) compared with the secondary native forest site (24·7 kg Na+ ha?1 year?1, 18·9 kg K+ ha?1 year?1 and 4·4 kg Mg2+ ha?1 year?1). However, calcium deposition beneath the native forest stand was higher (15·9 kg Ca2+ ha?1 year?1) compared with the pine stand (12·6 kg Ca2+ ha?1 year?1). Copyright © 2002 John Wiley & Sons, Ltd.  相似文献   

2.
Four techniques for soil erosion assessment were compared over two consecutive seasons for bare-fallow plots and a maize-cowpea sequence in 1985 at IITA, Ibadan, Nigeria. The techniques used were: tracer (aluminium paint), nails (16 and 25), the rill method, and the Universal Soil Loss Equation (USLE). Soil loss estimated by these techniques was compared with that determined using the runoff plot technique. There was significantly more soil loss (P < 0·01) in bare-fallow than in plots under maize (Zea mays) or cowpea (Vigna unguiculata). In the first season, soil loss from plots sown to maize was 40·2 Mg ha?1 compared with 153·3 Mg ha?1 from bare-fallow plots. In the second season, bare-fallow plots lost 87·5 Mg ha?1 against 39·4 Mg ha?1 lost from plots growing cowpea. The techniques used for assessing erosion had no influence on the magnitude of soil erosion and did not interfere with the processes of erosion. There was no significant difference (P < 0·05) between soil erosion determined by the nails and the runoff plot technique. Soil loss determined on six plots (three under maize, three bare-fallow) by the rill technique, at the end of the season, was significantly lower (P < 0·05) than that determined by the runoff plot technique. The soil loss estimated by the rill method was 143·2, 108·8 and 121·9 Mg ha?1 for 11, 11, and 8 per cent slopes respectively, in comparison with 201·5, 162·0, and 166·4 Mg ha?1 measured by the runoff plot method. Soil loss measured on three bare-fallow plots on 10 different dates by the rill technique was also significantly lower (P < 0·01) than that measured by the runoff plot. In the first season the USLE significantly underestimated soil loss. On 11, 11, and 8 per cent slopes, respectively, soil loss determined by the USLE was 77, 92, and 63 per cent of that measured by the runoff plot. However, in the second season there was no significant difference between soil loss determined by the USLE and that determined by the conventional runoff plot technique.  相似文献   

3.
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   

4.
Winter wheat–summer fallow is the conventional cropping system employed on >1·5 million ha within the Columbia Plateau of eastern Washington and northern Oregon. Wind erosion contributes to poor air quality in the region, yet little is known concerning the magnitude of soil and PM10 (particulate matter of ≤10 µm in aerodynamic diameter) loss from agricultural lands. Therefore, loss of soil and PM10 was assessed from a silt loam in eastern Washington during 2003 and 2004. Field sites were maintained in fallow using conventional tillage practices in 2003 (9 ha field) and 2004 (16 ha field) and instrumented to assess horizontal soil flux and PM10 concentrations at the windward and leeward positions in the field during high‐wind events. Soil flux was measured using creep and airborne sediment collectors while PM10 concentrations were measured using high‐volume PM10 samplers. Aggregate size distribution of parent soil and eroded sediment was characterized by rotary and sonic sieving. Six high‐wind events occurred over the two year period, with soil loss ranging from 43 kg ha?1 for the 12–22 September 2003 event to 2320 kg ha?1 for the 27–29 October 2003 event. Suspension‐sized particulates (<100 µm in diameter) comprised ≥90 per cent of the eroded sediment, indicating that direct suspension may be an important process by which the silt loam eroded. The corresponding loss of PM10 for these two events ranged from 5 to 210 kg ha?1. Loss of PM10 comprised 9–12 per cent of the total soil loss for the six events. This study suggests that the relatively small loss of PM10 from eroding agricultural fields maintained in summer fallow can affect air quality in the Columbia Plateau. Therefore, alternative tillage practices or cropping systems are needed for minimizing PM10 emissions and improving air quality in the region. Copyright © 2006 John Wiley & Sons, Ltd.  相似文献   

5.
Knowledge of soil loss rates by water erosion under given climate, soil, topography, and management conditions is important for establishing soil conservation schemes. In Galicia, a region with Atlantic climatic conditions in Spain, field observations over the last decade indicate that interrill, rill and ephemeral gully erosion may be an important sediment source. The aim of this work was to assess concentrated erosion rates, describe types of rills and ephemeral gullies and determine their origin, evolution and importance as sediment sources. Soil surface state and concentrated flow erosion were surveyed on medium textured soils, developed over basic schists of the Ordenes Complex series (Coruña province, Spain) from 1997 to 2006. Soil surface state was characterized by crust development, tillage features and roughness degree. Soil erosion rate was directly measured in the field. Concentrated flow erosion took place mainly on seedbeds and recently tilled surfaces in late spring and by autumn or early winter. During the study period, erosion rates were highly variable and the following situations could be distinguished: (a) no incision or limited rill incision, i.e. below 2 Mg ha?1 year?1; (b) generalized rill and ephemeral gully incision in the class of mean values between 2·5 and 6·25 Mg ha?1 year?1, this was the most common erosion pattern; and (c) heavy erosion as observed during an extremely wet winter period, between October 2000 and February 2001, with erosion figures that may be about ten orders of magnitude higher, up to 55–60 Mg ha?1 year?1. Therefore, low values of soil losses are dominant, but also large values of rill and ephemeral gully erosion occurred during the study period. Copyright © 2009 John Wiley & Sons, Ltd.  相似文献   

6.
After the Valley Complex Fire burned 86 000 ha in western Montana in 2000, two studies were conducted to determine the effectiveness of contour‐felled log, straw wattle, and hand‐dug contour trench erosion barriers in mitigating postfire runoff and erosion. Sixteen plots were located across a steep, severely burned slope, with a single barrier installed in 12 plots (four per treatment) and four plots left untreated as controls. In a rainfall‐plus‐inflow simulation, 26 mm h?1 rainfall was applied to each plot for 1 h and 48 L min?1 of overland flow was added for the last 15 min. Total runoff from the contour‐felled log (0·58 mm) and straw wattle (0·40 mm) plots was significantly less than from the control plots (2·0 mm), but the contour trench plots (1·3 mm) showed no difference. The total sediment yield from the straw wattle plots (0·21 Mg ha?1) was significantly less than the control plots (2·2 Mg ha?1); the sediment yields in the contour‐felled log plots (0·58 Mg ha?1) and the contour trench plots (2·5 Mg ha?1) were not significantly different. After the simulations, sediment fences were installed to trap sediment eroded by natural rainfall. During the subsequent 3 years, sediment yields from individual events increased significantly with increasing 10 min maximum intensity and rainfall amounts. High‐intensity rainfall occurred early in the study and the erosion barriers were filled with sediment. There were no significant differences in event or annual sediment yields among treated and control plots. In 2001, the overall mean annual sediment yield was 21 Mg ha?1; this value declined significantly to 0·6 Mg ha?1 in 2002 and 0·2 Mg ha?1 in 2003. The erosion barrier sediment storage used was less than the total available storage capacity; runoff and sediment were observed going over the top and around the ends of the barriers even when the barriers were less than half filled. Published in 2007 by John Wiley & Sons, Ltd.  相似文献   

7.
Exceptional rainfall events cause significant losses of soil, although few studies have addressed the validation of model predictions at field scale during severe erosive episodes. In this study, we evaluate the predictive ability of the enhanced Soil Erosion and Redistribution Tool (SERT‐2014) model for mapping and quantifying soil erosion during the exceptional rainfall event (~235 mm) that affected the Central Spanish Pyrenees in October 2012. The capacity of the simulation model is evaluated in a fallow cereal field (1.9 ha) at a high spatial scale (1 × 1 m). Validation was performed with field‐quantified rates of soil loss in the rills and ephemeral gullies and also with a detailed map of soil redistribution. The SERT‐2014 model was run for the six rainfall sub‐events that made up the exceptional event, simulating the different hydrological responses of soils with maximum runoff depths ranging between 40 and 1017 mm. Predicted average and maximum soil erosion was 11 and 117 Mg ha?1 event?1, respectively. Total soil loss and sediment yield to the La Reina gully amounted to 16.3 and 9.0 Mg event?1. These rates are in agreement with field estimations of soil loss of 20.0 Mg event?1. Most soil loss (86%) occurred during the first sub‐event. Although soil accumulation was overestimated in the first sub‐event because of the large amount of detached soil, the enhanced SERT‐2014 model successfully predicted the different spatial patterns and values of soil redistribution for each sub‐event. Further research should focus on stream transport capacity. Copyright © 2014 John Wiley & Sons, Ltd.  相似文献   

8.
Soil is an essential resource for human livelihoods. Soil erosion is now a global environmental crisis that threatens the natural environment and agriculture. This study aimed to assess the annual rate of soil erosion using distributed information for topography, land use and soil, with a remote sensing (RS) and geographical information system (GIS) approach and comparison of simulated with observed sediment loss. The Shakkar River basin, situated in the Narsinghpur and Chhindwara districts of Madhya Pradesh, India, was selected for this study. The universal soil loss equation (USLE) with RS and GIS was used to predict the spatial distribution of soil erosion occurring in the study area on a grid-cell basis. Thematic maps of rainfall erosivity factor (R), soil erodibility factor (K), topographic factor (LS), crop/cover management factor (C), and conservation/support practice factor (P) were prepared using annual rainfall data, soil map, digital elevation model (DEM) and an executable C++ program, and a satellite image of the study area in the GIS environment. The annual rate of soil erosion was estimated for a 15-year period (1992–2006) and was found to vary between 6.45 and 13.74 t ha?1 year?1, with an average annual rate of 9.84 t ha?1 year?1. The percentage deviation between simulated and observed values varies between 2.68% and 18.73%, with a coefficient of determination (R2) of 0.874.  相似文献   

9.
Nitrogen (N) fertilization may profoundly affect soil microbial communities. In this study, a field fertilization experiment was conducted in temperate grassland in Inner Mongolia, China to examine the effect of N fertilization on soil microbial properties and the main factors related to the characteristics of soil microbial community. Soil microbial biomass carbon (MBC) and microbial functional diversity along an N gradient were measured over three months (June to August). The result showed that N fertilization significantly decreased MBC under high N treatment (N200, 200 kg N ha?1 y?1) compared with the control (N0, 0 kg N ha?1 y?1) in the three months. Microbial functional diversity in July and August were significantly increased by low N treatment (N50, 50 kg N ha?1 y?1). Among the three fertilization treatments, microbial functional diversity under N200 in the three months was significantly lower than that of N50. The decrease of MBC and functional diversity under N200 were mainly due to the significant decline of plant belowground biomass under high N treatment. The increase of functional diversity under N50 treatment was due to the higher plant aboveground biomass as a result of the higher soil moisture availability. This finding highlighted that the higher N fertilization (N200) was not suitable for the growth and improvement of functional diversity of the soil microbial community, and that site and plant community play an important role in regulating the characteristics of soil microbial community.  相似文献   

10.
Most studies on runoff and soil loss from olive orchards were performed on plots, despite the fact that measurements that examine a range of erosive processes on different scales are essential to evaluate the suitability of the use and soil management of this type of land. The main environmental limitations of much of the land used for olive orchards in the Mediterranean are the steep slopes and the shallow soil depth – and this was the case in the study area. Soil erosion and runoff over two hydrological years (2005–2006 and 2006–2007) were monitored in an olive orchard microcatchment of 6·1 ha under no‐tillage with spontaneous grass in order to evaluate its hydrological and erosive behaviour. Moreover, soil parameters such as organic matter (%OM), bulk density (BD) and hydraulic saturated conductivity (Ks) were also examined in the microcatchment to describe management effects on hydrological balance and on erosive processes. In the study period, the results showed runoff coefficients of 6·0% in the first year and 0·9% in the second. The differences respond to the impact of two or three yearly maximum events which were decisive in the annual balances. On the event scale, although maximum rainfall intensity values had a big influence on peak flows and runoff, its importance on mean sediment concentrations and sediment discharges was difficult to interpret due to the likely control of grass cover on volume runoff and on soil protection. In the case of annual soil erosion, they were measured as 1·0 Mg ha?1 yr?1 and 0·3 Mg ha?1 yr?1. Both are lower than the tolerance values evaluated in Andalusia (Spain). These results support the implementation of no‐tillage with spontaneous grass cover for sloping land, although the reduced infiltration conditions determined by Ks in the first horizon suggest grass should be allowed to grow not only in spring but also in autumn. In addition, specific measurements to control gullies, which have formed in the terraced area in the catchment, should be included since it is expected that they could be the main sources of sediments. Copyright © 2010 John Wiley & Sons, Ltd.  相似文献   

11.
Post‐fire rehabilitation treatments are commonly implemented after high‐severity wildfires, but few data are available about the efficacy of these treatments. This study assessed post‐fire erosion rates and the effectiveness of seeding, straw mulching, and contour felling in reducing erosion after a June 2000 wildfire northwest of Loveland, Colorado. Site characteristics and sediment yields were measured on 12 burned and untreated control plots and 22 burned and treated plots from 2000 to 2003. The size of the hillslope plots ranged from 0·015 to 0·86 ha. Sediment yields varied significantly by treatment and were most closely correlated with the amount of ground cover. On the control plots the mean sediment yield declined from 6–10 Mg ha?1 in the first two years after burning to 1·2 Mg ha?1 in 2002 and 0·7 Mg ha?1 in 2003. Natural regrowth caused the amount of ground cover on the control plots to increase progressively from 33% in fall 2000 to 88% in fall 2003. Seeding had no effect on either the amount of ground cover or sediment yields. Mulching reduced sediment yields by at least 95% relative to the control plots in 2001, 2002, and 2003, and the lower sediment yields are attributed to an immediate increase in the amount of ground cover in the mulched plots. The contour‐felling treatments varied considerably in the quality of installation, and sediment storage capacities ranged from 7 to 32 m3 ha?1. The initial contour‐felling treatment did not reduce sediment yields when subjected to a very large storm event, but sediment yields were significantly reduced by a contour‐felling treatment installed after this large storm. The results indicate that contour felling may be able to store much of the sediment generated in an average year, but will not reduce sediment yields from larger storms. Copyright © 2006 John Wiley & Sons, Ltd.  相似文献   

12.
Crop canopies and residues have been shown to intercept a significant amount of rainfall. However, rainfall or irrigation interception by crops and residues has often been overlooked in hydrologic modelling. Crop canopy interception is controlled by canopy density and rainfall intensity and duration. Crop residue interception is a function of crop residue type, residue density and cover, and rainfall intensity and duration. We account for these controlling factors and present a model for both interception components based on Merriam's approach. The modified Merriam model and the current modelling approaches were examined and compared with two field studies and one laboratory study. The Merriam model is shown to agree well with measurements and was implemented within the Agricultural Research Service's Root Zone Water Quality Model (RZWQM). Using this enhanced version of RZWQM, three simulation studies were performed to examine the quantitative effects of rainfall interception by corn and wheat canopies and residues on soil hydrological components. Study I consisted of 10 separate hypothetical growing seasons (1991–2000) for canopy effects and 10 separate non‐growing seasons (1991–2000) for residue effects for eastern Colorado conditions. For actual management practices in a no‐till wheat–corn–fallow cropping sequence at Akron, Colorado (study II), a continuous 10‐year RZWQM simulation was performed to examine the cumulative changes on water balance components and crop growth caused by canopy and residue rainfall interception. Finally, to examine a higher precipitation environment, a hypothetical, no‐till wheat–corn–fallow rotation scenario at Corvallis, Oregon, was simulated (study III). For all studies, interception was shown to decrease infiltration, runoff, evapotranspiration from soil, deep seepage of water and chemical transport, macropore flow, leaf area index, and crop/grain yield. Because interception decreased both infiltration and soil evapotranspiration, no significant change in soil water storage was simulated. Nonetheless, these findings and the new interception models are significant new contributions for hydrologists. Published in 2006 John Wiley & Sons, Ltd.  相似文献   

13.
Wind erosion from agricultural fields contributes to poor air quality within the Columbia Plateau of the United States. Erosion from fields managed in a conventional winter wheat–summer fallow rotation was monitored during the fallow period near Washtucna, WA, in 2003 and 2004. Loss of soil and PM10 (particulates ≤10 µm in diameter) was measured during six high wind events (sustained wind speed at 3 m height >6·4 m s?1). Soil loss associated with suspension, saltation and creep as well as PM10 emission was used to validate the Wind Erosion Prediction System (WEPS) erosion submodel. Input parameters for WEPS simulations were measured before each high wind event. The erosion submodel produced no erosion for half of the observed events and over‐predicted total soil loss by 200–700 kg ha?1 for the remaining events. The model appears to over‐predict total soil loss as a result of overestimating creep, saltation and suspension. The model both over‐predicted and under‐predicted PM10 loss. High values for the index of agreement (d > 0·5) suggest that the performance of the model is acceptable for the conditions of this study. While the performance of the model is acceptable, improvements can be made in modeling efficiency by better specifying the static threshold friction velocity or coefficients that govern emissions, abrasion and breakage of silt loams on the Columbia Plateau. Copyright © 2006 John Wiley & Sons, Ltd.  相似文献   

14.
Research on arable sandy loam and silty clay loam soils on 4° slopes in England has shown that tramlines (i.e. the unseeded wheeling areas used to facilitate spraying operations in cereal crops) can represent the most important pathway for phosphorus and sediment loss from moderately sloping fields. Detailed monitoring over the October–March period in winters 2005–2006 and 2006–2007 included event‐based sampling of surface runoff, suspended and particulate sediment, and dissolved and particulate phosphorus from hillslope segments (each ～300–800 m2) established in a randomized block design with four replicates of each treatment at each of two sites on lighter and heavier soils. Experimental treatments assessed losses from the cropped area without tramlines, and from the uncropped tramline area, and were compared to losses from tramlines which had been disrupted once in the autumn with a shallow tine. On the lighter soil, the effects of removal or shallow incorporation of straw residues was also determined. Research on both sandy and silty clay loam soils across two winters showed that tramline wheelings represented the dominant pathway for surface runoff and transport of sediment, phosphorus and nitrogen from cereal crops on moderate slopes. Results indicated 5·5–15·8% of rainfall lost as runoff, and losses of 0·8–2·9 kg TP ha?1 and 0·3–4·8 t ha?1 sediment in tramline treatments, compared to only 0·2–1·7% rainfall lost as runoff, and losses of 0·0–0·2 kg TP ha?1 and 0·003–0·3 t ha?1 sediment from treatments without tramlines or those where tramlines had been disrupted. The novel shallow disruption of tramline wheelings using a tine once following the autumn spray operation consistently and dramatically reduced (p < 0·001) surface runoff and loads of sediment, total nitrogen and total phosphorus to levels similar to those measured in cropped areas between tramlines. Results suggest that options for managing tramline wheelings warrant further refinement and evaluation with a view to incorporating them into spatially‐targeted farm‐level management planning using national or catchment‐based agri‐environment policy instruments aimed at reducing diffuse pollution from land to surface water systems. Copyright © 2010 John Wiley & Sons, Ltd.  相似文献   

15.
Modifications are made to the revised Morgan–Morgan–Finney erosion prediction model to enable the effects of vegetation cover to be expressed through measurable plant parameters. Given the potential role of vegetation in controlling water pollution by trapping clay particles in the landscape, changes are also made to the way the model deals with sediment deposition and to allow the model to incorporate particle‐size selectivity in the processes of erosion, transport and deposition. Vegetation effects are described in relation to percentage canopy cover, percentage ground cover, plant height, effective hydrological depth, density of plant stems and stem diameter. Deposition is modelled through a particle fall number, which takes account of particle settling velocity, flow velocity, flow depth and slope length. The detachment, transport and deposition of soil particles are simulated separately for clay, silt and sand. Average linear sensitivity analysis shows that the revised model behaves rationally. For bare soil conditions soil loss predictions are most sensitive to changes in rainfall and soil parameters, but with a vegetation cover plant parameters become more important than soil parameters. Tests with the model using field measurements under a range of slope, soil and crop covers from Bedfordshire and Cambridgeshire, UK, give good predictions of mean annual soil loss. Regression analysis of predicted against observed values yields an intercept value close to zero and a line slope close to 1·0, with a coefficient of efficiency of 0·81 over a range of values from zero to 38·6 t ha?1. Copyright © 2007 John Wiley & Sons, Ltd.  相似文献   

16.
Abstract

This study presents an analysis of three hydrological years (2007/08, 2008/09 and 2009/10) of precipitation, runoff and sediment yield collected from a small (669.7 ha) semi-arid watershed in southeastern Spain (Lanjarón). At the watershed outlet the runoff, suspended sediment concentration, total solute concentrations and dissolved nutrients (N-NO3, N-NH4, H2PO4 and K) in streamflow were continuously monitored. The runoff was highly variable, ranging between 53.4 and 154.7 mm year?1, with an average of 97.6 mm year?1. In contrast, sediment yields were more regular, averaging 1.8 Mg ha?1 year?1. The hydrological response of the watershed depended mainly on rainfall intensity. Formerly, 32% of the watershed was forested and runoff was more regular, despite the typical Mediterranean rainfall cycle; however, due to forest area reduction to 17% and the increase in abandoned farmland area (18%) in recent decades, the runoff variability has increased. Greater amounts of solutes (32.7 Mg ha?1 year?1) were exported, so that this water is considered as poor for irrigation use. The temporal nutrient export was related to seasonal discharge fluctuations as well as daily concentrations. In addition, the nutrient concentrations of the water discharged were lower than threshold limits cited in water-quality standards for agricultural use and for potable water, with the exception of K (65.9 mg L?1), which may degrade surface waters as well as irrigated soils. Thus, hydrological and erosive processes depended on the watershed features, but also on prior conditions in combination with the characteristics of rainfall episodes.

Citation Durán, Z.V.H., Francia, M.J.R., Garcia, T.I., Rodríguez, P.C.R., Martínez, R.A., and Cuadros, T.S., 2012. Runoff and sediment yield from a small watershed in southeastern Spain (Lanjarón): implications for water quality. Hydrological Sciences Journal, 57 (8), 1610–1625.  相似文献   

17.
Recent studies in the Mediterranean area have shown gully erosion to have a very significant contribution to total soil loss. In the Penedès vineyard region (NE Spain), between 15 and 27% of the land is affected by large gullies and gully‐wall retreat seems to be an ongoing process. Multi‐date digital elevation model (DEM) analysis has allowed computation of sediment production by gully erosion, showing that the sediment production rates are very high by the, up‐to‐date, usual global standards. Here, we present a study carried out using large‐scale multi‐date (1975 and 1995) aerial photographs (1 : 5000 and 1 : 7000) to monitor sediment yield caused by large gullies in the Penedès region (NE Spain). High‐resolution DEMs (1 m grid) were derived and analysed by means of geographical information systems techniques to determine the gully erosion rates. Rainfall characteristics within the same study period were also analysed in order to correlate with the soil loss produced. Mass movement was the main process contributing to total sediment production. This process could have been favoured by rainfalls recorded during the period: 58% of the events were of an erosive character and showed high kinetic energy and erosivity. A sediment production rate of 846 ± 40 Mg ha?1 year?1, a sediment deposition rate of 270 ± 18 Mg ha?1 year?1 and a sediment delivery ratio of 68·1% were computed for a gully area of 0·10 km2. The average net erosion within the study period (1975–95) was 576 ± 58 Mg ha?1 year?1. In comparison with other methods, the proposed method also includes sediment produced by processes other than only overland flow, i.e. downcutting, headcutting, and mass movements and bank erosion. Copyright © 2003 John Wiley & Sons, Ltd.  相似文献   

18.
A database composed of 673 natural rainfall events with sediment concentration measurements at the field or plot scale was analysed. Measurements were conducted on similar soil type (loess soils prone to sealing phenomenon) to apprehend the variability and complexity involved in interrill erosion processes attributable to soil surface conditions. The effects of the dominant controlling factors are not described by means of equations; rather, we established a classification of potential sediment concentration domain according to combination of the dominant parameters. Thereby, significant differences and evolution trends of mean sediment concentration between the different parameter categories are identified. Further, when parameter influences interact, it allows us to discern the relative effects of factors according to their respective degree of expression. It was shown that crop cover had a major influence on mean sediment concentration, particularly when soil surface roughness is low and when maximum 6‐min intensity of rainfall events exceeds 10 mm h?1: mean sediment concentration decreases from 8·93 g l?1 for 0–20 per cent of coverage to 0·97 g l?1 for 21–60 per cent of coverage. The established classification also indicates that the increase of the maximum 6‐min intensity of the rainfall factor leads to a linear increase of mean sediment concentration for crop cover over 21 per cent (e.g. from 2·96 g l?1 to 14·44 g l?1 for the 1–5 cm roughness class) and to an exponential increase for low crop cover (e.g. from 3·92 g l?1 to 58·76 g l?1 for the 1–5 cm roughness class). The implication of this work may bring perspective for erosion prediction modelling and give references for the development of interrill erosion equation. Copyright © 2002 John Wiley & Sons, Ltd.  相似文献   

19.
Reliable assessment of the spatial distribution of soil erosion is important for making land management decisions, but it has not been thoroughly evaluated in karst geo‐environments. The objective of this study was to modify a physically based, spatially distributed erosion model, the revised Morgan, Morgan and Finney (RMMF) model, to estimate the superficial (as opposed to subsurface creep) soil erosion rates and their spatial patterns in a 1022 ha karst catchment in northwest Guangxi, China. Model parameters were calculated using local data in a raster geographic information system (GIS) framework. The cumulative runoff on each grid cell, as an input to the RMMF model for erosion computations, was computed using a combined flow algorithm that allowed for flow into multiple cells with a transfer grid considering infiltration and runoff seepage to the subsurface. The predicted spatial distributions of soil erosion rates were analyzed relative to land uses and slope zones. Results showed that the simulated effective runoff and annual soil erosion rates of hillslopes agreed well with the field observations and previous quantified redistribution rates with caesium‐137 (137Cs). The estimated average effective runoff and annual erosion rate on hillslopes of the study catchment were 18 mm and 0.27 Mg ha?1 yr?1 during 2006–2007. Human disturbances played an important role in accelerating soil erosion rates with the average values ranged from 0.1 to 3.02 Mg ha?1 yr?1 for different land uses. The study indicated that the modified model was effective to predict superficial soil erosion rates in karst regions and the spatial distribution results could provide useful information for developing local soil and water conservation plans. Copyright © 2014 John Wiley & Sons, Ltd.  相似文献   

20.
In Lutzito catchment on Barro Colorado Island, Panama, extraordinarily high suspended‐sediment yields of 1–2 Mg ha?1 year?1 were generated despite the dense forest cover coinciding with erosion‐resistant soils. We hypothesized that ant mounding activity is an important zoogeomorphological mechanism in this area, providing relevant quantities of easily transportable material at the soil surface. To test this hypothesis, all ant mound material was collected collected for dry mass determination from thirty 4 m2 plots installed in the study area every 1–3 days during the 39‐day sampling period. Additionally, three ground‐nesting ant species responsible for mounds in the study area, Ectatomma ruidum, Trachymyrmex cornetzi and Strumigenys marginiventris, were identified. On the basis of the total of 1.38 kg of material collected in the wet season of 2011, the estimate for the whole 8 months wet season amounts to 725 kg ha?1. As this value is in the same order of magnitude as sediment output, it shows that ants may act as important ecosystem engineers and contribute to sediment production here by providing large quantities of fine‐grained, readily erodible material at the soil surface for subsequent transport to the streambed. Copyright © 2014 John Wiley & Sons, Ltd.  相似文献   

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