An experimental study on the influences of water erosion on wind erosion in arid and semi-arid regions

Complex erosion by wind and water causes serious harm in arid and semi-arid regions. The interaction mechanisms between water erosion and wind erosion is the key to further our understanding of the complex erosion. Therefore, in-depth understandings of the influences of water erosion on wind erosion is needed. This research used a wind tunnel and two rainfall simulators to investigate the influences of water erosion on succeeding wind erosion. The wind erosion measurements before and after water erosion were run on semi-fixed aeolian sandy soil configured with three slopes(5°, 10° and 15°), six wind speeds(0, 9, 11, 13, 15 and 20 m/s), and five rainfall intensities(0, 30, 45, 60 and 75 mm/h). Results showed that water erosion generally restrained the succeeding wind erosion. At a same slope, the restraining effects decreased as rainfall intensity increased, which decreased from 70.63% to 50.20% with rainfall intensity increased from 30 to 75 mm/h. Rills shaped by water erosion could weaken the restraining effects at wind speed exceeding 15 m/s mainly by cutting through the fine grain layer, exposing the sand layer prone to wind erosion to airflow. In addition, the restraining effects varied greatly among different soil types. The restraining effects of rainfall on the succeeding wind erosion depend on the formation of a coarsening layer with a crust and a compact fine grain layer after rainfall. The findings can deepen the understanding of the complex erosion and provide scientific basis for regional soil and water conservation in arid and semi-arid regions.     

沙柳方格沙障对库布齐沙漠沙丘粒度分布的影响

为定量探讨沙柳方格沙障对沙粒粒度组成与特征的影响,以流动沙丘(LS)、设障2a沙丘(TS)和设障6a沙丘(SS)为研究对象,在沙丘不同部位、不同土层和障格内不同位置进行取样,分析样品的粒度组成与特征。结果表明:1)随着设障年限的增加,粘粒和粉粒含量增加,细砂含量下降,SS粘粒和粉粒含量与TS和LS的含量差异显著,而TS和LS二者间差异不明显;LS、TS各粒级含量在三个层次间差异均不明显,而SS 0-5cm的粘粒、粉粒以及极细砂粒体积含量较其他2层差异显著。2)SS的频率分布曲线变化幅度小于TS和LS的频率分布曲线变化幅度。各沙丘的平均粒径MZ、分选系数δ、偏度SK、峰度KG的大小顺序均表现为SS相似文献   

隔沙层对盐碱地土壤水盐运动的影响

在80~100 cm范围土层设置沙层,对土壤电导率和含水量进行为期6个月的观察,分析隔沙层对土壤水盐运动的影响。结果表明:80~100 cm层沙层在大降雨量时能够提高土壤含水量;降雨量小,蒸发强烈的5~7月份,隔沙处理能够使土壤积盐程度较对照减少50%~70%;隔沙层延缓沙层以上土壤水分的下渗,从而提高降雨对土壤盐分的淋洗作用。当降雨量接近蒸发量的时候,隔沙处理土壤就能明显脱盐,而在此雨量下,对照只能保证土壤不发生积盐或少量积盐。雨季结束之后,隔沙处理土壤脱盐率较对照提高10%~35%,并能够使土壤脱盐过程持续到10月份,对植物生长十分有利。     

渭河下游水沙变化趋势分析

本文通过对近6年渭河下游水沙量数据的统计和分析得出,渭河下游河段年内多沙期较河流主汛期有所提前;年径流量和年输沙量的变化趋势基本一致,而且自60年代至2005年华县站的水沙量持续呈递减趋势;河流的冲淤情况与该河段的降雨量有着直接的关系,当年平均降雨量小的时候河流以淤积为主,当年平均降雨量大的时候河流以冲蚀为主。针对这些特征,分析了渭河下游目前存在的主要问题。     

巴图湾水库风沙入库量的估算

风沙入库给干旱、半干旱地区的水库带来了严重的填淤危害。本文通过对内蒙古乌审旗南部巴图湾水库岸边流动沙丘不同部位风速与风沙流的同步观测,计算出库岸流动沙丘表面的平均输沙率。利用巴图湾水库1986~2005年9月份的5期TM遥感影像统计出水库两岸受不同风向影响的流动沙丘断面的平均长度,结合巴图湾水库附近乌审旗河南乡气象站1985~2004年的气象资料,统计出不同风向大于起沙风的风速年均持续时间,初步计算出巴图湾水库的年均入库风沙量。结果表明:(1)巴图湾水库的年均入库风沙量为3.65万t,其中西岸风沙入库量为3.55万t,东岸为0.10万t。西岸风沙危害最为严重,是治沙工作的重点。(2)巴图湾水库的风沙入库具有明显的时间性和方向性。受季风气候的影响,风沙入库的方向会随着风向的变化而改变。东南风与西北风是造成东西两岸风沙入库的主要风向。西北风对风沙入库量的贡献最大。(3)在大于起沙风的风速中,5~12 m/s风速段是风沙入库的主要风速。当风速中7 m/s以上的风速持续时间有一个较小的增加时,入库风沙量将会有一个巨大的增加。(4)库岸半固定沙丘的风沙入库,降尘和风水复合侵蚀引起的库岸坍塌也是入库风沙量的重要组成部分。因此,巴图湾水库的实际年入库风沙量应该大于3.65万t。     

Freeze-thaw effects on erosion process in loess slope under simulated rainfall

Seasonal freeze-thaw processes have led to severe soil erosion in the middle and high latitudes. The area affected by freeze-thaw erosion in China exceeds 13% of the national territory. So understanding the effect of freeze-thaw on erosion process is of great significance for soil and water conservation as well as for ecological engineering. In this study, we designed simulated rainfall experiments to investigate soil erosion processes under two soil conditions, unfrozen slope (UFS) and frozen slope (FS), and three rainfall intensities of 0.6, 0.9 and 1.2 mm/min. The results showed that the initial runoff time of FS occurred much earlier than that of the UFS. Under the same rainfall intensity, the runoff of FS is 1.17-1.26 times that of UFS; and the sediment yield of FS is 6.48-10.49 times that of UFS. With increasing rainfall time, rills were produced on the slope. After the appearance of the rills, the sediment yield on the FS accounts for 74%-86% of the total sediment yield. Rill erosion was the main reason for the increase in soil erosion rate on FS, and the reduction in water percolation resulting from frozen layers was one of the important factors leading to the advancement of rills on slope. A linear relationship existed between the cumulative runoff and the sediment yield of UFS and FS (R²>0.97, P<0.01). The average mean weight diameter (MWD) on the slope erosion particles was as follows: UFS0.9 (73.84 μm)>FS0.6 (72.30 μm)>UFS1.2 (72.23 μm)>substrate (71.23 μm)>FS1.2 (71.06 μm)>FS0.9 (70.72 μm). During the early stage of the rainfall, the MWD of the FS was relatively large. However, during the middle to late rainfall, the particle composition gradually approached that of the soil substrate. Under different rainfall intensities, the mean soil erodibility (MK) of the FS was 7.22 times that of the UFS. The ratio of the mean regression coefficient C₂ (MC₂) between FS and UFS was roughly correspondent with MK. Therefore, the parameter C₂ can be used to evaluate soil erodibility after the appearance of the rills. This article explored the influence mechanism of freeze-thaw effects on loess soil erosion and provided a theoretical basis for further studies on soil erosion in the loess hilly regions.     

陕北黄土高原多沙粗沙区乡村聚落土壤水蚀定位观测研究

为研究乡村聚落的土壤侵蚀,在陕北榆林、绥德、延安建立观测站,于2003年对乡村聚落中的户间道路、户间空地、院落在降雨时的次径流泥沙含量、平均含沙量、次侵蚀强度及观测期降雨形成的总侵蚀强度,进行了观测与分析。其观测结果,均说明户间道路、户间空地径流平均含沙量较大,榆林为29.37g/L、29.96g/L,缓德为21.06g/L、17.53g/L、延安为54.6g/L2、9.18g/L,而院落平均径流含沙量较小,榆林、绥德、延安分别为9.47g/L、8.64g/L、14.87g/L。观测期降雨侵蚀总强度,三个观测站均以户间道路最大,分别为1142t/km2、2156.6t/km26、285.7t/km2;户间空地次之,分别为744.5t/km2、1192.6t/km2、1953.2t/km2;院落较小,分别为161.1t/km23、78.7t/km2、1274.3t/km2。说明乡村聚落土壤侵蚀不可忽视,应加强防治。     

An experimental study on the influences of wind erosion on water erosion

In semi-arid regions, complex erosion resulted from a combination of wind and water actions has led to a massive soil loss and a comprehensive understanding of its mechanism is the first step toward prevention of the erosion. However, the mutual influences between wind erosion and water erosion have not been fully understood. This research used a wind tunnel and two rainfall simulators and simulated two rounds of alternations between wind erosion and water erosion(i.e., 1~(st) wind erosion–1~(st) water erosion and 2~(nd) wind erosion–2~(nd) water erosion) on three slopes(5°, 10°, and 15°) with six wind speeds(0, 9, 11, 13, 15, and 20 m/s) and five rainfall intensities(0, 30, 45, 60, and 75 mm/h). The objective was to analyze the influences of wind erosion on succeeding water erosion. Results showed that the effects of wind erosion on water erosion were not the same in the two rounds of tests. In the 1~(st) round of tests, wind erosion first restrained and then intensified water erosion mostly because the blocking effect of wind-sculpted micro-topography on surface flow was weakened with the increase in slope. In the 2~(nd) round of tests, wind erosion intensified water erosion on beds with no rills at gentle slopes and low rainfall intensities or with large-size rills at steep slopes and high rainfall intensities. Wind erosion restrained water erosion on beds with small rills at moderate slopes and moderate rainfall intensities. The effects were mainly related to the fine grain layer, rills and slope of the original bed in the 2~(nd) round of tests. The findings can deepen our understanding of complex erosion resulted from a combination of wind and water actions and provide scientific references to regional soil and water conservation.     

陕晋蒙三角地带能源基地风沙沙源物质的初步研究

本文从堆积风沙物质的空间条件、风沙物质的类型及分布、风沙物质的演变及其区域分异规律四个方面论述区内土地沙漠化的物质基础。区内现代地貌及其营力特征表现为风与流水的交替作用。主要的风沙沙源物质为基岩风蚀和基岩风化壳的分选搬运;河湖相松散堆积物;河流阶地堆积物以及古风沙、风尘堆积物。初步将沙黄土分为粉沙质沙黄土和细沙质沙黄土。风沙物质的演变具有多旋回性、继承性、改造性以及演变因素的复杂性。自Q_2以来至少经历了14个风沙活动旋回。风沙物质的空间分布具有扩散性和交错分布的模式及镶嵌环带结构,即库布齐和毛乌素沙地两个核心,围绕这两个核心的是细沙质沙黄土环带。     

Transport mechanism of eroded sediment particles under freeze-thaw and runoff conditions

Hydraulic erosion associated with seasonal freeze-thaw cycles is one of the most predominant factors, which drives soil stripping and transportation. In this study, indoor simulated meltwater erosion experiments were used to investigate the sorting characteristics and transport mechanism of sediment particles under different freeze-thaw conditions (unfrozen, shallow-thawed, and frozen slopes) and runoff rates (1, 2, and 4 L/min). Results showed that the order of sediment particle contents was silt>sand>clay during erosion process on unfrozen, shallow-thawed, and frozen slopes. Compared with original soils, clay and silt were lost, and sand was deposited. On unfrozen and shallow-thawed slopes, the change of runoff rate had a significant impact on the enrichment of clay, silt, and sand particles. In this study, the sediment particles transported in the form of suspension/saltation were 83.58%-86.54% on unfrozen slopes, 69.24%-84.89% on shallow-thawed slopes, and 83.75%-87.44% on frozen slopes. Moreover, sediment particles smaller than 0.027 mm were preferentially transported. On shallow-thawed slope, relative contribution percentage of suspension/saltation sediment particles gradually increased with the increase in runoff rate, and an opposite trend occurred on unfrozen and frozen slopes. At the same runoff rate, freeze-thaw process had a significant impact on the relative contribution percentage of sediment particle transport via suspension/saltation and rolling during erosion process. The research results provide an improved transport mechanism under freeze-thaw condition for steep loessal slopes.     

灌木林优化配置格局对土壤风蚀的影响

低覆盖度时,灌木林的水平配置格局成为制约土壤风蚀的重要因素。以宁夏盐池县风沙区人工灌木林基地为试验区,研究了不同下垫面类型和不同配置格局的灌木沙障对风速、近地表输沙率和地表粗糙度的影响。结果表明:灌木林的防治土壤风蚀能力与灌木林的种类、高度和配置格局有直接关系:行带式配置能显著提高灌木林的防风效果,其中以沙柳林效果最佳;三行一带、平均高1.5m、行距1.5m、插深0.5m配置规格的沙柳沙障对地表土壤风蚀的控制效果最好,但防护范围限15倍带高以内;在行数一定的情况下,沙障高度越低,控制土壤风蚀能力越强。     

黄河流域粗泥沙集中来源区径流及输沙特征分析

本研究以黄土高原粗泥沙集中来源区面积最大且连续的区域(即北起皇甫川流域南至佳芦河流域地区)为研究对象,以1960~1999年为研究时段,分析了该区内水沙变化特征。结果表明:降水变化的作用和人类活动的影响已交叉融合在一起,使得该区降雨量、径流量、输沙量呈现减少的趋势。在同一时段内,皇甫川流域的降雨损失量最大,而秃尾河流域的降雨损失量最小。40年间皇甫川和佳芦河流域的洪峰和沙峰出现的月份基本上吻合,而孤山川、窟野河和秃尾河流域的输沙量最大的月份同时或滞后于径流量最大的月份。孤山川流域的水沙异源,长时段序列又进一步掩盖了其水沙关系,使得该流域的水沙关系较差,其余4条流域的水沙关系较好,且呈正相关增长趋势。     

Impacts of land disturbance and restoration on runoff production and sediment yield in the Chinese Loess Plateau

Land disturbance and land restoration are important factors influencing runoff production and sediment yield in the semi-arid loess regions of China. This study compared the runoff production and sediment yield during the early stage after land disturbance(ESLD) with those during restoring stage after land disturbance(RSLD). Grey relational analysis was used to analyse the importance of each one of the influencing factors(vegetation, rainfall, soil and topography) in affecting the runoff production and sediment yield. Our results showed that during ESLD, topography was the most critical factor controlling the runoff production, while soil was the most important factor controlling the sediment yield. During RSLD, vegetation was more important in affecting runoff production, while rainfall was more important in affecting sediment yield. In additional, this study demonstrated that both the runoff production and the sediment yield can be effectively reduced by restoring vegetation on severely-disturbed lands, thus providing an important theoretical basis for better implementations of the Grain for Green Program. Our results revealed that the vegetation types of Hippophae rhamnoides+Pinus tabulaeformis and H. rhamnoides are better plant selections for land restoration in this area, especially for relatively gentle slopes(i.e., less than 20 degrees).     

基于M-DEM黄土人工锄耕坡面微地形特征研究

黄土人工锄耕坡面微地形是地表径流和土壤侵蚀过程的重要影响因素。文中在1.0 mm/min雨强的人工模拟降雨试验条件下,采用微地形激光扫描测量方法获取5°人工锄耕坡面微地形相对高程,并进行拟合模型参数验证,进而构建了能反映真实地表情况的高精度M-DEM,并在ArcGIS中对其特征参量进行量化研究。结果表明:黄土人工锄耕坡面微地形起伏较小,整体属于凸形斜坡;虽在某些区域容易形成地表径流,但径流变化比较平缓,不容易形成较大的水流;微地形水系分维能较好地反映复杂微地形特征。论文可为在微地形层面进一步揭示黄土耕作坡面土壤侵蚀机理研究提供数据支持和方法参考。     

Estimation of the quantity of aeolian saltation sediments blown into the Yellow River from the Ulanbuh Desert,China

The Ulanbuh Desert borders the upper reach of the Yellow River.Every year,a mass of aeolian sand is blown into the Yellow River by the prevailing wind and the coarse aeolian sand results in serious silting in the Yellow River.To estimate the quantity of aeolian sediments from the Ulanbuh Desert blown into the Yellow River,we simulated the saltation processes of aeolian sediments in the Ulanbuh Desert.Then we used a saltation submodel of the IWEMS(Integrated Wind-Erosion Modeling System)and its accompanying RS(Remote Sensing)and GIS(Geographic Information System)modules to estimate the quantity of saltation sediments blown into the Yellow River from the Ulanbuh Desert.We calibrated the saltation submodel by the synchronous observation to wind velocity and saltation sediments on several points with different vegetation cover.The vegetation cover,frontal area of vegetation,roughness length,and threshold friction velocity in various regions of the Ulanbuh Desert were obtained using NDVI(Normalized Difference Vegetation Index)data,measured sand-particle sizes,and empirical relationships among vegetation cover,sand-particle diameters,and wind velocity.Using these variables along with the observed wind velocities and saltation sediments for the observed points,the saltation model was validated.The model results were shown to be satisfactory(RMSE less than 0.05 and|Re|less than 17%).In this study,a subdaily wind-velocity program,WINDGEN,was developed using this model to simulate hourly wind velocities around the Ulanbuh Desert.By incorporating simulated hourly wind-velocity and wind-direction data,the quantity of saltation sediments blown into the Yellow River was calculated with the saltation submodel.The annual quantity of aeolian sediments blown into the Yellow River from the Ulanbuh Desert was 5.56×106t from 2001 to 2010,most of which occurred in spring(from March to May);for example,6.54×105tons of aeolian sand were blown into the Yellow River on 25 April,2010.However,in summer and winter,the saltation process occasionally occurred.This research has supplied some references to prevent blown sand hazards and silting in the Yellow River.     

坡度对黄土坡面径流溶质迁移特征的影响

通过田间模拟降雨试验,分析了坡度对坡面物质迁移特性的影响.结果显示,坡度对坡面物质迁移的影响十分显著;降雨强度一定时,坡度达到15°左右时,径流量达到最大;坡度对径流养分流失量的影响是通过径流量起主导作用,径流量大相应径流携带养分流失总量增加.利用幂函数对径流溶质浓度变化过程进行了拟合,结果显示幂函数可以很好反映田间坡面溶质随地表径流变化过程,说明在侵蚀环境下径流溶质浓度变化过程符合幂函数.     

Interactions between wind and water erosion change sediment yield and particle distribution under simulated conditions

Wind and water erosion are among the most important causes of soil loss, and understanding their interactions is important for estimating soil quality and environmental impacts in regions where both types of erosion occur. We used a wind tunnel and simulated rainfall to study sediment yield, particle-size distribution and the fractal dimension of the sediment particles under wind and water erosion. The experiment was conducted with wind erosion firstly and water erosion thereafter, under three wind speeds(0, 11 and 14 m/s) and three rainfall intensities(60, 80 and 100 mm/h). The results showed that the sediment yield was positively correlated with wind speed and rainfall intensity(P<0.01). Wind erosion exacerbated water erosion and increased sediment yield by 7.25%–38.97% relative to the absence of wind erosion. Wind erosion changed the sediment particle distribution by influencing the micro-topography of the sloping land surface. The clay, silt and sand contents of eroded sediment were also positively correlated with wind speed and rainfall intensity(P<0.01). Wind erosion increased clay and silt contents by 0.35%–19.60% and 5.80%–21.10%, respectively, and decreased sand content by 2.40%–8.33%, relative to the absence of wind erosion. The effect of wind erosion on sediment particles became weaker with increasing rainfall intensities, which was consistent with the variation in sediment yield. However, particle-size distribution was not closely correlated with sediment yield(P>0.05). The fractal dimension of the sediment particles was significantly different under different intensities of water erosion(P<0.05), but no significant difference was found under wind and water erosion. The findings reported in this study implicated that both water and wind erosion should be controlled to reduce their intensifying effects, and the controlling of wind erosion could significantly reduce water erosion in this wind-water erosion crisscross region.     

北京平原土壤机械组成和抗风蚀能力的分析

土壤遇风起沙是风沙活动产生的最根本原因,它的基本点有二:一是具有足以使砂粒产生运动的一定强度的起沙风;二是土壤颗粒小、质地干燥疏松,具有遇风起沙产生运动的属性。本文分析了北京土壤的机械组成特征和结构性能等。叙述了在永定河边部一些地块的野外风沙观测和沙风洞试验,证实土壤结构性、干松程度、植被覆盖状况是决定土壤抗风蚀性能的三要素。最后,试用不易蚀因子含量评价北京平原土壤的抗风蚀能力。     

Evaluation of an erosion-sediment transport model for a hillslope using laboratory flume data

Climate change can escalate rainfall intensity and cause further increase in sediment transport in arid lands which in turn can adversely affect water quality. Hence, there is a strong need to predict the fate of sediments in order to provide measures for sound erosion control and water quality management. The presence of microtopography on hillslopes influences processes of runoff generation and erosion, which should be taken into account to achieve more accurate modelling results. This study presents a physically based mathematical model for erosion and sediment transport coupled to one-dimensional overland flow equations that simulate rainfall-runoff generation on the rill and interrill areas of a bare hillslope. Modelling effort at such a fine resolution considering the flow connection between interrill areas and rills is rarely verified. The developed model was applied on a set of data gathered from an experimental setup where a 650 cm×136 cm erosion flume was pre-formed with a longitudinal rill and interrill having a plane geometry and was equipped with a rainfall simulator that reproduces natural rainfall characteristics. The flume can be given both longitudinal and lateral slope directions. For calibration and validation, the model was applied on the experimental results obtained from the setup of the flume having 5% lateral and 10% longitudinal slope directions under rainfall intensities of 105 and 45 mm/h, respectively. Calibration showed that the model was able to produce good results based on the R2(0.84) and NSE(0.80) values. The model performance was further tested through validation which also produced good statistics(R2=0.83, NSE=0.72). Results in terms of the sedigraphs, cumulative mass curves and performance statistics suggest that the model can be a useful and an important step towards verifying and improving mathematical models of erosion and sediment transport.     

陕北黄土丘陵区窑洞侵蚀产沙分析

本文研究因在陕北黄土丘陵区建筑窑洞和塌窑而引发的土壤侵蚀问题,对窑洞的侵蚀产沙时间、空间进行分析,指出产沙主要来自建窑和塌窑时,产沙堆积空间主要位于窑洞院子前缘斜坡和坍塌窑洞的洞口坡地上;认为建窑和塌窑的土壤流失系数是不同的,并分别测算了各自的流失系数。