Assessment of Sedimentation Impacts on Small Dams—A Case of Small Reservoirs in the Lotsane Catchment

Sedimentation is a major problem for agricultural dams in Botswana, as it reduces the storage capacity and life span of the reservoirs. The process of sedimentation starts from day one of the impounding of water in any given reservoir. Even though a provision is made for every reservoir during planning for a certain storage capacity, specifically for sediment deposition, called dead storage, a major portion of the sediment gets deposited for many years of the reservoir’s life in areas other than the dead storage, and this trend cannot be reversed at easy cost. This study is aimed at the analysis of prevailing sedimentation processes in the nearby dozens of dams found in the Lotsane catchment located within the Limpopo Basin of Botswana, and focuses on assessment of annual sedimentation rate. A spatial analysis and modelling study was conducted based on the Revised Universal Soil Loss Equation and GIS to determine sediment yield and degree of impact of each reservoir for a given landscape, rainfall and catchment heterogeneity. Field observations and soil sampling were carried out in order to determine the factors that lead to reservoir sedimentation. Spatial data on the dams in Lotsane catchment were also collected from Ministry of Agriculture, which were used for ground-truthing, GIS-based calculations and model validation. The average sediment rate and sediment delivery ratio were found to be 1.74 t/ha/year and 81%, respectively. These are useful parameters to estimate service life of the dams and plan remedial measures related to sedimentation problems.

不同配置乡村植被缓冲带阻控径流污染特征研究

植被缓冲带是河湖的重要生态空间屏障,对于减缓人类活动对河湖的直接干扰、阻隔农业面源污染等具有重要意义。为系统研究不同类型缓冲带对农田氮磷等污染物的拦截功效,本研究在定远张山设计8个缓冲带小区,结合自然降雨方式,持续两年观测不同缓冲带对地表径流及其主要污染物(TN、TP、COD)的削减效果。结果表明:林地和3°、8°横垄耕地缓冲带对径流的拦截效率较高,减流率分别达到了62.4%、52.0%和60.6%,径流量随雨强增大先升高后下降。与8°坡耕地缓冲带相比,降坡(3°)处理竖垄、横垄缓冲带泥沙流失量分别降低53.3%、50.9%。降雨产流的养分流失以氮素和有机质为主,林地缓冲带对径流NH4+-N的拦截率平均高达95.2%,此外降坡和横垄耕作措施也能有效减少径流冲刷的氮素流失。不同处理缓冲带对径流TP均有较好的拦蓄效果。3°、8°横垄耕地缓冲带CODMn流失量较低,拦截率达到53.0%、58.6%。林地缓冲带中高覆盖度的植被和发达的根系能够有效减缓降雨对地表的冲刷,减少径流和养分流失。在南方丘陵山地的乡村地区实施横坡垄作是拦蓄径流、降低面源污染风险的有效措施。

秸秆和生物炭对紫色土坡耕地产流产沙与氮素流失的影响

[目的]探究不同添加量的秸秆和生物炭对紫色土坡耕地的具体改良效果,从而为合理防治三峡库区水土流失提供理论参考。[方法]采用人工模拟降雨的方法,以裸坡为对照,研究了紫色土中添加水稻秸秆(施用量4,7,10 t/hm^(2))和生物炭(含量13,39,65 t/hm^(2))对紫色土坡耕地产流产沙与氮素流失的影响。[结果](1)高强度降雨条件下,紫色土混掺生物炭加快了坡面产流进程,而施加碎混秸秆能延长起始产流时间、削减产流速率;(2)紫色土添加生物炭后累积产沙量较对照增加了0.64%~66.29%,而施加碎混秸秆后减少了42.58%~70.27%,且施加碎混秸秆对坡面产沙的抑制效应远强于对坡面产流的控制作用;(3)地表径流中氮素流失过程以NO-3-N为主,且TN,NO-3-N和NH+4-N的流失量和养分流失模数整体表现为生物炭处理最大,碎混秸秆处理最小。[结论]紫色土坡耕地施加碎混秸秆能促渗阻流、有效控制水土及养分流失,而短期施加生物炭可能会产生负面影响。

直升机整体式惯性粒子分离器研究现状

整体式惯性粒子分离器是一种直升机进气防护装置,其性能优异、应用广泛,对于保护直升机发动机、延长其使用寿命具有重要意义。本文从4个方面对整体式惯性粒子分离器的研究现状进行归纳总结,包括:总结了现有直升机进气防护装置的类型及相关气动参数,梳理了整体式惯性粒子分离器现有的研究方法及取得的相关成果,分析了影响整体式惯性粒子分离器工作性能的因素,并展望了整体式惯性粒子分离器未来的发展方向。研究成果可为今后开展整体式惯性粒子分离器研究及优化设计提供一定参考。

基于投影寻踪回归方法的微压过滤冲洗池水头损失与过滤效率预测模型

以微压过滤冲洗池的水头损失与过滤效率为考核指标,考虑进水流量、矿化度、含沙量与滤网孔径4个因素进行正交试验设计,采用投影寻踪回归方法PPR分析各个因素对考核指标的影响权重,选取20组试验数据建立含沙微咸水条件下微压过滤冲洗池水头损失和过滤效率的预测模型,探究了含沙微咸水对微压过滤冲洗池的水头损失和过滤效率的影响。研究结果表明,影响微压过滤冲洗池水头损失的因素由大到小依次为进水流量、含沙量、矿化度、滤网孔径;影响过滤效率的因素由大到小依次为含沙量、进水流量、矿化度、滤网孔径;构建的PPR预测模型的预测精度整体合格率达100%;当进水流量为6~7 m^(3)/h、含沙量为0.5~1.0 g/L、矿化度为0~2.0 g/L及滤网孔径为0.125~0.180 mm时,水头损失存在最小值;当进水流量为9~10 m^(3)/h、含沙量为1.75~2.00 g/L、矿化度为0~3.0 g/L及滤网孔径为0.125~0.150 mm时,过滤效率存在最大值。物理模型的试验结果可为微压过滤冲洗池的实际应用提供研究基础。

碎石含量对三峡库区坡耕地土壤氮磷流失特征的影响

坡耕地是三峡库区水土流失的主要来源,导致土壤养分的损失,严重影响库区生态环境建设与社会经济可持续发展。库区坡耕地土壤浅薄化和砾质化特征明显,但目前对含碎石坡耕地土壤侵蚀和养分流失特征的研究尚不多见。该研究通过设置3个降雨梯度(60、90、120 mm/h)和4种碎石含量(0、10%、20%、30%),开展人工模拟降雨试验,分析各试验条件下含碎石土壤产流产沙和氮磷流失特征。结果表明:1)碎石主要通过改变土壤结构以增大产流产沙量来促进氮磷流失,而对相应流失速率与流失浓度的变化规律影响较小,不同碎石含量下泥沙产量的变异系数更高,且泥沙中不同碎石含量下的氮磷流失量显著性差异更强(P<0.05);2)泥沙中累计磷流失量略微大于氮流失量,有效磷几乎不随泥沙流失,有效氮约占全氮流失量的15%;径流中氮素流失量几乎为磷素的10倍且以有效氮为主,占总氮流失量的75%,有效磷占总磷流失量的25%;3)不同碎石含量下有效氮流失规律大致相同,径流中硝态氮约占有效氮流失量的70%,而泥沙中则以铵态氮为主,约占65%;4)不同碎石含量下土壤中氮磷元素均以随侵蚀产沙流失为主,累计产沙量与氮磷元素随侵蚀产沙流失量均在20%碎石含量下达到极大值,10%碎石含量下流失量相对较小,因此泥沙库区坡耕地氮磷流失防治应以减少侵蚀产沙为主,注意大雨暴雨多发季节的水质监测与施肥控制。同时可对土中碎石进行清除使其保持在不高于10%水平。研究结果可为三峡库区含碎石坡耕地水土流失防治和氮磷流失治理提供科学参考。

黄土丘陵沟壑区坡面水沙尺度传递效应及其影响因素分析

[目的]探究坡面水沙运动过程中的尺度效应,阐明黄土高原丘陵沟壑区水沙运动尺度效应影响机制,进而为水沙传递机理研究及黄河流域水沙综合治理提供科学支撑。[方法]基于黄河子洲径流试验站4个径流场径流泥沙资料,通过对比分析次降雨事件下不同坡长产流产沙过程,揭示了坡面产流产沙的尺度传递效应。提出尺度传递效率概念,用来表征上下层级间水沙传递关系,进而探究了径流泥沙传递效率的影响因素。[结果](1)不同降雨类型特征因素对坡面产流产沙的影响不同,降雨历时主要影响坡面产流产沙能力,平均雨强主要影响坡面产流产沙起始时间;(2)次降雨事件下,不同坡长的径流传递是较为理想的平衡传递机制,且随坡长增加,径流的传递能力呈减小趋势。而在40~60 m坡长条件下,泥沙的传递表现为非平衡传递过程,随坡长增加,泥沙的传递能力呈先增大后减小的变化趋势;(3)不同尺度坡面水沙传递效率的影响因素不同,径流深、平均雨强及雨后表层土壤含水率是影响水沙尺度效率传递的主要因素。[结论]黄土丘陵沟壑区坡面产流产沙能力受降雨特性及坡长的影响,水沙沿程传递存在明显的折损或增益的尺度效应,水沙传递效率受雨强、径流及土壤湿度等多重因素的调控。

南方典型红壤区不同枯死率芒萁的水土流失阻控效应

[目的]探究芒萁植丛不同枯死率(100%,50%和0%)下坡面的产流产沙规律,揭示不同生长状态下芒萁的水土流失阻控效果。[方法]采用人工模拟降雨试验,对不同芒萁枯死率下坡面产流产沙过程随雨强的变化特性进行了定量分析。[结果](1)不同降雨强度和芒萁枯死率下径流速率随降雨历时呈前期缓慢或快速增长,后期趋于稳定。较小雨强下,侵蚀速率除裸坡外随降雨历时呈前期缓慢增加、后期趋于稳定状态;较大雨强下,侵蚀速率随降雨历时变化呈前期快速增加,中后期逐渐下降趋于稳定。(2)除2 mm/min雨强下的累积产流量外,其余处理条件下累积产流产沙量差异明显,且产沙量随芒萁枯死率的增加而增加。(3)两种雨强不同处理下坡面累积产流量和累积产沙量关系符合幂函数模型(R2>0.99)。[结论]两种雨强芒萁植丛不同枯死率下径流速率和侵蚀速率随降雨历时变化前期迅速增加、后期逐渐波动稳定,各处理下累积径流量与累积产沙量的函数关系拟合回归效果良好,证实了枯死芒萁亦可在中国南方红壤侵蚀区起到良好的水土流失阻控效果。

野外模拟降雨条件下高寒草甸区植被退化和人工植被恢复坡面的产流产沙过程

[目的]青藏高原是我国重要生态屏障,高寒草甸是其重要组成部分,水土保持功能是高寒草甸重要生态服务功能。开展青藏高原高寒草甸区水土流失过程研究对减少人为扰动水土流失、保障西南地区生态安全具有重要意义。[方法]选取青藏高原高寒草甸未退化、轻度退化、中度退化、裸坡与人工植被恢复5种不同类型坡面,通过野外模拟降雨试验,分析不同雨强条件下,不同植被退化与恢复坡面产流产沙过程,揭示植被退化与人工植被恢复坡面土壤侵蚀机理与水沙关系。[结果](1)高寒草甸未退化坡面与人工植草恢复坡面因其根系较为致密,其水分下渗能力相对较弱,故初始产流时间相对较短;而对于轻度退化坡面,侧流与纵向入渗能力相对较强,初始产流时间相对较长。(2)在常规降雨条件下(30,60 mm/h),轻度退化坡面产流量最小,减流效益最高,达到77.13%;人工恢复坡面产流量与未退化坡面接近,略高于轻度退化坡面;而裸土坡面累计产流量最大,且显著高于其他坡面;极端降雨条件下(90 mm/h)未退化坡面产流量激增,仅低于裸坡并明显高于人工植被恢复坡面。(3)在常规降雨条件下(30,60 mm/h),人工恢复植被坡面减沙效益最高,分别达到81.97%和89.82%,其次是未退化坡面,且随着植被退化程度增大,减沙效益逐渐降低;但在极端降雨条件下,人工恢复植被和未退化坡面减沙效益几乎相同,而中度退化坡面产沙量是未退化坡面的4.59倍;轻度退化坡面虽然具有较好的减流效益,但是减沙效益相对较差。[结论]研究结果可为高寒草甸区植被恢复与生态安全提供重要科学依据。

网式过滤器水头损失动态变化规律

网式过滤器是微灌系统的关键部件之一,对过滤杂质,减缓滴头堵塞起到重要作用,但过滤器水头损失往往随拦截杂质的增多而增大,导致滤网破损或系统被迫停机。为明晰过滤器水头损失变化规律,该研究采用文献数据归纳分析和试验相结合的方法,对7种网式过滤器水头损失数据开展聚类分析;以Y型网式过滤器为例,测试不同流量、泥沙浓度和沙粒级配对过滤器水头损失的影响,以减少水头损失激增、提高拦沙效果为主要目标开展综合评价,优选过滤器适宜的运行工况。结果表明:1)不同类型网式过滤器水头损失随时间变化可分为平稳增加阶段和突然增加阶段,突然增加阶段的水头损失增长速率更大,堵塞均匀度均大于1。2)相同流量和浓度下,以>100~125μm泥沙为主的Ⅲ级配和以>125~150μm泥沙为主Ⅳ级配含沙水较以>54~75μm泥沙为主Ⅰ级配和以>100~125μm泥沙为主Ⅱ级配含沙水更容易产生水头损失激增。相同流量下,高浓度工况更容易出现水头损失激增;相同浓度下,流量为3.5 m^(3)/h时最容易使过滤器水头损失激增。3)CRITIC-TOPSIS综合评价结果表明排名前3的分别是流量2.5 m^(3)/h、泥沙浓度60 mg/L工况下Ⅲ、Ⅳ和Ⅱ级配含沙水,综合得分指数分别为0.726、0.712和0.711;低泥沙浓度、大颗粒级配和高泥沙浓度、小颗粒级配在流量2.5 m^(3)/h时综合性能好,高泥沙浓度、大颗粒级配在流量4.5 m^(3)/h综合性能好,低泥沙浓度、小颗粒级配在3种流量下综合性能差异不大。研究可为减少过滤器水头损失和增加运行时长提供参考。

弃渣扰动对藏东山地草甸坡面产流产沙的影响

[目的]明晰铁路修建中弃渣工程扰动引起的水土流失响应,揭示弃渣堆积前后及其植被恢复对藏东生态脆弱的山地草甸区坡面尺度水土流失的影响。[方法]选取未扰动、轻度扰动、重度扰动、覆土恢复4个类型的坡面,建立原位径流小区,通过人工模拟降雨试验,开展了坡面产流产沙过程的研究。[结果](1)坡面的溅蚀量随扰动强度的增大而增加,下坡向的溅蚀量为上坡溅蚀量的1.14~2.67倍。(2)轻度扰动坡面、重度扰动坡面和覆土恢复坡面的初始产流时间分别缩短为未扰动坡面的53.8%~66.7%,34.6%~46.7%,86.7%~92.9%。(3)未扰动坡面、轻度扰动坡面、重度扰动坡面和覆土恢复坡面的产流速率分别为44~86,104~147,200~373,46~95 ml/(min·m^(2)),产沙速率分别为0.026~0.055,0.05~0.098,1.034~2.189,0.047~0.077 g/(min·m^(2))。[结论]覆土恢复坡面的水土保持能力较轻度扰动和重度扰动坡面有显著提高,但距未扰动坡面仍有差距,需采取其他植被或工程措施对工程扰动坡面加以恢复。

惯性基准法在地铁轨道检测中的应用

地铁的使用寿命与地铁轨道的损耗状况有关,及时地发现轨道问题,并加以修复可以有效提高地铁使用寿命;为了提升城市地铁的使用寿命,研究构建了一个基于惯性基准法的地铁轨道波磨损耗检测系统;该系统以惯性基准法为核心,配合加速度计,及检测车辆,对地铁轨道的波磨损耗情况进行检测;结果显示,惯性基准法的检测标准差,总是低于弦测法的检测标准差,检测长度为400 m时,弦测法的检测标准差为0.79 mm,而惯性标准法的检测标准差为0.72 mm;基于惯性基准法的检测系统的检测结果与实际情况基本一致;研究构建的地铁轨道波磨损耗检测系统的检测成本更低,且检测精度符合实际应用需求。

Nutrient Losses in Soils on Loess Plateau

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GRACE observed mass loss in the middle and lower Yangtze basin

Anthropogenic architectures have a significant impact to the environment. The Three Gorges Dam(TGD),as the largest dam in the world, is a typical example, and has influenced the mass anomalies transported by the flow downstream in the Yangtze River since June 2003. However, the evidence of TGD influence on downstream mass transportation is not documented. In this study, we analyze the monthly gravity solutions from GRACE to investigate the downstream mass variations of Yangtze River. From our results,the considerable mass loss is detected in the downstream of TGD. By comparing our estimations with the in situ water level data of TGD, we find that the mass variations derived from GRACE at Datong station decreases shortly after the impoundment of TGD. This confirms a strong connection between them.Furthermore, by comparing with the in situ sediment load and river discharge at Yichang and Datong gauging stations, we find that the sediment load data shows a similar mass loss signature while the river discharge of both stations has stay at a relative stable level. This indicates that further study is still needed to understand the mechanism better.

SWAT Model Application to Assess the Impact of Intensive Corn-farming on Runoff, Sediments and Phosphorous loss from an Agricultural Watershed in Wisconsin

The potential future increase in corn-based biofuel may be expected to have a negative impact on water quality in streams and lakes of the Midwestern US due to increased agricultural chemicals usage. This study used the SWAT model to assess the impact of continuous-corn farming on sediment and phosphorus loading in Upper Rock River watershed in Wisconsin. It was assumed that farmers in the area where corn was rotated with soybean would progressively skip soybean for continuous corn as corn became more profitable. Simulations using SWAT indicated that conversion of corn-soybean to corn-corn-soybean would cause 11% and 2% increase in sediment yield and TP loss, respectively. The conversion of corn-soybean to continuous corn caused 55% and 35% increase in sediment yield and TP loss, respectively. However, this increase could be mitigated by applying various BMPs and/or conservation practices such as conservation tillage, fertilizer management and vegetative buffer strips. The conversion to continuous corn tilled with conservation tillage reduced sediment yield by 2% and did not change TP loss. Increase in P fertilizer amount was roughly proportional to increase in TP loss and 11% more TP was lost when fertilizer was applied four months before planting. Vegetative buffer strips, 15 to 30 m wide, around corn farms reduced sediment yield by 51 to 70% and TP loss by 41 to 63%.

Mitigating the Impact of Climate Change by Reducing Evaporation Losses: Sediment Removal from the High Aswan Dam Reservoir

Scientists in Egypt are particularly interested in the sustainable management of water and land resources. Global climate change will have a dramatic impact on the Egyptian water and land resources as well as its coastline and agriculture. Egypt is likely to become one of the most vulnerable countries in the world in the next several decades. Many climate scenarios predict that climate change will severely affect rainfall in the Nile basin and the flow of the Nile River in general and the High Aswan Dam Reservoir (HADR) in particular. Global warming and the higher temperatures will lead to higher evaporation rates, which, in turn, will result in less water availability at the HADR. Egypt’s Ministry of Water Resources and Irrigation predicts that the evaporation losses will, compared to the mean annual evaporation rates for the last 30 years, be approximately 3% to 10% higher by the year 2100. Since the construction of the High Aswan Dam fifty years ago, high sediment loads are a tremendous problem. 6.6 Billion Cubic Meter (km3) of sediments were deposited in the HADR during this period. The sediment has raised the lakebed level as well as the water level and caused a larger surface area. These developments have decreased the storage capacity of HADR and have increased the evaporation rate. The presented paper investigates the impact of lowering the lakebed by removing sediments from the HADR with a distinct emphasis on evaporation losses. A digital elevation model for the HADR was developed to describe the hydrological characteristics and to assess the consequences of removing sediment deposits. The results show that the removal of sediments will reduce evaporation losses by about 1.1 km3 projected for 2100, which represents 6.5% of the total projected evaporation losses.

Assessment of Runoff, Sediment Yields and Nutrient Loss Using the Swat Model in Upper Indus Basin of Pakistan

The main objective of this study is to understand the runoff, sediment yield and water quality of the Upper Indus River Basin of Pakistan. To achieve this goal, specific objectives have been met which include, setup of a hydrological model using Soil and Water Assessment Tool (SWAT) then calibration and validation of the hydrological model using river discharges and in the end investigating the performance of the hydrological model by SWAT. This research will have great impacts on socio-economic conditions of Pakistan because study of upper Indus River basin is imperative to provide data needed for its management, and to warrant that it is sustainable to support the increasing population and conservational flows. A set of programmable mapping components MapWindow Geographic Information System (GIS) was used which is an open source GIS based mapping application. It is SWAT used spatially distributed information on elevation, land use, slope and soil. The program Sequential Uncertainty Fitting ver.2 (SUFI-2) in a combination of uncertainty analysis and calibration of outputs was used in SWAT-CUP. SWAT model used input data, which have climate information to obtain results. The observed climate data of temperature gauges and rain gauge were used as input in the SWAT model;the calibration results for three discharge stations were produced. The initial P-factor value was satisfactory but more iteration to attempt narrow uncertainty band with improving goal function, resulted in small percentage of observed data within uncertainty band. A warm up period of three years (1979-1982) was used for simulation of SWAT model. The model was calibrated for selected three catchments for the period 1982-2000 and validated for period 2001-2010. Results are quite comparable with the observed flows.

基于近20年《中国水土保持公报》的水土流失治理分析

水土保持是生态文明建设的重要组成部分,也是反映经济社会发展与生态环境质量动态平衡的重要综合指标。基于近20 a的《中国水土保持公报》,分析了水土流失现状,总结了水土保持工作进展,深入探究了水土流失动态变化成因及水土保持阶段性成效,研究成果对评价水土保持工作成效具有重要理论意义。研究结果表明:①与20世纪80年代末相比,2020年全国水土流失面积下降了26.6%,相较于20世纪初下降了24.4%;②2011年以前水土流失以中度及以上强度为主,2018年以后轻度流失面积占比超过60%;③水土流失综合治理是水土流失面积降低的主要原因;近20 a来,11条主要江河年总输沙量下降了72.4%,年输沙量与累计水土流失治理面积呈显著的负相关关系(R 2=0.90)。现阶段我国水土流失治理由“面”向“点”纵深推进,水土保持工作迈入高质量发展。研究成果可为我国水土保持工作评价及水土保持高质量发展提供定量数据和理论基础。

黄河中游多沙粗沙区水土流失治理面临的关键问题与发展对策

黄河中游多沙粗沙区是黄土高原乃至全国水土流失最为严重、生态环境最为脆弱的地区之一。根据黄河流域生态保护和高质量发展国家战略对水土保持的新需求,在总结黄河多沙粗沙区土壤侵蚀状况、水土流失治理现状与成效基础上,分析了目前水土流失治理面临的关键问题,提出了构建区域水土流失防治新格局、建立多沙粗沙区水土保持空间管控制度、加强水土保持重大基础科技问题及关键技术研究、创新生态治理与乡村振兴融合发展模式、加快推动水土保持体制机制创新等对策建议。

Estimation of soil erosion and sediment yield in Wadi El Hachem watershed(Algeria)using the RUSLE-SDR approach

One of the most common types of soil degradation is water erosion.It reduces soil quality at the erosion site and may cause sedimentation issues at the deposition site.This phenomenon is estimated using a variety of models.The Revised Universal Soil Loss Equation(RUSLE)model is the most often used,due to its consistence and low data requirement.It is useful for estimating annual soil loss at the watershed scale.To investigate the relationship between soil erosion and sediment deposition,the combined RUSLE and Sediment Delivery Ratio(SDR)models are used.The Wadi El Hachem watershed is a coastal and mountainous Mediterranean basin with rugged topography and high degree of climatic aggressiveness.Both of these characteristics can have an immediate effect on soil erosion and sediment yield.This research includes estimating the Average Annual Soil Loss(A)and Sediment Yield(SY)in the Wadi El Hachem watershed,mapping different RUSLE factors as well as A and SY,and studying the influence of rainfall erosivity(R)on A and SY in dry and rainy years.The A results vary from 0 to 410 t·ha^(-1)·yr^(-1)with an annual average of 52 t·ha^(-1)·yr^(-1).The Renfro's SDR model was selected as the best model for estimating SY,with standard error,standard deviation,coefficient of variation,and Nash–Sutcliffe efficiency(NSE)values of 0.38%,0.02,0.07%,and 1.00,respectively.The average SY throughout the whole watershed is around 27 t·ha^(-1)·yr^(-1).The SY map for the entire Wadi El Hachem watershed revealed that sediment production zones are mainly concentrated in the Northeast of the basin,at the basin’s outlet,and in the tributaries of the dam.The simulation results of soil loss and sediment yield in dry and rainy years revealed that R is one of the main factors affecting soil erosion and sediment deposition in the Wadi El Hachem watershed.The mean difference in R factor between dry year and rainy year is 671 MJ·mm·ha^(-1)·h^(-1)·yr^(-1).As a result of this fluctuation,the soil loss and sediment yield have increased by 15 and 8 t·ha^(-1)·yr^(-1),respectively.The results of this research can be used to provide scientific and technical support for conservation and management strategies of the Wadi El Hachem watershed.