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.

A METROD PREDICTING RESPONSE OF SEDIMENT YIELD TO POSSIBIE CHANGE OF PRECIPITATION DUE TO GLOBAL GREENHOUSE WARMING:AN EXAMPIE FROM NORTH FRINGE OF THE LOESS PLATEAU, CHINA

Starting from the supposition of time-space substitution, the Langbein-Schumm's Law was applied to deal with response of fluvial erosion System to the changes in mean annual Precipitation induced by global green-house warming. As a result, a simple method was put forward to predict change in sediment yield, with Ningxia Hui Autonomous Region in the northern fringe of the Loess Plateau of China as an example. Results show that, even the change in mean annual precipitation is the same, the direction and magnitude of the resultant chang in sediment yteld would be quite different in fferent physico-geographical zones. When mean annual precipitation is increased, sediment yield in arid or semi-arid areas with a mean anntal Peripitation of less than 400 mm will be increased, while sediment yield in sub-humid or humid areas with a mean annual precipitation of more than 400 mm will be decreased.Additionally, the complex response of fluvial erosion system in time series due to the lag of change in vegetation behind the changn in precipitation has also been qualitatively discussed in this paper.

Evaluation of Sediment Yield Predicting Models of Ghana

Fluvial sediment transport data is a very important data for effective water resource management.However,acquiring this data is expensive and tedious hence sediment yield modeling has become an alternative approach in estimating river sediment yields.In Ghana,several sediment yield predicting models have been developed to estimate the sediment yields of ungauged rivers including the Pra River Basin.In this paper,10 months sediment yield data of the Pra River Basin was used to evaluate the existing sediment yield predicting models of Ghana.A regression analysis between predicted sediment yield data derived from the models and the observed suspended sediment yields of the Pra Basin was done to determine the extent of estimation of observed sediment yields.The prediction of suspended sediment yield was done for 4 out of 5 existing sediment yield predicting models in Ghana.There were variations in sediment yield between observed and predicted suspended sediments.All predicted sediment yields were lower than observed data except for equation 3 where the results were mixed.All models were found to be good estimators of fluvial sediments with the best model being equation 4.Sediment yield tends to increase with drainage basin area.

Effect of grass coverage on sediment yield in the hillslope-gully side erosion system

By scouring experiments, the changeable process and characteristics of sediment yield in the hillslope-gully side erosion system with different coverage degrees and spatial locations of grass were studied. Five grass coverage degrees of 0, 30%, 50%, 70%, 90%, three spatial locations of grass （upslope, mid-slope, low-slope） and two water inflow rates of 3.2 L/min, 5.2 L/min were applied to a 0.5 by 7 m soil bed in scouring experiments. Results showed that the sediment yield decreased with the increase of grass coverage degree at 3.2 L/min water inflow rate in scouring experiments and the sediment yield with different grass locations on the sloping surface was in the order of upper 〉 middle 〉 lower. At 5.2 L/min water inflow rate, the differences of sediment yield among various grass coverage degrees were increased, whereas the changeable tendency of sediment yield with different grass locations on the whole sloping surface was not very obvious. The proportion of sediment yield from the gully side increased in an exponential relationship with the increase of grass coverage degree When the grass was located on the lower position of hillslope, the influence for accelerating gully erosion is the greatest.

Estimation of runoff and sediment yield in the Redrock Creek watershed using AnnAGNPS and GIS

Sediment has been identified as a significant threat to water quality and channel clogging that in turn may lead to river flooding. With the increasing awareness of the impairment from sediment to water bodies in a watershed, identifying the locations of the major sediment sources and reducing the sediment through management practices will be important for an effective watershed management. The annualized agricultural non-point source pollution(AnnAGNPS) model and newly developed GIS interface for it were applied in a small agricultural watershed, Redrock Creek watershed, Kansas, in this pilot study for exploring the effectiveness of using this model as a management tool. The calibrated model appropriately simulated monthly runoff and sediment yield through the practices in this study and potentially suggested the ways of sediment reduction through evaluating the changes of land use and field operation in the model for the purpose of watershed management.

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 ero- sion firstly and water erosion thereafter, under three wind speeds （0, 11 and 14 m/s） and three rainfall intensities （60, 80 and 100 ram/h）. The results showed that the sediment yield was positively correlated with wind speed and rain- fall 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 posi- tively 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.

Modeling and analysis of effects of precipitation and vegetation coverage on runoff and sediment yield in Jinsha River Basin

This paper focuses on the effects of precipitation and vegetation coverage on runoff and sediment yield in the Jinsha River Basin. Results of regression analysis were taken as input variables to investigate the applicability of the adaptive network-based fuzzy inference system （ANFIS） to simulating annual runoff and sediment yield. Correlation analysis indicates that runoff and sediment yield are positively correlated with the precipitation indices, while negatively correlated with the vegetation indices. Furthermore, the results of stepwise regression show that annual precipitation is the most important factor influencing the variation of runoff, followed by forest coverage, and their contributions to the variation ofrunoffare 69.8% and 17.3%, respectively. For sediment yield, rainfall erosivity is the most important factor, followed by forest coverage, and their contributions to the variation of sediment yield are 49.3% and 24.2%, respectively. The ANFIS model is of high precision in runoff forecasting, with a relative error of less than 5%, but of poor precision in sediment yield forecasting, indicating that precipitation and vegetation coverage can explain only part of the variation of sediment yield, and that other impact factors, such as human activities, should be sufficiently considered as well.

Water Yield and Sediment Yield Simulations for Teba Catchment in Spain Using SWRRB Model: Ⅱ. Simulation Results

Simulated results of water yield, sediment yield, surface runoff,subsurface runoff, peak flow, evapo- transipiration, etc., in theTeba catchment, Spain, using SWRRB (Simulator for Water Resources inRural Basins) model are presented and the related problems arediscussed. The results showed that water yield And sediment yieldcould be satisfactorily simulated using SWRRB model. The accuracy ofthe annual water Yield simulation in the Teba catchment was up to83.68/100, which implied that this method could be effectively Usedto predict the annual or inter-annual water yield and to realize thequantification of geographic elements And processes of a river basin.

Material component to non-linear relation between sediment yield and drainage network development:an flume experimental study

This paper examines the experimental study on influence of material component to non-linear relation between sediment yield and drainage network development completed in the Lab. The area of flume drainage system is 81.2 m2, the longitudinal gradient and cross section slope are from 0.0348 to 0.0775 and from 0.0115 to 0.038, respectively. Different model materials with a medium diameter of 0.021 mm, 0.076 mm and 0.066 mm cover three experiments each. An artificial rainfall equipment is a sprinkler-system composed of 7 downward nozzles, distributed by hexagon type and a given rainfall intensity is 35.56 mm/hr.cm2. Three experiments are designed by process-response principle at the beginning the ψ shaped small network is dug in the flume. Running time spans are 720 m, 1440 minutes and 540 minutes for Runs I, IV and VI, respectively. Three experiments show that the sediment yield processes are characterized by delaying with a vibration. During network development the energy of a drainage system is dissipated by two ways, of which one is increasing the number of channels (rill and gully), and the other one is enlarging the channel length. The fractal dimension of a drainage network is exactly an index of energy dissipation of a drainage morphological system. Change of this index with time is an unsymmetrical concave curve. Comparison of three experiments explains that the vibration and the delaying ratio of sediment yield processes increase with material coarsening, while the number of channel decreases. The length of channel enlarges with material fining. There exists non-linear relationship between fractal dimension and sediment yield with an unsymmetrical hyperbolic curve. The absolute value of delaying ratio of the curve reduces with time running and material fining. It is characterized by substitution of situation to time.

Modelling the Effects of Land-use Change on Runoff and Sediment Yield in the Weicheng River Watershed, Southwest China

As a major sediment area in the upper Yangtze River, Jialing River basin experienced substantial land-use changes, many water conservancy projects were constructed from the 1980 s onward to promote water and soil conservation. The water and sediment yield at the watershed outlet was strongly affected by these water conservation works, including ponds and reservoirs, which should be considered in the modelling. In this study, based on the observed data of the Weicheng River catchment, the relationships between precipitation, runoff, vegetation, topography and sediment yield were analyzed, a distributed runoff and sediment yield model(WSTD-SED) was developed, and the hydrological processes of different land-use scenarios were simulated by using the model. The main results are summarized as follows: 1) there is an alternating characteristic in river channels and reservoirs in the Jialing River hilly area, with scour occurring in wet years and deposit occurring in dry years. 2) Most of the sediment deposited in river channels and reservoirs is carried off by the largest flood in the year. 3) The model yielded plausible results for runoff and sediment yield dynamics without the need of calibration, and the WSTD-SED model could be usedto obtain qualitative estimates on the effects of land use change scenarios. 4) The modelling results suggest that a 10% increase in cropland(dry land) reforestation results in a 0.7% decrease in runoff and 1.5% decrease in sediment yield.

Impacts of precipitation variation and soil and water conservation measures on runoff and sediment yield in the Loess Plateau Gully Region, China

The Loess Plateau of China has experienced a lengthy drought and severe soil erosion.Changes in precipitation and land use largely determine the dynamics of runoff and sediment yield in this region. Trend and mutation analyses were performed on hydrological data(1981–2012) from the Yanwachuan watershed in the Loess Plateau Gully Region to study the evolution characteristics of runoff and sediment yield. A time-series contrasting method also was used to evaluate the effects of precipitation and soil and water conservation(SWC) on runoff and sediment yield. Annual sediment yield declined markedly from 1981 to 2012 although there was no significant change in annual precipitation and annual runoff. Change points of annual runoff and annual sediment yield occurred in 1996 and 1997,respectively. Compared with that in the baseline period(1981–1996), annual runoff and annual sediment yield in the change period(1997–2012)decreased by 17.0% and 76.0%, respectively, but annual precipitation increased by 6.3%. Runoff decreased in the flood season and normal season, but increased in the dry season, while sediment yield significantly declined in the whole study period. The SWC measures contributed significantly to the reduction of annual runoff(137.9%) and annual sediment yield(135%) and were more important than precipitation. Biological measures(forestland and grassland) accounted for 61.04% of total runoff reduction, while engineering measures(terraces and dams) accounted for 102.84% of total sediment yield reduction. Furthermore, SWC measures had positive ecological effects. This study provides a scientific basis for soil erosion control on the Loess Plateau.

Impact of Climate Change and Deforestation on Stream Discharge and Sediment Yield in Phu Luong Watershed, Viet Nam

The purpose of this paper is to apply ＂Soil and Water Assessment Tool （SWAT）＂ model to assess the impacts of climate change and deforestation on stream discharge and sediment yield from Phu Luong watershed in Northern Viet Nam. Among the three climate change scenarios B 1, B2, and A2, representing low, medium, and high levels of greenhouse gas emission, respectively were set up for Viet Nam, the B2 scenario was selected for this study. Two land use scenarios （S1-2030 and $2-2050） were formulated combination with climate change in WSAT simulation. In B2 climate change scenario, mean temperature increases 0.7℃（2030） and 1.3 ℃ （2050）; annual rainfall increases 2.1% （2030） and 3.80% （2050） respect to baseline scenario. The results show that the stream discharge is likely to increase in the future during the wet season with increasing threats of sedimentation.

Impact of Land-Use Practices on Sediment Yield in the Dhrabi Watershed of Pakistan

Soil erosion by water is one of the most important land degradation processes in the sloping rainfed lands in Pakistan. A study was conducted in the Dhrabi watershed of Pakistan to evaluate sediment yield associated with rainfall-runoff under various land-use practices. Five sub-catchments with sizes varying from 1.5 to 350 ha were selected for measurement of rainfall, runoff and sediment yield. Soil conservation techniques were also introduced to reduce the soil erosion. All runoff events occurred in the summer especially during monsoon season （July-September）. Sediment yield of two small gully catchments ranged from 4.79 to 8.34 t/ha/yr in 2009, a relatively dry year. In 2010, the annual sediment yield was 8.15 to 12.31 t/ha. Terraced catchment with arable crops produced annual 4.1 t/ha of sediment as compared to 12.31 t/ha by the adjacent gully catchment showing high potential of terraces in reducing erosion. Runoff coefficients calculated for these catchments vary from 0.09 to 0.75. The macro and micro nutrients present in the sediment indicate that these nutrients are being depleted due to soil erosion.

Principal Denudation Processes and Their Contribution to Fluvial Suspended Sediment Yields in the Upper Yangtze River Basin and Volga River Basin

This paper synthesized the principal land denudation processes and their role in determining riverine suspended sediment yields(SSY) in two typical geographical environments of the Upper Yangtze River Basin in China and the Volga River Basin in Eastern Europe. In the Upper Yangtze River Basin, natural factors including topography, climate,lithology and tectonic activity are responsible for the spatial variation in the magnitude of denudation rates.Human disturbances have contributed to the temporal changes of soil erosion and fluvial SSY during the past decades. On one hand, land use change caused by deforestation and land reclamation has played an important role in the acceleration of sediment production from the central hilly area and lower Jinsha catchment; On the other hand, diverse soil conservation practices(e.g., reforestation,terracing) have contributed to a reduction of soil erosion and sediment production since the late 1980 s.It was difficult to explicitly decouple the effect of mitigation measures in the Lower Jinsha River Basindue to the complexity associated with sediment redistribution within river channels(active channel migration and significant sedimentation). The whole basin can be subdivided into seven sub-regions according to the different proportional inputs of principal denudation processes to riverine SSY. In the Volga River Basin, anthropogenic sheet, rill and gully erosion are the predominant denudation processes in the southern region, while channel bank and bed erosion constitutes the main source of riverine suspended sediment flux in the northern part of the basin. Distribution of cultivated lands significantly determined the intensity of denudation processes.Local relief characteristics also considerably influence soil erosion rates and SSY in the southern Volga River Basin. Lithology, soil cover and climate conditions determined the spatial distribution of sheet, rill and gully erosion intensity, but they play a secondary role in SSY spatial variation.

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）.

Simulation of Runoff and Sediment Yield for a Kaneri Watershed Using SWAT Model

Watershed as an entry point acts as a beginning to address the issues of sustainable rainwater management for improving livelihoods. Extraction of watershed parameters using Geographical Information System (GIS) and use of simulation models is the current trend for hydrologic evaluation of watersheds. In the present study, the open Source Tool Quantum GIS 2.2.0 was used for preparation of maps to verify the spatial extent of the area. The Soil and Water Assessment Tool (SWAT) having an interface with Arc-View GIS software (ArcGIS 10.1 with Arc SWAT 2012 extension) was selected for the estimation of runoff and sediment yield from Kaneri watershed, located in Western Maharashtra region. The coefficient of determination (R2) for the monthly and yearly runoff was obtained as 0.849 and 0.951 respectively for the calibration period 1979 to 2000 and 0.801 and 0.950 respectively for the validation period 2001-2013. The R2 value in estimating the monthly and yearly sediment yield during calibration period was computed as 0.722 and 0.788 respectively. The R2 for monthly and yearly sediment yield values for validation period was observed to be 0.565 and 0.684 respectively.

Estimation of Sediment Yield of Govindsagar Catchment, Lalitpur District, (U.P.), India, Using Remote Sensing and GIS Techniques

Soil erosion is a global phenomenon, which results in sedimentation and siltation of reservoirs of major rivers. Remote sensing data provide a synoptic view from which several surface parameters can be derived to assess the sedimentation yield in the reservoirs. Hence estimation of sediment yield has become one of the important tasks for planners, engineers and decision makers. The present study in Govindsagar catchment, Lalitpur District, Uttar Pradesh (India), has been carried out using IRS LISS III data to analyse land use/cover characteristics besides drainage basin characterstics. Subsequently, Sediment Yield Index (SYI) of Govindsagar catchment has been estimated using surface derivatives and morphometric parameters using empirical formulae. Integration of results obtained from satellite data and morphometric analysis suggests that the Govindsagar catchment has very low rate of sediment yield i.e. 0.07 ha·m/year indicating a gentle slope and sustainable land use practices in the catchment. Low sediment yield also suggests less erosion in the catchment areas and healthy land use/cover scenario.

Features of Runoff and Sediment Yield of Different Shrub-Grass Combination Modes for Highway Side Slope in Hilly Areas of Central Sichuan Province

[Objective] Indigenous plants with favorable water and soil conservation effects were screened for the shrub planting.[Method] Suining-Ziyang-Meishan Highway in the hilly areas of central Sichuan Province was taken for example,through sorting out plant species investigated in the route planning,3 indigenous shrub species(Neosinocalamus affinis,Vitex negundo and Coriaria nepalensis) and 3 indigenous herbaceous species(Setaria viridis,Miscanthus floridulus,Artemisia argyi) were selected.Rainfall simulation experiment was adopted to compare runoff and sediment yields of different combination modes and ratios under constant rainfall intensity(20 mm/min).[Result] Different combination modes under constant rainfall intensity all showed better water and soil conservation effects than that of control group did.For example,runoff appeared 1'-4'05"later,sediment yield reduced by 6.56-33.86 g respectively.Among all combination modes,runoff and sediment yield showed great difference after 20 min of constant rainfall,V.negundo+S.viridis had the lowest runoff(1,700 ml) and sediment yield(60.71 g);C nepalensis+A. argyi had the highest runoff(1,920 ml) and sediment yield(84.02 g).[Conclusion] Given the same planting conditions such as side slope and seeding quantity,and also the same planting techniques,in the hilly areas of central Sichuan Province,the combination of V.negundo and S.viridis can greatly improve the water and soil conservation capacity of highway.

Assessing the Effect of Natural Controls and Land Use Change on Sediment Yield in a Major Andean River:The Magdalena Drainage Basin,Colombia

马格达莱纳河是哥伦比亚安第斯山区的一个世界级的河流网络，该河流年产沙量约为150Mt，是全世界10大主要产沙河流之一。在本研究中，我们探讨主要自然因子和人类活动对马格达莱纳河流域产沙模式的影响，重建该区森林砍伐和农业活动时空模式，探讨土地利用变化与产沙趋势的关系。我们的研究结果表明，整个马格达莱纳河流域的产沙量可以用自然变量（包括径流量和最大河水流量）来解释。这两个因子解释了产沙量58％的变化。含沙率和土地利用的时间分析表明，在过去10～20年里流域侵蚀呈现增加的趋势。许多人类活动的影响，包括森林覆被在20年里减小了近40％．农业和牧场增加了65％、土壤保持差、开矿活动，以及城市化的加速，都促进了该地区域尺度上产沙量的增加。

Impacts of Climate Change on Spatial and Temporal Distribution of Runoff and Sediment Yield in Xixi Watershed of Jinjiang Basin

Based on meteorologic data in Xixi Watershed from 1972 to 1979, the SWAT model was applied to simulate the response of runoff and sediment yield in Xixi Watershed to climate change under 24 kinds of climate change scenarios, and then the spatial and temporal distribution of change rates of the runoff and sediment were analyzed. The results showed that the runoff yield would increase with the increase of precipitation or decrease of temperature, and the sediment yield would increase with the increase of precipitation or increase of temperature; the runoff would be more sensitive to variations in precipitation than to variations in temperature, and precipitation change would lead to more obvious change in the run- off yield; the temporal distribution of change rates of the runoff and sediment yield would be uneven in the 12 months, and the variation trends of the two change rates in the 12 months would be accordant; the spatial distribution of change rates of the runoff and sediment yield would be uneven in the sub-watersheds, and the change rate of the runoff yield would be bigger in the sub-watersheds where the runoff yield in the basic period would be smaller. This study can provide decision-making basis for sustainable development of Jinjiang Basin.