Influence of Vegetation on Runoff and Sediment in Wind-water Erosion Crisscross Region in the Upper Yellow River of China

All characteristics of vegetation,runoff and sediment from 1960 to 2010 in the Xiliu Gully Watershed,which is a representative watershed in wind-water erosion crisscross region in the upper reaches of the Yellow River of China,have been analyzed in this study.Based on the remote sensing image data,and used multi-spectral interpretation method,the characteristics of vegetation variation in the Xiliu Gully Watershed have been analyzed.And the rules of precipitation,runoff and sediment's changes have been illuminated by using mathematical statistics method.What′s more,the influence mechanism of vegetation on runoff and sediment has been discussed by using the data obtained from artificial rainfall simulation test.The results showed that the main vegetation type was given priority to low coverage,and the area of the low vegetation coverage type was reducing year by year.On the country,the area of the high vegetation coverage type was gradually increasing.In a word,vegetation conditions had got better improved since 2000 when the watershed management project started.The average annual precipitation of the river basin also got slightly increase in 2000–2010.The average annual runoff reduced by 37.5%,and the average annual sediment reduced by 73.9% in the same period.The results of artificial rainfall simulation tests showed that the improvement of vegetation coverage could increase not only soil infiltration but also vegetation evapotranspiration,and then made the rainfall-induced runoff production decrease.Vegetation root system could increases the resistance ability of soil to erosion,and vegetation aboveground part could reduce raindrop kinetic energy and splash soil erosion.Therefore,with the increase of vegetation coverage,the rainfall-induced sediment could decrease.

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.

Influence of vegetation parameters on runoff and sediment characteristics in patterned Artemisia capillaris plots

Vegetation patterns are important in the regulation of earth surface hydrological processes in arid and semi-arid areas. Laboratory-simulated rainfall experiments were used at the State Key Laboratory of Soil Erosion and Dryland Farming on the Loess Plateau, Yangling, northwestern China, to quantify the effects of Artemisia capillaris patterns on runoff and soil loss. The quantitative relationships between runoff/sediment yield and vegetation parameters were also thoroughly analyzed using the path analysis method for identifying the reduction mechanism of vegetation on soil erosion. A simulated rainfall intensity of 90 mm/h was applied on a control plot without vegetation （Co） and on the other three different vegetation distribution patterns： a checkerboard pattern （CP）, a banded pattern perpendicular to the slope direction （BP）, and a single long strip parallel to the slope direction （LP）. Each patterned plot received two sets of experiments, i.e. intact plants and roots only, respectively. All treatments had three replicates. The results showed that all the three other different patterns （CP, BP and LP） of A. capillaris could effectively reduce the runoff and sediment yield. Compared with Co, the other three intact plant plots had a 12%-25% less runoff and 58%-92% less sediment. Roots contributed more to sediment reduction （46%-70%）, whereas shoots contributed more to runoff reduction （57%-81%）. BP and CP exhibited preferable controlling effects on soil erosion compared with LP. Path analysis indicated that root length density and plant number were key parameters influencing runoff rate, while root surface area density and root weight density were central indicators affecting sediment rate. The results indicated that an appropriate increase of sowing density has practical significance in conserving soil and water.

Effects of land-use pattern change on rainfall-runoff and runoff-sediment relations:a case study in Zichang watershed of the Loess Plateau of China

The purpose of this article is to identify the effect of land use pattern on rainfall runoff and runoff sediment relations in Zichang Watershed of the Loess Plateau. From 1986 to 1997, many farmlands changed into grassland or woodland, especially the farmland in steep slope positions or far away from the river. The change of land use pattern altered the rainfall runoff and runoff sediment relationships, and led to higher slope of trend curves(STCs) of annual rainfall runoff mass curve and runoff sediment mass curve in 1990s than that in 1980s. It is implied that more soil and water loss yielded in 1990s. In order to reduce soil loss, more attentions should be paid to land use pattern and some grass or other herbaceous filter strips should be built along rivers.

Temporal Change of Runoff and Sediment Load and their Differential Response to Human Activities:A Case Study for a Well-vegetated Mountain Watershed of Southern China

This study examined the temporal trends of runoff and sediment load and their differential response to human activities in the Lishui river,a tributary of the Yangtze river in southern China.The long-term observation data at four gauging stations,generally involving two periods from 1954 to 1985 and from 2007 to 2011,were used.We detected no significant temporal trend for both the annual runoff volume(Q) and the annual suspended Sediment Load(SL) over more than 30 years before 1985.The flow duration curves and the Suspended Sediment Concentration(SSC) also hold constant before 1985.Compared with the period before 1985,SL has decreased by about 80% though Q remains unchanged for the period after 2007.Detailed examination shows that the flow duration curves after 2007 have changed with a significant decrease in the high-flow component,which acts as a major cause for the decreasing SL.In addition,SSC has decreased by several times,which also contributes to the decrease in SL after 2007.Both decreases in high-flow discharges and in SSC can be linked with recent human activities,mainly including vegetation establishment and dam constructions.The constant Q and the decreasing SL are also reported for the main stream of the Yangtze River and other major rivers in southern China,although they are orders of magnitude larger than our study area in drainage area size.The present study highlights the importance of high-flow discharges on SL and suggests that the use of SL is more appropriate to reflect environmental change than Q.

Spatio-temporal trends and causes of variations in runoff and sediment load of the Jinsha River in China

The Jinsha River Basin is an important basin for hydropower in China and it is also the main runoff and sediment source area for the Yangtze River,which greatly influence the runoff and sediment in the Three Gorges Reservoir.This study aims to characterize the spatial distribution,inter-annual variation of runoff and sediment load in the Jinsha River Basin,and to analyze the contribution of rainfall and human activities to the runoff and sediment load changes.The monitoring data on runoff,sediment load and precipitation were collected from 11hydrological stations in the Jinsha River Basin from1966 to 2016.The data observed at the outlet of the basin showed that 71.4%of the runoff is from the upper reaches of the Jinsha River Basin and the Yalong River,while 63.3%of the sediment is from the lower reaches(excluding the Yalong River).There is no significant increase in runoff on temporal scale in the Jinsha River Basin,while it has an abrupt change in runoff in both upstream and midstream in 1985,and an abrupt change in downstream in 1980 and2013.The sediment load demonstrated a significantincreasing trend in the upstream,no significant reducing trend in the midstream,but significant reducing trend in the downstream.The sediment load in upstream showed abrupt change in 1987,in midstream in 1978 and 2014,in downstream in 2012.Rainfall dominated runoff variation,contributing more than 59.0%of the total variation,while human activity,including reservoirs construction,the implementation of soil and water conservation projects,is the major factor to sediment load variation,contributing more than 87.0%of the total variation.

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

Watershed is considered to be the ideal unit for management of the natural resources. Extraction of water-shed parameters using Remote Sensing and Geographical Information System (GIS) and use of mathematical models is the current trend for hydrologic evaluation of watersheds. The Soil and Water Assessment Tool (SWAT) having an interface with ArcView GIS software (AVSWAT2000/X) was selected for the estimation of runoff and sediment yield from an area of Suni to Kasol, an intermediate watershed of Satluj river, located in Western Himalayan region. The model was calibrated for the years 1993 & 1994 and validated with the observed runoff and sediment yield for the years 1995, 1996 and 1997. The performance of the model was evaluated using statistical and graphical methods to assess the capability of the model in simulating the run-off and sediment yield from the study area. The coefficient of determination (R2) for the daily and monthly runoff was obtained as 0.53 and 0.90 respectively for the calibration period and 0.33 and 0.62 respectively for the validation period. The R2 value in estimating the daily and monthly sediment yield during calibration was computed as 0.33 and 0.38 respectively. The R2 for daily and monthly sediment yield values for 1995 to 1997 was observed to be 0.26 and 0.47.

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.

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.

Grey Relational Analysis on the Effects of Rainfall Factors on Runoff and Sediment in the Sloping Farmland with Different Plants in the Central South of Shandong Province

[Objective] The aim was to study the main rainfall factors influencing runoff and sediment in the sloping farmland with different plants in the central south of Shandong Province.[Method] Through grey relational analysis,the effects of different rainfall factors on runoff and sediment with different plants in the central south of Shandong were studied.[Result] In the sloping farmland with different plants,the effects of rainfall factors on runoff and sediment weren’t consistent.Rainfall was the dominant influencing factor of runoff,but PI30 had the greatest influence on runoff in natural grassland.Meanwhile,rainfall intensity was the main influencing factor of sediment,but PI had the greatest influence on sediment in Astragalus adsurgens Pall.plot.The compound factor had the minimal influence on runoff and sediment in Arachis hypogaea plot and natural grassland.In A.adsurgens Pall.plot,rainfall intensity had the minimal impact on runoff,but the compound factor had the least effect on sediment.[Conclusion] The study could provide theoretical references for the comprehensive control of slope soil erosion,the optimum utilization and sustainable development of land.

Sediment Load in Runoff Under Laboratory and Field Simulated Rainfall

Soil erosion is one of the most important problems in the Loess Plateau of China affectingsustainable agriculture. Near Luoyang (Henan Province, China), field plots were constructed tomeasure soil erosion rates under conventional tillage practices using field-simulated rainfall.Field rainfall experiments were carried out to compare previous results from laboratoryrainfall simulations on the same soil for interrill conditions. Although in the laboratoryexperiments, a strong correlation was found between the stream power of the runoff water andthe unit sediment load, this sediment transport equation overestimated the field rainfallsimulation results. Another sediment transport equation derived by Nearing et al. for rillerosion was in better agreement with the results of the field experiments, although it alsooverestimated these values. The measured sediment load values during the field rainfallsimulations were also lower than those found during field experiments on the same soil but witha loosened surface layer. This difference indicates the importance of soil physical conditionof surfce like soil structure and aggregate size, which may contribute to the discrepancybetween the field and laboratory experiment results.

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.

Relationship Between Watershed Landscape Pattern Change and Runoff-Sediment in Wind-Water Erosion Crisscross Region

This paper selected the typical wind-water erosion crisscross region Xiliugou watershed for research to reveal the impact of the landscape pattern change of the underlying surface in wind-water erosion crisscross region where soil erosion is most serious on rainfall and runoff as well as erosion and sediment.Based on the Landsat TM image data and measured data of runoff-sediment in that watershed,the paper analyzed the characteristics of watershed landscape pattern change and runoff-sediment and explored the relationship between landscape index and runoff-sediment yield by means of GIS and Fragstats.The results were included as follows.(1)Grassland was the dominant landscape.In terms of the number of patches and area change rate,from 1985 to 2010,cultivated land,forest land and construction land were most stable,followed by unused land.Unused land,grassland and cultivated land experienced the most dramatic conversion and maximally affected by human activities.(2)The inter-annual difference between annual runoff and annual sediment load was significant.Compared with the annual sediment load,the trend of decreasing runoff was more obvious.The correlation coefficient of runoff-sediment was 0.67,representing a significant correlation.(3)There was a significant correlation between the landscape index and runoff-sediment.The runoff was negatively correlated with the largest patch index,patch cohesion index,aggregation index and contagion index,but positively correlated with landscape morphology index and landscape division index.And the sediment was negatively correlated with the contagion index,aggregation index and plaque cohesion index,but positively correlated with other landscape indexes.The results indicate that with the increase of the largest patch index,patch cohesion index and aggregation index,the rainfall infiltration capacity increase obviously and the soil erosion reduce significantly.Therefore,increasing the largest patch index,patch cohesion and aggregation index of the watershed landscape can enhance the function of water storage and soil conservation as well as ecological optimization in the windwater erosion crisscross region.The results can provide theoretical support for the ecological environment construction and comprehensive utilization of water and soil resources.

Runoff and Sediment Modeling Using SWAT in Gumera Catchment, Ethiopia

This study was undertaken to examine the applicability of the SWAT model in Gumera river basin upstream of Lake Tana, Ethiopia for simulating stream runoff and sediment load. The area of river basin was discretized into 24 sub-catchments using ArcSWAT interface of the model. The semi automated Sequential Uncertainty Fitting (SUFI2) and fully automated Parameter Solution (ParaSol) calibration process built in SWAT calibration and uncertainty program (SWAT-CUP) were used to calibrate the model parameters using time series of flow and sediment load data of 1994 to 2002 and validated with the observed data from years 2003 to 2006. The performance of the model was evaluated using statistical and graphical methods to assess the capability of the model in simulating the runoff and sediment yield for the study area. The coefficient of determination (R2) and NSE values for the daily runoff by using [ParaSol] optimization technique was obtained as 0.72 and 0.71 respectively for the calibration period and 0.79 and 0.78 respectively for the validation period, R2 and NSE values of monthly flow calibration using SUFI2 are 0.83 and 0.78 respectively for validation it was 0.93 and 0.93. For monthly sediment yield by using SUFI2 calibration technique the model evaluation coefficients R2 and NS for calibration was computed as 0.61 and 0.60 respectively, for validation it was 0.84 and 0.83 respectively. The sensitivity analysis on 13 runoff producing parameters was also carried out and discussed.

Forecasting of Runoff and Sediment Yield Using Artificial Neural Networks

Runoff and sediment yield from an Indian watershed during the monsoon period were forecasted for differ-ent time periods (daily and weekly) using the back propagation artificial neural network (BPANN) modeling technique. The results were compared with those of single- and multi-input linear transfer function models. In BPANN, the maximum value of variable was considered for normalization of input, and a pattern learning algorithm was developed. Input variables in the model were obtained by comparing the response with their respective standard error. The network parsimony was achieved by pruning the network using error sensitiv-ity - weight criterion, and model generalization by cross validation. The performance was evaluated using correlation coefficient (CC), coefficient of efficiency (CE), and root mean square error (RMSE). The single input linear transfer function (SI-LTF) runoff and sediment yield forecasting models were more efficacious than the multi input linear transfer function (MI-LTF) and ANN models.

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%.

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.

Experimental research on the influence of two cultivation practices on rainfall runoff-and (sandy and muddy) sediment-generating processes in purple soil environment

Rainfall simulations have been conducted to study the soil erosion process of purple soil in two cultiva-tion practices—contour cultivation and downslope cultivation. Results showed that under the two cultivation prac-tices,the surface runoff can be described by the logarithmic function formula. In the initial period of rainfall,the amount of runoff increased with the rainfall duration and 20 minutes later it became relatively constant. The chang-ing process of soil erosion rate may be described by the logarithmic function formula. The erosion rate increased with the rainfall duration and 20 minutes later it also became constant. Under downslope cultivation condition,the soil erosion rate increased more significantly than that under contour cultivation condition in the case of gentle rain-fall intensity,and there is no obvious difference in erosion rate for downslope cultivation and contour cultivation practices. However,with increasing rainfall intensity the soil erosion rate under the downslope cultivation condition could be more than 30 times that under the contour cultivation condition. But this kind of difference would be re-duced to some extent in the case of heavy rain.

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.

Sediment yield and erosion–deposition distribution characteristics in ephemeral gullies in black soil areas under geocell protection

Investigating the effect of geocells on the erosion and deposition distribution of ephemeral gullies in the black soil area of Northeast China can provide a scientific basis for the allocation of soil and water conservation measures in ephemeral gullies.In this study,an artificial simulated confluence test and stereoscopic photogrammetry were used to analyze the distribution characteristics of erosion and deposition in ephemeral gullies protected by geocells and the effect of different confluence flows on the erosion process of ephemeral gullies.Results showed that when the confluence flow was larger,the effect of geocell was more evident,and the protection against ephemeral gully erosion was stronger.When the confluence flow rates were 0.6,1.8,2.4,and 3.0 m^(3)/h,ephemeral gully erosion decreased by 37.84%,26.09%,21.40%,and 35.45%.When the confluence flow rates were 2.4 and 3.0 m^(3)/h,the average sediment yield rate of the ephemeral gully was close to 2.14 kg/(m^(2)•min),and the protective effect of ephemeral gully erosion was enhanced.When the flow rate was higher,the surface fracture of the ephemeral gully was more serious.With an increase in confluence flow rate,the ratio of erosion to deposition increased gradually,the erosion area of ephemeral gullies was expanded,and erosion depth changed minimally.In conclusion,geocell measures changed erosion patterns by altering the rill erosion/deposition ratio,converting erosion from rill erosion to sheet erosion.