Relationship between drought and soil erosion based on the normalized differential water index(NDWI)and revised universal soil loss equation(RUSLE)model

The Langat River Basin in Malaysia is vulnerable to soil erosion risks because of its exposure to intensive land use activities and its topography,which primarily consists of steep slopes and mountainous areas.Furthermore,climate change frequently exposes this basin to drought,which negatively affects soil and water conservation.However,recent studies have rarely shown how soil reacts to drought,such as soil erosion.Therefore,the purpose of this study is to evaluate the relationship between drought and soil erosion in the Langat River Basin.We analyzed drought indices using Landsat 8 satellite images in November 2021,and created the normalized differential water index(NDWI)via Landsat 8 data to produce a drought map.We used the revised universal soil loss equation(RUSLE)model to predict soil erosion.We verified an association between the NDWI and soil erosion data using a correlation analysis.The results revealed that the southern and northern regions of the study area experienced drought events.We predicted an average annual soil erosion of approximately 58.11 t/(hm^(2)·a).Analysis of the association between the NDWI and soil erosion revealed a strong positive correlation,with a Pearson correlation coefficient of 0.86.We assumed that the slope length and steepness factor was the primary contributor to soil erosion in the study area.As a result,these findings can help authorities plan effective measures to reduce the impacts of drought and soil erosion in the future.

Spatial distribution of soil moisture,salinity and organic matter in Manas River watershed,Xinjiang,China

With the classical statistical and geostatistical methods, the study of the spatial distribution and its in- fluence factors of soil water, salinity and organic matter was carried out for 0-70 cm soil layers in Manas River watershed. The results showed that the soil moisture data from all soil layers exhibited a normal distribution, with average values of 14.08%-21.55%. Geostatistical analysis revealed that the content of soil moisture had a moder- ate spatial autocorrelation with the ratios of nugget/sill ranging from 0.500 to 0.718, which implies that the spatial pattern of soil moisture is influenced by the combined effects of structural factors and random factors. Remarkable spatial distributions with stripped and mottled features were found for soil moisture in all different soil layers. The landform and crop planting had a relatively big influence on the spatial distribution of soil moisture; total soil salinity was high in east but low in west, and non-salinized soil and lightly salinized soil appeared at the northwest and southwest of the study area. Under the effect of reservoir leakage, the heavily salinized soils are widely distributed in the middle of the study area. The areas of the non-salinized and lightly salinized soils decreased gradually with soil depth increment, which is contrary to the case for saline soils that reached a maximum of 245.67 km2 at the layer of 50-70 cm. The types of soil salinization in Manas River watershed were classified into four classes： the sulfate, chloride-sulfate, sulfate-chloride and chloride. The sulfate salinized soil is most widely distributed in the surface layer. The areas of chloride-sulfate, sulfate-chloride, and chloride salinized soils increased gradually along with the increment of soil depth; the variation range of the average values of soil organic matter content was be- tween 7.48%-11.33%. The ratios of nugget/sill reduced gradually from 0.698 to 0.299 with soil depth increment, which shows that the content of soil organic matter has a moderate spatial autocorrelation. The soil organic matter in all soil layers met normal distribution after logarithmic transformation. The spatial distribution patterns of soil or- ganic matter and soil moisture were similar; the areas with high organic matter contents were mainly distributed in the south of the study area, with the lowest contents in the middle.

Spatiotemporal features of soil and water loss in Three Gorges Reservoir Area of Chongqing

Soil and water loss has been the most serious eco-environmental problem in the Three Gorges Reservoir Area of Chongqing.In this paper the authors studied the spatiotemporal features of soil and water loss from 1999 to 2004 based on RS and GIS techniques.The results showed that:(1) The soil and water loss area decreased from 1999 to 2004.(2) Soil and water loss mainly exists in purple soil,yellow soil,limestone soil,paddy soil and yellow brown soil distributed areas.(3) The dry slope land and sparse woodland that are intensively influenced by human activities experienced most serious soil and water loss.(4) Soil and water loss in the study area indicated an obvious vertical differentiation characteristic.(5) There is a significant correlation between soil and water loss and slope.(6) There is no obvious correlation between soil and water loss and aspect.(7) Soil and water loss mainly exists in the values of R between 300 and 340 distribution area.The very-high soil and water loss has obvious correlation with R.

Influence of Superplasticizer Type and Dosage on Early-age Drying Shrinkage of Cement Paste with Consideration of Pore Size Distribution and Water Loss

We introduced a parameter r_s(the radius of the pores where the meniscus forms),which is composed of two factors,i e,water loss and cumulative pore size distribution(PSD),to provide a better explanation of the influence of superplasticizers(SPs)on early-age drying shrinkage.In our experiments,it is found that the addition of three types of SPs leads to a significant increase in the early-age drying shrinkage of cement paste,and drying shrinkage increases with the dosage of SPs.Based on the results above,we further studied the mechanism of the effects of SPs on the early-age drying shrinkage of cement paste by PSD and water loss,which are two components of r_s.The experimental results indicate that r_s can be a better index for the early-age drying shrinkage of cement-based materials with SPs than a single factor.In addition,the effects of SPs on other factors such as hydration degree and elastic modulus were also investigated and discussed.

IMPACTS OF DIFFERENT TYPES OF LAND USE ON PROCESSES OF SOIL AND WATER LOSS OVER PURPLE SOIL SLOPELAND

Based on natural precipitation observations, impacts of different types of land use on processes of soil and water loss over purple soil related slopeland were studied by simulated rainfall experiments. Measurement data revealed that rainstorms and slope length are the essential factors accountable for soil and water loss on purple soil slopeland for intense rill erosion can be caused on 10 meter long purple soil slopes by high intensity rainfall. Under circumanstances of rainstorms, annual hedge plants grown on slopeland of 25 degrees can cause a reduction of runoff by 22 43 percent and that of erosion induced sand content by 94 98 percent. Stone bund horizontal terraces can lead to a runoff reduction by 62 67 percent in comparison with steep slopelands and that of erosion induced sediment by 97.8 99 percent. Soil and water loss can be substantially decreased on steep slopes by hedge plants with a cost of only 10 20 percent that of the stone bund horizontal terraces. Hence it is an effective way to control soil and water loss in terms of slopeland amelioration and utilization in the Three Gorges Reservoir Area.

Distribution characteristics of dissolved organic carbon in annular wetland soil-water solutions through soil profiles in the Sanjiang Plain,Northeast China

Overwhelming evidence reveals that concentrations of dissolved organic carbon （DOC） have increased in streams which brings negative environmental impacts. DOC in stream flow is mainly originated from soil-water solutions of watershed. Wetlands prove to be the most sensitive areas as an important DOC reserve between terrestrial and fluvial biogeosystems. This reported study was focused on the distribution characteristics and the controlling factors of DOC in soil-water solutions of annular wetland, i.e., a dishing wetland and a forest wetland together, in the Sanjiang Plain, Northeast China. The results indicate that DOC concentrations in soilwater solutions decreased and then increased with increasing soil depth in the annular wetland. In the upper soil layers of 0-10 cm and 10-20 cm, DOC concentrations in soil-water solutions linearly increased from edge to center of the annular wetland （R^2 = 0.3122 and R^2 = 0.443）. The distribution variations were intimately linked to DOC production and utilization and DOC transport processes in annular wetland soil-water solutions. The concentrations of total organic carbon （TOC）, total carbon （TC） and Fe（II）, DOC mobility and continuous vertical and lateral flow affectext the distribution variations of DOC in soil-water solutions. The correlation coefficients between DOC concentrations and TOC, TC and Fe（II） were 0.974, 0.813 and 0.753 respectively. These distribution characteristics suggested a systematic response of the distribution variations of DOC in annular wetland soil-water solutions to the geometry of closed depressions on a scale of small catchments. However, the DOC in soil pore water of the annular wetland may be the potential source of DOC to stream flow on watershed scale. These observations also implied the fragmentation of wetland landscape could bring the spatial-temporal variations of DOC distribution and exports, which would bring negative environmental impacts in watersheds of the Sanjiang Plain.

Profile distribution and seasonal dynamics of water-extractable carbohydrate in soils under mixed broad-leaved Korean pine forest on Changbai Mountain

Carbohydrate represents an important part of the soil labile organic carbon pool. Water soluble carbohydrate drives the C cycle in forest soil by affecting microbial activity and hot water extractable car- bohydrate is thought related to soil carbon sequestration due to the asso- ciation with soil aggregation. In a temperate forest region of northeast China, Changbai Mountain, we investigated the abundance, spatial dis- tribution, and seasonal dynamics of cool and hot-water extractable car- bohydrate in soils under mixed broad-leaved Korean pine forest. The concentrations of cool-water extractable carbohydrate （CWECH） in three soil layers （0-5, 5-10, 10-20 cm） ranged from 4.1 to 193.3 g.kg-1 dry soil, decreasing rapidly with soil depth. On an annual average, the CWECH concentrations in soils at depths of 5-10 and 10-20 cm were 54.2% and 24.0%, respectively, of that in the 0-5 cm soil layer. CWECH showed distinct seasonal dynamics with the highest concentrations in early spring, lowest in summer, and increasing concentrations in autumn. Hot-water extractable carbohydrate （HWECH） concentrations in three soil layers ranged from 121.4 to 2026.2 g.kgq dry soil, which were about one order of magnitude higher than CWECH. The abundance of HWECH was even more profile-dependent than CWECH, and decreased more rapidly with soil depth. On an annual average, the HWECH concentration in soils 10-20 cm deep was about one order of magnitude lower than that in the top 0-5 cm soil. The seasonality of HWECH roughly tracked that of CWECH but with seasonal fluctuations of smaller amplitude. The car- bohydrate concentrations in cool/hot water extracts of soil were positively correlated with UV254 and UV2s0 of the same solution, which has implications for predicting the leaching loss of water soluble organic carbon.

A policy and technical measures for controlling soil and water loss in the Loess Plateau of China

Loess Plateau is the most serious region of soil and water loss in China and the world. The sediment carried into the Yellow River amounts to 1.6 billion tons every year. This paper reviews the factors and reasons for erosion in this area, and puts forward a comprehensive controlling policy on the basis of the principles of ecology and practise of Chinese scientists for 40 years. In conformity with the policy, a number of technical measures for controlling soil and water loss are suggested.

Topographic differentiation simulation of crop yield and soil and water loss on the Loess Plateau

De-farming slope farmland has been an effective measure in recent years for the improvement of the eco-environment and the mitigation of soil and water loss on the Loess Plateau. This paper, taking the Yangou Basin as a case study and using day-by-day mete- orological data of Yah＇an station in 2005, simulated and analyzed the quantitative relation between crop yield, soil and water loss and topographic condition with the aid of WIN-YIELD software. Results show that： 1） topographic gradient has important influence on crop yield. The bigger gradient is, the lower the crop yield. Yields of sorghum and corn decrease by 15.44% and 14.32% respectively at 25° in comparison to the case of 0°. In addition, yields of soya, bean and potato decrease slightly by 5.26%, 4.67% and 3.84%, respectively. The influences of topographic height and slope aspect on crop yield are slight. 2） Under the same topographic condition, different crops＇ runoff and soil loss show obvious disparity. Topographic gradient has important influence on soil and water loss. In general, the changing trend is that the soil and water loss aggregates with the increase of gradient, and the maximal amount occurs around 20°. The influence of topographic height is slight. Topographic aspect has a certain effect, and the fundamental characteristic is that values are higher at the aspect of south than north. 3） Topographic gradients of 5° and 15° are two important thresholds. The characteristic about soil and water loss with the variation of topographic gradients show that： the slope farmland with gradient less than 5° could remain unchanged, and the slope farmland more than 15° should be de-farmed as early as possible.

Impact of slash disposal on soil and water loss and the growth of planted seedlings

The three methods of slash disposal in this experiment were no treatment, strip piling and burning. The results obtained from this study showed that the soil erosion, water and nutrient loss were higher in the logged areas by burning than in the logged areas by no treatment and strip piling. The soil and water loss was not serious when the slope degree of the logged area was less than 16o. The survival rate of planted seedlings was higher and the growth was better in the logged areas followed by burning than in the logged areas by no treatment and strip piling. Burning should not be used when the slope was more than 23o.

Study on Soil and Water Loss Characteristic of the Railway Construction in Mountain Area

The factor of human project activity is often the immediate cause resulting in soil and water loss. The Baoji-Lanzhou second railway in construction is an example. The soil and water loss law caused by earth and stone mountain railway engineering construction in the northwestern China is studied systematically and that caused possibly by the road bed project, the road moat project, the field project, the tunnel project and the service road project in construction is probed. At the same time, the type, t...

Risk Assessment and Change Monitoring of Soil and Water Loss in Ruijin City Based on RS and GIS

The land use information extraction technology for the high-resolution remote sensing images of the Gaofen No. 1 satellite was construc-ted. According to the spectral, band, texture and shape attributes, land use types were divided, and the changing laws of land use types were ana- lyzed. Aftewards,according to the Table of Grading Standard of Sooil Erosion Intensity（SL190-96）,as well as vegetation coverage index NDVI slope, the risks of soil and water loss were assessed. Meanwhile, the level, scale, location and scope of changes in the risks of soil and water loss were monitored by using spatial visualization and spatial statistical techniques. The results showed that the area of areas without soil erosion and moderate soil erosion areas decreased obviously from 2015 to 2017, and the decreases were up to 22.929 3 and 13.626 3 km2 respectively. The ar-ea of mild soil erosion areas increased fast, and the increase reached 31.140 0 km2. The area of extremely strong soil erosion areas increased by 7.267 4 km2. In the city, moderate and strong soil erosion areas reduced, while extremely strong soil erosion patches increased fast, which was mainly related to road construction and construction and development of orchards. The extremely strong soil erosion areas were distributed in the shape of a banded loop, surrounded the suburbs of the city, and shrank towards the center of Ruijin City. The constructed technology to monitor the changes in land use and soil and water loss, as well as the changing laws of land use and soil and water loss provide the theoretical basis and plan-ning basis of soil and water conservation for urban planning departments and soil and water conservation departments.

Substantive Characteristics of Water and Soil Conservation and Ecological Civilization Construction in China

Water and soil conservation is an important part of eco-civilization con-struction. It is a major part of eco-construction and lifeline of social and economy development. Therefore, water and soil conservation is of great significance in maintaining eco-safety. The research concluded status quo and characters of water and soil losses in China and analyzed water and soil conservation and construction of eco-civilization from the perspectives of water and soil conservation and con-struction of eco-civilization.

Effects of water salinity and content on particle size distribution and soil strength

The effect of NaCl on soil strength was investigated in this project based on salinity concentrations of 0 g/L, 5 g/L, 20 g/L, and 50 g/L as well as varying water contents of 15%-20%. Laser particle size analyzer was also performed to explain possible effects. From particle size analysis and strength tests, it is hypothesized that the strength of the soil is increased with the addition of certain salinity concentrations until there are reversed effects, which is between 20 g/L and 50 g/L from our study. The increase of strength is suggested to be the affect of a greater variety of particle sizes. Since NaCI plays a role in the particle size distribution, it also plays a role in the strength of soils. The degree of the effect of the water content also differs from concentrations, and could be due to the variation of hydration film thickness on particles, which is affected by the ions introduced from water.

Effect of Typical Vegetation Restoration Pattern on Soil and Water Conservation in Yuanmou Dry-hot Valley of Yunnan Province

In Yuanmou dry-hot valley of Yunnan Province,three typical vegetation restoration patterns including production forest transformed from sloping fields to terracing,ecological afforestation within the gully and ecological aforestation in gully head and slope were selected to compare their effects on soil and water conservation.Soil and water loss,soil infiltration rate and the soil moisture dynamics of soil profile with the depth of 0-100 cm of these three patterns and their controls were observed by established standard observation plots in rainy season.The results showed that the soil and water loss of ecological afforestation and production forest terrace reduced by over 30% and 60% compared with their controls（without growth of any vegetation）respectively,showing significant control effect on the soil and water loss.Vegetation restoration also apparently increased the infiltration rate of soil（increased by 100%-200%）.In rainy season,the soil moisture content of ecological afforestation and production forest terrace increased by over 30% and 100% compared with their controls.This indicated that vegetation restoration will not lead to soil aridity during the rainy season;vegetation restoration not only reduced the loss of surface water and soil fine particles,but also enhanced the infiltration of precipitation.These two effects made the soil moisture content increase throughout the profile.

Study on Relative Soil and Water Conservation Benefits of Ridge Tillage in Different Terrain Conditions in the Black Soil Area of Northeast China

Ridge tillage, which is a very common and important tillage measure in the black soil area of northeast China, has some soil and water conservation bene- fits, but has little attention. It is very important to explore the spatial distribution of the ridge direction of the arable land and its soil and water conservation benefits in different terrain conditions in the black soil area. So Binxian County of Heilongjiang Province was selected as the study area, and 168 field investigation units were ex- tracted by stratified sampling method and investigated. According to equations of slope gradient factor and slope gradient in ridge direction, and based on the soft- ware of Arcmap, SPSS and Excel, the investigation data of soil and water loss in Binxian County were analyzed and counted, The results show that in plain, hilly and mountainous areas, the average ground slope gradients are 1.92°, 6.20° and 8.27° respectively, and the average slope gradients along ridge direction are 1.33°, 4.52°and 6.45° respectively, which account for about 70%, 73% and 78% of the average ground slope gradients in the same terrain condition; the relative quantities of soil erosion in the present ridge tillage condition account for about 55%, 69% and 67% respectively of that in down-slope ridge tillage conditions, so the present ridge tillage has obviously relative soil and water conservation benefits. Based on these results, the reasons of the present ridge tillage status were analyzed, and some reform measures were proposed. The results could not only help to comprehend the spatial distribution and soil and water conservation benefits of ridge tillage in the black soil area of Northeast China, but also provide scientific references for the layout of local soil and water conservation measures.

The Effect of Land Use Change on Soil and Water Quality in Northern Iran

Rapid urbanization has led to extensive land-use changes,particularly in developing countries.This research is aimed to investigate the role of land use and its effect on soil and water quality in Ziarat watershed focusing on four land uses:forest,pasture,cultivated and urban development.Soil samples were taken from a depth of 0-30 cm on each land use and were analyzed by completely randomized split-plot design in two geographical directions.Results showed that bulk density(BD),electrical conductivity(EC),pH,calcium carbonate equivalent(CCE),and soil particle density(DS) of the soil samples in pastures,cultivated and urban areas increased and the mean weight diameter(MWD),soil porosity(F),organic carbons(OC),total nitrogen(TN),exchangeable cations(Ca 2+,Mg 2+,K +,Na +),cation exchange capacity(CEC) and soil microbial respirations(SMR) decreased,respectively in comparison with the forest soils.For water quality evaluations,sodium adsorption ratio(SAR),electrical conductivity(EC),pH,total dissolved solids(TDS),bicarbonate(HCO 3),chloride(Cl),total hardness(TH),calcium(Ca 2+),potassium(K +),sodium(Na +) and magnesium(Mg 2+) were investigated in two areas:Nahrkhoran and Abgir stations.Results showed that the concentration of TDS,EC and HCO 3 in Naharkhoran station is higher than that in Abgir station.On the other hand,the concentration of TDS,EC and HCO 3 in Abgir station are the relatively higher due to its location.Total hardness had the same trend during the study years except in the last three years;however,TH showed an increase of 25% TH in Naharkhoran for the last two years.Cl,K + and SAR in Naharkhoran station increased by 61%,22%,78% and 56% respectively,in comparison with Abgir station.This study demonstrated that the trend of soil degradation and mismanagement of land use may increase the frequency of urban floods and human health problems.

Applicability of Fractal Models in Estimating Soil Water Retention Characteristics from Particle-Size Distribution Data

Soil water retention characteristics are the key information required in hydrological modeling. Frac-tal models provide a practical alternative for indirectly estimating soil water retention characteristics fromparticle-size distribution data. Predictive capabilities of three fractal models, i.e, Tyler-Wheatcraft model,Rieu-Sposito model, and Brooks-Corey model, were fully evaluated in this work using experimental datafrom an international database and literature. Particle-size distribution data were firstly interpolated into20 classes using a van Genuchten-type equation. Fractal dimensions of the tortuous pore wall and the poresurface were then calculated from the detailed particle-size distribution and incorporated as a parameter infractal water retention models. Comparisons between measured and model-estimated water retention cha-racteristics indicated that these three models were applicable to relatively different soil textures and pressurehead ranges. Tyler-Wheatcraft and Brooks-Corey models led to reasonable agreements for both coarse- andmedium-textured soils, while the latter showed applicability to a broader texture range. In contrast, Rieu-Sposito model was more suitable for fine-textured soils. Fractal models produced a better estimation of watercontents at low pressure heads than at high pressure heads.

PRIMARY ANALYSIS ON GROUNDWATER,SOIL MOISTURE AND SALINITY IN FUKANG OASIS OF SOUTHERN JUNGGAR BASIN

Soil salinity is the most important factor affecting vegetation distribution,and the secondary salinization has affected the development of oasis agriculture.In arid areas the spatial variation of soil moisture and sa lt content is marked-ly affected by groundwater,irratio nal irrigation in artificial oasis.By analyzing the soil moisture,salt content and groundwa-ter table in different areas of old oasis,new oasis and desert in Fukang Oa sis,it is shown that topography and l and use are main factors affecting the change of groundwater table,the redistribution of soil moisture and salt cont ent.When undis-turbed by human,the groundwater tab le rises from mountain to belt of grou nd water spillage,the groundwater t able rises mightily in plain because of the artificial irrigation,and the secondary salinization of soil is very seriou s.In oasis the ground-water table raises compared with that in the natural desert at the same latitude.In old oasis of upper reaches o f river salt has not been concentrated too much in rhizosphere because this area is the belt of groundwater drainage,soil t exture is coarse,the groundwater table is very low,and the salt in soil is drained i nto the groundwater.The new oasis has been the areas of salt accumulation becau se of the artificial irrigation,the salt content in soil is higher than th at in old oasis,so some cultivated fields here had to be thrown out because of the serious s econdary salinization.

Impacts of water and soil erosion in upstream watershed of Nenjiang River

Making a brief analysis of the water and soil loss present situation in Daxing＇anling area which locates to the upstream region of Nenjiang River, and giving the water and soil loss of this area that have been made near 20 years, as well as the factors of the water and soil loss. According to the factors corresponding prevention measure and forecast model have been put forward, make a brief introduction to this model in this article. It is helpful to improve the local soil conservation and sustainable development.