Displays

Suitable and practicable best management practices (BMPs) are needed to develop effective and efficient watershed management under future climate change scenarios. Tons river basin is an agricultural-based watershed having a great significance to the States of Madhya Pradesh and Uttar Pradesh. Identification of critical erosion prone areas of the Tons River basin and implementation of BMPs for the future scenarios (2030-2050) using RCP 4.5 and RCP 8.5 scenarios is the main aim of this study. In this study, the Soil and Water Assessment Tool (SWAT) model was calibrated and validated for simulation of runoff and sediment yield using the Sequential Uncertainty Fitting (SUFI-2) technique. The values of coefficient of determination (R2), Nash–Sutcliffe efficiency (NSE), percent bias (PBIAS) and RMSE-observations standard deviation ratio (RSR) were 0.71, 0.70, -8.3 and 0.54 respectively during the calibration period whereas in validation the values were 0.72, 0.71, -3.9 and 0.56 respectively. Thus, the SWAT model can be employed in the Tons river basin of India for critical area prioritization and river basin planning and management under future scenarios.

How to cite: Pandey, A., Kc, B., Kalura, P., and Chowdary, V. M.: Critical area prioritization for river basin planning and management under future scenarios using SWAT model, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-3970, https://doi.org/10.5194/egusphere-egu2020-3970, 2020.

The aim of this study was to investigate how the spatial distribution of grass influenced run-off and erosion from a hillslope with loess and cinnamon soils in the rocky area of Northern China. We set up a trial to test the two soils with different treatments, including bare soil (BS), grass strips on the upper (UGS) and lower (DGS) parts of the slope, grass cover over the entire slope (GS), and a grass carpet on the lower part of the slope (GC), under simulated rainfall conditions. The results showed that the run-off coefficients for the loess and cinnamon soils decreased by between 4% and 20% and by between 2% and 37%, respectively, when covered with grass. Grass spatial distribution had little effect on the run-off, but more effect on erosion than vegetation coverage degree. The most effective location of grass cover for decreasing hillslope erosion was at the foot, and the high efficiency was mainly due to controlling of rill formation and sediment deposition. The soil loss from GS, DGS, and GC on the loess and cinnamon soils was between 77% and 93% less and 55% and 80% less, respectively, compared with the loss from BS. However, the soil characteristics had little effect on soil erosion for well-vegetated slopes. The results highlight the importance of vegetation re-establishment at the foot of hillslope in controlling soil erosion.

How to cite: Pan, C. and Ma, L.: How grass contributes to controlling hillslope erosion, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-9170, https://doi.org/10.5194/egusphere-egu2020-9170, 2020.

Weeds are one of the major problems in agriculture, they can reduce yield, interfere with harvest and serve as hosts to possibly harmful organisms. For a successful agricultural production, weed issue must be tackled in the begging, during the germination-emergence phase. With different management systems weed seed bank is exposed to different field conditions which may favour or obstruct the germination. One of these conditions is the presence or the absence of crop residues on the soil surface, very common in the newer agricultural practices, such as Conservation Agriculture. In this work the germination of eight weed species: Abuthilon theophrasti, Setaria glauca, Digitaria sanguinalis, Sorghum halepense, Amaranthus retroflexus, Sonchus oleraceus, Chenopodium album and Echinochloa crus-galli, was examined under the residues of two crop species maize (Zea mays) and wheat (Triticum sp.). For each weed species 200 seeds were used, while three different quantities of residues were used for the two crops, the quantity measured in one square meter of the field (1), half of that quantity (0,5) and a half more than the one measured in the field (1,5), plus control, without residues. The experiment was conducted at the experimental farm of the University of Padova in Legnaro (PD) in a 8x2x3 factorial design with three blocks, plus three control repetitions. Seeds of each weed species were sown in an area of 20 cm². Before the beginning of the experiment, the soil from the designated areas was removed and sterilized at 105°C in order to prevent contamination by the seeds already present in the soil. Once the soil was sterilized and restored to the field, the seeds were sown on the surface of the soil and covered with the respective quantity of the respective crop residue or left uncovered in the case of control. The experiment started on December 2018, and the seeds were left undisturbed during the winter, imitating natural conditions. Seeds started germinating on March 2019 and were controlled twice a week until the end of germination process, all germinated plants were removed and counted. ANOVA and LSD analysis were performed on cumulated germination data. Only quantity of residues and weed species resulted significant as factors (p-value < 0,000). The results showed that the quantity 1 and 1,5 can reduce the germination from 10 to 30% respectively, while quantity 0,5 can in fact increase germination by 15%. As for the weed species, they were all more inhibited by the higher concentrations of residues, but in respect to control it was observed that some of them seemed to be favoured by the low presence of residues S. halepense and A. theophrasti, not particularly influenced were A. retroflexus, E. crus-galli and S. oleraceus, while C. album, D. sanguinalis and S. glauca showed major germination rate reduction. In conclusion, to obtain the weed inhibitory effect, it seems very important to pay particular attention to the homogeneity of the distribution of the crop residues on the soil surface, low residue density areas could favour weeds.

How to cite: Nikolić, N., Loddo, D., and Masin, R.: Influence of crop residues on weed emergence, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-1494, https://doi.org/10.5194/egusphere-egu2020-1494, 2020.

Climate change and various human activities have resulted in noticeable changes in watershed hydrological and soil erosion regimes. In this study, a comprehensive investigation was conducted to distinguish between the effects of climate variables and those of land use and land cover change (LUCC) variables on runoff and sediment discharge in a watershed located at upper reaches of the Yangtze River. Statistical analysis results revealed significant and slight increasing trends in runoff and sediment discharge, respectively. Abrupt changes occurred in 1974 and 1995, which divided the entire time series into a decrease–increase–decrease tendency pattern; this pattern was the response to climate changes and the Reforestation and Returning Farmland to Forest project in China. In addition, redundancy analysis was used for partition statistical analyses, and the contributions of climate change and LUCC to runoff and sediment discharge were at the ratio of 4:1. Since 1990, the effect of LUCC has increased notably and its relationship with hydrological variables changed from positive to negative in approximately 1995. Finally, simulations performed using the distributed Basic Pollution Calculation Center (BPCC) model confirmed that climate and LUCC variables reduced the runoff depth and sediment load between 1980 and 2003. The contributions of climate fluctuation and LUCC to runoff depth were at the ratio of 5:1, and those to sediment load were at the ratio of 3:1, which exhibited the dominant role of climate change and the high sensitivity of sediment load to human interference. Overall, the results of distributed hydrological modeling were consistent with those of statistical analyses. The results provided detailed information and explained the mechanics underlying hydrological processes and soil erosion.

How to cite: Zhang, H.: Comprehensive evaluation of the effects of climate change and land use and land cover change variables on runoff and sediment discharge, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-2970, https://doi.org/10.5194/egusphere-egu2020-2970, 2020.

The benefits of soil and water conservation measures during snowmelt process is rarely studied in Northeast China. Based on the observation results of snowmelt erosion of Jixing runoff plots (Meihekou City, Jilin Province)in spring in 2015 and 2016, combined with the previous results of rainfall erosion, the practice factor values of soil and water conservation measures, the numbers of soil erosion events, the runoff depth and erosion modulus between snowmelt and rainfall conditions were compared to investigate the difference of effects of the soil and water conservation measures on snowmelt and rainfall erosion. The results show that the practice factor values range from 0.001 to 0.46, while the best measure for prevention of snowmelt erosion is the ecological restoration measure, with the characteristics of shorter period, less amount of snowmelt runoff. The effect of the cut-off drain measure, a typical engineering measures, on snowmelt erosion is mainly controlling the amount of snowmelt runoff. The erosion modulus and runoff depth of the shrub ridging are larger compared with the contour ridge and furrow planting, another kind of tillage measure, under snowmelt condition. Both two types of soil erosion, namely snowmelt and rainfall erosion, should be taken into account in planning and design of soil and water conservation measures in areas with snowmelt erosion, especially for the cultivated land.

How to cite: Xu, X. Q., Fan, H. M., Tan, J., Jia, Y., and Wu, M.: Comparison of Practice Factor Values of Soil and Water Conservation Measures Under the Condition of Snowmelt and Rainfall Erosion, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-2834, https://doi.org/10.5194/egusphere-egu2020-2834, 2020.

The vegetation and stability of Pisha sandstone slopes are insufficient due to its inherent properties, such as low erosion resistance, strength, water stability, and high porosity. In this paper, a new flexible slope protection method, which considers the combination of hydraulic polyurethane(W-OH) and planting mate technology, is proposed to realize the ecological restoration and prevent soil erosion of the steep Pisha sandstone slopes. The properties of consolidated body of W-OH and Pisha sandstone were investigated. Furthermore, the optimal proportion of the nutrient substate was obtained by orthogonal test via laboratory and on-site experiments. The results illustrate that with 5% W-OH, the average compressive strength and water stability index of the consolidated body can reach about 6.70 and 3.71 times higher than the blank group. The on-site experiments demonstrate that the vegetation coverage of the optimal group reaches 85% after three months curing, which is 5.2 times that of the blank group.

How to cite: Zhao, Y., Yang, C., Qu, F., Wu, Z., Liang, Z., and Ma, W.: Flexible slope protection for the steep Pisha sandstone slopes based on hydraulic polyurethane combined with planting mate, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-16511, https://doi.org/10.5194/egusphere-egu2020-16511, 2020.

Rocky desertification has long been identified as an adverse geo-environmental hazard to both humans and the environment. With increasing rocky desertification, karst ecosystem is one of the most severely-threatened ecosystems in the world due to its thin soil layer. As a typical karst landform, the Karst Gabin Basin in the southwest China is characterized by the presence of large arable land, frequent agricultural activities, and prominent soil and water loss. In this study, land use and land-cover change between 1980 and 2015 was investigated based on multi-temporal remote sensing images. InVEST model was used to calculate regional water production. The results showed that there was a decrease in the acreage of cultivated land and water body, but a slight increase in that of residential land. Meanwhile, there was an significant increase in forest land and grassland. During the study period, restored area was greater than degraded area. Water production area was divided into three ecological zones based on water yield capacity. Our finding showed that conservation strategy had a significant influence on land use change in this area, which also served as a basis for rational planning in the karst Gabin basin.

How to cite: Yu, Y., Liu, H., Zhang, W., and Wu, X.: Land use change and water production function in the Karst Gabin Basin: A regional study from southwest China (1980-2015), EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-13002, https://doi.org/10.5194/egusphere-egu2020-13002, 2020.

The damage and risk to the environment and human health consequent to traditional agricultural practices urged the development of innovative techniques and more environmentally friendly processes and compounds. Nanotechnology can improve the precision in the processes and the coordination of the management strategies of agricultural production. Therefore, innovative and groundbreaking tools have recently been developed employing natural and engineered nanomaterials to deliver agrochemicals to plants for both improving nutrition, stimulate plant growth, improve the quality of the soil and protect plants, while reducing the impact of these compounds on the environment and human health. Electrospinning (ES) is a highly versatile and inexpensive nanotechnology that allows to design and fabricate continuous non-woven polymer fibers with diameters ranging from micrometer to nanometer when a strong electrical field acts on a droplet of a solution with sufficient viscoelasticity. The resulting fibers can assume complex shapes, creating a multitude of structures with a broad spectrum of different properties (porosity, permeability, high fiber interconnectivity, nano-scale interstitial spaces, biomimetism and bioinspiration, etc.). 
Since the limitation of iron availability is a crucial condition in plant nutrition, the polymer fabrics here proposed, mimicking the natural strategy adopted by nongraminaceous and graminaceous species (Strategy I and II, respectively), were designed to make available to the plants the insoluble iron (Fe III) widely present in ecosystems by releasing selected iron-chelating molecules. Therefore, we investigated a model system based on ES biodegradable nanofibrous textiles with different shapes capable of releasing natural iron-chelators into soil/water by controlled rates (depending on the membrane morphology). The present study first focused on the production and functionality of a biodegradable nanofibrous polymer (polyhydroxybutyrate-PHB) scaffold, that is naturally produced by microorganisms and algae).  Because of its fragility, PHB was then blended with another biodegradable polymer (polycaprolactone-PCL), and then properly bio-loaded. The resulting polymer blend, due to the physical properties of PCL, resulted softer and mechanically more resistant than the previous one (PHB) and it was poorly affected by sudden changes in temperature. Both polymers are water insoluble and present low environmental impact, and are commonly investigated and used in drug delivery structures. The effectiveness and toxicity of both functional systems mimicking Strategy I and II concepts and dynamics were tested in two different plant hydroponic cultures. Such regenerative and sustainable agricultural practices based on natural sources and waste reduction, inspired by the principles of a circular bio-economy (European Environment Agency, report n. 2/2016), aimed at replacing the use of chemicals and traditional raw materials, improving health and environmental conditions, as required by the original principles of a circular economy, and at facing the increasing risk level for our natural capital.

How to cite: Macagnano, A., Mari, M., Scarascia-Mugnozza, G., and De Cesare, F.: A sustainable model for agriculture based on nanofibrous biodegradable polymers mimicking natural strategies, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-19686, https://doi.org/10.5194/egusphere-egu2020-19686, 2020.

Due to the hard surface and the lack of necessary soil environment for vegetation growth, the rock slope protection and ecological restoration is one of the research focuses nowadays. In this paper, we proposed a flexible slope protection method based on the vegetation membrane to protect the rock slopes including river and road slope. The vegetation membrane is a kind of organic bags which is perfused by a mechanical equipment with plant seeds, soil, sand, vermiculite, rice husk, adhesive material, water retaining agent with water in a certain proportion, forming a suitable environment for vegetation growth. Then the membrane is fixed on the rock slope by the anchor bolt in different specifications and quantities according to the different slope conditions. The results show that the minimum proportions of total nitrogen, phosphoric acid, potassium in the vegetation membrane are 5%, 25% and 10%, respectively. The tension load of the anchor bolt can reach 50 ~ 100 kg in different lengths. The vegetation coverage rate on the rock slope by this method can reach more than 80% in three months and the rock slope is much more stable. Additionally, two demonstrations of different rock slopes protected by this technique are briefly described and the good control effects are obtained. It will provide a new method for protecting steep and rock slopes.

How to cite: Liang, Z., Wu, Z., and Gao, H.: Study on the application of rock slope protection and ecological restoration technique based on vegetation membrane, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-8906, https://doi.org/10.5194/egusphere-egu2020-8906, 2020.

Unsaturated soils are those in which pore is filled partially with water and partially with air. They are the most relevant porous medium to human activities, and cover almost all the soils near the ground surface. Hydraulic conductivity (HC) is one of the most important and useful properties of unsaturated soils in numerous studies, including governing flow process, settlement of soil foundations, migration of groundwater and gas hydrate. Unfortunately, direct measurement of HC for unsaturated soils is very difficult with high uncertainty due to its nature of complexity and limited experimental conditions. Thus, indirect estimation of HC from soil water characteristic curve (SWCC) becomes an alternative way and being widely used all over the world.

Because of the difficulty to reach high suction at the residual state of unsaturated soils, however, the SWCC obtained by laboratory experiments is often incomplete, which will lead to an unreliable estimation of hydraulic conductivity. However, no study has been published on how to estimate hydraulic conductivity of unsaturated soils with incomplete SWCC. In response to this situation, an innovative method was proposed based on the classical van Genuchten model and Mualem model. The proposed method was evaluated by extensive experimental data from existing literature and proved to have an excellent performance in predicting a complete SWCC for a wide range of soils. Also, it exhibits certain superiority in predicting hydraulic conductivity. The limitations of the proposed method were comprehensively discussed, and its corresponding improvement strategies were also addressed. This paper presents a practical way to obtain a more reliable hydraulic conductivity from incomplete SWCC.

How to cite: Ren, X., Fang, Q., and Chen, X.: How to predict hydraulic conductivity of unsaturated soils from an incomplete soil water characteristic curve?, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-5083, https://doi.org/10.5194/egusphere-egu2020-5083, 2020.

In arid areas prone to desertification and soil erosion, the effectiveness of agricultural bench terraces in increasing soil moisture is dependent on their correct implementation. However, despite its relevance for securing food production in many areas of the world, the relationship between proper terracing implementation and the landscape capacity of holding soil moisture is still not understood. Moreover, spatial patterns of Soil Water Content (SWC) within the same terraced hillslope are weakly studied. The present work analyses SWC variations in four newly implemented terraced sites in Tigray Region, Ethiopia: Teshi, Ruba Feleg, Michael Emba and Enda Chena. Field SWC data were collected for the dry season of 2017 (February, March and April) from the upper, middle and lower part of each terraced site, including a non-terraced benchmark area. In all sites, terraced areas show SWC significantly higher than non-terraced ones (p < 0.05), with the lower part of the terraced hillslope more humid than the others for the whole period analyzed. A Multiple Linear Regression (MLR) analysis of SWC was conducted in order to highlight possible dependencies of SWC values. MLR highlighted significant dependency of SWC from the date of analysis, the position of the sample in the terraced slope, as well as a significant positive correlation of SWC with the percent of Water Stable Aggregates (WSA) analyzed at the study sites. Since high soil disturbance induces low soil aggregates stability, this result shows how measures to reduce soil disturbance during implementation can significantly increase SWC of radical terraces. Overall, the results of the present paper testify the good performances of bench terraces in Northern Ethiopia in terms of water conservation, and this first benchmark study can inform future terracing implementation in some arid and semi-arid agricultural areas of the world.

The abstract is based on Mesfin, S.; Almeida Oliveira, L.A.; Yazew, E.; Bresci, E.; Castelli, G. Spatial Variability of Soil Moisture in Newly Implemented Agricultural Bench Terraces in the Ethiopian Plateau. Water 2019, 11, 2134.

How to cite: Castelli, G., Mesfin, S., Almeida Olivera, L. A., Bresci, E., and Yazew, E.: Spatial Analysis of Soil Water Content in Newly Implemented Agricultural Bench Terraces in the Ethiopian Plateau, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-1127, https://doi.org/10.5194/egusphere-egu2020-1127, 2020.

The Pisha sandstone area on the Ordos Plateau of China is the primary source of coarse sediment of the Yellow River. Sediment size distribution and selectivity greatly affect sediment transport and deposition. Hence, sediment transport processes and size selectivity by overland flow on Pisha sandstone slopes were investigated in this study. Experiments were run with Pisha sandstone soil (bulk density of 1.35 g/cm³) under rainfall intensities of 87 and 133 mm/h with a 25° slope gradient, and the duration of simulated rainfall is 1 h. Sediment and runoff were sampled at 2-min intervals to examine the size distribution change of the eroded sediment. The particle composition, enrichment rate, fractal dimension, and time distribution characteristics of median grain size (d₅₀) of eroded sediment were comprehensively analyzed. Statistical analyses showed that the erosion process of Pisha sandstone slope mainly transported coarse sediment. More than 40% of eroded sediment particles were coarse sediment, which will become the main sediment in the lower reaches of the Yellow River bed. The particle size of eroded sediment tended to gradually decrease with the continuous rainfall but remained larger than the background value of Pisha sandstone soil after refinement. The fractal dimension was positively correlated with the slope flow velocity, while the d₅₀ was negatively correlated with the slope flow velocity. Overall, these findings show a strong relationship between the sediment transport and flow velocity, which indicates that the selectivity and transportation of sediment particles on the Pisha sand slopes is mainly influenced by the hydrodynamic parameters of overland flow. This study provides a methodology and data references for studying the particle selectivity characteristics of eroded sediment and provides a scientific basis for revealing the mechanism of erosion and sediment yield in the Pisha sandstone area of China.

How to cite: Zhang, P., Xiao, P., and Yang, C.: Experimental study of sediment transport processes and size selectivity of eroded sediment on steep Pisha sandstone slopes, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-2269, https://doi.org/10.5194/egusphere-egu2020-2269, 2020.

The response of extreme rainstorm to global climate pattern changes in the loess plateau

Shaobo Long^1,3、Jianen Gao^1,2,3*、Huijuan Li⁵、Zhe Gao⁴、minmin Qiang^1,3、Sixuan Liu^1,3

1. Institute of Soil and Water Conservation, Northwest Agriculture and Forestry University, 712100, Yangling, Shaanxi, China.
2. Institute of Soil and Water Conservation, Chinese Academy of Sciences and Ministry of Water Resources, 712100, Yangling, Shaanxi, China.
3. Research Center on Soil and Water Conservation, Ministry of Water Resources, 712100, Yangling, Shannxi, China.
4. College of Water Resources and Architectural Engineering, Northwest Agriculture and Forestry University, 712100, Yangling, Shaanxi, China.
5. Institute of Geographic Sciences and Natural Research, CAS, 100101, Beijing, China.

Abstract: The loess plateau is the region with the most serious soil and water problems in the world, the soil erosion mainly occurs in the season of rainfall, especially the extreme rainstorm has great influence on soil erosion. In recent years, under the background of global climate change, extreme rainstorm occurs frequently in the loess plateau, causes a series of soil damage, was difficult to predict. Therefore, it is a great significance to study the rule of extreme rainstorm for the soil erosion in the loess plateau. Based on the daily rainfall data of 56 meteorological stations and global sea surface temperatures (SST) data in the last 60 years, the effects of El Niño on extreme rainstorm were studied by using empirical orthogonal function (EOF), wavelet transform, and other statistical methods. The results show:

• (1) The extreme rainstorm has obvious spatial distribution characteristics, which decreases gradually from the south to the north of the loess plateau; Temporal variation of extreme rainstorm has obvious decadal oscillation, showing a decreasing trend from 1982 to 2012 and an increasing trend after 2012.
• (2) There was a significant positive correlation between the time coefficient of EOF1 for SST and the extreme rainstorm (P < 0.05). Wavelet analysis shows that Both extreme rainstorm and SST anomaly have a 30-year cycle, with the time change becoming more dramatic after 2012.
• (3) El Niño has obvious influence on the extreme rainstorm in the loess plateau region. Extreme rainstorm can be predicted about 1 year in advance by the change of SST anomaly. This is of great significance to the study of extreme rainfall erosion in the loess plateau.

Keywords: The loess plateau; Extreme rainstorm; El Niño

Funding:

1. The National key Research and Development Program of China (No.2017YFC0504703).
2. National Natural Science Foundation of China (No. 41877078, 41371276).
3. Knowledge Innovation Program of the Chinese Academy of Sciences (No.A315021615).

How to cite: long, S.: The response of extreme rainstorm to global climate pattern changes in the loess plateau, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-16507, https://doi.org/10.5194/egusphere-egu2020-16507, 2020.

The Loess Plateau of China is known for its severe soil and water loss problems. Terracing is one of the most important soil and water conservation measures there. Our understanding of the effects of terraces on soil and water conservation and its mechanism is limited by observation data on runoff and soil erosion as well as the influences from local environmental characteristics. In this study, we applied a physically-based distributed hydrological model (Integrated Hydrology Model, InHM) to an experimental terrace in Wangmaogou watershed of the Loess Plateau, and validated it with the measured soil water content. Our results suggested that terrace construction can substantially reduce runoff by changing the flow direction, especially during heavy rainfall events. This reduction in runoff would be greatly attenuated when ridges are damaged due to lack of maintenance. Under the rainfall intensity of 120 mm/h, compared with hillslope, a well-maintained terrace could reduce runoff by 100%, while the terrace without ridges could only reduce 28% runoff. Besides, ridges not only prevented water from flowing out of platforms, but also helped maintain the risers from terrace failure by decreasing about 20% of the saturation rate at the risers. Our results also emphasized the importance of evaporation, which could make up to 15% of the total water loss even during the rainfall events. Given the effects of terraces on water conservation, it is essential for the land use management of the Loess Plateau to take into account of the terracing approach, as well as a good maintenance of ridges.

How to cite: Chen, X., Ran, Q., Hong, Y., and Ye, S.: Impacts of terracing on hydrological processes: a case study in Wangmaogou watershed of the Loess Plateau, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-12222, https://doi.org/10.5194/egusphere-egu2020-12222, 2020.

Twenty selected watersheds were divided into five small watershed sets according to location in Liaoning Province (LN), China. Watersheds and slopes were extracted from a 1:50,000 DEM, and gully data for each watershed were obtained by remote sensing interpretation. The gullies and associated slopes within the small watersheds were identified, and the distributions of gully density, proportion of dissected land, and gully length-width ratio in each small LN watershed and in the five small watershed sets were obtained. The correlations between the small watershed sets and the gully distributions throughout LN demonstrate regional distribution differences, and the watershed area has a great influence on both the area and length of gullies. Regional differences are present in the gully density and the proportion of dissected land in the small watersheds. The distribution of gullies with respect to slope depends on both the gully parameters and the proportion of terrain in the different slope grade ranges. The distribution results for the five small watershed sets are similar to those from a census of the Liaoning-Around Bohai mountainous and hilly sub-region. The gully density and proportion of dissected land in LN showed a single-peak curve with respect to slope, with slope thresholds of 8° and 5°, respectively. The constructed distribution equation has a high degree of fit. The comprehensive distributions of gully density, proportion of dissected land, and length-width ratio with slope indicate that gully erosion in LN is serious within the slope range of 3~8°.

How to cite: Fan, H. M. and Wang, D. C.: Distribution characteristics of gullies with slope gradient in Northeast China, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-2875, https://doi.org/10.5194/egusphere-egu2020-2875, 2020.

After extensive research on different methods to measure particle size distribution (PSD), soil scientists are proposing the laser diffraction method (LDM) as a standard method for soil texture analysis. However, the effects of different pretreatments on particle size analysis of dry steppe soils with LDM has not been tested so far. This study aims to evaluate different pretreatment methods with the purpose to disperse aggregates and remove binding agents in Chernozem and Kastanozem soils. To cover a wide range of different land-use types and farming methods, 112 surface soil samples were taken from 13 fields on four different test sites in Kazakhstan. Before LDM analysis, all samples were pretreated with either H₂O₂ to remove organic carbon or HCl to remove carbonates. The results showed that removing organic matter with H₂O₂ led to complete sample dispersion while HCl pretreatment caused incomplete dispersion, likely due to aggregation by calcium ions released by the dissolution of carbonates.

How to cite: Koza, M., Prays, A., Bondarovich, A., Akshalov, K., Conrad, C., and Schmidt, G.: How does pretreatment of dry steppe soils affect particle size analysis by laser diffraction? , EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-9415, https://doi.org/10.5194/egusphere-egu2020-9415, 2020.

Agricultural terraces are known to be related to complex hillslope hydrology, characterized by surface and sub-surface water flows. Locally high fluxes or accumulation of water can be responsible for terrace wall failures, such as collapse and piping. There is a need for both scientific research and applied sustainable viticulture to better understand these processes. A key challenge is to find a suitable balance between highly integrated but local field measurements, and a more approximate but widespread approach such as remote sensing. In this study, two distinctive methodologies were applied in order to locate and explain terrace wall failure observed in a north-Italian vineyard: a field-based vs. a remote sensing approach. The field-based approach was based on spatially distributed measurements of topsoil soil moisture content using Time Domain Reflectometry (TDR) instrument. This survey revealed high relative soil water concentration at the damaged terraces, in both wet and dry conditions. Furthermore, a unique cross-sectional saturation profile was found above the damaged walls, with the highest values found near the edges. The remote sensing approach was based on a photogrammetric survey and subsequent high-resolution digital terrain analysis and modeling using the Topographic Wetness Index (TWI) and SIMulated Water Erosion model (SIMWE). Results showed how the formation of surface water flow patterns explains the location of damaged walls. These findings show both the opportunities and limitations of the two approaches. Field measurements provided more conclusive information about the location of walls at risk (high predictive potential), but this approach is relatively labour-intensive (low upscaling potential) as compared to a remote sensing approach. The latter can be a powerful tool for acquiring fully distributed estimations of wall failure over larger non-instrumented areas.

How to cite: Pijl, A., Quarella, E., Vogel, T. A., D'Agostino, V., and Tarolli, P.: Looking high and low: comparing a UAV-based and a ground-based methodology for the detection of vineyard terrace failures, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-3048, https://doi.org/10.5194/egusphere-egu2020-3048, 2020.

Pisha sandstone region is the most vulnerable and the most dramatic area of soil erosion, and it is also the concentrated area of the coarse sediment entering into the Yellow River. It is of great significance to research the anti-erosion and vegetation promotion technology in the Pisha sandstone region. Based on the new concept of anti-erosion and vegetation promotion, surface composition, chemical properties and particle structure of the Pisha sandstone particles were analyzed, and the lithologic mechanism of the easy-corrosion of the Pisha sandstone was revealed. High-tech materials suitable for anti-erosion and vegetation-promoting of Pisha sandstonewas developed. A Pisha sandstone dam using modified silt has been built. The field experiments were monitoredfor the effects of the anti-erosion and vegetation-promoting technology on controlling soil erosion. The results showed that: (1) The grain structureand pore cementation of Pisha sandstone leading to the high affinity of the Pisha sandstone and water; The high content of montmorillonite, calcite and feldspar and the development of pore micro-structure in the Pisha sandstone are the main reasons for the poor soil erosion resistance of the Pisha sandstone. (2) Anti-erosion and vegetation-promoting materials(W-OH) based on hydrophilic polyurethane resin combined with anti-UV stabilizer, aquasorb and vegetation growth promoter can encapsulate the Pisha sandstone particles and composethe composite with Pisha sandstone for erosion resistance and vegetation promotion, degradationcontrol freeze-thaw resistance, hydrolysis resistance and environmental friendliness. (3) The simulation analysis of materials and technology for the dam construction was carried out by using mechanics and chemical experiments. The dam design scheme and key procedures were further verified based on the field experiment, and the dam construction using modified materials of pisha sandstone was developed. The silt damusing modified Pisha sandstone was built in the Erlaohugou watershed. The dam height is 10.03 m, the controlled watershed area is 0.31 km², and the total storage capacity is 32,600 m³. (4) According to the grading of different slopes of the Pisha sandstone and the diversity of its composition, the allocation model of the anti-erosion and vegetation-promoting treatment measures for the Pisha sandstone was proposed. In the top of the slope area, three-dimensional ecological measures such as grass, shrub and arbor mixed with intercepting ditch and other engineering measures were arranged. The technology of spraying anti-erosion and vegetation-promoting materials of low-concentration and planting vegetation measures was used on gentle slopes; the measures of spraying anti-erosion and vegetation-promoting materials of high-concentration combined with vegetation growth was adopted in steep slopes,and the consolidation material is sprayed to prevent weathering and gravity erosion of the Pisha sandstone. (5) The analysis of field plot data showed that the Anti-erosion and vegetation-promoting composite materials and the measures had obvious effects of controlling slope runoff, reducing soil erosion and vegetation restorationcompared with the bare soil plot, the runoff was reduced by more than 70%, the sediment yield was reduced by more than 90%, and the vegetation coverage was reached over 95%.

How to cite: Xiao, P., yao, W., zhang, P., and yang, C.: Research on the Technologyof Anti-Erosion and Vegetation Promotion for Pisha Sandstone Region in the Middle Yellow River Basin, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-3990, https://doi.org/10.5194/egusphere-egu2020-3990, 2020.

 Heavy metal contamination in soils of mining area accompanies contaminations in drainage and vegetation. The traditional soil survey methods for heavy metal contamination requires significant investment of time, labor, and money although the methods can drive accurate assessment. Moreover, the point-based survey is problematic to understand spatial distribution with limited sample numbers. Remote sensing approaches may provide alternative solutions to understand spatial distribution of contamination with minimal investment of time and labor. It is very critical to understand spectral signals associated with heavy metal concentration to apply the phenomenon to remote sensing approaches. This study investigated spectral signals associated with heavy metal concentration in mine soils based on chemical analysis, mineral composition analysis, and spectral analysis. The study site is a Pb-Zn skarn ore deposit located in Gangwon province, South Korea, where the ore was formed by granite intrusion to slate and limestone. The chemical analysis revealed that the soils are contaminated with heavy metals. Mineral composition classified the soils into two time with silicate/clay mineral group and silicate/carbonate/clay mineral groups. Spectral analysis showed that sensitive spectral bands to heavy metal concentration is located in SWIR region for silicate/clay mineral group and VNIR region for silicate/carbonate/clay mineral group. It reveals that mineral composition and geochemical reaction play an important role in spectral signals manifested by heavy metal concentration.

How to cite: Kim, H., Yu, J., Kim, J., Koh, S., and Lee, B.: Spectral Sensitivity of Heavy Metal Concentration in Mine Soils: A case study of Gagok mine, South Korea, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-12424, https://doi.org/10.5194/egusphere-egu2020-12424, 2020.

Understanding the dynamics of basin-scale water budgets over the Tibetan Plateau (TP) is significant for hydrology and water resource management in the southern and eastern Asia. However, a detailed water balance analysis is limited by the lack of adequate hydro-climatic observations in this region. In this study, we investigate the spatiotemporal variation of water budget components (e.g. precipitation P, evapotranspiration ET and runoff Q etc.) in the Yarlung Tsangpo River basin (YTB) of southeast TP during the period of 1975-2015 through using multi-source datasets (e.g. insitu observation, remote sensing data products, reanalysis outputs and model simulations etc.). The change trend of water budget components and vegetation parameters was analyzed in the YTB on interannual scale. The results indicated that the detailed water budgets are different from upstream to downstream YTB due to different temperature, vegetation cover and evapotranspiration, which are mainly affected by different climate conditions. In the whole basin, precipitation that are mainly during June to October was the major contributor to the runoff. The P and Q were found to show a slight but insignificant decrease in most regions of YTB since the late 1990s, which showed positive relationships with the weakening Indian summer monsoon. While the ET showed an insignificant increase across most of the YTB, especially in the middle basin. The runoff coefficient (Q/P) exhibited an indistinctively decreasing trend which may be, to some extent, due to the overlap effects of ET increase and snow and glacier changes. The obtained results offer insights into understanding the evolution mechanism of hydrological processes in such a data-sparse region under changing environment.

How to cite: Jiang, Y. and Xu, Z.: Spatiotemporal characteristics of water budget dynamic in the Yarlung Tsangpo River basin of Tibetan Plateau based on multi-source datasets , EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-12197, https://doi.org/10.5194/egusphere-egu2020-12197, 2020.

Among the environmental problems that could affect agriculture, one of the most critical is ponding. Ponding is the water storage on the surfaces in concavities or small depressions, due to soil saturation. It can seriously affect crops and the management of agricultural landscapes. It is caused by prolonged rainfall events, soil type, or by wrong mechanization practices. Indeed, the increased pressure of heavy machinery can cause topsoil compaction or a subsoil hard pan directly under the ploughing depth, inducing run-off, soil loss and waterlogging. In order to better understand this issue, and therefore provide suitable solutions to reduce ponding risk, it is necessary to represent in details the surface morphology. In the last decade, a range of new remote-sensing techniques have led to a dramatic increase in terrain information, providing new opportunities for a better understanding of Earth surface processes based on geomorphic signatures. Among these, the Unmanned Aerial Vehicles (UAVs) combined with the Structure-from-Motion (SfM) photogrammetry technique represent undoubtedly the most interesting advance in the Earth observation and understanding of Earth surface processes. UAV-acquired imagery may provide a low-cost, rapid, and flexible alternative to airborne LiDAR for geomorphological mapping.

In this work UAV-SfM data are used to obtain high-resolution Digital Terrain Model (DTM) useful to analyze and evaluate the risks of water ponding at farm level in a mid-size agricultural Mediterranean catchment in northern Italy. Intensive photogrammetric surveys were carried out using a UAV while a GNSS in RTK (Real-Time Kinematic) mode was used to collect Ground Control Points (GCPs) and Check Points (CPs), fundamental for georeferencing process and SfM error analysis. The potential water depth was calculated using the Relative Elevation Attribute (REA) algorithm, a methodology successfully used in other contexts (Tarolli et al. 2019). The detection of more pronounced concavities and convexities allowed an estimation and mapping of the potential ponding conditions, thus providing a useful indication for a better environmental management in agriculture.

References

Tarolli, P, Cavalli, M., Masin, R., (2019). High-resolution morphologic characterization of conservation agriculture. Catena, 172, 846–856, doi: 10.1016/j.catena.2018.08.026

How to cite: Straffelini, E., Chen, X., Cucchiaro, S., Michieli, S., Chen, J., and Tarolli, P.: Estimation of potential surface ponding in agriculture using UAV-SfM, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-4655, https://doi.org/10.5194/egusphere-egu2020-4655, 2020.

Gannan forest is an important safety barrier in southeast China. In recent years, Ecological engineering such as Natural Forest Protection, Close Hillsides for Forestry and so on have been implemented in this area. But its ecosystem service value is in a decrease. Especially the soil erosion is serious. The analysis on the dynamic trend of water and soil conservation ecosystem service value and its formation mechanism is of big practical and theoretical significance. In our study, land use change is considered as entry point, while land use remote sensing data and spatial statistic data are used as our database. Logistic-CA-Markov complex model is constructed to predict the space-time evolution trend of forest land use under different circumstance. Based on the prediction, water and soil conservation ecosystem service value is evaluated using assessment approaches like shadow project approach and production cost method. Strategies to promote the ecosystem service are then put forward.

How to cite: Fu, C., Yang, L., and Wu, Y.: Temporal-Spatial Assessment of Water and Soil Conversation Value of Gannan forest in China, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-2858, https://doi.org/10.5194/egusphere-egu2020-2858, 2020.

Affected by global climate change, water shortages and other extreme weather, water scarcity in world is alarming sign. China is suffering from severe water shortage in northern areas due to multiple reasons such as declining of runoff of main rivers to northern areas and serious rainfall shortage. This article provides the evidences regarding the feasibility and their technical, financial, political, socioeconomic, environmental from the aspects of two projects, Tunnel and Tianhe projects. The Tianhe water diversion project is expected to bring 2.5 billion cubic meters of precipitation in the Sanjiangyuan area, 200 million in the Qilian Mountains area and 120 million in the Qaidam area every year. On the other hand, the Tibet-Xinjiang Tunnel, which would be the longest water divert tunnel in the world, plan to divert the water from Tibet to Xinjiang using a 1000-kilometer tunnel. The project is expected to turn Xinjiang into California, which could carry 10 to 15 billion tons of water each year. These two projects are anticipated to solve the problem of water, food and drought in the country. In addition, the integrated telecoupling helps to promote ecosystem services research and governance, identify knowledge gaps, guide research design, and strengthen the interaction between researchers and stakeholders.

How to cite: Abbasi, N. A. and Xu, X.: Water sustainability: the prospect of transfer projects in China, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-1766, https://doi.org/10.5194/egusphere-egu2020-1766, 2020.

Preferential flow is expected to provide an important pathway to replenish soil water at deep soil layers in arid or semiarid areas; however, few studies have addressed this topic, especially in semiarid Loess hillslopes. This study aimed to quantify the effect of stand origin and slope position on the contribution of preferential flow to total infiltration and spatial variations in water flow. A blue dye tracer experiment was conducted to visualize water flow in Robinia pseudoacacia plantation (PL), natural forestland (NF), and natural grassland (NG) at the upslope, midslope, and downslope, and semivariance analysis was used to determine spatial variability at the centimeter scale. The results showed that role of macropore flow was dominant in upslope and midslope, and larger in NF than that in PL and NG, due to presence of abundant root systems in the upper soil of NF. Moreover, contribution of preferential flow at the upper slope in NF was larger than that in PL. At the downslope, the role of rock fragments coverage at the downslope was emphasized, leading lateral flow dominant at the downslope in PL and NG. In addition, contribution of preferential flow and vertical variability of infiltration at the downslope in PL was higher than that in NF. The findings demonstrate that compared with PL, NF has a more positive impact on increasing infiltration and preferential flow that can replenish deep soil water, and reducing surface runoff and soil erosion. The presence of rock fragments coverage can make lateral flow dominant at the downslope on the Loess hillslope, related to water movement along the slope toward streams and catchment outlets.

How to cite: Ma, L., Mei, X., and Zhu, Q.: Effect of stand origin and slope position on infiltration pattern and preferential flow on a Loess hillslope, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-1830, https://doi.org/10.5194/egusphere-egu2020-1830, 2020.

In recent years, due to the rapid development of the China, various production and construction projects have produced many exposed slopes which need to be restored by special recovery measures. However, the regulation effects of vegetation on sediment of slopes with different ecological recovery measures are different. Taking the reconstruction slope of large-scale open pit mine, highway and other demonstration projects as an example, this study analyzed the precipitation, rainfall density, runoff and sediment variation characteristics of 91 rainfalls, and explained the mechanism of vegetation configuration on sediment production on slopes. The results were shown that: (1) the vegetation coverage, early water content and total porosity were the key factors restricting the runoff generation on the slope, among which grey correlation were 0.72, 0.74 and 0.79 respectively. The total porosity, litter thickness and vegetation coverage were the key limiting factors of sediment yield on slope, and their grey correlation degree were 0.64, 0.60 and 0.58 respectively. (2) the comprehensive contribution degree P could reflect the influence of engineering and plant measures on slope sediment production. The analysis showed that the P value of most slopes with engineering and plant measures ranged from 0.31 to 0.77, and the larger the value, the better the effect of reducing soil erosion was. Sediment reduction effect of interlocking bricks greening measure and runoff reduction effect of vegetative carpet greening with coconut fiber measure were the best which P value were separately 0.77 and 0.55. (3) The comprehensive assess coupling model for vegetation-soil system were derived based on vegetation quantitative characteristics, diversity data, soil physicochemical properties and soil and water conservation benefits. Typical protection measures were ordered according to coupling degree (Cd). Three kinds of rocky slopes in mountainous area including metal net hanging combined with spray seeding measure, earth retaining with brick setting measure, ecological bags measure were recommended. Five kinds of soil slopes in mountainous area including grass protection, metal nets within ecological bags, geo-grid cell measure, six arises brick with hollow measure and vegetative carpet greening with coconut fiber measure were recommended. Two kinds of loose slopes including vegetative carpet greening with coconut fiber measure and ecological bags measure were recommended. Six arises brick with hollow measure was recommended in plain soil slopes. In conclusion, the combination of engineering measures and plant measures should be adopted for protection, so as to achieve the purpose of preventing and controlling soil and water loss.

How to cite: yan, Z. and tingning, Z.: Ecological protection effects on typical slopes with various combination of engineering measures and plant measures, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-14017, https://doi.org/10.5194/egusphere-egu2020-14017, 2020.

Sediment provenance is an important factor in understanding soil erosion processes or assessing the ecological effects of soil and water conservation measures. Sediment fingerprinting is an effective technique used globally for identifying sediment sources. Few studies have examined sediment sources at different spatial scales. In this study, sediment fingerprinting was used with a Bayesian mixing model to quantify the relative contributions of different sediments to streambeds in the Hebei catchment (ca. 28.0 km²) and its sub-catchment (ca. 3.5 km²) in the black soil region of Northeast China. Three potential sediment sources were identified: cultivated topsoil, uncultivated topsoil, and gullies. A similar number of sediment samples were collected for each source in both catchments: 71 and 69 sediment samples from the sub-catchment and Hebei catchment, respectively. Five uniformly distributed streambed sediment samples were collected from each catchment. The results showed a significant difference in the spatial variability of fingerprinting properties between the two catchments (p < 0.01). The spatial variability in fingerprint properties of cultivated topsoil and gully soil was more sensitive to scale than that of uncultivated topsoil. The optimum composite fingerprint that was used to discriminate potential sediment sources differed between the sub-catchment and Hebei catchment. Cultivated topsoil and gully soil were the main sediment sources, comprising more than 95% of the streambed sediment. There were significant differences (p < 0.01) in the contributions of cultivated topsoil and gully soil at different spatial scales. Cultivated topsoil contributed 47.8% and 42.0% in the sub-catchment and Hebei catchment, respectively, whereas gully soil contributed 49.6% and 55.3% (mean absolute fit >0.95). The upper stream segment mainly received sediment from the gullies (>60%) and the contribution from cultivated topsoil gradually increased downstream.

How to cite: Huang, D.: Effects of spatial scale on fingerprinting properties and sediment contributions in the black soil region of Northeast China, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-2075, https://doi.org/10.5194/egusphere-egu2020-2075, 2020.

Rainfall erosivity (R factor), in the Universal Soil Loss Equation (USLE) , a climate index, is used worldwide to assess and predict the potential of rainfall to cause erosion. The temporal variation in rainfall erosivity, informs of abrupt change and trend, are critical for soil loss prediction. To find a simple and effective method for accurate detection of abrupt change and trend has implication for soil and water conservation planning. In this paper, a four-step framework is proposed to detect abrupt change and trend in rainfall erosivity time series, i.e., evaluate the significance of variation in rainfall erosivity time series at three levels: no, weak and strong, abrupt change and trend detection for rainfall erosivity,  estimation of correlation coefficient between the variation component and rainfall erosivity series, remove the variation component with the largest correlation coefficient from the rainfall erosivity series, repeat the above steps for the new series until variance coefficient was insignificance. The first step is based on an index of Hurst coefficient. The trend detection is implemented using both Spearman rank and Kendall rank correlation test. For abrupt change ,three kinds of methods (Mann-Kendall, Moving T and Bayesian test) are employed.  This framework is applied to the annual rainfall erosivity series of the Three Gorges Reservoir , China. There was a large uncertainty in detecting variability with a single test method. Application of the proposed framework can reduce uncertainty  associated with soil erosion assessment and achieve more accurate regional soil and water management. 

How to cite: Qian, F., Hu, B., Liu, H., and Liu, J.: A framework of abrupt changes and trends detection for rainfall erosivity , EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-2489, https://doi.org/10.5194/egusphere-egu2020-2489, 2020.

The Pisha sandstone area which distributed in Ordos of Inner Mongolia was the main source area of Yellow River sediment, The area has a characteristic of serious composite erosion and fragile ecological environment, So, which identifying the critical force occurrence conditions of compound erosion is an important prerequisite to prevent and control the multiple composite erosion. Using the method such as field observation, simulation experiments and literature review, this study preliminarily summarizes the dynamic critical conditions and key influencing factors of water erosion, wind erosion and freeze-thaw erosion.(1)Water erosion is affected by rainfall, rainfall intensity and soil moisture status, Rainfall and rainfall intensity are the two critical factors under the certain soil moisture status. the one critical conditions of water erosion was P > 34mm under the soil moisture of θ_v≈10%, and the other critical conditions was rainfall intensity I > 1.2mm/min (soil moisture θ_v＞36%) or rainfall intensity I > 3.1mm/min（soil moisture θ_v＜4%). (2)The wind erosion is affected by the surface covering particles and soil moisture. When the wind speed reaches more than 5 m/s, the soil particles of diameter d < 0.5 mm will be blown up. So the wind erosion is easier happens on exposed surface and slipped particles. Increasing the surface covering and water content can reduce wind erosion; (3)Freeze-thaw mainly occurs from November to March of each year, which destroys soil structure mainly through soil mass melting and particle fall down. The alternation times and moisture content of freeze-thaw are the key factors that affect freeze-thaw erosion. When the soil moisture is more than 10% and the freeze-thaw alternation is more than 10 times, the freezing and cracking damage is obvious. Therefore, the phenomenon of sliding and peeling off the exposed steep slope is common in Pisha sandstone area. (4)Multi dynamic composite erosion distributed by seasonal in the year, Wind and freeze-thaw composite erosion happened in the transition of autumn to winter and winter to spring, Water erosion mainly occurred in summer, and accompanied by wind erosion, Meanwhile, wind and freeze-thaw erosion products were all carried away by runoff. The results can provide theoretical basis for the measures selection of composite erosion control.

Key words: Pisha sandstone area, composite erosion, water erosion critical, wind erosion critical, freeze-thaw erosion critical, influencing factors

How to cite: Yang, C., Xiao, P., and Zhang, P.: Study on the critical dynamics of compound erosion in the Pisha sandstone area, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-4314, https://doi.org/10.5194/egusphere-egu2020-4314, 2020.

The rapid development of expressway provide convenience for our life. But during the construction and operation, the slope instability is a serious ecological problems which can threat the normal use of the expressway. As slope protection is essential, the ecological slope protection is an environmental friendly method to reinforce the slope stability as the root can make contribution to the soil shear strength. From the macro perspective, the soil reinforced ability of root system is greatly affected by the structure and distribution morphology of plant root system. So it is crucial to study the influence of root distribution characteristics on the soil shear strength. As the structure of plant root has typical fractal feature, fractal dimension which is the most important quantitative parameter is chosen to establish the relationship with the soil strength. Because the structure of the plant roots is very complex and no two roots are identical, it is difficult to find the same root to conduct contrast tests. But at least four tests with different cell pressures are essential to obtain the cohesion and internal friction angel. Thus 3d printing method is a superior choice to ensure each test condition is as same as possible. The purpose of this study is to explore the relationship between the root fractal dimension and soil cohesion, and internal friction angel. In order to reduce the influence of root difference on the triaxial compression test, 3D printing method is applied to make simulative plant roots which can maintain the fractal dimension. So single variable experiment could be guaranteed, the general rule between fractal dimension of root system and soil reinforced ability can be revealed. Four roots of Cynodon dactylon with different fractal dimension were chosen to establish 3D printing model. Corresponding to each fractal dimension, four triaxial compression test were conducted with four cell pressure. The results indicate that both of the cohesion and internal friction rise with the increasing of the fractal dimension, but the influence of fractal dimension on cohesion is slight compared with the influence on the internal friction. That is to say, the root with larger fractal dimension possess better reinforced effect on slope soil by increasing the the internal friction.

How to cite: li, J. and zhang, Y.: Influence of root fractal dimension on soil shear strength with 3D printing method, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-4894, https://doi.org/10.5194/egusphere-egu2020-4894, 2020.

Abstract: The particulate matter (PM) in coal mining can bring pollution to the surrounding environment and have adverse effect on human health. In order to prevent and control the PM pollution in coal mine and better understand the PM transportation in the air, spatial and temporal distribution of PM concentration in two typical coal mining methods were studied in the arid desert region of northwest China. The mass concentrations of particulate matters, i.e., PM1, PM2.5, PM10 and TSP (total suspended particulate), were monitored by portable environmental particulate matter meter during two windy seasons—spring and winter in a typical opencast coal mine and an underground coal mine. The results show that:

(1) In the opencast mine, high concentrations of PM appeared in the mining area (MA) . Average PM10 and TSP concentration were 1950.18 μg·m^-3 and 2393.56 μg·m^-3 respectively in spring, while PM1 and PM2.5 concentration were 6.22 μg·m^-3 and 42.58 μg·m^-3 in winter. In the underground mine, it was concentrated in the coal yard (CY), average PM10 and TSP concentration were 920.95 μg·m^-3 and 1225.89 μg·m^-3 respectively in spring, while PM1 and PM2.5 concentration were 8.64 μg·m^-3 and 35.93 μg·m^-3  in winter.

(2) The variations of pollution index (PI) showed similar patterns in both spring and winter— that is, high in the morning then achieved maximum value exceeded 10, and decreasing from noon at the opencast mine entrance (ME), the mining area (MA), road in the mine (RM), and the coal storage yard (CS). However, the PI rose in the evening in spring, but decreased in winter. In the CY of the underground mine, the PI was high during the day; whereas in the evening it decreased in spring and increased in winter.

(3) In the opencast mine, the PM10 and TSP concentrations varied more obviously from season to season and from area to area than the concentrations of PM1 and PM2.5. Barometric pressure had the most significant influence on PM1, PM2.5 and PM10. Wind speed had the greatest influence on TSP. In the underground mine, the variation patterns of the concentration of the four different-sized particulate matters were basically the same from area to area. The concentrations of PM1 and PM2.5 had greater seasonal variation than PM10 and TSP. The most important meteorological factors were temperature and barometric pressure for PM1 and PM2.5, while air humidity had the greatest impact on PM10 and TSP.

Considering the above results, it is recommended to control the daily occurrence and spread of particulate matter at 08:00 and 18:00 in the opencast mine, and from 08:00 to 16:00 in the underground mine. Primary attention should be given to the influence of wind speed and relative humidity changes on the diffusion of coarse particles(PM10 and TSP) in spring, while the influence of changes in barometric pressure on the diffusion of fine particles(PM1 and PM2.5) should be considered in the mining area in winter for both the two typical coal mining methods. The diffusion of coarse particulate matter in the opencast mine and of fine particulate matter in the underground mine are the main issues to be considered, while it is essential to prevent and control the spread of fine particles in the areas of roadways.

How to cite: Wang, R. and Liu, Y.: Temporal and Spatial Distributions of Particulate Matters under Two Coal Mining Methods in Arid Desert Region of Northwest China, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-6590, https://doi.org/10.5194/egusphere-egu2020-6590, 2020.

The operation of the Three Gorges Reservoir (TGR) altered the distribution of the soil properties, the plant community composition and biomass in the water-level fluctuation zone (WLFZ). However, the vertical variation of soil erosion resistance in the WLFZ of the TGR is still unclear and need to be further evaluated. The objectives of this study were to assess the vertical variation of soil resistance to rill erosion in the WLFZ of the TGR and to identify the factors influencing these variations. Soil samples from 150-155 m, 155-160 m, 160-165 m, 165-170 m and 170-175 m were taken along a slope profile at the same time from the WLFZ of the TGR area. All the samples subjected to scour under the combinations of five slope gradients (8.74%, 17.63%, 26.79%, 36.40% and 46.63%) and five flow rates (5, 10, 15, 20 and 25 L min^–1) by using a slope-adjustable steel hydraulic flume (4 m length, 0.4 m width, 0.2 m depth). The results showed that soil properties and biomass parameters were affected by the elevations of the WLFZ. The average soil detachment capacity fluctuated with the increase of elevation, maximum and minimum value of  which were located at the 165-170 m and 155-160 m, respectively. The soil detachment capacity was significantly negatively correlated with MWD (P<0.05), but not positively correlated with other properties (P>0.05).  The rill erodibility also fluctuated with the increase of elevation. Correlation analysis showed that rill erodibility corresponding to runoff shear stress and stream power respectively had significantly negative correlation with MWD (P<0.05), and rill erodibility corresponding to unit energy of water-carrying section had significant negative correlation with MWD (P<0.01). Therefore, the soil aggregate stability was the major factor responsible for the vertical variation in soil erosion resistance. In addition, critical shear stress, critical stream power and critical unit energy of water-carrying section ranged from 1.1950 to 1.6427 Pa, from 0.0132 to 0.3045 N•m^-1•s^-1 and from 0.0052 to 0.0062 m, respectively, all of them showed obvious fluctuations with the increase of elevation. These research results highlighted the effect of elevation on soil erosion resistance in the WLFZ and provide theoretical guidance for the establishment of soil and water loss prediction model as well as the development of soil and water conservation planning and controlling in the TGR area.

How to cite: Xiao, H.: Vertical variation of soil erosion resistance in the water-level fluctuation zone of the Three Gorges Reservoir, China , EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-12464, https://doi.org/10.5194/egusphere-egu2020-12464, 2020.

To study the mechanism of vegetation on gravity erosion may provide the theoretical basis for the design of soil and water conservation on the Loess Plateau, China. This study explores the effects of vegetation on the gravity erosion using the models of loess gully sidewall with the slope degree of 70 ° and height of 1.5 m under series of rainfall simulations, in which vegetational and bare lands were used, respectively. The experimental results are shown as follows: (1) The influence of the vegetation on the total amount of gravity erosion may be ignored. The average amount of gravity erosion for each event of rainfall on the vegetational sidewall was only decreased by 12% compared with that on the bare sidewall. (2) The plant had a positive effect on the mass failures after rainfalls. The ratio of the failure mass volume after rainfall to the total on the planted slope was almost 12%, while the ratio on the bare slope was only 1%. (3) The vegetation on the gully sidewall had different influences on the varied types of gravity erosion. Compared with those on the bare land, the average amounts of the avalanche and mudslide on the vegetational slope was decreased by 72% and 69%, respectively. In the meantime, the average amount of landslide in the vegetational slope was increased by 220% compared with that in bare slope. (4) The effects of vegetation on gravity erosion were caused by several factors. The plant roots may reinforce the soil and reduce the amount of gravity erosion, but the self-gravity of the plant and increase of the permeability on the planted slope might increase the gravity erosion. In addition, the soil permeability was increased by the plant roots, which could intensify the landslides. As a result, the plant practice was preferable for the sidewall vulnerable to mudslide. The results may be referred to analyze the mechanism of gravity erosion and design the control of mass failure.

How to cite: Zhao, X. and Xu, X.: Effects of Plants for Gravity Erosion on the Loess Gully Sidewall under Intense Rainfalls, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-1767, https://doi.org/10.5194/egusphere-egu2020-1767, 2020.