Effects of Typical Soil and Stratification Thickness on Water Infiltration Characteristics in Central Ningxia

In order to compare the influence of different soil types and stratification on water infiltration capacity,two main types of soil in the desert steppe,sierozem(S)and aeolian sandy soil(A),were selected,and infiltration simulation tests were conducted on homogeneous soil and layered soil(layer thickness 5,10,and 20 cm),respectively.The results show that during the whole experiment,there was a small difference between S5A95(aeolian sandy soil 95 cm thick was covered with sierozem 5 cm thick)and S10A90(aeolian sandy soil 90 cm thick was covered with sierozem 10 cm thick)in the wetting front process,infiltration rate and cumulative infiltration,but there was a significant difference between S5A95 and S20A80(aeolian sandy soil 80 cm thick was covered with sierozem 20 cm thick).In the initial infiltration stage,there was no significant difference between A5S95(sierozem 95 cm thick was covered with aeolian sandy soil 5 cm thick)and A10S90(sierozem 90 cm thick was covered with aeolian sandy soil 10 cm thick).However,with the increase of infiltration time,the wetting front process,A5S95,A10S90 and A20S80 had significant differences in terms of wetting front process,infiltration rate and cumulative infiltration.The infiltration capacity of A was significantly higher than that of S.Combined with linear R 2 value and model parameters,the three infiltration models were comprehensively compared,and the fitting process and results of the general empirical model for the infiltration process of homogeneous soil and layered soil showed good results.Three models were used to simulate the water infiltration process of layered soil with different textures,and the order of the effect is as follows:general empirical model>Kostiakov model>Philip model.Soil type and layer thickness had a great influence on water infiltration process.When sierozem was covered with aeolian sandy soil 20 cm thick,the infiltration capacity was the best.As aeolian sandy soil was covered with sierozem 10 cm thick,the infiltration effect was the worst.Therefore,once coarse graying occurs on the surface of sierozem(the thickness of sand is more than 20 cm)or when the content of fine particles overlying aeolian sandy soil(the thickness of silt and clay soil is more than 10 cm)during ecological restoration is high,the soil hydrological characteristics will change significantly,which may lead to changes in vegetation types and even ecosystem structure.

Three-year field study on grass growth and soil hydrological properties in biochar-amended soil

Field monitoring was conducted to investigate and quantify the long-term effects of peanut shell biochar on soil-grass interaction over three years.Three 10 m5 m grassed plots were constructed in completely decomposed granitic soil.Two of them were amended,respectively,with 5%and 10%biochar contents(m^(3)/m^(3))for grass growth,while the third was without biochar amendment.During the threeyear monitoring,plant characteristics,saturated water permeability(k_(s))of grassed soil and soil suction were measured.The monitored results show that the grass leaf area index(LAI)and root length density(RLD)with biochar amendment were improved by 38%and 200%,respectively.In the grassed plot without biochar,a threshold RLD existed with a value of 1.7 cm/cm^(3),beyond which k_(s) raised pronouncedly.The threshold RLD increased by 52%when biochar content increased from 0%to 10%.This implies that biochar may restrict the increase in k_(s) of grassed soil due to the rise in the threshold RLD.The presence of biochar and grass can retain over 100%higher suction after heavy rainfalls,while 54%lower peak suction under evapotranspiration(ET)compared with the non-amended plot.Biochar can alleviate the negative effects on hydraulic properties caused by plant growth and reduce ET-induced excessive water loss.A 5%peanut shell biochar content is recommended for the long-term management of vegetated earthen infrastructures.

An Analytical Solution for One-Dimensional Water Infiltration and Redistribution in Unsaturated Soil

Soil infiltration and redistribution are important processes in field water cycle, and it is necessary to develop a simple model to describe the processes. In this study, an algebraic solution for one-dimensional water infiltration and redistribution without evaporation in unsaturated soil was developed based on Richards equation. The algebraic solution had three parameters, namely, the saturated water conductivity, the comprehensive shape coefficient of the soil water content distribution, and the soil suction allocation coefficient. To analyze the physical features of these parameters, a relationship between the Green-Ampt model and the algebraic solution was established. The three parameters were estimated based on experimental observations, whereas the soil water content and the water infiltration duration were calculated using the algebraic solution. The calculated soil water content and infiltration duration were compared with the experimental observations, and the results indicated that the algebraic solution accurately described the unsaturated soil water flow processes.

Effect of Pisha sandstone on water infiltration of different soils on the Chinese Loess Plateau

The infiltration of water into soil is one of the most important soil physical properties that affect soil erosion and the eco-environment, especially in the Pisha sandstone area on the Chinese Loess Plateau. We studied the one-dimensional vertical infiltration of water in three experimental soils, created by mixing Pisha sandstone with sandy soil, irrigation-silted soil, and loessial soil, at mass ratios of 1：1, 1：2, 1：3, 1：4, and 1：5. Our objective was to compare water infiltration in the experimental soils and to evaluate the effect of Pisha sandstone on water infiltration. We assessed the effect by measuring soil bulk density（BD）, porosity, cumulative infiltration, infiltration rate and saturated hydraulic conductivity（Ks）. The results showed that Pisha sandstone decreased the infiltration rate and saturated hydraulic conductivity in the three experimental soils. Cumulative infiltration over time was well described by the Philip equation. Sandy soil mixed with the Pisha sandstone at a ratio of 1：3 had the best water-holding capacity. The results provided experimental evidence for the movement of soil water and a technical support for the reconstruction and reclamation of mining soils in the Pisha sandstone area.

Observation and modeling on irregular purple soil water infiltration process

The infiltration process is a critical link between surface water and groundwater. In this research, a specific device to observe infiltration processes in homogeneous and heterogeneous soils with triangular and inverted triangular profiles was designed, and the Green-Ampt model was employed for the process simulation. The results indicate that(1) the wetting front in coarse texture soils transports faster than in fine texture soils;(2) for the homogeneous case, the wetting front in triangularshaped soils transports faster than the inverted triangular type, but the triangular-shaped soils show a lower infiltration rate;(3) in the initial step, the wetting front in triangular-shaped soils shows higher transport speed, but depicts lower speed with increase in the time;(4) both the wetting front and infiltration rate show a significant exponential relation with the time. From these findings, an empirical model was developed which agrees well with the observed data and provides a useful method for this field of soil research.

Development of an Ontology-Based Knowledge Network by Interconnecting Soil/Water Concepts/Properties, Derived from Standards Methods and Published Scientific References Outlining Infiltration/Percolation Process of Contaminated Water

The present work deals with the development of an Ontology-Based Knowledge Network of soil/water physicochemical & biological properties (soil/water concepts), derived from ASTM Standard Methods (ASTMi,n) and relevant scientific/applicable references (published papers—PPi,n) to fill up/bridge the gap of the information science between cited Standards and infiltration discipline conceptual vocabulary providing accordingly a dedicated/internal Knowledge Base (KB). This attempt constitutes an innovative approach, since it is based on externalizing domain knowledge in the form of Ontology-Based Knowledge Networks, incorporating standardized methodology in soil engineering. The ontology soil/water concepts (semantics) of the developed network correspond to soil/water physicochemical & biological properties, classified in seven different generations that are distinguished/located in infiltration/percolation process of contaminated water through soil porous media. The interconnections with arcs between corresponding concepts/properties among the consecutive generations are defined by the relationship of dependent and independent variables. All these interconnections are documented according to the below three ways: 1) dependent and independent variables interconnected by using the logical operator “depends on” quoting existent explicit functions and equations;2) dependent and independent variables interconnected by using the logical operator “depends on” quoting produced implicit functions, according to Rayleigh’s method of indices;3) dependent and independent variables interconnected by using the logical operator “related to” based on a logical dependence among the examined nodes-concepts-variables. The aforementioned approach provides significant advantages to semantic web developers and web users by means of prompt knowledge navigation, tracking, retrieval and usage.

Effects of mixed-based biochar on water infiltration and evaporation in aeolian sand soil

Aeolian sandy soil in mining areas exhibits intense evaporation and poor water retention capacity.This study was designed to find a suitable biochar application method to improve soil water infiltration and minimize soil water evaporation for aeolian sand soil.Using the indoor soil column method,we studied the effects of three application patterns(A(0-20 cm was a mixed sample of mixed-based biochar and soil),B(0-10 cm was a mixed sample of mixed-based biochar and soil and 10-20 cm was soil),and C(0-10 cm was soil and 10-20 cm was a mixed sample of mixed-based biochar and soil)),four application amounts(0%(control,CK),1%,2%,and 4%of mixed-based biochar in dry soil),and two particle sizes(0.05-0.25 mm(S1)and<0.05 mm(S2))of mixed-based biochar on water infiltration and evaporation of aeolian sandy soil.We separately used five infiltration models(the Philip,Kostiakov,Horton,USDA-NRCS(United States Department of Agriculture-Natural Resources Conservation Service),and Kostiakov-Lewis models)to fit cumulative infiltration and time.Compared with CK,the application of mixed-based biochar significantly reduced cumulative soil water infiltration.Under application patterns A,B,and C,the higher the application amount and the finer the particle size were,the lower the migration speed of the wetting front.With the same application amount,cumulative soil water infiltration under application pattern A was the lowest.Taking infiltration for 10 min as an example,the reductions of cumulative soil water infiltration under the treatments of A2%(S2),A4%(S1),A4%(S2),A1%(S1),C2%(S1),and B1%(S1)were higher than 30%,which met the requirements of loess soil hydraulic parameters suitable for plant growth.The five infiltration models well fitted the effects of the treatments of application pattern C and S1 particle size(R2>0.980),but the R2 values of the Horton model exceeded 0.990 for all treatments(except for the treatment B2%(S2)).Compared with CK,all other treatments reduced cumulative soil water infiltration,except for B4%(S2).With the same application amount,cumulative soil water evaporation difference between application patterns A and B was small.Treatments of application pattern C and S1 particle size caused a larger reduction in cumulative soil water evaporation.The reductions in cumulative soil water evaporation under the treatments of C4%(S1),C4%(S2),C2%(S1),and C2%(S2)were over 15.00%.Therefore,applying 2%of mixed-based biochar with S1 particle size to the underlying layer(10-20 cm)could improve soil water infiltration while minimizing soil water evaporation.Moreover,application pattern was the main factor affecting soil water infiltration and evaporation.Further,there were interactions among the three influencing factors in the infiltration process(application amount×particle size with the most important interaction),while there were no interactions among them in the evaporation process.The results of this study could contribute to the rational application of mixed-based biochar in aeolian sandy soil and the resource utilization of urban and agricultural wastes in mining areas.

Diesel oil infiltration in soils with selected antecedent water content and bulk density

The effects of soil texture, initial water content and bulk density on diesel oil infiltration in fine sand and silty clay loam materials were evaluated. Three physical and two empirical equations express diesel oil infiltration through soils with time, with coefficients of determination greater than 0.99. Diesel oil infiltrates more quickly in the fine sand than in the silty clay loam material. Diesel oil infiltration rates are found to decrease with increasing initial water content and bulk density for the silty clay loam material. The infiltration rate of diesel oil in the fine sand material increases slightly with increasing initial water content. The diesel oil saturated conductivity(Kdiesel) decreases with increasing bulk density for the silty clay loam column. Diesel oil sorptivity(S) decreases linearly with increased initial water content and bulk density of the silty clay loam material. Changes in empirical parameters relative to initial water content and bulk density are similar to the parameter S.

Evaluation of Infiltration Capacity and Water Retention Potential of Amended Soil Using Bamboo Charcoal and Humus for Urban Flood Prevention

In Japan, floods occur frequently in urban areas because non-infiltrating areas are seeing increased urbanization. To prevent floods, urban basins must improve the infiltration capacity and water retention of the whole basin. There are several basic technologies for river basin management, such as infiltration trenches or rainwater storage. However, a method of soil amendment that prevents flood disasters has not been established. This study aims to evaluate the infiltration capacity of soil amendments using bamboo charcoal and humus. A constant-head infiltration test and rainfall simulation were conducted to evaluate the properties of the soil amendments. The constant-head infiltration test＇s results showed that soils mixed with 30% humus had the greatest potential for influencing initial and final infiltration rates, and the more the mixing rates of bamboo charcoal and humus were increased, the higher the water retention capacity. The results of the rainfall simulation showed that soils mixed with 30% humus had the highest final infiltration rates and lowest multiplication spillage. To reduce the runoff volume using soil amendment technology, it is important to delay overland flow, and the hydraulic properties of the soils mixed with bamboo charcoal and humus were as effective as those of granite soils.

Modelling the water diversion of a sustainable cover system under humid climates

Extreme rainfall significantly threatens the safety of the landfill cover system,especially under humid climates.This study aims to provide design recommendations for a sustainable landfill cover system consisting of a low-permeability soil layer underlying a two-layer capillary barrier for humid climates.First,the numerical back-analysis was conducted for verification against a series of flume model tests.Then,a parametric study was performed to investigate the effects of inclination angle,particle size and layer thickness on the lateral diversion length(DL)of the three-layer cover system under the 100-year return period rainfall of humid climates.The results show that the water lateral DL of the cover system can be greatly enhanced by increasing the inclination angle from 3°to 18°.Moreover,the bottom layer of the cover system with a coarser d10 was more susceptible to the impact of the heavy rainfall,while this can be alleviated by increasing the thickness of the bottom layer.A dimensionless number,defined as the ratio of thickness and d_(10) of the bottom layer,is proposed for designing lateral diversion of the three-layer cover system under humid climates.To preserve the maximum DL,it is suggested that the proposed dimensionless number should be larger than 95 and 110 for the design of rainfall events with 50-year and 100-year return periods for humid climates,respectively.

A Dynamic Model for Simulating Atmospheric, Surface and Soil Water interactions in Hillslope of Loess Area Under Natural Conditions and Its Application

The mechanism of atmospheric, surface and soil water interactions (water transformation) in hillslope under natural conditions was analyzed, and a dynamic model was developed to simulate infiltration, overland flow and soil water movement during natural rainfall in hillslope, by bringing forward concepts such. as rainfall intensity on slope and a correction coefficient of saturated soil water content for soil surface seal. Some factors, including slope angle, slope orientation and raindrop inclination, which affect the rainfall amount on slope, were taken into account while developing the dynamic model. The effect of surface seal on infiltration and water balance under a boundary condition of the second kind was also considered. Application of the model in a field experiment showed that the model simulated precisely the infiltration, overland flow and soil water movement in hillslope under natural rainfall conditions.

Soil and water loss in the Lancang River-Mekong River watershed (in Yunnan section, China) and its control measures

According to a lot of hydrological and environmental monitoring data, the condition of soil and water loss in the Lancang River Mekong River watershed (in Yunnan section, China) is described. The occurrence and development of soil and water loss is analyzed. The conclusion is that: (1) generally, the situation of soil and water loss in the Lancang River Mekong River watershed (in Yunnan section, China) is light, however, soil and water loss in some regions is serious, especially in the middle reach area of the river; (2) soil and water loss in the Lancang River Mekong River (in Yunnan section, China) watershed presents developing tendency and it is mainly caused by human beings. In accordance with these results, the control measures for soil and water loss are discussed.

Application of HYDRUS-1D in understanding soil water movement at two typical sites in the North China Plain

Recharge and discharge, such as rainfall infiltration and evapotranspiration in vertical direction, are major processes of water cycle in the shallow groundwater area of the North China Plain. During these processes, soil water movement in the unsaturated zone plays an important role in the transformation from rainfall infiltration to groundwater. The soil water movement models were developed by using HYDRUS-1D software at two typical experimental sites in Cangzhou(CZ) and Hengshui(HS) with different soil, vegetation and similar climate conditions. As shown in the results, the comparison in precipitation infiltration features between the two sites is distinct. The soil water experiences strong evaporation after precipitation infiltration, which accounts for 63% of the total infiltration at the HS site where the soil is homogenous. It is this strong evaporation effect that leads to slight increase of soil water storage. At the CZ site, where the soil is heterogeneous, the evaporation effect exists from July to October of the simulation period. The total evaporation accounts for 33% of the total infiltration, and the evaporation rate is slow. At the end of the simulation period, the soil water storage increases and the water table decreases, indicating a strong storage capacity at this site.

Tillage and Rice-Wheat Cropping Sequence Influences on Some Soil Physical Properties and Wheat Yield under Water Deficit Conditions

Adopting a better tillage system not only improves the soil health and crop productivity but also improves the environment. A field experiment was conducted to investigate the effects of tillage and irrigation management on wheat (Triticum aestivum L.) production in a post-rice (Oryza sativa L.) management system on silty clay loam soil (acidic Alfisol) for 2003-2006. Four irrigation levels (RF: rainfed;I1: irrigation at crown root initiation (CRI);I2: irrigation at CRI + flowering;I3: irrigation at CRI + tillering + flowering), and two tillage systems (ZT: zero tillage and CT: conventional tillage) were tested. Zero tillage compared to CT, resulted in higher bulk density (1.34 vs 1.23 Mg –3), lower total porosity (48.7 vs 52.9%), higher penetration resistance (1.51 vs 1.37 MPa), lower saturated hydraulic conductivity (1.60 vs 92.0 mm h–1), lower infiltration rate (9.40 vs 36.6 mm h–1) and higher volumetric available water capacity (7.9 vs 7.5%) in the surface 0.15 m soil layer. Irrigation levels significantly affected crop water use, wheat yield, and water use efficiency (WUE). Average total water use was 461, 491, 534 and 580 mm under RF, I1, I2 and I3 treatments, respectively. Grain and straw yield of wheat were statistically the same under ZT and CT during 2003-2004;the values, averaged over four irrigation levels were 2.10 and 2.38 Mg a–1 for grain, and 3.46 and 3.67 Mg a–1 for straw, respectively. Grain yield declined by 22%, 11% and 8% of I3 (2.32 Mg ha–1) with RF, I1 and I2 treatments, respectively, under ZT;and by 13%, 8% and 5% of I3 (2.61 Mg ha–1) with RF, I1 and I2 treatments under CT. Average values of WUE were 4.33 kg ha–1 m–1 and 2.35 m3–1 grain for the ZT and CT treatments. Wheat yield increased with increased irrigation levels for all the cropping seasons. Results from this study concluded that ZT system was better compared to the CT system even with lower yields due to lower input costs for this treatment.

Short Term Leguminous Trees-Tillage Interactions and Their Effect on Soil-Water Content in a Semi-Arid Agroforestry Parkland

Agricultural activities that encourage slashing, burning and ploughing greatly affect the soil structure and soil organic matter on which soil water retention depends. In this study, we hypothesized that inclusion of rotational leguminous tree species improves soil water retention in a semi-arid conservation agriculture system. In a study done in Kibwezi, semi-arid eastern Kenya, results showed that the amount of water retained in the different soil strata from plots with different tree species and tillage practices was highly significant (P = 0.032). Plots with planting basins and Gliricidia sepium and Faidherbia albida tree species retained more water in both the upper and lower strata. Plots with G. sepium tree species under planting basins and zero tillage under F. albida had significantly higher soil organic carbon levels than plots that were managed under ridges and ploughing (P = 0.002). On the other hand, bulk density in plots with planting basins and zero tillage and ridges ranged between 1.35 g/cm3 and 1.53 g/cm3. Conventional tillage plots had bulk density values of 1.65 g/cm3 and 1.72 g/cm3 in the upper and lower strata respectively. The time-dependent nature of rotational leguminous tree species on soil organic matter and soil water retention in the semi-arid conservation agriculture system highlights the importance of considering these species for improving organic carbon and water retention for improved crop production.

Electrical capacitance volume tomography for measurement soil water infiltration in vessel experiments

Electrical capacitance volume tomography(ECVT) is a recently-developed technique for real-time,non-invasive 3D monitoring of processes involving materials with strong contrasts in dielectric permittivity.This work is first application of the method to visualization of water flow in soil.We describe the principles behind the method,and then demonstrate its use with a simple laboratory infiltration experiment.32 ECVT sensors were installed on the sides of an empty PVC column.Water was poured into the column at a constant rate,and ECVT data were collected every second.The column was then packed with dry sand and again supplied with water at a constant rate with data collected every second.Data were analyzed to give bulk average water contents,which proved consistent with the water supply rates.Data were also analyzed to give 3D images(216 voxels) allowing visualization of the water distribution during the experiments.Result of this work shows that water infiltration into the soil,wall flow,progress of the unstable wetting front and the final water distribution are clearly visible.

Soil water resources use limit in the loess plateau of China

Soil water is a key factor limiting plant growth in water-limited regions. Without limit of soil water used by plants, soil degradation in the form of soil desiccation is easy to take place in the perennial forestland and grassland with too higher density or productivity. Soil water resources use limit (SWRUL) is the lowest control limit of soil water resources which is used by plants in those regions. It can be defined as soil water storage within the maximum infiltration depth in which all of soil layers belong to dried soil layers. In this paper, after detailed discussion of characteristics of water resources and the relationship between soil water and plant growth in the Loess Plateau, the definition, quantitative method, and practical applications of SWRUL are introduced. Henceforth, we should strengthen the study of SWRUL and have a better understanding of soil water resources. All those are of great importance for designing effective restoration project and sustainable management of soil water resources in water- limited regions in the future.

Soil micro-penetration resistance as an index of its infiltration processes during rainfall

Rainfall infiltration is one of the most important driving factors of geological hazards, ecological environment problems, and engineering accidents. Understanding the principle of soil wetting during rainfall infiltration and its influence on soil mechanical properties is crucial for preventing geological hazards. In this study, micro-penetration tests coupled with moisture monitoring were performed to investigate the infiltration process during wetting through the measured change in mechanical characteristics. Results show that penetration resistance increases in the deep layer gradually. With increasing infiltration time,the wetting front keeps moving downward, and its range becomes wider. A slight increase of the penetration resistance in the shallow layer(d ≤ 17.5 mm) is observed. However, the penetration resistance in the middle layer(22.5 mm ≤ d ≤ 32.5 mm) decreases firstly before a slight increase. In the deep layer(d ≥ 37.5 mm), the penetration resistance decreases continuously during infiltration. Based on the measured water content profile during infiltration, it is found that the evolution of soil mechanical characteristics is fully responsible by the infiltration-induced re-distribution of water content along depth. Generally, the penetration resistance decreases exponentially with increasing water content in the soil. When the water content is low, wetting can weaken soil strength significantly, whereas this effect diminishes when the moisture surpasses a certain threshold. The results highlight that the penetration curves and water content profile show close inter-dependency and consistency, which verifies the feasibility of using micro-penetration to investigate rainfall infiltration and wetting process in surface soil layer or laboratory small-scale soil samples. This method enables fast, versatile and high-resolution measurements of infiltration process and moisture distribution in soil.

Hydro-mechanical response with respect to the air ventilation for water filtration in homogeneous soil

When water penetrates into soil,interstitial air can become trapped by the infiltrating water.Neglecting the effect of air ventilation could cause deviations in the predicted pore water pressure and the associated effective stress.This study aims at the effect of air ventilation on the coupled hydro-mechanical responses in homogeneous soil during infiltration.A schematic concept of infiltration conditions(open-and closed-valve)in homogeneous soil is proposed for investigating their impacts on the pore water pressure and effective stress.Experiments of vertical soil column filled with Ottawa sand(ASTM C77820/30)were designed for two types of air ventilation(namely,open and closed infiltration).The evolution of pore water pressure at the cylinder bottom was recorded,and served as a benchmark problem for evaluating the coupled hydro-mechanical response.Coding with the commercial software,GeoStudio,was employed for the dynamic behaviors of pore-water and-air pressures as well as the evolving effective stress.It was found in both the experiments and numerical investigations that the infiltration condition plays a crucial role for the ascending rate of pore water pressure as well as the associated effective stress.These results illustrate the inevitable impacts of the air ventilation conditions on the mechanical properties of the soil during infiltration.