Changes In Hydraulic Properties Research Articles

Numerical Simulation of Rainfall-Induced Erosion on Infiltration and Slope Stability

In slopes where a mixture of coarse and fine particles is present, the infiltration of rainfall can cause the migration of fine particles. This migration alters the hydraulic properties of the soil and has implications for slope stability. In this study, the slope under investigation is a tailings dam composed of loosely consolidated soil with a wide particle size distribution. Due to rainfall infiltration, fine particles tend to migrate within the voids of the coarse particle framework, leading to changes in hydraulic properties and inducing slope instability. The classical internal erosion constitutive model, known as the Cividini and Gioda erosion criterion, is commonly used to predict the behavior and effects of fine particle erosion in geotechnical engineering. However, certain parameters in this erosion criterion equation, such as long-term density, are challenging to obtain through experiments. To investigate the coupled evolution of seepage and erosion within landfill slopes under the influence of rainfall infiltration and to understand the mechanisms of slope instability, this research assumes the erosion of fine particle suspension and adopts the Worman and Olafsdottir erosion criterion to establish a coupled model of unsaturated seepage and internal erosion. The developed model simulates the coupled response of seepage and erosion in unsaturated landfill slopes under three different rainfall intensities. It is then combined with the infinite slope model to quantitatively analyze the impact of fine particle migration on soil permeability and slope stability. The numerical simulations provide the following findings: The Worman and Olafsdottir erosion criterion, unlike the Cividini and Gioda erosion criterion, only requires the determination of the soil’s gradation curve to estimate the erosion rate. Internal erosion primarily occurs within the leading edge of moisture penetration, accelerating the advancement of the wetting front and reducing slope stability. When the rainfall intensity is lower than the saturated permeability coefficient, the influence of internal erosion can be disregarded. However, under rainfall intensities equal to or greater than the saturated permeability coefficient, considering internal erosion results in a difference in the depth of the wetting front of up to 34.2 cm after 6 h in the R2 scenario. The safety factor without considering internal erosion is 1.12, whereas considering internal erosion yields safety factors between 1.08 and 1.09. In the R3 scenario, the difference in the depth of the wetting front reaches 53.8 cm after 6 h, with a safety factor of 1.12 without considering internal erosion and safety factors between 1.06 and 1.07 when considering internal erosion.

Cross-well multilevel pumping tests – A novel approach for characterizing the changes of hydraulic properties during gas storage in shallow aquifers

Gas leakage may occur in pipelines or subsurface storage sites. The appearance of a new gas phase in the geological subsurface can impede groundwater flow and increase total media compressibility, with both effects increasing with larger gas phase volumes. In near-surface aquifers, these changes can be assessed by determining changes in hydraulic conductivity and specific storage using conventional pumping tests. These allow an observer to detect and delineate the occurrence of a new gas phase. In this study, this idea was tested using methane gas and hydrogen gas injection experiments, which were conducted at the TestUM field site in Germany. A series of multi-level cross-well and depth-oriented pumping tests were conducted before and after injection of the hydrogen and methane gas phases. The results show a significant decrease of hydraulic conductivity and a significant increase of specific storage estimated from the drawdown data due to the presence of the gas phases. Hydraulic conductivity and specific storage were found to vary by up to 86% and 65,900% respectively after gas phase injection, while repeated baseline tests yielded a variation of less than 28% and 340% prior to gas phase injection. These changes are correlated, and their occurrence and magnitude can be used to roughly locate the gas phases. As only standard hydrogeological field equipment and evaluation techniques are required, this approach represents a new monitoring option to detect an intruding gas phase in near-surface aquifers.

Studying The Effects of Forest Fire on Consistency Limits of Sandy Soils: A Case Study, Kozağaç, Muğla

The changes in physical, chemical, and mineralogical properties of topsoil after forest fires and their relevancy with erosion risk have been so far studied for different geographical regions and ecosystems. It is well known that the risk of erosion increases due to the loss of shear strength and the changes in hydraulic properties after the fire. The consistency limits are strongly related to the shear strength of the soil. Nevertheless, a few studies evaluated the consistency limits of naturally burned soils. In addition, determination of the consistency limits of sandy soils can be very challenging owing to their low plasticity. The temperatures produced by the forest fire that occurred on the left flank of an irrigation dam in Muğla, Kozağaç village affected the topsoil. Hence, grain size distribution, soil organic content (SOM), and Atterberg limits of 24 soil specimens collected from the burned and unburned locations were studied. It was found that the grain size distribution of the burned soil did not significantly change whereas clay content and Atterberg limits increased, and SOM decreased. The methodology followed in this study and the results can be served as a base for future studies of fire effects on sandy soils.

Effects of water and salt stresses on plant growth and xylem hydraulic properties of tomato.

Xylem is the main tissue for water transport in plants, and the changes of hydraulic properties in which would affect plant water relations and fruit water accumulation. It remains unclear regarding the responses of xylem anatomy and hydraulic properties to water and salt stresses in tomato plants and their relationships with plant growth and fruit water content. We conducted a pot experiment in a greenhouse to investigate the responses of plant growth, fruit water content, and xylem hydraulic properties of a cherry tomato (Hong Baoshi) and a medium-fruited tomato (Beifan 501). There were three treatments, control with a soil water content (θ) of 75%-95% of field capacity (FC) and an initial electrical conductivity (EC) of 0.398 dS·m-1; water stress with θ of 75%-95% of FC (before flowering) and 45%-65% of FC (from flowering until maturity) and an EC of 0.398 dS·m-1; and salt stress with θ of 75%-95% of FC and an EC of 1.680 dS·m-1. Results showed that water and salt stresses decreased the cross-sectional stem area and xylem vessel diameter by 22.0%-40.7% and 10.0%-18.3%, respectively, and reduced the specific hydraulic conductivity of stem and the hydraulic conductivity of peduncle by 8.8%-41.1% and 12.9%-28.4%, respectively. Those changes inhibited plant growth and reduced aboveground fresh weight, fruit size, fresh weight and water content, with a more pronounced negative effect in the medium-fruited tomato. More-over, fruit water content was positively correlated with the specific hydraulic conductivity of stem and peduncle. In conclusion, water and salt stresses would inhibit plant growht, fruit fresh weight, and consequently tomato yield, due to their negative effects on xylem hydraulic properties of the tomato plant. Medium-fruited tomatoes are more susceptible to water and salt stresses than cherry tomatoes.

Relating Immediate Changes in Bulk Density to Changes in Hydraulic Properties on a Silty Clay Loam Under Different Tillage Systems in the Czech Republic

Relating Immediate Changes in Bulk Density to Changes in Hydraulic Properties on a Silty Clay Loam Under Different Tillage Systems in the Czech Republic

Application of induced polarization imaging across different scales to understand surface and groundwater flow at the Hofermuehle landslide

Understanding changes in hydraulic properties of the subsurface is critical to delineate areas susceptible for groundwater accumulation and the triggering of landslides. Laboratory studies have demonstrated the possibility to estimate the hydraulic conductivity from induced polarization (IP) measurements. However, to-date only rare studies have been applied at the field scale and none has evaluated the frequency-dependence in field IP imaging data. We show that the application of petrophysical models linking hydraulic conductivity (K) and IP at 1 Hz, resolves for the same estimations from frequency-domain measurements as well as from time-domain IP. Moreover, our IP images reveal an evident frequency-dependence between 0.1 and 240 Hz in the electrical properties, which is also observed in lab measurements conducted in soil samples. To account for this, we fit a Cole-Cole model to our multi-frequency IP results and evaluate models linking K and the normalized chargeability, gaining a subsurface model of the hydraulic conductivity with enhanced resolution. Our results reveal clear variations at depth in the electrical conductivity and polarization associated with the presence of a plane of instability and the sliding plane. We also resolve lateral changes delineating areas with K below 10-6 m/s, which may act as barriers for groundwater flow. To evaluate our results we also estimate the hydraulic conductivity using a joint inversion algorithm that directly solves for porosity and saturation through the simultaneous inversion of seismic refraction and electrical resistivity tomography data. We observed consistent hydraulic conductivity images obtained through the inversion of the IP data and the joint inversion, with such model being in agreement with existing information of the site. We resolve a 3D model of the hydraulic conductivity at the Hofermuehle landslide from IP data that reveals the geometry of areas with poor drainage that may lead to land sliding.

Using petrographically observable microstructure to predict hydromechanical changes in a complex siliciclastic storage site during CO2 injection

The complex geologic history of sandstone CO2 storage sites can result in separate rock units that control chemomechanical weakening. Here we document the chemical and mechanical changes that may occur during CO2 injection operations, linking potential mechanical instability to diagenesis and burial history. Using Southwest Partnership Morrow B sandstone, we combined flow of either a CO2-rich formation water or formation water through experimental cores followed by four indirect tensile strength tests per sample on siderite-chlorite- and kaolinite-cemented lithofacies. Coupled experiments were informed using petrography and µ-X-ray computed tomography. We found alteration of ankerite, siderite, chlorite, and calcite cement, and precipitation of an iron-rich phase in reacted samples. Alteration caused changes in hydraulic properties and elastic velocity, but no change in tensile strength. Tensile strength was maintained due to the low abundance and non-load-bearing texture of ankerite, the stability and precipitation of siderite prior to compaction, and the precipitation of calcite both before and during/after compaction. Results suggests that alteration of the Morrow B sandstone due to CO2 injection will enhance permeability near the wellbore with no increased risk of tensile failure, although intervals cemented with early diagenetic carbonate cement may be more susceptible to compaction. No weakening supports the long term sustainability of CO2 injection for EOR and climate change mitigation in the Farnsworth Unit.

Solid grain migration on hydraulic properties of fault rocks in underground mining tunnel: Radial seepage experiments and verification of permeability prediction

When fault fracture zones are encountered in the mining tunnel excavation, the water-conducting pathway is easily formed by the granular structure of the broken surrounding rock, probably resulting in water inflow hazards. Therefore, the configuration and hydrological characteristics of existing faults are key factors for the safe mining tunnel construction. In this paper, one-dimensional (1D) radial seepage experiments were carried out under variable grain size distribution (GSD) and water pressure (WP). Hydraulic properties were investigated, including porosity and permeability under the 1D radial grain migration. Experimental results show that the permeability and porosity increase with time, and the occurrence process of water inflow can divide into four stages, including the rapid increase, decelerated increase, slow climbing, and stable period. After the seepage experiment, the porosity of the sample increases gradually from the top to the bottom and reaches the maximum at the lowermost part (outlet), indicating that the spatial distribution of the porosity exhibits the non-uniform property. Through comparisons of grain migration under different conditions, it is concluded that, with the decrease of GSD and the increase of WP, more severe fine grain migration can be occurred, leading to great changes in hydraulic properties. In addition, three prediction models were verified by the testing results, and Carman-Kozoeny model shows the highest accuracy. In the same predictive model, if a sample has a smaller grain migration capacity, then there is a higher prediction accuracy of the sample. By means of Carman-Kozoeny model, it is predicted that there is a higher final permeability in the position closer to the water outlet. Based on the research results, a series of strategies were proposed to prevent and control water inflow in fault rocks.

Modeling of biofilm growth and the related changes in hydraulic properties of porous media

Pore blocking is considered to dominate the hydraulic conductivity in solute transport processes. Biomass accumulation is effective in reducing the hydraulic conductivity of porous medium. In this paper, the sphere model and the cut-and-random-rejoin-type model were adopted to establish mathematical equations for hydraulic characteristics of porous media caused by biological clogging. A new mathematical correlation was proposed to address the coupling effect of hydraulic, biofilm growth fields on the basis of thorough review on Kozeny-Carman equation relevant researches. The time-dependent solution were investigated with the consideration of a series of different model factors. The study found that there are similar phenomena both in the sphere model and in the cut-and-random-rejoin-type model. When the pores of the porous media are filled with biofilms, the pore volume is continuously reduced, and the porosity of the porous media continues to decrease. Macroscopically, it is manifested as a decrease in permeability. The model image analysis shows that growth of biofilm in a porous medium reduces the total volume and the average size of the pores and directly affects the permeability of pores. But this effect is not permanent, the pores will not be completely blocked, and the permeability will not drop to zero.

Greater, but not necessarily better: The influence of biochar on soil hydraulic properties

AbstractBiochar is recommended as a soil amendment for its positive influence on soil hydrological properties, which results in improved soil fertility and crop yield. Much research in the last decade has been conducted in field and laboratory conditions on the effect of biochar on the hydraulic properties of soil. However, reported results in the literature are substantially inconsistent. Here we performed a meta‐analysis to capture the variations in change in hydraulic properties of arable soils after application of different rates of biochar. The meta‐analysis revealed that high biochar rates (>50 t ha−1) compared to low rates (<20 t ha−1) significantly improved dry bulk density in sandy and clay soils, in field and laboratory experiments. However, field capacity only improved in laboratory experiments on sandy soils. The plant available water, permanent wilting point and saturated hydraulic conductivity did not significantly increase at high rates of biochar application compared to the low rates when applied to different types of soils in both field and laboratory experiments. We discuss possible reasons for this, including hydrophobicity of the biochar with future research directions. We concluded that the current evidence does not support the notion that the application of biochar improves soils' available water capacity.Highlights Meta‐analysis clarifies the influence of biochar on soil hydraulic properties. Biochar addition at higher rates only improves the water holding capacity of sandy soils. Biochar types and pyrolysis temperatures do not influence soil hydraulic properties. The efficiency of biochar may depend on its pore size distribution and hydrophobicity.

Developmental and water deficit-induced changes in hydraulic properties and xylem anatomy of tomato fruit and pedicels.

Xylem water transport from the parent plant plays a crucial role in fruit growth, development, and the determination of quality. Attempts have been made to partition the hydraulic resistance of the pathway over the course of development, but no consensus has been reached. Furthermore, the issue has not been addressed in the context of changing plant and fruit water status under water deficit conditions. In this study, we have conducted a rigorous investigation into the developmental changes that occur in the hydraulic properties of tomato fruits and their pedicels under well-irrigated and water deficit conditions, based on hydraulic measurements, fruit rehydration, dye-tracing, light and electron microscopy, and flow modeling. We found that a decline in water transport capacity during development did not occur in the xylem pathway leading up to the fruit, but within the fruit itself, where the effect might reside either inside or outside of the xylem pathway. The developmental pattern of the hydraulic resistance of the xylem pathway was not significantly influenced by water deficit. The changes in xylem flow between the fruit and the parent plant resulting from the reduced driving force under water deficit could explain the reduced accumulation of water in the fruit. This study provides new insights that aid our understanding of xylem water transport in fleshy fruits and its sensitivity to water deficit from a hydraulic perspective.

How to relevantly characterize hydraulic properties of saline and sodic soils for water and solute transport simulations

Proper sets of soil hydraulic parameters are important for modeling water flow and solute transport. Using field saline water and laboratory tap water, this study systematically analyzed and compared laboratory saturated hydraulic conductivity, Kls and soil water retention curve, SWRC of saline soil within three soil multi-layered profiles to find out the adequate initial hydraulic parameter set of a hydrological model. Falling and constant head methods were applied on three undisturbed samples per pedogenic horizon. SWRC were established on the same samples, using both saline and tap water. Results showed the spatial variability of hydraulic properties in vertical and horizontal dimensions when comparing soil profiles' properties. The constant head method with saline water resulted in the highest Kls values followed by the falling head method with saline water, the constant head method with fresh water, and the falling head method with fresh water. The differences in Kls were up to two orders of magnitude when comparing all datasets. Fresh water reduced soil water retention significantly. A significant correlation between the hydraulic properties and some physical and chemical properties suggests that the effects of soil texture, structure, calcium carbonate and gypsum content, and CEC (clay mineralogy) were larger than those of salt content. The change in hydraulic properties and the dependency on the procedure use may be attributed to aggregate breakdown and plugging of macropores, clay heterogeneity and dispersion, calcium carbonate and gypsum dissolution, all damaging soil structure. Simulation runs illustrated that hydraulic properties obtained with saline water resulted in better model performance than when using the conventional procedures with fresh/tap water. A proper set of initial hydraulic parameter values is an important step in model calibration and thus must be characterized correctly. Therefore, to hydraulically characterize saline soil, procedures should be standardized. Moreover, the approach and results of this study may provide a reference for characterization of soil hydraulic properties of saline and sodic soils effectively.

Managing biofilm growth and clogging to promote sustainability in an intermittent sand filter (ISF)

The sustainability of rural sanitation includes the long-term welfare of both rural and urban societies. As a commonly used rural sanitation technology, operation of intermittent sand filters (ISF) is impacted by biofilm clogging inside the ISF. In this study ISF performance is studied at low hydraulic loading rates (HLR) to explore the interaction between biofilm growth and wastewater treatment efficiency. CW2D/HYDRUS, a simulation model which does not include media hydraulic property changes caused by biofilm growth, is utilized as a numerical control to contrast the effects of biofilm growth inside an experimental ISF. A paired experiment with simulation demonstrate that biofilm clogging comprised dominantly of heterotrophs occurred in the top layers of the ISF. Lowered HLR slows clogging development but not final clogging extent. The biofilm clogging development zone offers adequate removal of applied biodegradable COD and NH4+ − N. However, the spatial distribution of heterotrophs and biodegradable COD does not match the denitrification requirement of the resulting NO3− − N. A simultaneous nitrification and denitrification (SND) potential is manifested in the clogging development zone, but lowered HLR reduces media moisture level to a less favorable level for denitrification. Furthermore, slowed water movement under lower HLR aggravates the accumulation of NO3− − N, which can potentially result in counterproductive salt accumulation. Since biofilm growth is a natural and self-adaptive response to wastewater application, this study suggests accepting limited, managed biofilm growth and clogging in ISFs. In addition, this study calls for further research to manage biofilm growth and clogging for long-term ISF sustainability.

Permeability Enhancement From a Hydraulic Stimulation Imaged With Ground Penetrating Radar

AbstractWe present evidence of permeability enhancement from hydraulic stimulation experiments in fractured crystalline rock. A total of 9.49 m3 was injected in two fractured intervals of a 300 m long borehole. Repeated Ground Penetrating Radar (GPR) measurements in the same borehole were carried out prior to and following the stimulation. The initial measurements revealed fractures in the vicinity of the borehole that could be traced up to distances of 50 m away. The data measured post‐stimulation were used in a difference‐imaging approach to illuminate changes in the GPR reflections caused by the stimulations. The changes delineate the enhancement of a large and complex fracture network. These changes likely correspond to changes in local aperture, thus permeability. Our results indicate that borehole GPR yields unique information on subtle changes in hydraulic properties within a relatively large volume and provides a new perspective on the characterization and monitoring of deep geothermal reservoirs.

Effect of salinity on soil structure and soil hydraulic characteristics

Revealing the influences of soil salinity on soil structure and hydraulic properties contributes to understanding the mechanism of salinity restraining rehabilitation of saline sodic soil in coastal area. After being passed through a 1 mm sieve, silt loam and silty clay were irrigated with saline water to achieve different soil salinities to highlight the effect of irrigation salinity on aggregate formation from primary particles. Three irrigation events with different saline water were conducted in the same 2 mo interval in soil columns; the soil columns were subjected to natural evaporation during the interval. The soil salinity, soil structure, soil–water characteristic curve, and saturated hydraulic conductivity (Ks) results were determined after the end of the third drying subprocess. The results showed that the proportion of water-stable macroaggregates (0.25–2 mm) in the silt loam and silty clay increased as the soil salt content (SSC) increased. Under the same matric suction, the retention capacity and plant-available water capacity (PAWC) of the silt loam first increased and then decreased, with the SSC increasing to a maximum of approximately 14.5 g kg−1. The retention capacity of the silty clay increased with the SSC, whereas the PAWC decreased with the SSC. The Ksof the silt loam increased with SSC. This study reveals the effects of soil salinity on aggregate formation from primary particles in wetting–drying cycles and describes the corresponding changes in hydraulic properties, which influence the rehabilitation of saline sodic soils in coastal areas.

Change in hydraulic properties of the rhizosphere of maize under different abiotic stresses

Root growth alters the rhizosphere thereby affecting root uptake of water and nutrients. However, the influence of abiotic stress on this process is poorly understood. In this study we investigated the effects of water and salinity stresses (both in isolation and combined) on maize (Zea mays L.). Seedlings were grown in pots packed with a loamy sand soil for two weeks and then subjected to water and salinity stresses, together with an unstressed control. After an additional two weeks, plants were removed from the pots and the soil aggregates adhering to the roots were collected and scanned using X-ray Computed Tomography. The ability of the aggregates to conduct water was calculated from pore-scale simulation of water flow using the lattice Boltzmann method. It was found that both water and salinity stresses reduced the permeability of the rhizospheric aggregates, although the reduction under salinity stress was more significant than under water stress. Combining water and salinity stresses reduced the permeability of the rhizosphere by one order in magnitude compared to the unstressed rhizosphere. Abiotic stresses work with root-induced activity to reshape the rhizosphere. As water and nutrients need to pass through the rhizosphere before being taken up by roots, understanding such rhizosphere changes has an important implication in plant acquisition of soil resources.

Strontium retention of calcium zirconium aluminate cement paste studied by NMR, XRD and SEM-EDS.

This work concerns the hydration mechanism of calcium zirconium aluminate as a ternary compound appearing in the CaO-Al2O3-ZrO2 diagram besides the calcium aluminates commonly used as the main constitutes of calcium aluminate cements (CACs). Moreover, a state-of-the-art approach towards significant changes in hydraulic properties was implemented for the first time in this work, where the effect of structural modification on the hydration behavior of calcium zirconium aluminate was proved by XRD, 27Al MAS NMR and SEM-EDS. The substitution of Sr2+ for Ca2+ in the Ca7ZrAl6O18 lattice decreases the reactivity of Sr-substituted Ca7ZrAl6O18 in the presence of water. Since the original cement grains remain unhydrated up to 3 h (Ca7ZrAl6O18) or 72 h (Sr1.25Ca5.75ZrAl6O18) of curing period in the hardened cement paste structures, strontium can be considered as an inhibition agent for cement hydration. The complete conversion from anhydrous 27AlIV to hydrated 27AlVI species was achieved during the first 24 h (Ca7ZrAl6O18) or 7 d(Sr1.25Ca5.75ZrAl6O18) of hydration. Simultaneously, the chemical shift in the range of octahedral aluminum from ca. 4 ppm to ca. 6 ppm was attributed to the transformation of the hexagonal calcium aluminate hydrates and Sr-rich (Sr,C)3AH6 hydrate into the cubic phase Ca-rich (Sr,C)3AH6 or pure C3AH6 in the hardened Sr-doped cement paste at the age of 7 d. The same 27Al NMR chemical shift was detected at the age of 24 h for the reference hardened undoped Ca7ZrAl6O18 cement paste.

Temporal changes of hydraulic properties of overburden aquifer induced by longwall mining in Ningtiaota coalfield, northwest China

Characterizing the mining induced temporal changes of hydraulic properties of the overburden aquifer is significant for groundwater resource protection. Conventional hydrogeological methods (e.g. hydraulic test, physical model test and numerical simulation) of determining hydraulic properties of the overburden aquifer cannot quantitatively analyze the temporal changes of the hydraulic properties induced by mining disturbances. This paper demonstrates a quantitative determination for the temporal changes of parameters (compressibility, porosity and specific storage) in the overburden aquifer influenced by the mining processes, based on in-situ continuous measurements of groundwater level that was affected by earth tide, atmospheric loading and mining disturbances. The results showed that, when working face reached a certain distance (127 m from borehole J6 in this study), those parameters (compressibility, porosity and specific storage) of overburden aquifer began to show gradual decrease, with approximately up to two order of magnitudes. After the working face passed by the observation borehole J6, those properties of overburden aquifer recovered in about 80 days, which might reflect the characteristic of elastic deformation of the aquifer. Those findings of the mining induced parameters’ temporal changes could improve our understanding of the mining effects on aquifer system and could be meaningful in groundwater resource protection.

The Mechanism of Changes in Hydraulic Properties of Populus euphratica in Response to Drought Stress

Stable hydraulic conductivity in forest trees maintains the survival of trees which contribute to productivity in forest ecosystems. Drought conditions break down this relationship, but the mechanisms are poorly known. To increase the understanding of the mechanism of hydraulic characteristics during drought, we determined hydraulic parameters in Populus euphratica Oliv. (P. euphratica) in a time-series of drought using a high-pressure flow meter. We found that P. euphratica could enhance hydraulic transport in severe drought stress under a threshold of soil water content. Drought-induced loss of hydraulic conductance could seriously impair water transport capacity. The soil water content of about 4.5% in the rhizosphere could lead to canopy mortality yet maintain live roots. Hydraulic conductance could be changed under drought stress as a consequence of changes in the anatomical structure and physiology. Furthermore, there was also a trade-off between hydraulic efficiency and safety. The consideration of hydraulic efficiency was first within the range of hydraulic safety limit. Once the hydraulic safety limit was reached, safety would be taken as the first consideration and hydraulic efficiency would be reduced. Research on the mechanism of hydraulic properties in riparian plants in arid areas provides a scientific basis for riparian forest restoration.

Effects of Early Structural Changes of Engineered Soils on Green Roof and Bioretention Performance

Engineered soils play an important role in urban hydrology e.g. in the functioning of green roofs and storm water bioretention beds. Water infiltration, colloid transport and heat transport are affected by changes in pore system geometry particularly due to development of macropores and clogging by particles. The rate of pedogenesis is often faster than in natural soils due to higher loads of particles as well as by extreme water regimes. In the presented project we assess the temporal changes of hydraulic properties of engineered soils in typical bioretention beds and green roofs by conducting field scale experiments. The aim is to elucidate changes in hydraulic properties by studying the structural changes of soils at the microscale by invasive and noninvasive methods. The outcomes of the research will lead to improved design and management procedures for green roofs and bioretention beds.