spatial and temporal distribution of cyanobacterial soil crusts in the kalahari implications for soil surface properties localised patterns of erosion and deposition in vegetated semi arid rangelands have been shown to influence ecological change and biogeochemical cycles in the flat vegetated kalahari rangelands of southern africa the factors regulating erodibility of the fine sand soils and the erosivity of wind regimes require further investigation this paper reports on the spatial and temporal patterns of cyanobacterial soil crust cover from ten sites at five sampling locations in the semi arid kalahari and discusses the likely impact on factors regulating surface erodibility and erosivity cyanobacterial soil crust cover on kalahari sand varied between 11 and 95 of the ground surface and was higher than previously reported cover was inversely related to grazing with the lowest crust cover found close to boreholes and the highest in the game reserve and wildlife management zone in grazed areas crusts form under the protective canopies of the thorny shrub acacia mellifera fenced plot data showed that crusts recover quickly from disturbance with a near complete surface crust cover forming within 15 months of disturbance crust development is restricted by burial by wind blown sediment and by raindrop impact crusts had significantly greater organic matter and total nitrogen compared to unconsolidated surfaces crusts also significantly increased the compressive strength of the surface and thus decreased erodibility and changed the surface roughness establishing exactly how these changes affect aeolian erosion requires further process based studies the proportion of shear velocity acting on the surface in this complex mixed bush grass crust environment will be the key to understanding how crusts affect erodibility

evaluation of surficial stability for homogeneous slopes considering rainfall characteristics shallow slope failures in residual soil during periods of prolonged infiltration are commonly occurring in the world this study examines an infinite slope analysis to estimate the influence of infiltration on surficial stability of slopes by the limit equilibrium method an approximate method that accommodates the boundary condition of a uniform rainfall has been proposed to evaluate the likelihood of shallow slope failure that is induced by a particular rainfall event the method based on the mein and larson model which provides an explicit solution for preponding infiltration has been applied to various types of soil having measured unsaturated hydraulic properties to compare results with those obtained from the approximate method a series of numerical analyses were carried out according to the results with the use of properly estimated input parameters the approximate method was found to give results that compare reasonably well with those of more rigorous finite element analyses

isotopic identification of co2 from a deep origin in thermomineral waters of southeastern spain abstract the overexploitation of the alto guadalentin detrital aquifer has led to an unusually high gas content in the waters which is released as the hydrostatic charge decreases the predominant gas proved to be co 2 isotopic studies show that 18 o values are in the range 8 8 to 6 5 smow d ranges between 45 and 40 smow excess deuterium lies between 8 0 and 27 4 and 13 c values lie between 8 1 and 3 8 pdb this reveals that there is an enrichment in 18 o as well as mixing processes between meteoric and deep circulating waters tectonic and seismotectonic studies indicate crustal thinning in the studied region and numerous normal reverse and strike slip faults marked by positive thermal anomalies there is also evidence of present day tectonic activity

microbiotic soil crusts in the sahel of western niger and their influence on soil porosity and water dynamics abstract microbiotic soil crusts are common features of the surface of fallow land in western niger we investigated the interaction between these microbial covers and the porosity and water dynamics of soils at the surface of a sahelian landscape the soil pore system was examined by microscopic observations and mercury porosimetry the soil water retention capacity was measured using a richard pressure membrane apparatus runoff measurements were performed in situ at a 1 m2 scale under natural rainfall samples with dense cyanobacterial cover had microbially originated pores ranging from 0 04 and 50 m in size these samples also showed higher total soil porosity and retained two to four times more water than samples with thin microbial cover these properties are closely related to the hydrophobic nature of cyanobacterial components final runoff values obtained on densely covered surfaces were significantly higher compared to those measured on surfaces with thin microbial cover due to the geometry of the microbially originated pore system and its functioning

landsliding in partially saturated materials 1 rainfall induced landslides are pervasive in hillslope environments around the world and among the most costly and deadly natural hazards however capturing their occurrence with scientific instrumentation in a natural setting is extremely rare the prevailing thinking on landslide initiation particularly for those landslides that occur under intense precipitation is that the failure surface is saturated and has positive pore water pressures acting on it most analytic methods used for landslide hazard assessment are based on the above perception and assume that the failure surface is located beneath a water table by monitoring the pore water and soil suction response to rainfall we observed shallow landslide occurrence under partially saturated conditions for the first time in a natural setting we show that the partially saturated shallow landslide at this site is predictable using measured soil suction and water content and a novel unified effective stress concept for partially saturated earth materials

wind erodibility of soils at fort irwin california mojave desert usa before and after trampling disturbance implications for land management recently disturbed and control i e less recently disturbed soils in the mojave desert were compared for their vulnerability to wind erosion using a wind tunnel before and after being experimentally trampled before trampling control sites had greater cyanobacterial biomass soil surface stability threshold friction velocities tfv i e the wind speed required to move soil particles and sediment yield than sites that had been more recently disturbed by military manoeuvres after trampling all sites showed a large drop in tfvs and a concomitant increase in sediment yield simple correlation analyses showed that the decline in tfvs and the rise in sediment yield were significantly related to cyanobacterial biomass as indicated by soil chlorophyll a however chlorophyll a amounts were very low compared to chlorophyll a amounts found at cooler desert sites where chlorophyll a is often the most important factor in determining tfv and sediment yield multiple regression analyses showed that other factors at fort irwin were more important than cyanobacterial biomass in determining the overall site susceptibility to wind erosion these factors included soil texture especially the fine medium and coarse sand fractions rock cover and the inherent stability of the soil as indicated by subsurface soil stability tests thus our results indicate that there is a threshold of biomass below which cyanobacterial crusts are not the dominant factor in soil vulnerability to wind erosion most undisturbed soil surfaces in the mojave desert region produce very little sediment but even moderate disturbance increases soil loss from these sites because current weathering rates and dust inputs are very low soil formation rates are low as well therefore soil loss in this region is likely to have long term effects published in 2006 by john wiley sons ltd

stratigraphy and spatial and temporal paleoclimatic trends in southeastern eastern european loess paleosol sequences abstract the loess paleosol sections batajnica stari slankamen serbia mircea voda romania and stary kaydaky ukraine are presently located in areas of different types of steppe and are highly sensitive for recording climatic changes a stratigraphy for these three southeastern eastern european sections is presented based on pedostratigraphy and correlation of recently obtained susceptibility records with susceptibility data of other sections of the area koriten mostistea vyazivok of the chinese loess plateau and with the benthic 18o record of odp 677 six pedocomplexes were studied at the serbian and romanian sections and five at the ukrainian section the oldest are related to marine isotope stage mis 17 batajnica stari slankamen and mircea voda and mis 13 15 stary kaydaky some points concerning the existing loess chronostratigraphies of bulgaria ukraine and china are discussed comparative study of the profiles allows the tracing of paleoclimatic and paleoenvironmental changes in southeastern eastern europe in time and space reconstruction of paleoprecipitation based on susceptibility rainfall relationships and calculations of sedimentation rates are evaluated

effects of geology and human activity on the dynamics of salt water intrusion in three coastal aquifers in southern spain mathematical modelling of salt water intrusion processes in three aquifers on the southern coast of spain rio verde rio velez and castell de ferro reveals that although all three systems are subject to the same climate and seasonal over exploitation geological and human factors have very different effects on the dynamics of contamination in the rio verde aquifer the most important influence is the high volume of extractions occurring during the dry season in rio velez the intrusion is strongly controlled by infiltration of water from the river to the aquifer and in the castell de ferro system an intensely karstified carbonate massif lying in contact with both the sea water and the detrital aquifer represents the main entrance point for influx of sea water and subsequent washing of the aquifer we have undertaken a mathematical simulation of various possible measures to counteract intrusion according to the specific characteristics of the process in each aquifer these measures include artificial recharge use of natural recharge from the river as a hydraulic barrier and the construction of a low permeability barrier

luminescence chronology of the loess palaeosol sequence toshan northern iran a highly resolved climate archive for the last glacial interglacial cycle loess palaeosol sequences are highly resolved archives for palaeoenvironmental reconstruction and build an important link to correlate european and central asian loess sequences for the loess palaeosol sequence at toshan northern iran a luminescence based chronological framework was established the timing of dust accumulation and soil formation was investigated and thereby information on changes in palaeoenvironmental conditions in the region obtained for luminescence dating the 4e11 mm grain size fraction was used and the pirir290 approach was applied to polyminerals tests concerning bleachability dose recovery and anomalous fading were conducted the results show that residual doses have only minor influence on the determination of the equivalent dose the eemian mis 5e soil seems to be preserved but a chronological classification based on luminescence ages for this soil remains difficult the pirir290 age estimates from the lower part of the profile range from 104 9t o 127 8 ka lumi nescence ages from the central profile part point to an increase in dust accumulation starting around the mis 4 mis 3 transition furthermore a chronological framework for interstadial soils was developed indicating e g soil formation at around 40 ka during mis 3 and 26 ka during mis 2 the top part of the profile was dated to about 22 ka the age estimates show that the toshan loess profile is a highly resolved loess record providing a valuable climate archive for the last glacialeinterglacial cycle reflecting several climatic shifts represented by dust accumulation or enhanced degrees of soil formation stadials and interstadials

geological hazards in loess terrain with particular reference to the loess regions of china abstract the considerable morphodynamic energy provided by the continuing tectonic evolution of asia is expressed in high erosional potentials and very high rates of sediment production that make this continent unequalled as a terrestrial source of primary silt many of these environments are hazardous threatening human occupation health and livelihood especially in regions of dense population such as the loess lands of north china dry loess can sustain nearly vertical slopes being perennially under saturated however when locally saturated it disaggregates instantaneously such hydrocompaction is a key process in many slope failures made worse by an underlying mountainous terrain of low porosity rocks gully erosion of loess may yield very high sediment concentrations 60 by weight characteristic vertical jointing in loess influences the hydrology enlarged joints develop into natural sub surface piping systems which on collapse produce a loess karst terrain collapsible loess up to 20 m thick is common on the western loess plateau foundation collapse and cracked walls are common many rapid events following periods of unusually heavy monsoonal rain slope failure is a major engineering problem in thick loess terrain flow slide and spread types being common the results are often devastating in both urban and rural areas an associated hazard is the damming of streams by landslides the human population increases the landslide risk in china notably through imprudent land use practices including careless water management a number of environmentally related endemic diseases arise from the geochemistry of loess and its groundwaters including fluorosis cretinism kaschin beck disease keshan disease and goitre the chinese desert margins also have a major atmospheric dust problem the effect of such dust upon human health in these extensive regions including many large cities has yet to be evaluated but pneumoconiosis is thought to affect several million people in north and west china

shallow landslide hazard assessment using a physically based model and digital elevation data a model for the analysis of topographic influence on shallow landslide initiation is applied to an experimental mountain basin where high resolution digital elevation data are available the cordon catchment 5 km2 located in northern italy the model delineates those areas most prone to shallow landsliding due to surface topographic effects on hydrologic response the model is composed of two parts a steady state model for shallow sub surface runoff and an infinite slope coulomb failure model which assumes that the soil is cohesionless at failure an inventory of landslide scars is used to document sites of instability and to provide a test of model performance by comparing observed landslide locations with model predictions the model reproduces the observed distribution of landslide locations in a consistent way although spatial variations in soil strength and transmissivity which are not accounted for in the model influence specific distribution of landslide areas within regions of similar topographic control

analysis of rainfall induced infinite slope failure during typhoon using a hydrological geotechnical model rainwater infiltration during typhoons tends to trigger slope instability this paper presents the results of a study on slope response to rainwater infiltration during heavy rainfall in a mountain area of taiwan the green ampt infiltration model is adopted here to study the behavior of rainwater infiltration on slopes the failure mechanism of infinite slope is chosen to represent the rainfall induced shallow slope failure by combining rain infiltration model and infinite slope analysis the proposed model can estimate the occurrence time of a slope failure in general if a slope failure is to happen on a slope covered with low permeability soil failure tends to happen after the occurrence of the maximum rainfall intensity in contrast slope failure tends to occur prior to the occurrence of maximum rainfall intensity if a slope is covered with high permeability soil to predict the potential and timing of a landslide a method is proposed here based on the normalized rainfall intensity nri and normalized accumulated rainfall nar if the actual nar is higher than the nar calculated by the proposed method slope failure is very likely to happen otherwise the slope is unlikely to fail the applicability of the proposed model to occurrence time and the nar nri relationship is evaluated using landslide cases obtained from the literature the results of the proposed method are close to that of the selected cases it verifies the applicability of the proposed method to slopes in different areas of the world

intensive agriculture wetlands quarries and water management a case study campo de dalias se spain the intensive agricultural activities that have developed over the last 50 years in the campo de dalias almeria region have required large quantities of gravel and clay as the basic materials for the substrate over which crops are raised with this motive numerous gravel pits have been opened that have extracted several million cubic metres of material in recent years similar quantities of clay have been extracted from the distal sectors of the alluvial fans that descend from the sierra de gador and from within a large endoreic basin in the latter quarries some wetlands have developed probably because of the rise in the water table level in the aquifer over which they lie the gravel pits are situated in the apical sectors of the alluvial fans overlying hydrogeological units that are widely overexploited for this reason the gravel pits could be used for artificial recharge in addition to increasing the availability of water in the aquifer the risk of catastrophic flooding would also be reduced

controlling factors of hazardous debris flow in taiwan three unanticipated large scale debris flows occurred in various rock type areas during typhoons that passed through taiwan the present study identifies possible hazard factors and the triggering mechanism several investigative methods relevant to these ends were selected including aerial photo analysis discontinuity patterns and geomaterial characteristics in affected gullies conjoined discontinuities protruded to the point of material slumping and producing large volumes of debris in heavy rainfall such debris tends to flow downward into the gullies discontinuity distribution produces geometric models of potential failure in plane wedge and toppling forms these slumping materials had been introduced and had accumulated along the gullies under study rapidly increasing water pressure caused by heavy precipitation provided a powerful force that triggered the debris flow movement large masses of slurry changed into an effective cutting force to erode the sidewalls resulting in more masses of slumping materials converging in the gully and quickly funnelling down into the lower gullies

transient modeling of regional rainfall triggered shallow landslides this study investigates the transient modeling of regional rainfall triggered shallow landslides in unsaturated soil using the richards equation to model shallow landslides within a distributed regional scale framework infinite slope stability analysis coupled with the hydrological model with consideration of the fluctuation of time dependent pore water pressure and the soil water characteristic curve proposed by van genuchten was developed the validity of the proposed model is established through several test problems by comparing the numerical results with the analytical solutions a new procedure to set up wide range shallow landslide analysis and to integrate regional distribution variations for input data such as geology groundwater level hydrogeological characteristics and rainfall intensity and duration was presented the results obtained demonstrate that the computed distribution of the safety factor is consistent with the distribution of actual landslides in addition the fluctuation of pore water pressure in unsaturated soil dominates the stability of landslides during typhoons accompanied by heavy rainfall the findings observed in this study are a fundamental contribution to environmental effects for landslides in areas with higher occurrence and vulnerability to extreme precipitation

the landslide stage of the hsiaolin catastrophe simulation and validation 1 typhoon morakot struck southern taiwan in the summer of 2009 causing the most severe flooding since the 1950s in the early morning of august 9 rainfall triggered the hsiaolin landslide and the resulting debris avalanche covered the township of hsiaolin village kaohsiung around five hundred people were buried alive reconstruction of the runout of the debris avalanche would increase understanding of the large scale avalanches for future hazard mitigation purposes simulation of the debris avalanche runout can provide valuable information for this purpose a new continuum shallow water model is applied to flow over general topography the coulomb friction law is adopted the friction coefficient is initially determined by high pressure rotary shearing tests and subsequently fine tuned by an iterative procedure to minimize the difference between the simulation and the measurement the friction coefficients measured by laboratory tests are found to be in reasonable agreement with the best fit result of the simulation in addition voellmy rheology is applied but it is found that the role of the fluid viscous drag is insignificant the simulation result in the village area is further corroborated by near surface magnetic surveys these indicate that the northern part of the village is dislocated while the artifact structures of the southern part are buried near their original locations by comparing the landslide front and the flow direction of the simulation we are able to confirm as also described by survivors that the landslide swept the northern part of the village into the cishan river while the southern part was flooded subsequently by the debris from a dam breach about 20 min after the landslide

geochemical evolution and recharge of the shallow aquifers at tulul al ashaqif ne jordan shallow aquifers in the tulul ashqaf area in northeast jordan represent areas where relatively high recharge is occurring in an arid environment the significance of this phenomenon in terms of potential for water resource development in the area is related to the amount of recharge that is occurring as well as factors that may affect the water quality within the aquifers modeling of the geochemical evolution of these waters gives insight into these issues chemical data from rainwater surficial salts crushed basalt samples runoff and groundwaters were collected and the chloride mass balance approach was used by integrating these various data into geochemical mass balance models using netpath variations between rainwater chemistry the surficial salts and basalt and runoff exist suggesting various processes and sources and allows determination of the input into the groundwater geochemical modeling shows that the majority of chloride added to the groundwater after runoff events was salt from surface deposits and that the rainwater had undergone only small amounts of evaporation isotopic investigations of 18o 16o and 2h 1h of the waters confirm this result the results indicate that most of the water that falls over the study area percolates to the shallow groundwater with little evaporation less than 25 of the water evaporates prior to recharge water stored in the aquifer is affected by water rock interaction and little evidence suggests that evaporation is a factor in the chemical evolution of the waters of the shallow aquifers except in areas where salt efflorescence occurs

rainfall characteristics for anisotropic conductivity of unsaturated soil slopes the purpose of this study was to investigate the effects of the anisotropic ratio on the stability of slopes using the reliability index approach a numerical analysis of the relationship between the three rainfall patterns advanced normal and delayed and the anisotropic ratios was designed this study also considered three different soil properties sand silt and clay to simulate rain infiltration in this study probability analysis was used to evaluate the stability of unsaturated soil slopes the finite element computer program geo studio was used to simulate the process of rainwater infiltrating a slope the pore water pressure results evaluated from seepage analysis seep w were imported into the slope stability program slope w results for the anisotropic ratio of hydraulic conductivity indicate that when the anisotropic ratios become higher the reduction in the reliability index is insignificant in addition the simulation results indicated that when saturated hydraulic conductivity ks was less than rainfall intensities i the percentage probability of the occurrence of a landslide was larger than when ks was greater than i finally in the cases of anisotropic ks stability of the high ratio soil slopes was not found to be sensitive to the reliability index variation during the simulation period moreover when ks was greater than i slope stability decreased earlier than was the case in the opposite situation

biogenic soil crusts and soil depth a long term case study from the central negev desert highland wind blown soil degradation is a major problem in arid regions biogenic soil crust consists of a dense growth of many small organisms covering bare desert soil surfaces in arid regions worldwide these organisms perform essential services in the ecosystem for example soil surface stabilization and carbon and nitrogen fixation a unique service provided by biogenic crusts is the incorporation of large quantities of deposited atmospheric particles leading to a significantly enhanced rate of increase in soil depth in windy and arid environments a long term study over 42 months was conducted to investigate the contribution of a biogenic crust to the accumulation of atmospheric particles in an arid zone undisturbed and treated biogenic crusts were studied for their capacity to incorporate deposited particles atmospheric particles were found to accumulate on marble dust collectors at a rate of 120 g m 2 year 1 and on sterilized crust at a rate of 208 g m 2 year 1 while the accumulation rate on live intact crusts was 277 g m 2 year 1 suggesting a soil depth accretion rate on an undisturbed biogenic crust of 10 mm every 33 years maintenance of a healthy biogenic crust in dry land environments should therefore be a major consideration for improving soil quality and increasing soil depth in arid regions

a physically based model for the topographic control on shallow landsliding a model for the topographic influence on shallow landslide initiation is developed by coupling digital terrain data with near surface through flow and slope stability models the hydrologic model topog o loughlin 1986 predicts the degree of soil saturation in response to a steady state rainfall for topographic elements defined by the intersection of contours and flow tube boundaries the slope stability component uses this relative soil saturation to analyze the stability of each topographic element for the case of cohesionless soils of spatially constant thickness and saturated conductivity the steady state rainfall predicted to cause instability in each topographic element provides a measure of the relative potential for shallow landsliding the spatial distribution of critical rainfall values is compared with landslide locations mapped from aerial photographs and in the field for three study basins where high resolution digital elevation data are available tennessee valley in marin county california mettman ridge in the oregon coast range and split creek on the olympic peninsula washington model predictions in each of these areas are consistent with spatial patterns of observed landslide scars although hydrologic complexities not accounted for in the model e g spatial variability of soil properties and bedrock flow control specific sites and timing of debris flow initiation within areas of similar topographic control

soil water balance model for precipitation induced shallow landslides precipitation infiltration is one of the most significant triggering factors for slope failure occurrence in many places around the world knowledge of the mechanisms leading to precipitation induced slope failures is of great importance to the management of landslide hazard in this study a soil water balance model is developed to estimate soil water flux during the process of infiltration from rainfall data with consideration of storm periods and non storm periods two important assumptions in this study are given 1 instantaneous uniform distribution of the degree of saturation and 2 a linear relationship between evapotranspiration and the related degree of saturation for storm periods the brooks and corey model estimates both the soil water retention curve and soil water parameters the infiltration partition is employed by an infinite series solution of philip in conjunction with the time compression approximation for none storm periods evapotranspiration can be derived for the moisture depletion of soil water this study presents a procedure for calculating the safety factor for an unsaturated slope suffering from precipitation infiltration the process of infiltration into a slope due to rainfall and its effect on soil slope behavior are examined using modified mohr coulomb failure criterion in conjunction with a soil water balance model the results indicate that the matric suction which is closely related to slope stability is affected by the degree of saturation controlled by rainfall events

contribution of environmental isotopes to the understanding of complex hydrologic systems a case study sierra de gador se spain determining the content of 18o and deuterium in the groundwater at the southern edge of the sierra de gador between october 1991 and march 1993 has enabled identification of the flow system of the waters the recharge and mixing processes and the possible mechanisms of salinization analysis of the precipitation indicates the dominant source and direction of the air masses the local meteoric water line that is established indicates a primarily mediterranean origin for the precipitation recharging the aquifers the variation of 18o content with altitude 0 35 per mille per 100 m enables an estimation of the principal recharge area which corresponds to a zone between 1200 and 1800 m a s l 1997 john wiley sons ltd

recharge sources and hydrogeological effects of irrigation and an influent river identified by stable isotopes in the motril salobrena aquifer southern spain measurement of the stable isotopes oxygen 18 and deuterium in water is an important tool to characterize aquifer recharge sources in the driest areas of the mediterranean this application is of special interest due to the scarcity of water and the resulting common incidence of human influence on natural hydrological systems the motril salobrena detrital aquifer southern spain is a clear example of such an impact as inhabitants have designed irrigation systems and a dam was recently built across the course of the guadalfeo river which feeds the aquifer the sampling of river or ground water has allowed the determination of stable isotope contents oxygen 18 and deuterium both temporally and spatially and the relative importance of the main recharge sources in certain sectors in addition we were able to infer seasonal trends and to improve existing knowledge of the main flow paths and the position of a seasonal groundwater divide data analysis shows evaporation plays a minor role despite the high temperatures in the zone scarce rainwater influence and the overwhelming contribution of recharge from the guadalfeo river and from the carbonate aquifer escalate aquifer in contact with the motril salobrena aquifer irrigation return flow during the summer months comprises the main recharge due to the significant volumes of water that infiltrate the construction of the dam will almost certainly entail great changes in the current dynamics of the hydrogeology of the motril salobrena aquifer therefore knowledge of its behaviour is crucial in order to carry out sustainable use of its groundwater resources copyright 2011 john wiley sons ltd

saltwater intrusion into a small coastal aquifer rio verde almunecar southern spain abstract a mathematical simulation of the contact zone between fresh water and salt water in the rio verde aquifer via two models leads to a satisfactory understanding of the development over time of a saline wedge one of the two models is a finite element model taking both fluids to be immiscible the other is a finite difference model which considers the zone as being a single phase of variable density whereas the latter mass transport model gives more accurate information about the composition of the mixing zone the sharp interface model although somewhat less precise gives a 3 d picture of the freshwater saltwater contact the application of both models leads to the conclusion that the saline wedge is gradually encroaching inland

effects of degree of saturation on shallow landslides triggered by rainfall the empirical rainfall threshold concept and the physical based model are two commonly used approaches for the assessment of shallow landslides triggered by rainfall to investigate in detail the rainfall triggered shallow landslides many physical based models coupling the infinite slope stability analysis with the rainfall infiltration modeling in variably saturated soil were developed however in those physical based shallow landslide models the unit weight and the unsaturated shear strength were assumed constant rather than depending on the degree of saturation in this study the effects of the unit weight and the unsaturated shear strength as function of degree of saturation on rainfall triggered shallow landslides are examined several designed scenarios and a real case scenario are used to conduct the examinations the results show that not only the occurrence of shallow landslides but also the failure depth and the time to failure could be misassessed if the influences of degree of saturation on the unit weight and the unsaturated shear strength are neglected

numerical modelling of the potential effects of a dam on a coastal aquifer in s spain this study presents the results of a three dimensional variable density numerical modelling of the motril salobrena coastal aquifer and the possible effects of the entry into service in may 2005 of the rules dam located just 17 km from the coast present parameters of the motril salobrena aquifer show that the system s conditions are very similar to a natural regime the dam will substantially alter aquifer recharge as the entry flow through the alluvial sediments of the guadalfeo river will be entirely cut off or drastically reduced different scenarios reproducing the possible evolution of the aquifer under operation of the rules dam have been modelled in most cases results indicate that the conditions of the aquifer would worsen with a general advance of the freshwater saltwater interface the area with most risk of saltwater intrusion is the old mouth of the guadalfeo river where the mixing zone could advance 1200 m inland it is proposed that maintaining a 5 6 mm3 year 1 ecological flow in the guadalfeo river could prevent this saline advance this application demonstrates that variable density models are potentially useful tools for estimating the effects of dams on the hydrodynamic and hydrochemical conditions of a coastal aquifer copyright 2009 john wiley sons ltd

morphology and microstructure of microbiotic soil crusts on a tiger bush sequence niger sahel abstract microbiotic crusts resulting from the colonization of soil surfaces by communities of micro organisms dominated by cyanobacteria eucaryotic algae or lichens are widespread in arid and semi arid regions in the tiger bush of niger sahel microbiotic crusts occur in bare bands between densely vegetated bands the tiger bush soils are sandy loams with ph 4 7 6 5 three different microbiotic crusts are recognised forming strips parallel to the vegetation banding they are all formed mainly by filamentous cyanobacteria dominated by schizothrix other important genera are scytonema lyngbya microcoleus nostoc and phormidium the filamentous micro organisms trap sand particles and finer particles stick on the filament surfaces these effects enhance soil cohesion and resistance to erosion soil porosity is also increased by the microbial cover with additional pores delineated by filaments on the surfaces of crusts and porous organic bodies derived from microbial remains at depth the microbiotic crusts are essential components of the tiger bush ecosystem water leaving the lower sides of vegetated bands results in plant decay and on the upslope sides vegetation grows because of increased water supply microbial covers help resist erosion and increase water and nutrient retention thus providing substrates for the expansion of plants from adjacent vegetated bands

combined time domain electromagnetic soundings and gravimetry to determine marine intrusion in a detrital coastal aquifer southern spain summary marine intrusion is undoubtedly the most serious problem facing coastal aquifers that are exploited for use it is also an excellent indicator of the state of the aquifers resources this work proposes the combined application of two complementary geophysical techniques as an effective method for locating the saline wedge on one hand time domain electromagnetic soundings are the most reliable geophysical method for determining low resistivity zones that usually correspond to the presence of seawater although in some cases low resistivities may be due to the properties of the substrate on the other hand gravimetry allows a precise determination of the depth of the aquifer basement thus resolving the above uncertainty information provided by the lithological columns from boreholes has also allowed great precision in the calibration of the results from both techniques this methodology has been applied to the motril salobrena detrital coastal aquifer which has had no problems of marine intrusion to date nonetheless changes in soil use brought about by housing developments golf courses and a proliferation of hothouse agriculture comprise significant shifts in aquifer use in addition the construction of a dam which is drastically reducing the main recharge of the aquifer the guadalfeo river makes it likely there will be profound hydrogeological changes delimiting the extent of the saline wedge is therefore a fundamental step towards quantifying the effects of both the dam and the changes in soil use seawater saturated zones have a resistivity ranging from 0 5 to 5 m detrital sediments 8 400 m carbonates 80 300 m and schists from 2 to 60 m the current position of the saline wedge has been located at 100 200 m from the coastline indicating a healthy state for the aquifer areas with wide and narrow mixing zones have been noted and related to differences in the hydrogeological characteristics of the aquifer

late cenozoic base level variations of the caspian sea a review of its history and proposed driving mechanisms abstract the caspian sea is characterized by significant variations in its base level during the late cenozoic and provides an important repository for long term records of both regional climate and tectonics due to its position within the interior of the eurasian continent and at the northern margin of the ongoing arabia eurasia collision zone the caspian also serves as an important moisture source for eastern eurasia including the northern tibetan plateau and thus the history of caspian base level variations represents an important and poorly understood constraint on paleoclimate reconstructions throughout eurasia prior work in the caspian region has largely focused on developing biostratigraphic age divisions and investigating the history of connection between the caspian black and mediterranean seas as well as the global ocean recent geochronologic work in the caspian and related basins has questioned previous correlations of hydrologic events in these different basins as a result prior estimates of the chronology and magnitude of caspian sea level variations may be incorrect here we synthesize previous work to develop a new caspian base level curve starting at the beginning of the meotian regional stage 7 ma we also present a new synthesis of potential driving mechanisms for the large variations in caspian base level and speculate on a possible cause for the enigmatic akchagyl transgression this synthesis highlights the dynamic range of caspian sea level which varied from 200 m above to in excess of 1000 m below its current level during the late cenozoic and provides a basis for future work investigating the tectonic and climatic drivers behind variations in caspian base level

the loess record in southern tajikistan and correlation with chinese loess in the present study the chashmanigar loess soil sequence in southern tajikistan is studied this loess section has a paleomagnetic basal age of about 1 77 myr magnetic susceptibility color reflectance and grain size were systematically measured for closely spaced samples from the section paleosols consistently have a finer grain size distribution higher magnetic susceptibility redder color reflectance and lower dust sedimentation rate than loess horizons suggesting a colder drier and dustier environment during glacial periods than in interglacial periods the grain size record was tuned to variations in obliquity and precession of the earth s orbit the resulting magnetic susceptibility grain size and color reflectance time series all show well expressed astronomical periodicities during the pleistocene the mid pleistocene climate transition characterized by a shift of dominant climatic periods from 41 kyr to 100 kyr at about 1 0 0 8 myr is clearly documented in these proxy records comparison of the chashmanigar loess record with the lingtai loess section in china and the odp site 677 n 18 o record shows that during the entire pleistocene the climate cycles recorded by the central asian loess can be well correlated to the chinese loess and deep sea oxygen isotope records it is suggested that alternations of loess and soil horizons both in central asia and china could be basically forced by global ice volume variations although different wind systems have controlled the pleistocene loess transport and sedimentation in the two areas 2002 elsevier science b v all rights reserved

a distributed slope stability model for steep forested basins a distributed physically based slope stability model dslam based on an infinite slope model a kinematic wave groundwater model and a continuous change vegetation root strength model is presented it is integrated with a contour line based topographic analysis and a geographic information system gis for spatial data extraction and display the model can be run with either individual rainfall events or long term sequences of storms these inputs can be either actual storm records or synthesized random events based on monte carlo simulation the model is designed to analyze rapid shallow landslides and the spatial distribution of safety factor fs in steep forested areas it can investigate the slope stability problem in both temporal and spatial dimensions for example the impact of timber harvesting on slope stability either at a given time or through an extended management period the probability of landslide occurrence for a given year and the delivery of landslide sediments to headwater streams the dslam model was applied in a steep forested drainage of cedar creek in the oregon coast ranges using actual spatial patterns of timber harvesting and measured rainfall during a major storm which triggered widespread landslides in that area in 1975 simulated volume and number of failures were 733 m3 and 4 respectively these values agreed closely with field measurements following the 1975 storm however the effect of parameter uncertainty may complicate this comparison for example when soil cohesion values of 2 0 and 3 0 kpa were used the failure volume changed by factors of 2 04 and 0 41 respectively compared with the average condition of 2 5 kpa used in the simulation for soil depths 30 higher and lower than the standard condition the failure volume changed by factors of 2 0 and 0 27 respectively when maximum root cohesion changed from 12 5 kpa average condition to 10 kpa the failure volume increased 1 73 fold for the case of 15 kpa the failure volume changed by a factor of 0 55 the simulated failures caused by the storm were mostly in hollows the simulations show that the spatial distribution of fs is controlled mainly by topography and timber harvesting patterns and is greatly affected by groundwater flow patterns during major rainstorms most areas with fs 3 0 corresponded with the distribution of blocks clear cut in 1968 and all elements with fs 2 0 were in areas clear cut in 1968 areas with low fs 1 0 1 6 expanded dramatically during the rainstorm and decreased at a slow rate after the storm factors of safety in hollows declined sharply during the storm

model for the prediction of shear strength with respect to soil suction experimental studies on unsaturated soils are generally costly time consuming and difficult to conduct shear strength data from the research literature suggests that there is a nonlinear increas

influences of soil water characteristic curve on rainfall induced shallow landslides the analysis of slope instability induced by rainfall was usually performed using the main drying curve as the measurement of the main wetting curve is a more time consuming and costly task in this study the influences of the main drying and wetting curves on rainfall induced shallow landslides are examined three designed scenarios and a real case scenario are used to conduct this examination the prediction of shallow landslide occurrence is related to the main drying and wetting curves due to the strong relation between groundwater pressure head and hysteresis effect the main wetting curve may have a less minimum landslide triggering rainfall amount and a less rainfall duration threshold for landslide occurrence than the drying wetting curve for safety s sake an underestimation of shallow landslide occurrence may be produced by the commonly used main drying curve in addition besides the shallow landslide occurrence the failure depth and the time to failure are also influenced by the main drying and wetting curves the hysteresis effect should be taken into account for assessing rainfall induced shallow landslides

biogeomorphology of a mojave desert landscape configurations and feedbacks of abiotic and biotic land surfaces during landform evolution abstract terrestrial ecosystems can be more holistically understood by investigating the morphology of landscape mosaics the assemblage of their ecological communities and the linkages and feedbacks between the mosaics and communities the overarching objectives of this study were to 1 study the abiotic and biotic configurations of landform units as mosaics within a mojave desert chronosequence and 2 elucidate their potential feedbacks interactions and dynamics during landform evolution seven landform units distributed over three geomorphic ages were identified including young bars and swales intermediate aged flattened bars flattened swales and bioturbation units and old desert pavements and shrub zones these landform units were characterized according to abiotic and biotic land surface properties landform units were statistically distinct and predictable based on a specific suite of abiotic and biotic properties vascular plant functional group and biological soil crust community diversity varied with geomorphology with greatest diversity associated with bars and shrub zones and lowest diversity associated with desert pavements biological soil crust communities were controlled by geomorphic age surface rock size and protruding rocks with young bar units having the highest abundance and diversity perennial forbs were observed in old shrub zones with small rocks and few protruding rocks a high clast density and a finer sized clast distribution were found particularly in desert pavements and flattened swales and generally inhibited biological soil crust and plant cover evolutionary trajectories for landforms of a lower piedmont landscape can be dominated by either abiotic and biotic landform processes these two trajectories are distinctly different and are associated with their own unique linkages feedbacks and dynamics of abiotic and biotic land surface properties producing a highly diverse desert landscape

stability analyses of rainfall induced landslides the slope stability issues concerning rainfall induced slope failures are investigated and presented specifically the effect of both negative and positive pore water pressures on the stability of initially unsaturated slopes are carefully explained and coupled with infinite slope analysis methods in order to present a predictive formulation of slope failures that occur as a result of rainfall events the formulation serves as a baseline analysis method for evaluating potentially unstable soil slopes that are subject to surface infiltration and explains the various triggering mechanisms that may occur based on individual combinations of the slope geometry soil strength and infiltration parameters a procedural method is outlined for utilizing the analytical formulation to predict the change in the factor of safety for a slope subject to infiltration and a detailed analysis of a case study is presented to verify the method quantitative statements are made concerning the time and depth of failure in relationship to the soil slope and rainfall parameters

danube loess stratigraphy towards a pan european loess stratigraphic model abstract the danube river drainage basin is the second largest river catchment in europe and contains a significant and extensive region of thick loess deposits that preserve a record of a wide variety of recent and past environments indeed the danube river and tributaries may themselves be responsible for the transportation of large volumes of silt that ultimately drive loess formation in the middle and lower reaches of this large catchment however this vast loess province lacks a unified stratigraphic scheme european loess research started in the late 17th century in the danube basin with the work of count luigi ferdinand marsigli since that time numerous investigations provided the basis for the pioneering stratigraphic framework proposed initially by kukla 1970 1977 in his correlations of loess with deep sea sediments loess palaeosol sequences in the middle and lower reaches of the danube river basin were a key part of this framework and contain some of the longest and most complete continental climate records in europe covering more than the last million years however the very size of the danube loess belt and the large number of countries it covers presents a major limiting factor in developing a unified approach that enables continental scale analysis of the deposits local loess palaeosol stratigraphic schemes have been defined separately in different countries and the difficulties in correlating such schemes which often change significantly with advances in age dating have limited the number of basin wide studies a unified basin wide stratigraphic model would greatly alleviate these difficulties and facilitate research into the wider significance of these loess records therefore we review the existing stratigraphic schemes and define a new danube basin wide loess stratigraphy based around a synthetic type section of the mosorin and stari slankamen sites in serbia we present a detailed comparison with the sedimentological and palaeoclimatic records preserved in sediments of the chinese loess plateau with the oxygen isotope records from deep sea sediments and with classic european pleistocene stratigraphic subdivisions the hierarchy of danubian stratigraphic units is determined by climatically controlled environmental shifts in a similar way to the chinese loess stratigraphic scheme a new unified danube loess stratigraphic model has a number of advantages including preventing confusion resulting from the use of multiple national schemes a more transparent basis and the potential to set pleistocene palaeoenvironmental changes recorded in the danube catchment area into a global context the use of a very simple labelling system based on the well established chinese loess scheme facilitates interpretation of palaeoenvironmental information reported from the danube basin loess sites in a wider more accessible context that can be readily correlated world wide this stratigraphic approach also provides for the first time an appropriate framework for the development of an integrated pan european and potentially pan eurasian loess stratigraphic scheme

biomarkers in modern and buried soils of semi desert and forest ecosystems of northern iran abstract in northern iran mean annual precipitation and vegetation vary significantly over short distance from a semi desert to a forest biome these ecosystems likely responded differently on past climate changes we here aim at i testing the applicability of biomarkers leave derived n alkanes their stable carbon isotope composition and c and n stable isotopes of soil organic matter in loess derived soils to identify and differentiate past ecosystems and ii elucidating the variability of these biomarkers in palaeosols we sampled modern topsoils and palaeosol horizons within an ecological gradient covering a range in mean annual precipitation from 200 to 750 mm from the kopet dag semi desert to the hyrcanian forest on the footslopes of the alborz mountains c org n 13 c org 15 n and n alkanes and their compound specific 13 c were analyzed to characterize organic matter composition and sources in modern soils a systematic increase in c org and n was observed with precipitation the 15 n decreased from about 6 to 4 pointing to systematically more degraded organic matter in semi desert soils the leave wax specific ratio of nc 31 nc 33 nc 27 nc 29 n alkanes was 1 for semi desert soils and 13 c org showed no systematic trend in this gradient in loess and palaeosol profiles contents of c org n and n alkanes dropped about a factor 10 compared to modern soils the n alkane ratio and 15 n ratios remained on comparable levels as did the compound specific 13 c in n alkanes however bulk 13 c org was altered from about 27 in modern soil to 23 in loess palaeosols systematically higher c org and n values were observed in palaeo topsoils compared to loess and subsoil stable c isotopes varied rather unsystematically within loess palaeosol sequences while 15 n revealed trends within palaeosols however in contrasting directions with palaesol depth the temporal average n alkane ratio for all palaeosol horizons of one site systematically followed the modern precipitation gradient indicating that in all periods of soil formation a climatic gradient developed

cyanobacterial diversity and toxicity of biocrusts from the caspian lowland loess deposits north iran abstract biocrusts and adjacent sediments were collected from the so called loess plateau of northern iran and the loess deposits on the foothills of alborz mountains the mineralogical and granulometric analyses characterized sediments as quartz rich clayey or sandy silts cyanobacterial diversity colony morphology and grain stabilization were studied by light and scanning electron microscopy which showed glue like layers of cyanobacterial eps and dense networks of filamentous cyanobacteria immobilizing finer and bigger grains respectively amorphous tuft and globular cyanobacterial colony structures were also detected 15 cyanobacterial genera were identified in the biocrust samples including microcoleus vaginatus as the common species in all samples aphanocapsa aphanothece calothrix chroococcus chroococcidiopsis cyanosarcina hassallia homeothrix nostoc oculatella schizothrix scytonema tolypothrix and trichocoleus two biocrust samples showed traces of toxicity in a protein phosphatase inhibition assay targeting microcystins and similarly acting compounds the artemia salina assay revealed an elevated toxic response in one sample

shear strength characteristics of a residual soil shallow landslides in natural residual soils slopes are common all over the world the slip surfaces associated with these landslides are often situated above the groundwater table therefore it i

mechanism and failure process of qianjiangping landslide in the three gorges reservoir china the qianjiangping landslide is a large planar rock slide which occurred in july 14 2003 shortly after the water level reached 135 m in the three gorges reservoir china the landslide destroyed 4 factories and 129 houses took 24 lives and made 1 200 people homeless field investigation shows that the contributing factors for the landslide are the geological structure of the slope the previous surface of rupture the water level rise and continuous rainfall in order to reveal the mechanism and failure process of the landslide numerical simulation was conducted on qianjiangping slope before sliding based on the characteristics and the engineering conditions of the landslide the topography and the geological profiles of qianjiangping slope before sliding is reconstructed the seepage field of qianjiangping slope before sliding was simulated with the geostudio software the results show that ground water table rises and bends to the slope during the rise of water level and the slope surface becomes partially saturated within the period of continuous rainfall using the ground water table obtained above the failure process of qianjiangping slope is simulated with the flac3d software the results demonstrate that the shear strain increment displacement and shear failure area of the slope increased greatly after the water level rose and continuous rained and the landslide was triggered by the combined effect both of water level rise and continuous rainfall the development of shear strain increment displacement and shear failure area of the slope shows that the landslide was retrogressive in the lower part of the slope and progressive in the upper part of the slope

using stable hydrogen and oxygen isotopes to reveal monsoonal and related hydrological effects on meteoric water in the western pacific monsoon region a case study of the ilan region northeastern taiwan abstract this study analyzes the isotopic compositions 2h and 18o of meteoric waters including precipitation and stream water to reveal what major hydrological processes affect the hydrological regime of the ilan region northeastern taiwan the isotopic results indicate monsoonal flows as the fundamental factors affecting studied precipitation and stream water summer precipitation sourced from southerly air mass exhibits lower and deuterium excess de values than winter precipitation sourced from northerly air masses the 18o and de values are respectively 7 7 and 8 for summer precipitation and 3 3 and 24 for winter precipitation furthermore semi quantitative estimations using de evidence indicate that summertime southerly air masses generally contribute more to stream water than wintertime northerly air mass flows approximately 54 vs 46 however the contribution fractions are controlled by the orientation of catchments to the windward side of respective monsoonal flows northern catchments located on the windward side of southerly air masses receive about 60 of their water from precipitation condensed from the southerly air masses and 40 from the northerly air masses by comparison southern catchments located on the windward side of northerly air masses receive about 59 of their water from northerly air masses and 41 from southerly air masses additionally catchment effect induced from value is notable in stream basins with high elevations but this is not related to catchment sizes besides this altitude effect which is determined in terms of 18o values was derived using data from four precipitation stations of northern taiwan it ranges from 2 5 to 3 0 per 100 m depending on the season moreover based on the de evidence secondary evaporation effects are apparent with moisture recycling influencing inland summer precipitation and raindrop evaporation influencing inland winter precipitation

micromorphology and development of loess derived surface and buried soils along a precipitation gradient in northern iran abstract the northern footslopes of the alborz mountains and an extensive hill area in eastern golestan province are covered by thick 70 m loess deposits divided by different types of interstadial and interglacials paleosols the area shows a precipitation gradient of about 800 mm over 80 km north south along this gradient eight pedons of modern soils and six paleosols were selected in order to investigate the types of modern and past soil forming processes and to compare the degree of soil development of surface and buried soils the soils were described and sampled using standard sedimentological pedological laboratory analysis the soil ph and calcium carbonate contents show a decreasing trend with precipitation while soil organic carbon clay content and cation exchange capacity increase with rainfall the silt content however shows a decreasing trend with rainfall clay mineralogy of parental loess is illite chlorite smectite kaolinite from north to south the relative proportion of smectite in soil horizons increases reaching almost dominance in regions with typic xeric soil moisture regime smr 600 mm of rainfall in the areas with udic smr vermiculite increases and sometimes dominates micromorphology provides evidence for the formation of bt horizons and intensified decalcification and increase of clay mobilisation as indicated by b fabrics with increasing rainfall soils within the xeric and udic smrs are either alfisols or mollisols both showing clay illuviation features whereas clay mobilisation is very limited in the arid part of the area the paleosols show differential weathering degrees indicated by trends of increasing carbonate depletion clay mobilisation and clay enrichment with assumed paleo precipitation pedogenesis micromorphological properties and clay minerals in the last interglacial paleosols suggest similar climate controlled trends to those reflected in the modern soils

infinite slope stability under steady unsaturated seepage conditions 1 we present a generalized framework for the stability of infinite slopes under steady unsaturated seepage conditions the analytical framework allows the water table to be located at any depth below the ground surface and variation of soil suction and moisture content above the water table under steady infiltration conditions the framework also explicitly considers the effect of weathering and porosity increase near the ground surface on changes in the friction angle of the soil the factor of safety is conceptualized as a function of the depth within the vadose zone and can be reduced to the classical analytical solution for subaerial infinite slopes in the saturated zone slope stability analyses with hypothetical sandy and silty soils are conducted to illustrate the effectiveness of the framework these analyses indicate that for hillslopes of both sandy and silty soils failure can occur above the water table under steady infiltration conditions which is consistent with some field observations that cannot be predicted by the classical infinite slope theory a case study of shallow slope failures of sandy colluvium on steep coastal hillslopes near seattle washington is presented to examine the predictive utility of the proposed framework

correlation of loess paleosol sequences in east and central asia with se central europe towards a continental quaternary pedostratigraphy and paleoclimatic history abstract as recent small climatic fluctuations on a 102 103 year time scale can be correlated worldwide and represent a decline of mean annual temperature of only 1 c major climatic changes on at least a 105 year scale glacial interglacial cycles and probably a 104 year scale the approximate length of an interglacial must be of similar ages throughout the temperate climatic belt of the northern hemisphere this concept allows continental pedostratigraphical correlations detailed knowledge of the genesis of paleosols is needed to establish loess paleosol stratigraphies that can be used for paleoclimatic reconstruction most paleosols however are truncated and largely recalcified from overlying loess micromorphological studies allow primary and secondary carbonates to be distinguished and provide unequivocal evidence of clay illuviation this enables the recognition of typical loess weathered loess and the recognition of different genetic soil horizons such as cb bc ah bw and bt horizons for the brunhes epoch the sequence at karamaydan tadjikistan is more detailed than the corresponding section in luochuan china and even more than in se central europe except for the last glaciation the very good correlation with the deep sea oxygen isotope record which includes the development of an accurate astronomical time scale allows a detailed chronostratigraphical subdivision of the loess paleosol sequence in karamaydan which therefore should be regarded as a key sequence for reconstructing the climatic history of the brunhes epoch this implies that the loess paleosol sequences in se central europe are less complete than thought earlier pedocomplexes in karamaydan correspond with single paleosols in se central europe e g the f6 paleosol in stari slankamen correlates with pedocomplexes pk vi and v at karamaydan which were formed over a period of about 140 ka although pedogenesis was interrupted several times by loess deposition the f6 soil is therefore an example of a welded paleosol as are the f5 the f4 and the f2 paleosols in se central europe for most of the matuyama epoch the central and lower parts of the sequence at chashmanigar show more pronounced paleosols than the equivalent parts at luochuan in se central europe only at stari slankamen are three strongly developed though truncated paleosols f9 f11 above neogene sediments mineralogical investigations of the silt and clay subfractions show that there is little difference in the type and amount of pedogenic clay mineral formation between the holocene soils and the paleosols of the brunhes epoch at karamaydan and of the matuyama epoch at chashmanigar this suggests that the interglacial climates represented by the b or bt horizons of the buried paleosols of late middle and early pleistocene age were similar to that of the holocene

hazard analysis of li shan landslide in taiwan abstract in this study a method coupling limit equilibrium analysis monte carlo analysis and geography information system gis was implemented to evaluate landslide hazard with consideration of spatial uncertainties with the gis the three dimensional surface topography underground geomaterial distribution and groundwater level were processed for slope stability analysis in addition mechanical properties of the geomaterials were considered as random variables instead of single values slope sections and groundwater levels were also randomly adopted through a monte carlo sampling process a distribution of safety factor and probability of failure were determined this approach was applied to hazard assessment of the li shan landslide in central taiwan through a series of analyses the hazards of sliding bodies of the li shan landslide were estimated and ranked it shows the influence of ground water level is significant which reveals the importance of ground water control and monitoring the results show the safety of the northeast and southeast areas of the landslide have been significantly improved since the ground water levels have been lowered by the drainage system spatially the hazard moderately dissipates from center area in the post remediation phase

role of a cyanobacterial cover on structural stability of sandy soils in the sahelian part of western niger microbiotic soil crusts mostly formed by cyanobacteria are widespread on the surface of fallow land in western niger they lie adjacent to completely bare soils we have investigated the structural stability of these soils by testing aggregate breakdown under fast wetting slow wetting and mechanical breakdown the tests were effected on aggregates ranging from 3 to 5 mm in size these experiments were completed by micromorphological examinations under light and scanning electron microscope for all tests the fragment size distribution and the mean weight diameter mwd revealed the great stability of aggregates from soils with a cyanobacterial cover mwd 1 82 to 3 10 mm compared to those from soils devoid of cyanobacterial cover mwd 0 25 to 1 26 mm fast and slow wetting of microbiotic soil crust material induced a lesser disaggregation of aggregates compared to mechanical breakdown on the contrary fast wetting and mechanical breakdown of aggregates from soils devoid of cyanobacterial cover induced a greater disaggregation than slow wetting microscopic examination of microbiotic crusts revealed an intricate network of filamentous cyanobacteria and extracellular polymer secretions which binds and entraps mineral particles on the soil surface organo mineral aggregates ranging from 0 10 to 0 12 mm were observed below the superficial crusts filaments and residual organic matter bind tightly soil particles thus giving a compact structure the great stability of aggregates of soil with cyanobacterial cover is likely related to the binding and gluing effect of cyanobacteria and derived organic matter this is consistent with the positive correlation between mwd values and organic carbon content the present results thereby confirm the resistance to erosion of soil with microbial cover as indicated by field measurements

loess is almost totally formed by the accumulation of dust in 1990 marton pecsi published a paper entitled loess is not just the accumulation of dust this 1990 paper presented the case for considering aspects of loess formation other than the aeolian deposition of silty material pecsi argued that there is more to loess formation than simply the fact of aeolian deposition while not disputing the validity of much of pecsi s arguments a case can be made for considering that aeolian deposition is at the very heart of loess formation that the factor of aeolian deposition is so critical that other aspects are relatively unimportant pecsi appeared to suggest that aeolian deposition is just one of many factors relating to the formation of loess deposits this is not so aeolian deposition and the consequent formation of metastable structures is absolutely central but it is probably useful to consider the aeolian deposition is absolutely critical approach and the aeolian deposition is one of the factors approach in some more detail and in relation to each other some insights may accrue interesting things do happen after the deposition of the dust and this needs to be acknowledged

causative mechanisms of rainfall induced fill slope failures slope failures in fill slopes formed by loosely compacted completely decomposed granite in hong kong occur commonly during intense tropical rainstorms the stress path greatly influences the shear strength of the soil mass and is therefore crucial to the identification of slope failure mechanisms the soil mass in this case is largely unsaturated in situ hydrologic response to rainstorms indicates that soil suction is reduced by rainfall infiltration which often becomes the triggering factor in initiating slope instability the constant dead load tests on unsaturated loosely compacted completely decomposed granite appropriately simulate the field stress path of rainfall induced fill slope failure by reducing suction the tests indicate that matric suction contributes to the dilative or contractive behavior of the unsaturated soils the anisotropically consolidated undrained triaxial tests demonstrate the consistently contractive behavior of the specimens on this basis we delineate the in situ stress conditions leading to the initiation of rainfall induced fill slope failure and the stress paths of the transformation from local failures to flowage based on a systematic study of fill slope case records in hong kong implications of such mechanisms on fill slope stability are given

rainfall recharge relationships within a karstic terrain in the eastern mediterranean semi arid region israel δ 18o and δd characteristics annual rainfall variations and processes in the upper vadose zone exert a profound influence on the chemical and isotopic compositions of waters of carbonate aquifers in semi arid climatic zones in order to define these processes we have studied the surface temperatures during rainfall events the isotopic composition of rain infiltrating and groundwaters this study was carried out within a karstic terrain soreq cave israel located in cenomanian dolomitic rocks approximately 40 km inland of the mediterranean sea and 400 m above sea level the climate is typical of the eastern mediterranean semi arid conditions with a rainy winter and dry summer and the average annual rainfall in the area is 500 mm close monitoring indicates that the d and 18o values of individual rainstorm events decrease with increasing rainfall annual average isotopic values of years with rainfall of 500 600 mm do not vary systematically years with extreme rainfall values define a negative covariation between the 18o and rainfall the d 18o relationship of all rain events of more than 20 mm fall on the mediterranean meteoric water line mmwl with a slope of 8 and d excesses of 20 30 these rain events occur when mid winter surface temperatures are 5 to 10 c rainfall events of less than 20 mm mainly occurring at above 10 c have slopes of less than 8 and smaller d excess as a consequence of evaporation processes beneath the clouds two main water types infiltrating into the cave are recognized slow and fast drip slow drip occurs from the tips of stalactites and takes place throughout the year these waters represent seepage water that remains in the upper vadose zone for up to several decades fast drip emanates from fissures in the cave roof during the winter seasons these waters represent vadose flow with a short residence time of less than 1 year the infiltration of the fast drip water into the cave depends on the fracture system of the rock cover and on the intensity of the rainstorms in the inner parts of the cave where the rock cover is thick fast drip starts only after several massive 20 mm rainstorms whereas below a thin roof the response time of fast drip is a few hours to a few days after intensive rainstorms both fast and slow drip water fall on the mmwl indicating that they are derived mainly from the relatively intensive rainstorms that compose about 23 of the annual rainfall although fast dri water represents massive rainstorms their 18o and d values are nonetheless higher by 1 and 10 respectively relative to the average rainwater compisition this indicates that the fast drip water consists predominantly of water derived from intensive rainstorms admixed with a minor component of isotopically 18o and d enriched water which is represented by the slow drip waters the fast drip waters are derived mainly from massive rain events at surface temperatures of 5 to 10 c which thermally equilibrate with the host rock and upon reaching the cave they have already acquired the mean temperature 20 c of the cave

tracing infiltration and recharge using stable isotope in taihang mt north china the groundwater in headwater region is an important recharge source for the adjacent mountain front plain in order to reveal the relationship among precipitation soil water and groundwater from june to september in 2004 stable isotopes deuterium and oxygen 18 in precipitation and soil waters at the depths of 10 20 30 50 70 90 and 110 cm were analyzed at two sites covered by black locust robinia pseudoacia l site a and grass predominated by themeda triandra t japonica willd tanaka and bothriochloa ischaemum b ischaemum l keng site b in an experimental catchment at taihang mt north china respectively the 18o of precipitation in daily rain events shows large variations 13 3 to 4 3 with a mean of 8 1 the 18o and d of soil waters along profiles in two sites suggest that the influence of canopy cover was just up to 10 cm in top soil water the soil water moved over the zero flux plane at 70 cm in depth is expected to escape the evaporative effect at the end of september in both sites the results show that the stable isotope instead of tritium as tradition can be used to trace the soil water behaviors based on the movement of isotopic peak along the vertical profiles in this semi arid and semi humid mountainous region the infiltration depths of soil water in taihang mt are 12 and 10 mm day from june to september in 2004 in site a and site b respectively tracing by stable isotope recharge fluxes of soil water to local groundwater are of 3 8 and 3 2 mm day in site a and site b respectively the results provide desirable information for assessment of local groundwater resources

bacterially induced mineralization of calcium carbonate in terrestrial environments the role of exopolysaccharides and amino acids this study stresses the role of specific bacterial outer structures such as glycocalix and parietal polymers on calcium carbonate crystallization in terrestrial environments the aim is to compare calcium carbonate crystals obtained in bacterial cultures with those obtained during abiotically mediated synthesis to show implications of exopolysaccharides and amino acids in the mineralogy and morphology of calcium carbonate crystals produced by living bacteria this is done using various amounts of purified exopolysaccharide xanthan eps and l amino acids with a range of acidities amino acids and increasing xanthan content enhance sphere formation in calcite and vaterite regarding calcite the morphology of crystals evolves from rhombohedral to needle shape this evolution is characterized by stretching along the c axis as the amino acid changes from glutamine to aspartic acid and as the medium is progressively enriched in eps regarding vaterite the spherulitic habit is preserved throughout the morphological sequence and starts with spheres formed by the agglomeration of short needles which are produced in a xanthan free medium with glutamine monocrystals forming spheres increase in size as xanthan is added and the acidity of amino acids glutamic and aspartic acids is increased at high xanthan concentrations amino acids and mainly aspartic and glutamic acids induce vaterite precipitation the role of the carboxyl group is also probably critical because bacterial outer structures associated with peptidoglycan commonly contain carboxyl groups this role combined with the results presented here clearly demonstrate the influence of bacterial outer structure composition on the morphology and mineralogy of bacterially induced calcium carbonate this point should not be neglected in the interpretation of calcite cements and carbonate accumulations in terrestrial environments

geomorphological control on variably saturated hillslope hydrology and slope instability in steep topography the processes governing variably saturated subsurface hydrologic response and the interparticle stresses leading to shallow landslide initiation are physically linked however these processes are usually analyzed separately here we take a combined approach simultaneously analyzing the influence of topography on both hillslope hydrology and the effective stress fields within the hillslope itself clearly runoff and saturated groundwater flow are dominated by gravity and ultimately by topography less clear is how landscape morphology influences flows in the vadose zone where transient fluxes are usually taken to be vertical we aim to assess and quantify the impact of topography on both saturated and unsaturated hillslope hydrology and its effects on shallow slope stability three real hillslope morphologies concave convex and planar are analyzed using a 3 d physically based distributed model coupled with a module for computation of the probability of failure based on the infinite slope assumption the results of the analyses which included parameter uncertainty analysis of the results themselves show that convex and planar slopes are more stable than concave slopes specifically under the same initial boundary and infiltration conditions the percentage of unstable areas ranges from 1 3 for the planar hillslope 21 for convex to a maximum value of 33 for the concave morphology the results are supported by a sensitivity analysis carried out to examine the effect of initial conditions and rainfall intensity

analysis of physical testing of rainfall induced soil slope failures rainfall is a significant factor that triggers slope failures around the world this paper reports a series of physical tests which were conducted to simulate rain induced slope failures the experiments dealt with two scenarios including 1 rainwater infiltration into the slope and 2 slope failures induced by artificial rainfall with different initial conditions slope deformation and slope failures were observed and possible mechanisms were interpreted based on the experimental results the results confirm the hypothesis that pore water pressure and water content in a loose soil slope change rapidly and that water infiltration into cracks in the slope has a great impact on landslide development the observed slope failures can be divided into three types overall sliding failure partial sliding failure and flow slide the effect of slope gradient rainfall intensity and distribution of initial suction on the slope deformation and failure process are also summarized for possible applications under the similar conditions

middle and late pleistocene loess sequences at batajnica vojvodina serbia abstract loess sequences in the vojvodina region northern serbia reveal a continuous record of paleoclimatic variations during the middle and late pleistocene the most detailed stratigraphic information comes from remarkable exposures on the cliffs of the right danube bank from vukovar to belgrade the batajnica loess section has been recognized as one of the most complete middle and late pleistocene records in this region a more than 40 m thick loess paleosol succession represents environmental transition from relative thin loess layers and rubified soils in lower part of profile to thick loess and fossil chernozems characterizing the last three glacial interglacial cycles the proposed stratigraphic model is based on a detailed magnetic susceptibility ms record which is related to the deep sea isotope stratigraphy and on correlation with other eurasian loess records using the distinct ms pattern of selected loess paleosol couplets this new stratigraphic model suggests serious revision of previous chronological interpretations ms as function of depth shows a well known pattern of low values in loess and high values in paleosols indicating strong enhancement of magnetic minerals during soil formation with the exception of the recent soil v s0 which is strongly contaminated by archaeological artifacts the third paleosol v s3 reveals the highest values in ms and a very distinct double peak the rock magnetic signal at batajnica resembles the typical pattern of the enviromagnetic records determined from other eurasian loess sites the paleopedological interpretations rubification index values and rock magnetic record at batajnica yield valuable data for the reconstruction of paleoclimatic fluctuations for the last 5 glacial interglacial cycles at least moreover the record provides an important link between the classical central european loess sites and the central asian and chinese loess provinces

late pleistocene loess palaeosol sequences in the vojvodina region north serbia late pleistocene loess palaeosol sequences are widespread in the vojvodina region with thicknesses reaching a maximum of about 20 m our investigations include more than 40 of these loess sections geochronology of the last glacial loess palaeosol sequences based on lumines cence dating and amino acid racemisation provides correlations between upper pleistocene loess palaeosol sediments in vojvodina and comparable deposits at other european localities sedimentary logs of magnetic susceptibility grain size measurements and carbonate content combined with malacological evidence indicate two main relatively cold and arid phases during the last glacial period related to intensive accumulation of loess units l1l1 and l1l2 as well as many brief episodes of dry and windy climatic conditions suggesting a possible relationship with cold events recorded in the north atlantic region generally late pleistocene climate in the region was dry and relatively warm compared with glacial period sites in central europe and was characterised by sharp differences between glacial and interglacial modes new data and interpretations presented in this study emphasise the significance of loess palaeosol sequences in vojvodina for the reconstruction of the temporal and spatial evolution of late pleistocene palaeoclimate in this part of europe copyright 2007 john wiley sons ltd

loess soil sequence at toshan northern iran insights into late pleistocene climate change abstract the knowledge of palaeoclimate in iran is still limited however insight into the timing and the dynamics of quaternary climate change in iran might offer valuable information to improve the global palaeoclimate record the loess soil sequence of toshan provides the first high resolution record of late pleistocene climate dynamics in iran and complements the hitherto known sections at neka now deh and agh band to establish a pedostratigraphic record of the north eastern caspian lowland our spectroscopic and grain size analysis are combined to propose i a pedostratigraphical scheme for the sequence at toshan ii describe and estimate the degree of soil development of selected stratigraphical units iii infer palaeoclimatic information and provide iv a correlation with previous loess palaeosol records of n iran as based on pedostratigraphic assumptions the section at toshan hosts a strongly developed reddish brown argillic palaeosol bt as well as eight moderately to weakly developed brownish palaeosol horizons lacking clay illuviation features bw bwk these remnants of fossil soils are separated by finely textured loess and horizons that host characteristics of both loess and mineral subsoils cb cbk giving evidence for syngenetic soil formation the stratigraphical succession of palaeosols loess and syngenetically altered sediments covering the last ca 130 ka gives evidence for recurrent climate changes as well as fluctuations between dominance of soil formation or dust accumulation in relation to changes in moisture regime the formation of bt and bw bwk horizons is related to relatively humid and warm conditions likely corresponding with interglacial and interstadial climate

loess chronology of the caspian lowland in northern iran the loess palaeosol sequences of the caspian lowland in northern iran provide detailed archives of climate and environmental change showing a close relationship to global cooling and warming trends for the quaternary period the magnitude of these changes is under discussion owing to uncertainties in the chronologies for individual sites a chronological frame was set up for the last glacial loess record for three upper pleistocene key sections by infrared optically stimulated luminescence irsl in the caspian lowland irsl dating gives reliable ages for sediments covering at least the past 60 ka however for sediments older than 60 ka a significant age underestimation is likely the first strongly developed buried bt bwt horizons or pedocomplexes at the three sections under study correlate most likely with the last interglacial mis 5 at least four periods of increased sediment accumulation were determined for the last glacial period intercalated by periods of weak soil formation the loess palaeosol sequences in northern iran recorded coeval and similar major climatic changes as in south eastern central europe and central asia

using stable isotope analysis δd δ18o to characterise the regional hydrology of the sierra de gador south east spain water stress is rapidly increasing in many mediterranean coastal zones mainly due to expansion in agriculture and tourism in this paper we focus on the sierra de gador campo de dalias aquifer system southeastern spain in order to assess the capability of water stable isotope analysis deltad delta 18 o to refine the understanding on recharge of this karstic aquifer system different types of surface and groundwater were sampled along an altitudinal gradient from the recharge zone in the mountains to the coastal plain surface water is restricted to local runoff collected in closed reservoirs runoff amounts collected in three of these reservoirs were monitored together with the precipitation in their catchments meteorological maps were used to detect the origin of the precipitation generating the majority of the runoff the results were compared to literature data on local and regional precipitation the use of oxygen and hydrogen isotopic composition has proved to be a useful tool to explain the origin of groundwater in a mediterranean karstic system such studies are however not numerous and are often limited to local scale recharge for fast reacting systems this paper focuses on the delta 18 o deltad relationships of local precipitation to explain the isotopic variability of a large karstic aquifer system the isotopic compositions of groundwater sampled along an altitudinal gradient from the recharge zone to the coastal plain are well displayed in a deltad delta 18 o diagram on a mixing line connecting a pole of mediterranean waters to a pole of atlantic waters the atlantic signature predominates in the shallow groundwater of natural springs reflecting the rainfall which produced the local runoff sampled the mediterranean signature is mainly restricted to deep groundwater from boreholes in the coastal plain the existence of a degree of spatial separation of groundwater types demonstrates that groundwater flow in a complex karstic system is not always continuous the mediterranean signature of deep groundwater could be due to past extreme rainfall events during which connectivity between recharge and reservoir exists while at the same time the atlantic signature of recent winter rains dominates in shallow groundwater the assumption that an equilibrium in isotopic composition is established within a continuous aquifer and that therefore a slope lower than 8 in a deltad delta 18 o diagram indicates evaporation is not necessarily valid c 2002 elsevier science b v all rights reserved

a hydrostratigraphic simplification approach to build 3d groundwater flow numerical models example of a quaternary deltaic deposit aquifer the construction of 3d hydrogeological models for unconsolidated sedimentary aquifers remains particularly challenging especially in quaternary deposits simplifications at small or large scale are part of groundwater flow modeling and are often required due on the usual inherent complexity of the stratigraphic systems this study analyzes the effects of hydrostratigraphic simplifications on the accuracy of 3d numerical groundwater flow models such investigation is conducted from an initial detailed model of an aquifer located in the saguenay lac st jean region in canada and the considered simplifications are based on using the equivalent hydraulic conductivity concept different levels or approaches of simplification are applied to numerical simulated models and the results of the different scenarios are compared a root mean square rms calibration result of 3 79 m on the groundwater levels is obtained for the most detailed model while the rms ranges between 4 01 and 4 83 m with the simplified models such results illustrate a gain obtained in the calibration of the model with increasing level of hydrostratigraphic details but that this gain is relatively limited the proposed methodology for simplifying the hydrostratigraphic settings could be used by hydrogeological modellers for a wide variety of aquifers constituted of sedimentary granular material

importance of biological loess crusts for loess formation in semi arid environments the essential abiotic components for loess formation are material dust atmospheric circulation wind suitable surface conditions for the trapping of aeolian material and for the subsequent development of typical loess sedimentary structures in spite of the world wide distribution of loess deposits knowledge of the processes of dust accumulation and its transformation to mature loess sediment is still inadequate loess accumulation appears greatest during the most arid periods and in semi arid regions biological crusted surfaces bcs are of potentially great importance in loess formation especially in semi arid regions bcs are highly specialized extremophile communities and apparently play an important role in atmospheric dust trapping and erosion prevention results indicate that cyanobacterial strains isolated from current carpathian basin loess exhibit specific morphological and eco physiological characteristics that play a key role in loess formation warranting adoption of the new term biological loess crusts blc a model of the influence of cyanobacterial blc life strategies on loess formation explains trapping accumulation and preservation as well as loess texture and structure this potential significance of blc in the accumulation and preservation of loess sediments may be considered as a model suitable model database for recognition of bioorganic modification of geological strata mycosporine and scytonemin pigments can serve as blc biomarkers elucidating their role in soil evolution and in aiding paleoclimatic paleoenvironmental and paleovegetation reconstructions

modeling the stability of terraced slopes an approach from valtellina northern italy this study focuses on the relationships between hydrological processes and the stability of terraced slopes emphasis is given to the presence of dry stone retaining walls and how to explicitly consider them when performing a distributed stability analysis valtellina an alpine valley of northern italy is selected as study area in detail the slope uphill the village of tresenda affected by several superficial landslides since 1983 is studied dry stone walls heavily influence the hydrological and geotechnical processes at the slope scale and it is therefore crucial to consider them when performing a stability analysis on mountainous terraced areas walls are usually 0 60 1 00 m wide and therefore base maps digital elevation models and soil depth map with a horizontal resolution of 1 m have been appositely derived working at this horizontal resolution leads to the failure of some basic assumptions of the infinite slope method usually applied for distributed stability analysis in this study we propose an alternative approach based on the global method of equilibrium applied to sections of single terraces one cell wide a specific sensitivity analysis allowed to fix some constrains to the model in order to improve the reliability of the results under different mechanical and hydrological conditions the proposed stability model was calibrated and evaluated on recorded past rainfall events it resulted to be a good instrument for the identification of the most unstable areas when stressed with high pore water pressure conditions

a critical reevaluation of palaeoclimate proxy records from loess in the carpathian basin abstract in the carpathian basin loess is the most important archive of quaternary palaeoclimate evolution but only in the past two decades systematic and high resolution investigations were conducted those studies remarkably improved our knowledge of the regional past environmental change palaeoclimate inferences based on the magnetic susceptibility and grain size distribution as the most commonly used palaeoenvironmental proxies for the carpathian basin loess indicate colder and drier climatic conditions during glacials when compared to interglacials with an increasing number of studies using novel proxies in loess research such a traditional understanding of dry and cold glacials and humid and warm interglacials in the carpathian basin has been questioned as an illustrative example mollusc based climate reconstructions suggest generally warm and very dry summer conditions with mean july temperatures up to 21 c for the southern carpathian basin during the last glacial results based on stable carbon isotopes strongly oppose such high summer temperatures but studies based on n alkanes are in general agreement with the mollusc data when it comes to the vegetation reconstruction indicating mostly steppic conditions however n alkanes studies contradict warm and dry glacial conditions as indicated by mollusc based reconstructions pointing instead to cold and relatively humid glacials in addition there is an ongoing debate whether or not millennial scale climatic oscillations can be observed in the carpathian basin loess as well as whether this area was an important northern hemisphere dust source or rather a sink of far distance dust transport consequently the current state of the art of the palaeoclimate reconstructions from loess in the carpathian basin is rather inconsistent in order to make sense of the existing palaeoclimate data from the carpathian basin loess we have reevaluated and reinterpreted the available data we discuss and propose a coherent interpretation of rock magnetic grain size malacological stable carbon and nitrogen isotope n alkane and bacterial membrane lipid data for the last glacial cycle loess archives from the carpathian basin we show that glacial conditions in the carpathian basin led to a notable increasing north south gradient in temperature and an even stronger expressed decreasing trend in humidity and that most of the biomarker proxy data conducted in loess for the very dry southern part of the carpathian basin show a strong bias towards arid conditions in particular palaeotemperature reconstructions seem to be misleading glacial conditions were drier and colder than previously proposed summer temperatures likely under 15 c during glacials but notably warmer than in other parts of western central and eastern europe the vegetation consisted mostly of steppic environments during both glacials and interglacials we indicate that the carpathian basin has a potential to be a major dust source of the northern hemisphere during glacials although it was at the same time exposed to the deposition of fine far distance travelled dust moreover the main issues in the regional and continental correlation of loess are highlighted as well as the sensitivity of the carpathian basin loess to the millennial scale climate variability recorded in other northern hemisphere records finally we suggest that the onset of loess formation in the investigated area occurred during the middle pleistocene transition and it was probably related to intensive silt production related to glacier dynamics in the alpine ice cap

irrigation return flows in a mediterranean aquifer inferred from combined chloride and stable isotopes mass balances the supply of irrigation water often overcomes crop evapotranspiration and the resulting return flow may infiltrate and significantly contribute to an aquifer water budget despite its crucial importance for water resource management the proportion of irrigation water that contributes to groundwater recharge namely the return flow coefficient often remains difficult to assess here a chloride mass balance is combined with an isotopic mixing model d18o and dd to quantify return flow coefficients in the crau alluvial type aquifer southern france characterized by a long term traditional practice of flood irrigation local groundwater compositions are interpreted in terms of average recharge along different flow paths the high isotopic contrast between irrigation water and regional precipitation al lows the partitioning of recharge between rainfall infiltration and irrigation return flows isotopic mixing proportions are then used to decipher the chloride concentration of groundwater purely recharged by return flow this allows an original application of the chloride mass balance approach to estimate return flow coefficients which doesn t rely on any atmospheric chloride survey values around 0 53 0 16 were found for well defined stream lines averaging the functioning of the upstream aquifer which leads to a return flow rate of 1190 140 mm yr 1 these results are consistent with a local daily time series of recharge fluxes derived from the water table fluctuation method over the 2003 2009 period and in line with the spatial average previously quantified over the whole aquifer this study confirms the ability of geochemical tracers to provide recharge rates fully independent from flux measurements they can be further used to assess the irrigation efficiency in other similar systems or to monitor the variations of irrigation return flow which will result from the future modifications of land use irrigation practices and climate

distributed acquisition characterization and process analysis of multi field information in slopes the slope is a multiphase composite system including solid liquid and gas phases slope stability changes under the actions of stress temperature and seepage slopes will be very prone to landslide if in an unstable state in this paper considering the contributions of different fields to the landslide the distributed acquisition characterization and stability analysis of multi field information from slopes was studied systematically using distributed fiber optic sensing dfos technology a sensing system based on dfos was designed and developed for multi field information monitoring including stress temperature seepage and deformation the corresponding methods for data processing identification and methods for characterization description are also proposed on this basis the evolution of the slope is analyzed finally monitoring results of the dfos system from the majiagou landslide are shown as a case study for verification

composition and history of ground water in the western nile delta abstract a hydrochemical and environmental isotope investigation was conducted in the nile delta and adjacent desert fringes within the framework of a routine hydrogeological mapping project the aim of the study was to obtain additional insight into the historical groundwater flow pattern to differentiate between fossil ground water and contemporaneous recharge by nile water an inventory of existing chemical analyses was made 252 data points and an additional 27 new samples were taken which were also analysed for stable isotope 18 o and 2 h content and for nine samples 14 c and tritium in the majority of analyses irrespective of total salinity an enrichment in sodium was observed relative to the concentration resulting from direct mixing of nile water with sewater the na rich water is thought to have originated in the extreme arid period from 14000 to 10000 years b p last phase of the weichsel glaciation in which by direct evaporation of scarce rain trona minerals were formed at the surface and the ground water in phreatic aquifers gradually became saline the succeeding humid phase from 8000 to 5000 years b p when sea level was relatively high caused freshening on the desert fringes only because the delta floodplain was covered by clay the present arid phase which started at around 3500 years b p also marked the start of widespread floodplain irrigation groundwater levels on the desert fringes dropped as a result of both aquifer depletion by discharge to the qattara depression in the west and climatic effects this in turn initiated a freshening process in the quaternary and moghra aquifer of the delta nile water has since then reached wadi natrun 55 km to the west of the western floodplain border

the potential roles of biological soil crusts in dryland hydrologic cycles biological soil crusts bscs are the dominant living cover in many drylands of the world they possess many features that can influence different aspects of local hydrologic cycles including soil porosity absorptivity roughness aggregate stability texture pore formation and water retention the influence of biological soil crusts on these factors depends on their internal and external structure which varies with climate soil and disturbance history this paper presents the different types of biological soil crusts discusses how crust type likely influences various aspects of the hydrologic cycle and reviews what is known and not known about the influence of biological crusts on sediment production and water infiltration versus runoff in various drylands around the world most studies examining the effect of biological soil crusts on local hydrology are done by comparing undisturbed sites with those recently disturbed by the researchers unfortunately this greatly complicates interpretation of the results applied disturbances alter many soil features such as soil texture roughness aggregate stability physical crusting porosity and bulk density in ways that would not necessarily be the same if crusts were not naturally present combined these studies show little agreement on how biological crusts affect water infiltration or runoff however when studies are separated by biological crust type and utilize naturally occurring differences among these types results indicate that biological crusts in hyperarid regions reduce infiltration and increase runoff have mixed effects in arid regions and increase infiltration and reduce runoff in semiarid cool and cold drylands however more studies are needed before broad generalizations can be made on how biological crusts affect infiltration and runoff we especially need studies that control for sub surface soil features such as bulk density micro and macropores and biological crust structure unlike the mixed effects of biological crusts on infiltration and runoff among regions almost all studies show that biological crusts reduce sediment production regardless of crust or dryland type copyright 2006 john wiley sons ltd

identification of soil redistribution using 137cs for characterizing landslide prone areas a case study in sarno quindici italy debris flows are among the most hazardous and unpredictable processes whose hazard evaluation requires an understanding of the processes that govern sediment supply sediment bulking flow volume and deposition in line with this challenge we estimate the net soil redistribution rates in an area characterized by recurrent instability phenomena using 137cs as a tracer for monitoring soil dynamics an extension of this method by applying it to the case of major landslides is addressed specifically surveys of soil 137cs content at sites in the pizzo d alvano massif italy where a set of particularly damaging landslides occurred on 5 6 may 1998 are reported being this region prone to debris flows two zero order basins are examined one of which experienced a landslide event in that basin deposition is observed whereas the other shows a net loss of soil these results appear to be relevant particularly because the rate of hollow filling could be correlated with the magnitude and or frequency of debris flow occurrence or with some measure of the hazard presented by individual gullies