subsurface flow in a soil mantled subtropical dolomite karst slope a field rainfall simulation study abstract soil and epikarst co evolve resulting in complex structures but their coupled structural effects on hydrological processes are poorly understood in karst regions this study examined the plot scale subsurface flow characteristics from an integrated soil epikarst system perspective in a humid subtropical cockpit karst region of southwest china a trench was excavated to the epikarst lower boundary for collecting individual subsurface flows in five sections with different soil thicknesses four field rainfall simulation experiments were carried out under different initial moisture conditions dry and wet and rainfall intensities 114 mm h 1 high and 46 mm h 1 low on average the soil epikarst system was characterized by shallow soil overlaying a highly irregular epikarst surface with a near steady infiltration rate of about 35 mm h 1 the subsurface flows occurred mainly along the soil epikarst interface and were dominated by preferential flow the subsurface flow hydrographs showed strong spatial variability and had high steady state coefficients 0 52 and 0 36 for high and low rainfall intensity events irregular epikarst surface combining with high vertical drainage capacity resulted in high threshold rainfall depths for subsurface flows 67 mm and 263 mm for initial wet and dry conditions respectively the above results evidenced that the irregular and permeable soil epikarst interface was a crucial component of soil epikarst architecture and consequently should be taken into account in the hydrological modeling for karst regions

application of fluid rock reaction studies to in situ recovery from oil sand deposits alberta canada ii mineral transformations during an experimental statistical study of water bitumen shale reactions abstract solution mineral equilibria were calculated for the aqueous phase and x ray diffractograms obtained for the solids from the factorial experiment reported in part i of this series of papers in which a shale from the lower cretaceous mcmurray formation in the athabasca oil sand deposit of alberta in the presence or absence of bitumen was subjected to hydrothermal treatment with aqueous fluids of varying ph and salinity at two different temperatures for periods up to 92 hours data representing the departures from equilibrium and normalized x ray diffraction peak intensities were studied by statistical analysis of variance in addition to the dissolution of quartz montmorillonite was formed probably through a transitional illite montmorillonite interstratined layer structure with the reaction being favored by high ph of the aqueous phase the dissolution of siderite is significantly affected by time salinity and the interactions between ph and salinity time and salinity and ph temperature and time despite the restrictions imposed by a laboratory investigation the results demonstrate that mineral dissolution and transformation will be extensive during in situ recovery operations in oil sand deposits

assessment of multiple and interacting modes of soil loss in the karst critical zone southwest china swc abstract in southwest china swc soil loss is becoming a serious threat to the sustainable development of resources and the health of the environment a large number of studies have been conducted to investigate the causes e g environmental factors and human activities and impacts e g karst rocky desertification of soil loss however the following are some important problems related to soil loss in the karst of swc 1 although soil loss is caused by chemical weathering gravity and water interaction in karst the mechanisms by which soil loss takes place in the swc and their interaction are still not clear 2 subsurface soil loss varies under different geological and hydrological conditions and there is still no consensus on the common the ratio between surface soil erosion and underground soil loss 3 traditional methods for soil loss risk assessment are difficult to apply over the whole of swc and 4 a large number of studies have been published only in chinese and remain inaccessible to the international science community therefore a review paper is needed to address this gap and introduce the contributions of chinese researchers to soil loss in karst this paper proposes a novel modelling approach for the grouped soil loss styles and presents a comprehensive discussion for the mechanism causes and risk assessment of the various soil loss styles in swc karst

regional recharge to a karst aquifer estimated from chemical and isotopic composition of diffuse and localised recharge south australia the relative importance of different recharge mechanisms has been investigated for a karstic area in a subhumid to semi arid region of south australia the chemical and isotopic signature 2h and 18o of regional groundwater sampled from shallow bores in the study area as well as water from sinkholes swamps drainage bores and water extracted from soil in the unsaturated zone has been measured point estimates of recharge based on data from the unsaturated zone have been combined with temporal and spatial trends in the isotopic and chemical signature of the groundwater to provide a regional estimate for recharge for different land elements for approximately half of the study area which has predominantly clay soils recharge is low 10 mm year 1 and the groundwaters within the study area are derived from lateral flow from the east for the remaining area recharge has significantly increased since agricultural development and has affected the groundwater system groundwater within the vicinity of irrigation areas has shown marked increases in salinity over the past 30 years owing to the impact of irrigation drainage waters other areas not under irrigation but cleared of native vegetation and replaced by shallow rooting pastures also show increased salinity in parts where there are sandy soils in these areas saline soil water from the unsaturated zone has been displaced by the increased recharge since clearing the effect of clearing on areas of clay surface soils has not increased recharge to the same extent and groundwater salinity levels are largely unchanged areas where salinity levels are rising correlate well with increased 14c activity and depleted 13c concentrations of the groundwater suggesting that these isotopes may be an early indicator of areas of enhanced recharge

characterization of karst structures using quasi 3d electrical resistivity tomography karst is characteristically complex hydrogeologically due to a high degree of heterogeneity which is often typified by specific features for example cavities and sinkholes embedded in a landscape with significant spatial variability of weathering characterization of such heterogeneity is challenging with conventional hydrogeological methods however geophysical tools offer the potential to gain insight into key features that control the hydrological function of a karst aquifer electrical resistivity tomography ert is recognized as the most effective technique for mapping karstic features this method is typically carried out along transects to reveal 2d models of resistivity variability however karstic systems are rarely 2d in nature in this study ert is employed in valley and hillslope regions of a karst critical zone observatory chenqi watershed guizhou province china using a quasi 3d approach the results from the extensive geophysical surveys show that there is a strong association between resistivity anomalies and known karstic features they highlight the significance of a marlstone layer in channeling spring flow in the catchment and confining deeper groundwater flow evidenced by for example localized artesian conditions in observation wells our results highlight the need to analyze and interpret geophysical data in a three dimensional manner in such highly heterogeneous karstic environments and the value of combining geological and hydrogeological data with geophysical models to help improve our understanding of the hydrological function of a karst system

linear unit response functions as indicators of recharge areas for large karst springs abstract the delineation of groundwater recharge areas for karst springs is important for estimating groundwater supplies and for identifying sources and directions of contaminant movement this paper suggests the potential utility of spring discharge kernel functions analogous to instantaneous unit hydrographs for surface runoff in the identification of the recharge areas of large springs examples from southeastern missouri u s a show that when consistent methods are used for baseflow separation and excess precipitation determinations derived linear kernels are most physically realistic and have the least fitting error when the assumed spring recharge area is consistent with tracer study results

the erosional response of calcareous soils along a climatological gradient in southeast spain abstract the erosional response of calcareous soils along a climatological gradient in alicante se spain was studied the erosional response was defined in terms of indicators obtained from field rainfall simulation experiments and laboratory studies of soil aggregation measurements were made at seven sites on limestones and marls between benidorm with an annual average rainfall of 400 mm yr 1 and coll de rates annual rainfall 900 mm yr 1 the sites were on matorral vegetation affected to varying intensities by grazing and fire at the seven locations soil aggregation was studied by sieving by the single water drop test and by a microscan particle sizer rainfall simulation experiments were made on circular 55 cm diameter target area plots using the calvo simulator at an intensities between 35 and 59 mm h 1 on limestone it was found that on bare surfaces the coarse soil aggregation increases with depth at the highest sites and decreases at the lower sites the benidorm surface soil has the highest erodibility the least stable soils are at the lower intermediate sites on marls the aggregate stability is generally high in contrast to those under cultivation simulated runoff from the wetter limestone sites is very low the driest areas have the highest runoff and sediment yields trends with climate suggest that the erosional responses of the soils indeed increase with aridity and temperature but local factors have a large effect particularly at intermediate altitudes a clear relationship like that found in israel by lavee on a similar lithology does not exist

numerical versus statistical modelling of natural response of a karst hydrogeological system abstract structural and hydrodynamic characteristics of karst aquifers are mostly deduced from studies of global responses of karst springs hydrographs chemical or isotopic composition in this case global response is often used to make inferences with respect to infiltration and ground water flow processes as well as on the hydrodynamic parameters obviously the direct verification of these inferences is very difficult we have used an indirect method of verification introducing well defined theoretical karst structures into a finite element model and then analysing the simulated global response according to the currently accepted interpretation schemes as we know what we are introducing into the numeric model the consistency of the interpretation may be checked immediately the results obtained in the hydrogeological study of two karst basins in the swiss jura and from 2 d and 3 d numerical simulations show the difficulty of finding structural parameters and hydrodynamic behaviour from statistical methods alone i e correlation analyses discharge discharge and precipitation discharge in effect our first results show that the form of the correlograms depends on several factors besides the structure of the karst aquifer i on the form of the floods in other words the contrast between quick flow and base flow ii on the frequency of hydrological events during the period analysed and iii on the type of infiltration processes in other words the ratio of diffuse infiltration to concentrated infiltration obviously the variability of a karst hydrograph is a result of a combination of these factors distinction between them is not always possible on hydrographs and therefore on correlations discharge discharge and precipitation discharge

characterizing the heterogeneity of karst critical zone and its hydrological function an integrated approach spatial heterogeneity in the subsurface of karst environments is high as evidenced by the multi phase porosity of carbonate rocks and complex landform features that result in marked variability of hydrological processes in space and time this includes complex exchange of various flows e g fast conduit flows and slow fracture flows in different locations here we integrate various state of the art methods to understand the structure and function of this poorly constrained critical zone environment geophysical hydrometric and tracer tools are used to characterize the hydrological functions of the cockpit karst critical zone in the small catchment of chenqi guizhou province china geophysical surveys using electrical resistivity tomography ert inferred the spatial heterogeneity of permeability in the epikarst and underlying aquifer water tables in depression wells in valley bottom areas as well as discharge from springs on steeper hillslopes and at the catchment outlet showed different hydrodynamic responses to storm event rainwater recharge and hillslope flows tracer studies using water temperatures and stable water isotopes d and 18o could be used alongside insights into aquifer permeability from ert surveys to explain site and depth dependent variability in the groundwater response in terms of the degree to which new water from storm rainfall recharges and mixes with old pre event water in karst aquifers this integrated approach reveals spatial structure in the karst critical zone and provides a conceptual framework of hydrological functions across spatial and temporal scales

modeling complex flow in a karst aquifer abstract carbonate aquifers typically have complex groundwater flow patterns that result from depositional heterogeneities and post lithification fracturing and karstification various sources of information may be used to build a conceptual understanding of flow in the system including drilling data well tests geophysical surveys tracer tests and spring gaging these data were assembled to model flow numerically in germany s malm formation at a site where water disappears from the beds of ephemeral stream valleys flows through conduit systems and discharges to springs along surface water features modeling was performed by using a finite difference approach with drain networks representing the conduit component of flow laced throughout the porous medium along paths inferred on the basis of site data this approach represents an improvement over other karst models that attempt to represent a conduit by a single specialized model node at the spring location or by assigning a computationally problematic extremely high permeability to a zone by handling the conduit portion of this mixed flow system with drains a realistic interpretive flow model was created for this intricate aquifer

evaluation of electrical resistivity tomography ert for mapping the soil rock interface in karstic environments rocky desertification is a significant threat in the karst regions of southwest china studies of soil distribution can contribute to protecting and recovering the fragile karst ecosystem that is prevalent in this region with an underlying aim of being able to assess soil stocks in karstic environments this study evaluates the use of electrical resistivity tomography ert for delineating the soil rock interface using a synthetic model that recognizes the three dimensional nature of the subsurface experiments are performed to assess the impact of measurement errors and measurement configuration on recovery of the interface the inverted results show that the accuracy of the delineation of the soil rock interface decreases with the increase of measurement error and dipole spacing the results also show the importance of reliable estimation of measurement errors field based applications of ert at five exposed profiles in southwest china are also reported for the field data three dimensional modelling was necessary to account for the exposed face the field experiments show that ert can be effective at delineating the interface between soil and bedrock but resolution can be limited due to the scale of features or lack of contrast between soil and bedrock the method shows great promise as a means of assessing in a non invasive manner the soil bedrock interface and perhaps more significantly quantifying estimates of total soil stocks as we seek to quantify the vulnerability or resilience of this important landscape to anthropogenic and natural stresses

parsimonious recharge discharge modeling in carbonate fractured aquifers the groundwater flow in the gran sasso aquifer central italy summary in the carbonate fractured aquifer of the gran sasso central italy numerical simulations have been applied to validate a conceptual model of the recharge discharge cycle at regional scale to identify the effective aquifer features that mostly affect the spring discharges simple parsimonious models based on few key parameters whose effective values are well constrained by previous hydrological geological studies are used input data are represented by infiltration calculated considering rainfall snowmelt and runoff in endorheic basins and effective permeability distribution estimated by geological tectonic and hydrogeological settings of the aquifer discharges of tapped springs and tunnel drainages for the 1999 2009 period have been simulated after estimating the recharge area of each monitored spring by the hydrogeological setting and checking them by mean isotope elevation values discharge monitoring has been compared with the simulations obtaining a good agreement both at seasonal and yearly time basis the simulations will also be useful for previewing discharge in drought period and evaluating protection zones of tapped springs in the territory of a national park

groundwater balance estimation in karst by using a conceptual rainfall runoff model summary a conceptual rainfall runoff model is proposed for the estimation of groundwater balance components including the influences of time variant catchment boundaries and intercatchment groundwater flows karst underground is considered as a lumped system that contains 1 soil cover 2 epikarst zone and 3 vadose and phreatic zones the soil cover receives an average rainfall in catchment as the input into the system the epikarst zone is composed of a production store and a routing store the production store contributes to the loss of water in process of evapotranspiration the routing store contributes to the retention of percolated water and the lateral distribution of groundwater recharge between internal runoff and diffuse infiltration the vadose and phreatic zones accumulate groundwater in fissures fractures and vertical shafts and produce the vadose seepage vadose flow and shaft flow components of the karst spring discharge the parameter estimation and calculation procedure assemble the moisture balance and the groundwater balance approaches the rainfall runoff model is divided in two sub models the sub model based on the moisture balance of soil cover and epikarst production store calculates effective rainfalls the sub model based on the groundwater balance of vadose and phreatic zone calculates groundwater recharges the difference between the effective rainfalls and the groundwater recharges represents the contribution of epikarst zone and non conservative and time variant components to the groundwater balance the proposed methodology is applied to the jadro spring located near the city of split in croatia the calculated groundwater balance shows that the jadro spring aquifer contains a significant storage capacity in the vadose and phreatic zones during the year the aquifer may accumulate up to 140 millions m 3 the variability of calculated catchment area is explained with the time variant catchment boundary dependent on groundwater levels and the intercatchment groundwater flows from neighboring catchments the average catchment area of 396 km 2 is estimated by using the average monthly effective rainfalls and the average monthly groundwater recharges

erosion creep collapse mechanism of underground soil loss for the karst rocky desertification in chenqi village puding county guizhou china carbonate rocks distribute widely in china the total area of the carbonate rocks is about 3 430 000 km 2 and the exposed area of the carbonate is approximately 13 of china s territory in 2003 soil loss in yunnan guizhou and guangxi provinces reached 179 600 km 2 which is almost 40 1 of the total area causing rocky desertification in this study the erosion creep collapse mechanism of underground soil loss for the karst rocky desertification in chenqi village puding county guizhou province is proposed the mechanism occurs under the following geological environment slope surface undulation underlying bedrock surface fluctuation and thin and inhomogeneous soil overlying overlying soil generation by bedrock weathering underground karst development and large groundwater depth and lying water table under the bottom of soils the erosion creep collapse mechanism of underground soil loss in the karst slopes is explained as follows power loss due to human cultivation activities that destroy the soil structure hydraulic force formed by rainfall infiltration wet dry cycle generated by rainfall erosion effect caused by rainfall penetration creeping and flowing of plastic stream soil and collapse the erosion creep collapse mechanism of underground soil loss has seven steps disturbance of soils filled in underground karst cave by human activities internal soil erosion and partial collapse caused by hydraulic power internal free surface formation within the soil in the filled karst cave internal soil creeping soil pipe formation soil pipe collapse and ground surface collapse and filling soil loss develops slowly and sudden transportation occurs by collapse soil loss can be explained by the proposed mechanism and soil loss can be prevented by controlling soil collapse

focused groundwater flow in a carbonate aquifer in a semi arid environment summary an efficient conveyance system for groundwater is shown to have formed in a carbonate aquifer even though it is situated in a semi arid environment this conveyance system comprises preferential flow pathways that developed coincident with river channels a strong correlation between high capacity wells and proximity to higher order river channels i e within 2 5 km is used as evidence of preferential flow pathways factors that contributed to development of the preferential flow paths i karst development in carbonate rocks ii structural exhumation of a carbonate plateau and iii the requirement that the groundwater regime of the watershed has adequate capacity to convey sufficient quantities of water at the required rates across the full extent of the watershed recognition of these preferential pathways in proximity to river channels provides a basis to locate where high capacity wells are likely and unlikely and indicates that groundwater flow within the watershed is relatively rapid consistent with flow rates representative of karstic aquifers this understanding provides a basis for better informed decisions regarding water resource management of a carbonate aquifer in a semi arid environment

monthly karstic spring flow forecasting using a sequential gaussian simulation technique analyzing groundwater hydrologic equations related to karstic aquifers and spring hydrograph simulation have become the focus of many researches having double or triple porosity structure mixed flow nature and varying conduit permeability have made these formations become complex heterogenic systems with great temporal and spatial hydrodynamic variability in this paper a conditional sequential gaussian simulation sgs is used to simulate monthly flow data of five karstic springs with different hydrogeological properties located in zagros mountain chain in western iran to evaluate the performance of the sgs algorithm the results are compared with those of an autoregressive integrated moving average arima model the results demonstrate the efficiency of the sgs model in simulation of monthly flows compared to the arima model they also show the suitability of this model for handling uncertainty associated with karstic spring flows through generation of several equally probable stochastic realizations

recharge estimation of a small karstic aquifer in a semiarid mediterranean region southeastern spain using a hydrological model mediterranean aquifers are frequently subject to the joint effect of intensive exploitation and low recharge values besides groundwater is the only available water resource in many mediterranean regions groundwater recharge studies are therefore necessary to underpin water management practices this manuscript presents a methodology to estimate groundwater recharge in a small limestone aquifer of southeastern spain the hydrobal model is used to calculate daily soil water balances on the basis of hydrological and soil data as well as on vegetation cover deep drainage model outputs are converted into water table variations using a lumped model add on the adjustment between observed and calculated water table levels is in the order of r2 0 87 this correlation coefficient suggests that hydrobal is a useful tool to estimate groundwater recharge in the region in addition differences in groundwater recharge rates are observed for dry average and wet years estimated recharge rates range between 0 and 18 of the mean annual rainfall which corresponds to a net recharge of 0 to 59 mm year 1 recharge rates increase proportionally with precipitation r2 0 90 copyright 2012 john wiley sons ltd

effects of lithology and geomorphology on sediment yield in karst mountainous catchments abstract due to the characteristics of the lithology and the complexity of the geomorphology the karst areas of southwest china are experiencing severe soil erosion knowledge of the effects of lithology and geomorphology on sediment yield are therefore essential for developing measures to effectively control sediment delivery in this region the objective of this study was to investigate the relative importance of lithological and geomorphological factors for sediment yield in 40 selected karst mountainous catchments in southwest china because of the high co dependence of these variables a partial least squares regression plsr model was used to explore the quantitative relationships between annual sediment yield and 30 lithological and geomorphological factors results showed that the lithology and geomorphology were critically important to annual sediment yield and could explain 65 9 of the total variance in sediment yield the dominant lithological and geomorphological factors controlling annual sediment yield were karst coverage drainage density basin relief plane curvature elevation maximum elevation average slope dolomite coverage relative relief and catchment area this importance or these contributions of lithological and geomorphological factors to annual sediment yield provides a good reference for selecting key factors when developing soil erosion models this study yields a greater understanding of the influences of lithology and geomorphology on sediment yield and is helpful for better catchment management in karst regions

lumped and distributed approaches to model natural recharge in semiarid karst aquifers summary recharge is a key component of the hydrological balance in groundwater systems particularly in arid and semiarid settings recharge often takes place during isolated rainfall episodes as a result pumping might cause groundwater levels to fall continuously for long periods of time even if yearly abstractions remain below the average replenishment rate recharge is naturally difficult to quantify as it depends on a complex variety of factors indirect techniques based on mathematical models have long since been advocated as valuable means to estimate recharge this paper presents a methodology to estimate groundwater recharge in quick response semiarid karst aquifers lumped and distributed models are used to evaluate the fraction of rainfall that ultimately results in aquifer recharge as well as the correlation between the magnitude of rainfall events and infiltration rates modelling results are then compared with direct observations of the recharge processes and discussed to evaluate the implications of time scales this study is demonstrated through a case specific application to the ventos aquifer an intensively exploited carbonate system located in one of the driest areas of peninsular spain overall both approaches perform similarly although the lumped model exhibits a better agreement with field records results reflect the nonlinear nature of the rainfall recharge ratio the fraction of rainfall that ultimately recharges the aquifer seems to increase exponentially with the magnitude of the event

hydraulic properties of karst fractures filled with soils and regolith materials implication for their ecohydrological functions abstract in regions with shallow soils underlain by fractured bedrock hydrological processes of substrate are no longer only limited to soil layers however ecohydrological functions of bedrock fractures especially those filled with different soil and regolith materials have not been fully understood in this study we aimed to evaluate water transport and supplying capacities of the filled fractures through investigating hydraulic properties and explore their dominant influencing factors three typical fractures a vertical one filled with fine textured soil vsf a vertical one filled with soil and regolith materials vsrf and a non vertical one filled with coarse textured soil nsf were selected from a large newly excavated trench on a karst hillslope of southwest china stratified samples of fracture fillings were collected to measure saturated hydraulic conductivity k s water retention curves and basic physicochemical properties additionally twenty soil profiles in different topographic locations in the same study area were also analyzed in order to support the results derived from the filled fractures all fractures exhibited extremely high k s 87 149 mm h 1 in surface soil 0 10 cm which allowed rapid infiltration of rainwater into subsurface subsurface water transport was smooth when underlying fracture fillings were loamy with relatively high k s about 10 mm h 1 like in nsf but was blocked when they were clayey with low k s 1 like in vsf and vsrf all fracture fillings had abilities to hold water and available water was the most in nsf which provided an extra water source for plant growth in shallow soil regions the ecohydrological functions of the filled fractures often depend on the properties and layering of fracture fillings which was supported by those obtained from the twenty soil profiles these results are helpful for better understanding of the ecohydrological processes and functions of fractures filled with different materials in karst regions

behavior of five large spread footings in sand five square spread footings ranging in size from 1 mm to 3 mm were load tested up to 150 mm of settlement they were all embedded 0 75 m into a medium dense fairly uniform silty silica sand load settlement curves are presented as well as creep curves relating settlement and time under a constant load since the soil mass was instrumented with telltales and inclinometers vertical and horizontal movements in the soil mass were obtained as a function of depth and lateral extent conclusions are reached regarding how best to measure footing settlement how to present load test results new correlations for use in design creep settlement effect of cyclic loading and preloading on creep rate zone of influence under the footing mode of deformation of the soil mass and volume change observations twelve settlement methods six bearing capacity methods and the wave activated stiffness test are evaluated by comparing the predictions with the measurements many results of these large scale instrumented tests confirm findings at small scale of previous researchers

ground water behaviour in karst example of the ombla spring croatia abstract the hydro electric power plant hepp which will exclusively use water from a karst underground storage basin will be built in the vicinity of the abundant karst spring ombla in croatia this paper presents the results obtained by hydrogeologic hydrologic and hydraulic investigations related to the principles of ground water circulation in the karst the analyses included the determination of the effective porosity ne of the karst aquifer and the definition of the volume of large conduits and small fractures in the karst which form the aquifer volume the position and dimensions of large karst conduits have also been defined it was established that in three small springs zaton zavrelje and slavljan water overflows from the ombla spring in periods of high ground water levels it was also discovered that at certain periods the dupuit expression for steady state flow in an unconfined aquifer can be used in accordance with this it was possible to determine the values of hydraulic conductivity k in m s 1 for the ombla aquifer they range from 2 10 3 to 5 10 3 m s 1 and are inversely proportional to the ombla spring discharge continuous measurements of the ground water level by several piezometers located in the karst hinterland of the ombla spring and simultaneous measurement of the discharge made it possible to define discharge curves of the ombla spring dependent upon the ground water levels at various locations characteristic features of the discharge curves made the identification of the position and dimensions of the main karst conduits possible

role of underground fissure flow in near surface rainfall runoff process on a rock mantled slope in the karst rocky desertification area abstract because of the complex near surface double layer geologic structure i e surface and underground fissures of slopes in karst regions it is difficult to collect data on all flows especially the flows generated in underground fissures this lack of information leads to a poor understanding of the rainfall runoff process associated with soil loss in karst landscapes the goal of this study was to determine the output characteristics of surface subsurface and underground fissure flows and their conversion relationships as well as the role of underground fissure flow in the near surface rainfall runoff process using rainfall experiments the results revealed the following findings light rainfall intensities 15 and 30 mm h generated subsurface lateral flow and underground fissure flow whereas greater rainfall intensities generated surface runoff in addition to subsurface and underground flows ii the runoff drainage depths of all the above flows increased with increasing rainfall intensity while the runoff drainage coefficient exhibited no obvious regular change except for the surface runoff moreover the distribution ratio of surface runoff to total flow also increased with increasing rainfall intensity but decreased with increasing underground fissure degree while the distribution ratio of underground fissure flow exhibited the opposite trend iii underground fissure flow with distribution ratios of 27 8 78 0 dominated the total flow yield this study has significance for controlling soil erosion and water shortage in the karst rocky desertification region and also improves the understanding of the near surface rainfall runoff process in this region

role of epikarst in near surface hydrological processes in a soil mantled subtropical dolomite karst slope implications of field rainfall simulation experiments epikarst exerts a strong control on run off generation in karst regions but it is still unclear in karst regions our study aimed to demonstrate the effect of epikarst on near surface hydrological processes in a subtropical cockpit karst region of southwest china using plot scale rainfall simulation experiments with different rainfall intensities low and high and antecedent moisture conditions dry and wet a trench excavated to the epikarst lower boundary allowed identification of flow pathways in the entire soil epikarst architecture system thus facilitating the water balance calculations using a conceptual model with the assumption of a two stage hydrological evolution more than 70 of the total rainfall water moved vertically through the shallow soil layer and then was redistributed by the epikarst as subsurface flow occurring on the soil epikarst interface depression filling on epikarst surface water held by epikarst and deep percolation epikarst water regulation capacity defined as the sum of depression filling on epikarst surface water held by epikarst epikarst seepage flow and deep percolation was 58 mm wet antecedent condition and 223 mm dry antecedent condition total run off from the soil epikarst system was dominated by saturated subsurface flow showing a threshold process controlled by epikarst storage capacity storing as much as 181 mm of rainfall water under dry antecedent condition our study proved that despite the epikarst being relatively poorly developed and covered by a soil mantle it still exerted a strong influence on near surface hydrological processes and thus should be adequately considered in future modelling of water recharge and depletion dynamics in this integrated soil epikarst system copyright 2015 john wiley sons ltd

analytical 1d dual porosity equivalent solutions to 3d discrete single continuum models application to karstic spring hydrograph modelling abstract one dimensional analytical porosity weighted solutions of the dual porosity model are derived providing insights on how to relate exchange and storage coefficients to the volumetric density of the high permeability medium it is shown that porosity weighted storage and exchange coefficients are needed when handling highly heterogeneous systems such as karstic aquifers using equivalent dual porosity models the sensitivity of these coefficients is illustrated by means of numerical experiments with theoretical karst systems the presented 1d dual porosity analytical model is used to reproduce the hydraulic responses of reference 3d karst aquifers modelled by a discrete single continuum approach under various stress conditions simulation results show the relations between the dual porosity model coefficients and the structural features of the discrete single continuum model the calibration of the equivalent 1d analytical dual porosity model on reference hydraulic responses confirms the dependence of the exchange coefficient with the karstic network density the use of the analytical model could also point out some fundamental structural properties of the karstic network that rule the shape of the hydraulic responses such as density and connectivity

runoff generation sediment movement and soil water behaviour on calcareous limestone slopes of some mediterranean environments in southeast spain abstract an interpretation of soil hydrology and erosion data obtained from limestone areas in southeast spain is presented in the framework of recent hypotheses on runoff generation mechanisms in mediterranean environments the main objective is to synthesise and harmonise the data in theoretical concepts or behavioural models of hydrological functioning of mediterranean limestone slopes for this purpose data were collected in a typical limestone area with climatic characteristics ranging from subhumid to semiarid several sites were chosen with comparable slopes vegetation and soils along a transect of 20 km to carry out several research projects the data discussed in this paper consist of information on water redistribution within the soil profiles obtained from long duration up to 5 h rainfall simulation experiments with continuous monitoring of soil moisture at different depths runoff and sediment concentration data were obtained i from rainfall simulation experiments with different antecedent soil moisture conditions and ii as natural results from open gerlach plots on runoff and sediment movement over 4 years three conceptual models of water redistribution during the infiltration process could be observed two of them imply nonuniform water redistribution within the soil profile due mainly to macropore flow caused by specific soil surface characteristics at the plot scale runoff generated in bare patches is mainly hortonian in plots with previously wetted soils or soils with high infiltration capacities the generated runoff implies the saturation of the upper soil both types of runoff are discontinuous through time and space the runoff generation mechanisms at the slope scale have been synthesised into two conceptual models a hortonian discontinuous runoff model that takes place in the most degraded slopes or during high intensity rain events and a mixed runoff generation model in less degraded slopes or in previously wet soils where infiltration excess runoff as well as saturation excess runoff can happen on the same slope in both cases slopes behave as a patchwork of runoff and runon areas the size of the runoff or runon patches is dependent on the climatological conditions these control the hydrological disconnection between different parts of the slopes hortonian and saturation runoff can both be generated and infiltrated downslope

a step wise semi distributed simulation approach to characterize a karst aquifer and to support dam construction in a data scarce environment abstract karst systems provide significant volumes of drinking water for large parts of the world population due to chemical weathering karst systems are characterized by strong heterogeneity resulting in a complex flow and storage behaviour presently available karst modelling strategies account for the karstic heterogeneity but often a lack of data limits their applicability in data scarce regions in this study a step wise simulation approach with a semi distributed karst model is proposed to characterize a karst aquifer at a data scarce region in southwest iran and to evaluate the leakage potential related to a future dam construction project at a river that cuts through the aquifer observed groundwater level time series were applied to calibrate and validate the model in order to avoid over parameterization the karst aquifer was split into three sections down the hydraulic gradient at each section groundwater level observations were used to iteratively calibrate the model from the first to the last section a spatial split sample test and sensitivity analysis served to evaluate the prediction performance and the identifiability of the model parameters finally simple scenarios of the river infiltration into the aquifer were applied to evaluate the leakage potential of the aquifer for future dam constructions the spatial split sample test showed that the semi distributed model provided reliable predictions but prediction performance and parameter identifiability decreased from the first towards the last aquifer section most probably due to increased aquifer complexity and propagation of uncertainty from the up gradient model section using sensitivity analysis we also show that parameter sensitivities increase significantly if parameter estimation was applied simultaneously to all three aquifer subsections using the model to assess the leakage potential indicated that without further technical measures the all river flow would be able infiltrate into the aquifer and the dam would never be filled up completely

dating reservoir deposits to reconstruct sediment yields from a small limestone catchment in the yimeng mountain region china abstract in this study we use reservoir deposits to reconstruct sediment yields over the past 50 years from the quananzi catchment a small limestone catchment in the yimeng mountain region china three sediment cores were collected from the reservoir and the chronology of each core was established using 137cs and 210pbex dating the area specific sediment yields ssy for different time periods since dam construction were estimated from each core by referring to the original capacity curves of the reservoir the estimated ssy from the quananzi catchment in each core for each period ranged between 0 9 0 3 and 2 6 0 9 t ha 1 y 1 with a mean value of 1 8 0 6 t ha 1 y 1 which is low compared with reported ssy from catchments worldwide the mean value was only about 1 7 of the equivalent value reported from the jiangzhang catchment in the granite area of the yimeng mountain region this low ssy reflects the shortage of erodible luvisols resistance to erosion and the limited effect of human disturbance in this small limestone catchment the decrease in ssy from 1959 to1972 suggests that the effect of the deforestation that occurred in 1958 on soil erosion decreased with time the continual increase of ssy through the two subsequent periods after 1972 reflects the expansion and intensification of cultivation during this time however the decreased ssy over the latest period of 1998 2012 can be related to the limitations imposed by the karst landscape on cultivation and to the impact of increasing numbers of residents leaving the area since the end of the 1990s to become temporary migrant workers elsewhere resulting in a decrease in human activity in the area overall the trend in ssy reflects the general history of changing human disturbance in this small limestone catchment over the past 50 years the results indicate that reservoir deposits provide a means of estimating the historical sediment yields from a karstic environment

evaluating the structure characteristics of epikarst at a typical peak cluster depression in guizhou plateau area using ground penetrating radar attributes abstract epikarst defined as the skin of karst environment is widely developed in southwest china largely as a result of the subtropical monsoon climate typical sw china karst accommodates a dual hydrogeological structure with surface and subsurface hydrological systems the epikarst ecosystem of karst environments plays a key role in biogeochemical cycling and energy and material storage and transport due to low rates of soil formation derived from carbonate rock weathering the soil layer is shallow and scattered presenting interlocked features within carbonate rock research on epikarst structure is primarily based on section field survey with semi quantitative characterization often lacking a fully quantitative description of soil rock structural characteristics we utilized ground penetrating radar gpr attributes to interpret the structure of epikarst at a peak cluster depression in the guizhou karst plateau two typical types of epikarst slope profiles and one peak cluster depression in maguan town puding county were selected for study we used mala gpr equipment with 500 mhz and 50 mhz antennas to acquire data gpr data was processed conventionally and then average energy attributes average amplitude attributes and coherence attributes were extracted to interpret the structure of the two epikarst profiles and the soil depth of the depression the results show that i energy and coherence attributes can highlight the soil rock structure of the epikarst profiles with relative ease ii compared to the original returned image the energy attributes visualise the soil and rock medium more effectively and iii the coherence attributes can identify the reflection interface between complete bedrock and bedrock containing fissure and grikes epikarst in addition using the 50 mhz antenna we were able to determine the soil depth in depression with coherence attributes indicating a depth of 3 6 m very close to the real depth 3 58 m measured by our auger verification work gpr attributes provide evidence that the epikarst has developed a large number of fissures filled with soil or other materials but that the bedrock under the epikarst has few fractures gpr attributes are therefore helpful for increasing our confidence of studying the structure of slope epikarst structure and depression soil depth

inverse modeling of the hydrological and the hydrochemical behavior of hydrosystems characterization of karst system functioning inverse modeling of mass transfer characterizes the dynamic processes affecting the function of karst systems and can be used to identify karst properties an inverse model is proposed to calculate unit hydrographs as well as impulse response of fluxes from rainfall runoff or rainfall flux data the purpose of which is hydrograph separation contrary to what hydrologists have been doing for years hydrograph separation is carried out by using transfer functions in their entirety which enables accurate separation of fluxes as was explained in the companion paper pinault et al this issue the unit hydrograph as well as impulse response of fluxes is decomposed into a quick and a slow component and consequently the effective rainfall is decomposed into two parts one contributing to the quick flow or flux and the other contributing to the slow flow generation this approach is applied to seven french karstic aquifers located on the larzac plateau in the grands causses area in the south of france both hydrodynamical and hydrogeochemical data have been recorded from these springs over several hydrological cycles for modeling purposes karst properties can be represented by the impulse responses of flow and flux of dissolved species the heterogeneity of aquifers is translated to time modulated flow and transport at the outlet monitoring these fluxes enables the evaluation of slow and quick components in the hydrograph the quick component refers to the flush flow effect and results from fast infiltration in the karst conduit network when connection is established between the infiltration and phreatic zones inducing an increase in water head this component reflects flood events where flow behavior is nonlinear and is described by a very short transfer function which increases and decreases according to water head the slow component consists of slow and fast infiltration underground runoff storage in annex to drain systems and discharge from the saturated zone these components can be further subdivided by measuring chemical responses at the karst outlet using such natural tracers enables the slow component of the unit hydrograph to be separated into preevent water i e water of the reservoir and event water i e water whose origin can be related to a particular rainfall event these measurements can be used to determine the rate of water renewal since the preevent water hydrograph is produced by stored water when pushed by a rainfall event and the event water hydrograph reflects rainwater transfer separating the two components can yield insights into the characteristics of karst aquifers the modes of infiltration and the mechanisms involved in karstification as well as the degree of organization of the aquifer

validating the kagis black box gis based model in a mediterranean karst aquifer case of study of mela aquifer se spain this research was funded by the spanish ministry of science and innovation projects cgl2013 48802 c3 3 r and cgl2015 69773 c2 1 p and by the university of alicante projects gre15 19 and gre17 12

soil erosion rates in two karst peak cluster depression basins of northwest guangxi china comparison of the rusle model with 137cs measurements reliable estimation of erosion in karst areas is difficult because of the heterogeneous nature of infiltration and subsurface drainage understanding the processes involved is a key requirement for managing against karst rock desertification this study used the revised universal soil loss equation rusle to estimate the annual soil erosion rates on hillslopes and compared them with cs 137 budget in the depressions at two typical karst peak cluster depression basins in northwest guangxi southwestern china runoff plots data were used to calibrate the slope length factor l of the rusle model by adjusting the accumulated area threshold the rusle model was sensitive to the value of the threshold and required dems with 1 m resolution due to the discontinuous nature of the overland flow the average annual soil erosion rates on hillslopes simulated by the rusle were 0 22 and 0 10 mg ha 1 y 1 2006 through 2011 in the partially cultivated gz1 and the undisturbed gz2 basins respectively the corresponding deposition rates in the depressions agreed well with the cs 137 records when recent changes in precipitation and land use were taken into consideration the study suggests that attention should be given to the rusle l factor when applying the rusle on karst hillslopes because of the discontinuous nature of runoff and significant underground seepage during storm events that effectively reduces the effects of slope length c 2015 elsevier b v all rights reserved

semi distributed lumped model of a karst system under active management summary in this paper inverse modeling is used to characterize the regime of a karst aquifer subjected to extensive pumping in a conduit located upstream of its main outlet the systemic approach uses a transfer model that is based on computing the convolution integral of up to several signals e g efficient rainfall pumping to simulate flow rates and groundwater levels in both the karst conduit and the carbonate matrix at the aquifer outlet and in several parts of the catchment area the model is a semi distributed lumped model which simulates the hydrological response of a heterogeneous karst aquifer made up of different hydrologic compartments and is applied to the lez karst system france groundwater is abstracted near the system s major outlet at a higher rate than the low water spring discharge thereby mobilizing stored groundwater during low water periods active management the model s results are very satisfactory especially for the karst system outlet where the water levels are particularly well reproduced the model can also simulate the natural i e non pumping state of the karst system and thereby estimate the impact of active management on the water resource

modelling karst vadose zone hydrology and its relevance for paleoclimate reconstruction abstract understanding past climatic changes allows us to better understand how our planet will evolve in the future one important source of information on paleoclimate is the analysis of speleothems that develop in karst caves and conduits due to the dissolution and precipitation of calcite however there are many uncertainties in paleoclimatic reconstruction with speleothems one of them being hydrological variability up to now only few studies have considered the impact of hydrological variability on speleothem formation and composition this review paper will provide an introduction to hydrological processes that have the potential to affect speleothem composition and the hydrological modelling approaches that are able to account for them it presents the current state of knowledge on paleoclimatic reconstruction using speleothems and shows that many important flow and transport processes have not yet been included in the interpretation of these archives mostly due to a lack of field information to parametrize them possible directions of future research efforts therefore include a better exploration of karst vadose zone processes and new approaches to incorporate this information into simulation models finally we foresee the exciting advances in reconstructing paleohydrology using karst hydrology models combined with speleothem growth rate and geochemical composition to understand how past climate changes affected the hydrological cycle and water availability

effects of land use land cover and rainfall regimes on the surface runoff and soil loss on karst slopes in southwest china abstract surface runoff and soil loss from 2007 to 2010 related to land use and rainfall regimes in karst hill slopes in guizhou province southwest china were analyzed using the hierarchical clustering method sixty one rainfall events under the subtropical monsoon climate condition were classified into 5 types of rainfall regimes according to the depth maximum 30 min intensity and duration of rainfall in our study we first demonstrated that the amounts of surface runoff and soil loss on the karst hill slopes were very small compared to the non karst areas because the dual hydrological structure in the karst region including ground and underground drainage systems could influence the processes of rainfall recharge and runoff generation most rainfall water was transported underground through limestone fissures and fractures while little was in the form of surface runoff second the runoff and soil loss were affected by land use management and vegetation cover soil loss was intensified in a descending order to five types of land uses pastureland burned area cropland combination vegetation land young forestland third the runoff and soil loss exhibited remarkable variances among different rainfall regimes large runoff and soil loss were mainly created by heavy rainfall storms with a rainfall depth of more than 40 mm and a maximum 30 min rainfall intensity of over 30 mm h 1 in addition rainfall storms with large antecedent precipitations could also produce large runoff and soil loss these observations indicated that limestone fissures and fractures play important roles in surface runoff generation on karst limestone slopes due to their large storage capacity and high infiltration rate lastly the soil erosion risk in the karst pure limestone slope is quite high and should be paid particular attention especially in regards to over grazing because the soil loss created by a single heavy rainstorm in pastureland was 5 times the annual soil loss tolerance

detection of karst conduit patterns via hydraulic tomography a synthetic inverse modeling study abstract karst aquifers are geologic media that consist of enlarged solution conduits the geometry of such conduits is very difficult to delineate and its hydraulic parameters such as hydraulic conductivity k and specific storage ss are difficult to estimate hydraulic tomography ht shown to successfully map the hydraulic heterogeneity of porous and fractured rock aquifers may also be effective in karst aquifers in this study we utilize two synthetic karst aquifers with the branchwork and network conduit patterns bcp and ncp to explore the ability of ht to map conduit patterns and their hydraulic parameters prior to the ht analysis forward models are built to study groundwater flow through synthetic karst aquifers to generate data and to gain insights into flow patterns forward modeling results reveal that 1 flow rates at the outlet of the bcp model is higher than the ncp model even when the same water injection rates are applied at the wells 2 the location of the injection well has a significant impact on the flow rate at the outlet and 3 flow lines mainly follow the conduit pattern these results suggest that the accurate mapping of karst networks is critical next the ht analysis of these data is conducted using a set of six models bcp and ncp to map the heterogeneity of different conduit systems under steady state and transient flow conditions inverse modeling results reveal that the estimated k maps become more reliable as the number of injection tests and the corresponding monitoring data are increased in the ht analysis moreover the results of the bcp model is closer to the original conduit pattern in comparison to the ncp model a comparative study of three inverse models with different number of observation wells and assuming the availability of geological data has shown that a more reliable pattern of the conduits can be mapped by adding geological information even when a small number of observation wells are available overall our results confirm the feasibility of ht in detecting major conduits as well as being able to differentiate between the bcp and ncp network types

discussion of behavior of pile groups subject to excavation induced soil movement in very soft clay by d e l ong c f leung and y k chow

runoff and erosion processes on bare slopes in the karst rocky desertification area underground pore fissure and bedrock bareness are the main factors that lead to complicated mechanisms of soil erosion in karst regions the objectives of this study were as follows a to measure runoff and sediment generated from the surface and underground in the karst bare slope and b to analyse the impacts of underground pore fissures and bedrock bareness rates on soil erosion to achieve these objectives we designed an experiment in which underground pore fissure degrees and bedrock bareness rates were varied and their impacts on soil erosion were measured the results showed that runoff and sediment yields from the surface and underground increased with increasing rainfall intensity and the surface runoff was much more easily generated when the rainfall intensity was greater ii surface runoff yield first increased and then decreased with increasing bedrock bareness rates while the runoff yield in underground pore fissures increased with increasing bedrock bareness rates thus sediment production on the surface and in underground pore fissures showed the same pattern i e first decreased and then increased iii the surface runoff and sediment generally decreased with increasing degrees of underground pore fissures while that of underground pore fissures presented a different pattern and iv rainfall intensity bedrock bareness rates and underground pore fissure degrees were the important factors affecting soil erosion processes in karst bare slopes because the bedrock bareness rates and underground pore fissure degrees were the main factors causing the uneven distribution of runoff and sediment on soil surfaces and underground therefore soil and water loss in underground pore fissures was the special pattern and main difference in soil erosion processes in the karst region compared with other regions these results have theoretical and practical significance for understanding soil erosion mechanisms and controlling soil and water loss in karst regions

effects of rainfall infiltration and hysteresis on the settlement of shallow foundations in unsaturated soil the effects of rainfall infiltration and hysteresis on the settlement of shallow foundations in unsaturated soil were numerically investigated numerical solutions were verified against experimental data rainfall intensities and groundwater table positions factors that contribute to an additional settlement of shallow foundations were investigated through a series of parametric studies the effect of hysteresis on the settlement behavior of shallow foundations was considered by incorporating hysteretic soil water characteristic curves swcc that were obtained from the laboratory a reasonably good agreement of load settlement response and matric suction distribution was obtained between the numerical analysis results and the field measurements the parametric study showed that a reduction of matric suction due to rainfall infiltration induced the additional settlement of shallow foundations in unsaturated soil the groundwater table position appeared to affect the wetting induced settlement during rainfall due to the changes in matric suction in addition wetting swcc analysis produced a slight larger settlement up to 5 more than that produced by drying swcc therefore appropriate swccs i e drying or wetting should be used in numerical analysis in accordance with the conditions of the soils underneath the shallow foundations

a frequency domain approach to groundwater recharge estimation in karst this paper presents an alternative method for determining the values of parameters of a groundwater recharge model the phreatic zone of a karst aquifer is considered as the linear and time invariant filter that transforms the input signal of groundwater recharge rates into the output signal of spring discharges similarities between transfer functions of total rainfall rates and transfer functions of groundwater recharge rates are the basis for developing the parametric periodogram depending on parameters of a groundwater recharge model the values of parameters are estimated by minimizing the differences between the parametric periodogram and a periodogram of spring discharges the approximate whittle log likelihood function is the criterion for determining the optimal values of the parameters by using this frequency domain approach groundwater balance calculations are avoided so the method can be applied on unexplored karst aquifers when groundwater balance cannot be achieved without extensive geologic and hydrogeologic investigations the results of the applications on two springs located in the dinaric karst area in croatia are discussed

a new approach in assessing recharge of highly karstified terrains montenegro case studies the recharge of a karst aquifer in terms of its quantity and spatial distribution depends on various natural factors such as climate topography vegetation soil and geology selection of an adequate method for assessing recharge in karst is often a matter of dispute multi parameter methods using geographical information systems tools have recently been successfully developed and applied in karstic terrains of spain and lebanon specific local conditions such as highly karstified terrains could additionally complicate such an assessment the montenegro karstified terrains in the southern part of the external dinarides are characterized by a very high precipitation rate irregular seasonal distribution and absence of surface waters extremely high infiltration capacity of karst considering such conditions an attempt to apply existing knowledge and experiences to the development of an appropriate multi parameter method for assessing spatial distribution of autogenous recharge has been made the karstlop method has been developed applied and calibrated at catchments of several large karst springs of montenegro obtained results in tested catchment areas confirm that with some further improvements the karstlop method could be a useful tool to support research of karstic aquifers in similar highly karstified terrains

groundwater recharge in semi arid carbonate aquifers under intensive use the estepa range aquifers seville southern spain quantifying groundwater recharge in carbonate aquifers located in semi arid regions and subjected to intensive groundwater use is no easy task one reason is that there are very few available methods suitable for application under such climatic conditions and moreover some of the methods that might be applied were originally designed with reference to non carbonate aquifers in addition it is necessary to take into account the fact that in any given aquifer groundwater recharge is modified by the groundwater exploitation here we focus on four methods selected to assess their suitability for estimating groundwater recharge in carbonate aquifers affected by intensive exploitation the methods were applied to the estepa range aquifers of seville southern spain which are subjected to different degrees of exploitation two conventional methods were used chloride mass balance and daily soil water balance these results were compared with the results obtained by means of two non conventional methods designed for application to the carbonate aquifers of southern spain the aplis and eras methods the results of the different methods are analogous comparable to those obtained in nearby non exploited carbonate aquifers confirming their suitability for use with carbonate aquifers in either natural or exploited regimes in a semi arid climate

accelerated soil erosion in a karst area the burren western ireland abstract the burren is a plateau karst on the west coast of ireland it is characterized by thin soils patchy vegetation and large areas of bare rock supposedly a legacy of glacial erosion archeological and palynological evidence suggest that the area was well populated and forested in prehistoric times though now it is a marginal area agriculturally investigation of paleosols and of karren forms on ancient structures support the idea of an extensive cover of mineral soil removed by forest clearance initiated erosion over a relatively short period of time

modelling hydrological processes influenced by soil rock and vegetation in a small karst basin of southwest china hydrological processes in karst basins are controlled by permeable multimedia consisting of soil pores epikarst fractures and underground conduits distributed modelling of hydrological dynamics in such heterogeneous hydrogeological conditions is a challenging task basing on the multilayer structure of the distributed hydrology soil vegetation model dhsvm a distributed hydrological model for a karst basin was developed by integrating mathematical routings of porous darcy flow fissure flow and underground channel flow specifically infiltration and saturated flow movement within epikarst fractures are expressed by the cubic law equation which is associated with fractural width direction and spacing a small karst basin located in guizhou province of southwest china was selected for this hydrological simulation the model parameters were determined on the basis of field measurement and calibrated against the observed soil moisture contents vegetation interception surface runoff and underground flow discharges from the basin outlet the results show that due to high permeability of the epikarst zone a significant amount of surface runoff is only generated after heavy rainfall events during the wet season rock exposure and the epikarst zone significantly increase flood discharge and decrease evapotranspiration et loss the peak flood discharge is directly proportional to the size of the aperture distribution of soil moisture content smc primarily depends on topographic variations just after a heavy rainfall while smc and actual et are dominated by land cover after a period of consecutive non rainfall days the new model was able to capture the sharp increase and decrease of the underground streamflow hydrograph and as such can be used to investigate hydrological effects in such rock features and land covers copyright 2011 john wiley sons ltd

the influence of geomorphological position and vegetation cover on the erosional and hydrological processes on a mediterranean hillslope soil erosion and runoff rates are assumed to be highly dependent on slope position however little knowledge exists about the hydrogeomorphological processes at the pedon scale that support this idea in order to assess the hydrological and erosional behaviour of soils at different slope positions simulated rainfall experiments 55 mm was applied during one hour were carried out on a south facing slope with underlying limestone in south east spain in the mean terms the erosion rates 9 g m2 hr 1 and the runoff coefficients 12 were very low at the scale of measurement 0 25 m2 the slope position does not affect erosion rates when the measurements are carried out under extreme dry conditions during summer the low runoff rates found in summer under thunderstorms of high intensity 5 year return period and the runon into surfaces with higher infiltration rates resulted in no detectable direct surface runoff hortonian at the slope scale this implies that erosion as a consequence of surface overland flow will only take place during events of high magnitude 55 mm hr 1 and low frequency 5 years vegetation is the most important factor determining the soil erosion and runoff rates within the slope 1998 john wiley sons ltd

recharge and aquifer response northern guam lens aquifer guam mariana islands abstract the northern guam lens aquifer is an island karst aquifer in uplifted young highly conductive limestone calculations of recharge based on differences between daily rainfall and daily pan evaporation suggest that the maximum annual mass of water delivered to the freshwater lens is about 67 of mean annual rainfall hydrographs of daily well level responses plotted against daily rainfall indicate that the rate at which water is delivered to the lens is a function of rainfall intensity and the relative saturation of the vadose zone together these variables determine the degree to which stormwater is shunted into fast flow through preferred pathways that bypass the bedrock matrix rather than percolating slowly through the bedrock matrix data from the 40 year interval from 1956 to 1995 show that some 17 of rainfall on northern guam arrives in small amounts 5 0 cm day which tend to promote fast flow at the expense of percolation rapid recovery of the water table from rapid recharge suggests that the lens either takes such recharge into storage very rapidly discharges it rapidly without taking it into storage or some combination of both significant vadose buffering of recharge to the lens is indicated by the fact that simulations assuming that the recharge from precipitation received in any given month is transmitted to the lens during the same month consistently over predict observed peak mean monthly water levels and under predict the minima

soil functions and ecosystem services research in the chinese karst critical zone abstract covering extensive parts of china karst is a critically important landscape that has experienced rapid and intensive land use change and associated ecosystem degradation within only the last 50 years in the natural state key ecosystem services delivered by these landscapes include regulation of the hydrological cycle nutrient cycling and supply carbon storage in soils and biomass biodiversity and food production intensification of agriculture since the late 20th century has led to a rapid deterioration in critical zone cz state evidenced by reduced crop production and rapid loss of soil in many areas an ecological tipping point appears to have been passed as basement rock is exposed and rocky desertification dominates this paper reviews contemporary research of soil processes and ecosystems service delivery in chinese karst ecosystems with an emphasis on soil degradation and the potential for ecosystem recovery through sustainable management it is clear that currently there is limited understanding of the geological hydrological and ecological processes that control soil functions in these landscapes which is critical for developing management strategies to optimise ecosystem service delivery this knowledge gap presents a classic cz scientific challenge because an integrated multi disciplinary approach is essential to quantify the responses of soils in the chinese karst cz to extreme anthropogenic perturbation to develop a mechanistic understanding of their resilience to environmental stressors and thereby to inform strategies to recover and maintain sustainable soil function

effects of grass roots on the erodibility of topsoils during concentrated flow abstract traditional vegetative techniques to control gully development rely mainly on the effects of above ground biomass whereas little attention has been given to the role of below ground biomass yet in a context where above ground biomass may temporarily or spatially disappear e g due to fire or grazing roots can play an important role in protecting soil against erosion few studies have investigated the impacts of roots of natural vegetation such as grass on the resistance of topsoils in concentrated flow erosion zones although grasses grow in many environments therefore the objective of this study is to investigate the impact of root density and root length density of grass on the erodibility of root permeated saturated topsoils three plots were established on a sandy loam their treatments were 1 bare 2 low density drilled grass and 3 high density drilled grass simulating different root densities after one month topsoil samples were taken and subjected to concentrated flow using a hydraulic flume in the laboratory slope flow discharge mean velocity water temperature and sediment concentration were measured root density and root length density values were assessed relative soil detachment rates and mean flow shear stresses were calculated the results indicate a negative exponential relation between the relative soil detachment rate and root density as well as root length density independent of the applied flow shear stresses however the best relationship fitting the data is the hill curve indicating that relative soil detachment rates decrease to very low values 0 05 with an increase in root density from 0 to 4 kg m 3 or root length density from 0 to 400 km m 3 a comparison between the effects of vegetation cover on sheet and rill erosion rates and those of the root area ratio of grass roots on relative soil detachment rates reveals that grass roots are very effective in reducing soil detachment rates the equations obtained can be used to predict the effect of grass roots on soil erosion rates during concentrated runoff and to evaluate the ability of roots to increase topsoil resistance against erosion by concentrated flow calculations of relative erosion rates using the equations from the rusle and wepp models indicate that the observed trend is better predicted with the rusle model and the wepp model for croplands than with the wepp model for rangelands

identifying flow networks in a karstified aquifer by application of the cellular automata based deterministic inversion method lez aquifer france the distributed modeling of flow paths within karstic and fractured fields remains a complex task because of the high dependence of the hydraulic responses to the relative locations between observational boreholes and interconnected fractures and karstic conduits that control the main flow of the hydrosystem the inverse problem in a distributed model is one alternative approach to interpret the hydraulic test data by mapping the karstic networks and fractured areas in this work we developed a bayesian inversion approach the cellular automata based deterministic inversion cadi algorithm to infer the spatial distribution of hydraulic properties in a structurally constrained model this method distributes hydraulic properties along linear structures i e flow conduits and iteratively modifies the structural geometry of this conduit network to progressively match the observed hydraulic data to the modeled ones as a result this method produces a conductivity model that is composed of a discrete conduit network embedded in the background matrix capable of producing the same flow behavior as the investigated hydrologic system the method is applied to invert a set of multiborehole hydraulic tests collected from a hydraulic tomography experiment conducted at the terrieu field site in the lez aquifer southern france the emergent model shows a high consistency to field observation of hydraulic connections between boreholes furthermore it provides a geologically realistic pattern of flow conduits this method is therefore of considerable value toward an enhanced distributed modeling of the fractured and karstified aquifers

interpretation of pumping tests in a mixed flow karst system a long duration pumping test performed in the conduit of a mixed flow karst system mfks is analyzed and interpreted it constitutes a unique experiment of catchment wide response of a karst system with drawdowns measured both in the pumped conduit and in the matrix a modeling approach is proposed for this interpretation the developed double continuum model consists of two reservoirs karst conduits and the surrounding carbonate rocks between which flow exchange is modeled using the superposition principle and the hypothesis of darcian flow in the matrix considered as an equivalent porous media the karst conduits are assumed to have an infinite hydraulic conductivity model calibration results in a very good match relative root mean square rrms 2 3 with drawdown measured at the pumping well karst conduit it shows that the matrix hydrodynamic parameters hydraulic conductivity and storativity have a greater influence on the drawdown than the storage capacity of the conduit the accuracy of the model relies mostly on a very good knowledge of both pumping rate and natural discharge at the spring with and without pumping this type of approach represents an advance in double continuum modeling of karst systems it also provides a methodology for the management of water resources from karst aquifers

modelling of the functioning of karst aquifers with a reservoir model application to fontaine de vaucluse south of france summary this work deals with a rainfall discharge model applied to a well known karst aquifer a new approach is developed in order to minimize the fitting parameters here some of the model parameters do not result from a simple fitting as it was the case with earlier models i e some of them were assessed from the hydrograph analysis the conceptual model of the functioning is based on a production function based on a simple calculation of effective rainfall and a transfer function consisting of two reservoirs a slow discharge reservoir transfers the low flow and a rapid discharge reservoir feeds the high flow the model has three fitted parameters plus one for its initialisation three parameters are deduced from the hydrograph analysis over the entire time series for example the recession coefficient of the slow discharge reservoir is determined from the hydrodynamic analysis of the recession mangin a 1975 contribution a l etude hydrodynamique des aquiferes karstiques 3eme partie constitution et fonctionnement des aquiferes karstiques annales de speleologie 30 1 210 124 this model was tested over a ten years period on the fontaine de vaucluse french karst system the first hydrological year is used for fitting the model the nine other cycles validate the modelling the good quality of the model is proved by the nash criterion of 92 3 on the validation period moreover the simulation results were validated by a statistical analysis of measured and simulated time series the model successfully simulates both the high and low flow at the same time also it estimates the water volumes available in the different parts of the aquifer and it proposes a management tool capable of predicting the evolution of the discharge in different climate conditions

surface soil water content and its controlling factors in a small karst catchment spatial distribution of soil water content swc plays an important role in soil hydrological processes karst areas are especially heterogeneous with respect to soil distribution and properties and have not been adequately studied the purpose of this study was to characterize the surface swc and to discuss its controlling factors in a small karst catchment in guangxi china swc was measured using the gravimetric method along seven line transects crossing farmland shrub grassland shrubland and forestland as well as hillslopes and depressions soil bulk density capillary porosity macroporosity rock fragment content rc soil organic carbon and soil texture of the soil samples were also determined regression and sensitivity analysis methods were used to analyze the influence of soil properties on swc in both the wet and dry season generally swc was significantly higher in depressions than on hillslopes in the shrub grassland and shrubland swc decreased with increasing elevation whereas in the forestland no obvious trend along the transect was found soil porosity rc and soil texture were three main soil properties that influenced swc significantly moreover the distribution of swc along the line transects were coincidence with that of these soil properties the results document the spatial distribution of swc in a karst catchment in southwest china laying a foundation for a better understanding and modeling of hydrological processes in this complex landform

on the impact of topography and building mask on time varying gravity due to local hydrology we use 3 yr of surface absolute gravity measurements at three sites on the larzac plateau france to quantify the changes induced by topography and the building on gravity time series with respect to an idealized infinite slab approximation indeed local topography and buildings housing ground based gravity measurement have an effect on the distribution of water storage changes therefore affecting the associated gravity signal we first calculate the effects of surrounding topography and building dimensions on the gravity attraction for a uniform layer of water we show that a gravimetric interpretation of water storage change using an infinite slab the so called bouguer approximation is generally not suitable we propose to split the time varying gravity signal in two parts 1 a surface component including topographic and building effects 2 a deep component associated to underground water transfer a reservoir modelling scheme is herein presented to remove the local site effects and to invert for the effective hydrological properties of the unsaturated zone we show that effective time constants associated to water transfer vary greatly from site to site we propose that our modelling scheme can be used to correct for the local site effects on gravity at any site presenting a departure from a flat topography depending on sites the corrected signal can exceed measured values by 5 15 gal corresponding to 120 380 mm of water using the bouguer slab formula our approach only requires the knowledge of daily precipitation corrected for evapotranspiration therefore it can be a useful tool to correct any kind of gravimetric time series data

estimating groundwater recharge for an arid karst system using a combined approach of time lapse camera monitoring and water balance modelling groundwater is the principal water resource in semi arid and arid environments therefore quantitative estimates of its replenishment rate are important for managing groundwater systems in dry regions karst outcrops often show enhanced recharge rates compared with other surface and sub surface conditions areas with exposed karst features like sinkholes or open shafts allow point recharge even from single rainfall events using the example of the as sulb plateau in saudi arabia this study introduces a cost effective and robust method for recharge monitoring and modelling in karst outcrops the measurement of discharge of a representative small catchment 4 0 middle dot 104 m2 into a sinkhole and hence the direct recharge into the aquifer was carried out with a time lapse camera during the monitoring period of two rainy seasons autumn 2012 to spring 2014 four recharge events were recorded afterwards recharge data as well as proxy data about the drying of the sediment cover are used to set up a conceptual water balance model the model was run for 17 years 1971 to 1986 and 2012 to 2014 simulation results show highly variable seasonal recharge precipitation ratios between 0 and 0 27 in addition to the amount of seasonal precipitation this ratio is influenced by the interannual distribution of rainfall events overall an average annual groundwater recharge for the doline sinkhole catchment on as sulb plateau of 5 1 mm has estimated for the simulation period copyright c 2015 john wiley sons ltd c 2016 john wiley sons inc

the relation between surface rock fragment cover and semiarid hillslope profile morphology abstract rock fragment covers veneer hillslopes in many parts of the world and influence the operation of hydrologic and geomorphic processes on those surfaces the purpose of this investigation was the examine the spatial variability of rock fragment cover on morphological units of hillslopes in southeastern arizona u s a simple statistical models based upon hillslope gradient as well as a soil slope factor ssf were developed and validated for the estimation of percent rock fragment covers rfc on these units although reasonably accurate estimates were made using either hillslope gradient or the ssf it appears more efficient to utilize hillslope gradient alone likewise reasonably accurate estimates of rfc can be made using either a composite model for the entire hillslope or unit specific models however it appears more efficient to utilize the gradient composite model

simple procedure to simulate karstic aquifers a procedure to simulate karstic aquifers is presented it is based on a simulation of spring discharge using precipitation and where necessary temperature as input data the karstic aquifer system is considered to be divided into three zones the surface zone the unsaturated zone uz and the saturated zone sz each of these is described by a transfer function that determines the water supplied from the overlying zone water loss through evapotranspiration is calculated empirically and subtracted from the total precipitation in order to obtain the effective infiltration into the uz the transfer function characterizing the uz can be expressed as a convolution function the uz acts as a buffer delaying effective infiltration into the sz water discharge from the sz is described by the recession function of the spring and this becomes the transfer function that characterizes the emergence of water from the sz the model permits the simulation of the influence of pumped abstractions from the system by a simple modification of the transfer functions involved copyright 2007 john wiley sons ltd

review on groundwater recharge in carbonate aquifers from sw mediterranean betic cordillera s spain this paper presents a review of groundwater recharge assessment in some 50 carbonate aquifers of the extreme sw mediterranean domain betic cordillera southern spain an area highly vulnerable to climate change the selected aquifers represent a broad range of meteorological and geological conditions and consequently results can be expanded eastward to other mediterranean aquifers the methods most commonly applied for recharge assessment over the past 20 years are aquifer water budget and soil water balance while these methods support the first steps in groundwater management in spain precision in quantification requires other methods to be incorporated they include chloride mass balance diverse lumped model codes and empirical methods such as aplis in eastern areas of the betic cordillera where semiarid conditions prevail lumped and distributed models for recharge assessment and calibration are based on the time series of water table data the mean annual rainfall recharge and coefficient infiltration as percentage of rainfall are respectively 648 262 mm year and 38 a high correlation was observed between annual rainfall and annual recharge in all the studied aquifers however the infiltration coefficient can vary substantially even with the same annual rainfall recharge this reflects significant differences in the degree of surface karstification and the development of the vegetal cover soil epikarst system in the carbonate aquifers of the betic cordillera the results of this work may serve to improve the assessment and management of renewable water resources in western mediterranean carbonate aquifers the findings are moreover useful for future comparisons involving recharge assessments under different scenarios of climate change and changes in land use

hydraulic boundary conditions as a controlling factor in karst genesis a numerical modeling study on artesian conduit development in gypsum 1 a coupled continuum pipe flow model is employed to simulate the development of karst conduits in an artesian setting where aggressive water flows upward from an insoluble aquifer into a gypsum unit speleogenetic processes and controlling parameters are identified first for single conduit development it is demonstrated that transient flow from the conduit into the surrounding fissured system of the rock enhances solutional conduit enlargement moreover single conduit development is found to be highly sensitive to variations in initial diameter and hydraulic gradient simulating the solutional enlargement of pipe networks reveals that these two factors determine the resulting conduit pattern structural preferences are found to be essential for horizontal conduit development otherwise flow paths are solely enlarged in vertical direction following the hydraulic gradient hydraulic gradients that increase with time can limit the extension or completely inhibit the development of horizontal caves even if lateral conduit development was structurally preferred

simulation of the development of karst aquifers using a coupled continuum pipe flow model 1 this paper is intended to provide insight into the controlling mechanisms of karst genesis based on an advanced modeling approach covering the characteristic hydraulics in karst systems the dissolution kinetics and the associated temporal decrease in flow resistance karst water hydraulics is strongly governed by the interaction between a highly conductive low storage conduit network and a low conductive high storage rock matrix under variable boundary conditions only if this coupling of flow mechanisms is considered can an appropriate representation of other relevant processes be achieved e g carbonate dissolution transport of dissolved solids and limited groundwater recharge here a parameter study performed with the numerical model carbonate aquifer void evolution cave is presented which allows the simulation of the genesis of karst aquifers during geologic time periods cave integrates several important features relevant for different scenarios of karst evolution 1 the complex hydraulic interplay between flow in the karst conduits and in the small fissures of the rock matrix 2 laminar as well as turbulent flow conditions 3 time dependent and nonuniform recharge to both flow systems 4 the widening of the conduits accounting for appropriate physicochemical relationships governing calcite dissolution kinetics this is achieved by predefining an initial network of karst conduits protoconduits which are allowed to grow according to the amount of aggressive water available due to hydraulic boundary conditions the increase in conduit transmissivity is associated with an increase in conduit diameters while the conductivity of the fissured system is assumed to be constant in time the importance of various parameters controlling karst genesis is demonstrated in a parameter study covering the recharge distribution the upgradient boundary conditions for the conduit system and the hydraulic coupling between the conduit network and the rock matrix in particular it is shown that conduit diameters increase in downgradient or upgradient direction depending on the spatial distribution local versus uniform of the recharge component which directly enters the conduit system

assessing soil erosion in mediterranean karst landscapes of lebanon using remote sensing and gis abstract maps showing the potential for soil erosion at 1 100 000 scale are produced in a study area within lebanon that can be used for evaluating erosion of mediterranean karstic terrain with two different sets of impact factors built into an erosion model the first set of factors is soil erodibility morphology land cover use and rainfall erosivity the second is obtained by the first adding a fifth factor rock infiltration high infiltration can reflect high recharge therefore decreasing the potential of surface runoff and hence the quantity of transported materials infiltration is derived as a function of lithology lineament density karstification and drainage density all of which can be easily extracted from satellite imagery the influence of these factors is assessed by a weight rate approach sharing similarities between quantitative and qualitative methods and depending on pair wise comparison matrix the main outcome was the production of factorial maps and erosion susceptibility maps scale 1 100 000 spatial and attribute comparison of erosion maps indicates that the model that includes a measure of rock infiltration better represents erosion potential field investigation of rills and gullies shows 87 5 precision of the model with rock infiltration this is 17 5 greater than the precision of the model without rock infiltration these results indicate the necessity and importance of integrating information on infiltration of rock outcrops to assess soil erosion in mediterranean karst landscapes

new approaches to determine the ultimate bearing capacity of shallow foundations based on artificial neural networks and ant colony optimization in this study two different approaches are proposed to determine the ultimate bearing capacity of shallow foundations on granular soil firstly an artificial neural network ann model is proposed to predict the ultimate bearing capacity the performance of the proposed neural model is compared with results of the adaptive neuro fuzzy inference system fuzzy inference system and ann which are taken in literature it is clearly seen that the performance of the ann model in our study is better than that of the other prediction methods secondly an improved meyerhof formula is proposed for the computation of the ultimate bearing capacity by using a parallel ant colony optimization algorithm the results achieved from the proposed formula are compared with those obtained from the meyerhof hansen and vesic computation formulas simulation results showed that the improved meyerhof formula gave more accurate results than the other theoretical computation formulas in conclusion the improved meyerhof formula could be successfully used for calculating the ultimate bearing capacity of shallow foundations

inverse modeling for characterizing surface water groundwater exchanges 1 inverse modeling is presented and applied to the computation of groundwater inflow in a shallow aquifer the alsace aquifer west of the rhine river france by separating pressure head variations into three components recharge from rainfall and exchanges with surface water in the rhine river and in tributaries flowing out of the vosges mountains the point estimates are interpolated for the whole aquifer to visualize the proportion of contribution and the response times to represent the surface water groundwater exchange this method uses directly observed data of streamflow precipitation and pressure head without requiring either spatial description of the hydrosystem or knowledge of the boundary conditions on both sides of the rhine the border between france and germany several zones of the aquifer are shown to be strongly influenced by the hydrographical network where response times are short although the direct influence of the rhine is limited to its immediate surroundings it contributes to maintaining the low level of the alsace water table as a whole the response time of recharge from rainfall closely reflects the thickness of the vadose zone south of selestat and at the northern end of the alsace plain whereas it discloses the contours and the thickness of the loess terraces nearby and south of strasbourg to selestat

impacts of land use change on patterns of sediment flux in weraamaia catchment new zealand forest clearance between the 1890s and the early 1920s subsequent scrub growth and commencement of an afforestation program in 1979 modified the pattern and rate of sediment delivery to valley floors via shallow landslides and gully complexes in a steep headwater catchment 4 8 km2 in new zealand analysis of the historical record air photograph interpretation and field survey indicates that both erosion types occurred across the catchment in the 1938 storm aggrading channel beds and widening the active channel zone in contrast a 1 in 100 year event in 1988 cyclone bola induced numerous shallow landslides but erosion of gully complexes was largely restricted to subcatchments that retained pasture and the geomorphic impact of this event on channels was small the changing volume and calibre of materials delivered to the valley floor and the distribution of gully complexes altered patterns and rates of channel adjustment after the events and the resulting sediment flux development of gully complexes maintained coupling processes with channels for periods up to 102 years forming wide channels in downstream reaches upstream downstream connectivity along the trunk stream was altered by the formation of a large debris fan at the confluence with a tributary subjected to gully complex erosion in contrast slopes subjected to shallow landslides became decoupled from channels within 10 years accelerating channel degradation and narrowing effective conveyance of a large volume of fine grained materials promoted immediate aggradation of gentle gradient channels downstream as gully complex areas stabilized following an increase in forest and scrub cover channel courses became significant sediment sources although shallow landslide activity will continue to induce intermittent aggradation in the future it is inferred that average sediment yield will continue to diminish to levels approaching those experienced prior to clearcutting and the pattern of sediment flux will recover by 2030

application of fluid rock reaction studies to in situ recovery from oil sand deposits alberta canada i aqueous phase results for an experimental statistical study of water bitumen shale reactions abstract in situ recovery operations in oil sand deposits effectively represent man imposed low to intermediate temperature metamorphism of the sediments in the deposit in order to evaluate some of the reactions which occur a factorial experiment was earned out in which a shale from the lower cretaceous mcmurray formation in the athabasca oil sand deposit of alberta in the presence or absence of bitumen was subjected to hydrothermal treatment with aqueous fluids of varying ph and salinity at two different temperatures for periods up to 92 hours the aqueous fluid was analyzed and the analytical data subjected to statistical factor analysis and analysis of variance which enabled identification of the main processes namely cation exchange the production of two types of colloidal material and the dissolution of quartz there is also saturation of the aqueous phase by as yet unidentified total organic carbon and complete conversion and removal of all nitrogen in the shale to the aqueous phase these reactions have implications with regards to the economics of the in situ recovery process specifically with respect to the reuse and or disposal of the produced water and the plugging of the pore space and hence of reduction of permeability between the injection and production wells as a result of these experiments it is suggested that monitoring of the composition of the produced water from in situ recovery operations in oil sand deposits would be advisable

the hydrological response of soil surfaces to rainfall as affected by cover and position of rock fragments in the top layer rainfall experiments have been conducted in the laboratory in order to assess the hydrological response of top soils very susceptible to surface sealing and containing rock fragments in different positions with respect to the soil surface for a given cover level rock fragment position in the top soil has an ambivalent effect on water intake and runoff generation compared to a bare soil surface rock fragments increase water intake rates as well as time of runoff concentration and decrease runoff volume if they rest on the soil surface for the same cover level rock fragments reduce infiltration rate and enhance runoff generation if they are well embedded in the top layer the effects of rock fragment position on infiltration rate and runoff generation are proportional to cover percentage micromorphological analysis and measurements of the saturated hydraulic conductivity of bare top soils and of the top layer underneath rock fragments resting on the soil surface reveal significant differences supporting the mechanism proposed by poesen 1986 i e runoff generated as rock flow or as horton overland flow can partly infiltrate into the unsealed soil surface under the rock fragments provided that they are not completely embedded in the top layer hence rock fragment position beside other rock fragment properties should be taken into account when assessing the hydrological response of soils susceptible to surface sealing and containing rock fragments in their surface layers a simple model based on the proportions of bare soil surface soil surface occupied by embedded rock fragments and soil surface covered with rock fragments resting on the soil surface describes the runoff coefficient data relatively well

assessment of soil particle erodibility and sediment trapping using check dams in small semi arid catchments check dams can be used as a source of information for studies on sediment characteristics and soil particle erodibility in this study sediment yield and grain size distribution gsd were measured in twenty small catchments draining into a rock check dam in nw iran for different runoffs during 2010 2011 significant correlations were found between sediment yield and slope steepness vegetation cover and soil erodibility factor k of the catchments the erodibility of soil particles was determined using the comparison of gsd between sediment and original soil clay was the most erodible soil particle which showed 2 05 times more percentage in sediment than the original soil the erodibility of soil particles were strongly affected by the rainfall erosivity ei30 check dams showed more effectiveness in trapping coarse particles sand and gravel the effectiveness of check dams in trapping coarse particles enhanced with increase in the remaining capacity of check dams

discussion of axial compression of footings in cohesionless soils i load settlement behavior by sami o akbas and fred h kulhawy the discussers would like to commend the authors for their investigation of the characterization and parameterization of the load settlement behavior of axially loaded footings on cohesionless soils because of its importance in geotechnical practice in this discussion the discussers would like to 1 provide the results of a comparative assessment of the performance of loaddisplacement models in approximating the results of a set of fullscale load tests on large footings 2 stress the importance of investigating load displacement uncertainty by addressing quantitatively not only second moment statistics of model parameters but also the correlation between the parameters themselves and 3 examine the adequateness of load displacement models for the generation of multivariate distributions for simulation purposes a database of 30 footings on 12 different sands that were subjected to vertical loading in the field was used for these purposes the origins of these sands included natural marine deposits alluvial sediments aeolian dune sands and compacted sand fills the footings included 18 square 7 rectangular and 5 circular shallow foundations with the equivalent footing width b varying from 0 5 to 6 m only full scale foundations were considered to avert difficulties associated with 1 g model tests and scaling problems e g cerato and lutenegger 2007 a summary of the sand sites test locations sand origin index number in the database footing sizes embedment depth groundwater depth median grain size and cptu net cone tip resistance qnet representative of capacity is given in uzielli and mayne 2010 the applied stress was normalized by qnet settlement s was normalized by foundation width b three load displacement model types were considered

spatial variability of surface soil saturated hydraulic conductivity in a small karst catchment of southwest china soil saturated hydraulic conductivity ks is one of the most important parameters that determine soil water redistribution however it is little known in a karst area with thin discontinuous and rocky soils the purpose of this paper was to investigate the spatial variability of ks and its influencing factors in a small karst catchment with high heterogeneity in southwest china undisturbed surface 0 10 cm soil samples were collected with metal cylinders from an 80 m 80 m grid for measuring ks bulk density b non capillary porosity ncp and capillary porosity cp disturbed surface samples were taken with a shovel to measure soil organic carbon soc and rock fragment content rc environmental factors including topographical location slope and depression land use type forestland shrubland shrub grassland and farmland slope gradient slope exposure and elevation were investigated for each sampling point the results showed that ks value was relatively high 9 10 m d with a moderate variation and had a strong spatial dependence nugget sill value 0 06 ncp showed a very significantly p 0 05 but their interaction effects were significant this suggested that the influencing factors were more complex and they should be considered together in a karst area the mean ks value was the lowest in the forestland on the hillslope and in the farmland in the depression indicating where the surface runoff may appear easily such results could help to better understand the soil hydrological processes and contribute to the building of hydrological models in small karst catchments

spatial distribution of rock fragments on steep hillslopes in karst region of northwest guangxi china abstract rock fragments 5 mm in diameter at the soil surface and within the topsoil have a large effect on the intensity of various hydrologic and geomorphic processes however little information is available on the spatial distribution of rock fragments in subtropical regions the objective of this paper was to investigate the relationship between the spatial distribution of rock fragments and landforms on two different steep karst hillslopes in northwest guangxi southwest china on the first hillslope a disintegrated landslide failure with the presence of several large rock outcrops 2 m in height the spatial distribution of rock fragment cover had no obvious relationship with topographic position except that the mean cover percentage of small rock fragments 5 20 mm decreased from bottom to top on the second hillslope an avalanche slope without the presence of large rock outcrops the mean total rock fragment cover 5 600 mm increased from bottom 5 to top 21 with decreasing variability and rock fragments with various sizes 5 20 20 75 and 75 250 mm showed a similar increasing trend the mean total rock fragment cover increased linearly with slope gradient on the second hillslope and tended to increase and then decrease with gradient but their relationship was not obvious on the first hillslope this indicated that the spatial distribution of surface rock fragment cover had a close relationship with the presence of large rock outcrops and slope gradient however the median diameter d50 of the surface rock fragments had an increase decrease trend with slope gradient but there was no obvious relationship on both hillslopes with low overland flow therefore the dominant factor for the spatial distribution of rock fragment cover and size at the soil surface might not be soil erosion by water but slope gradient vegetation and geomorphologic condition of the slope the mean total volumetric rock fragment content 5 250 mm within the topsoil 10 20 cm thick increased linearly from bottom 16 to top 39 with slope gradient on the first hillslope and had a logarithmic increase from bottom 10 to top 27 with gradient on the second hillslope this suggested that rock fragment content within the topsoil was mostly controlled by slope gradient and topographic positions and had not a close relationship with the presence of large rock outcrops

quantification of temporal distribution of recharge in karst systems from spring hydrographs the estimation of the temporal distribution of recharge in karst aquifers is a challenge due to large heterogeneities in geometric and hydraulic parameters of the vadose and phreatic zone this article provides a time continuous approach for the estimation of inflow into the conduit system of a karst aquifer which consists of the sum of direct recharge and flow from the fissured matrix blocks into the conduit system the approach employs the first time derivative of the spring hydrograph and the recession coefficient of the conduit system for the determination of this function the first time derivative of the hydrograph describes the rate of change in spring discharge it reflects the ratio of inflow to and outflow from the conduit system the recession coefficient depends on the hydraulic diffusivity which controls the velocity of the signal transmission through the system as shown in parameter studies with a simplified serial two reservoir model direct recharge into the conduit system clearly dominates the early hydrograph response during recharge events even if the fraction of direct recharge represents just a few percent of total recharge this behaviour is caused by a large contrast in recession coefficients between conduit system and fissured matrix blocks the direct recharge component can therefore be separated from the estimated total inflow into the conduit system estimation of inflow into the conduit system of the gallusquelle spring swabian alb germany after a storm event yields similar results as those obtained from parameter studies the separation of the direct recharge component is in agreement with information from an independent isotope study the methodology has been further applied to a recharge event initiated by snowmelt as a result of daily variations of the air temperature a clearly diurnal cycle of inflow into the conduit system is estimated that is not easily recognizable from the spring hydrograph the applicability of the proposed methodology requires knowledge about the magnitude of the recession coefficient of the conduit system the characteristics of the conduit system become also apparent in the rapid transport of tracers the recession coefficient of the conduit system can for example directly be estimated from the reciprocal of the mean tracer travel time however for this type of analysis only tracer experiments covering the extent of the catchment should be taken into account for the gallusquelle catchment the recession coefficient obtained from the tracer experiment corresponds to that obtained from hydrograph recession analysis the estimated inflow into the conduit system and interpretation of temporal distribution of recharge is therefore based on a plausible and physically based parameter

application of modflow for simulating groundwater flow in the trifilia karst aquifer greece karst aquifers can have a complex flow as a result of the formation of large conduits from dissolution features as a result a three dimensional finite difference groundwater flow model equivalent porous media may not apply as the dual porosity nature of karst features and the effects of turbulent flow cannot be directly simulated statistical analysis of karst hydrographs of the trifilia aquifer in greece showed the existence of a slightly karstified mass with high primary porosity that regulates the flow an equivalent porous media model was developed to simulate the trifilia karst aquifer using modflow steady state and transient state calibration gave encouraging results for the equivalent porous media approach which does not consider pipe flow or turbulence detailed hydrogeological research conducted in the area helped define the aquifer hydraulic conductivity zones and extent and flux to from the aquifer only hydraulic conductivity and specific yield were adjusted during calibration as the flux to from the system was considered known and applied as boundary conditions small mean absolute and rms piezometric head error of the model under both steady and transient state conditions were achieved

effect of catchment properties on runoff coefficient in a karst area of southwest china frequent human activities and climate change in the karst region of southwest china since the 1950s have led to the investigation of response of runoff to climate and catchment properties runoff coefficient rc as an expression variable of the catchment response to rainfall is important to describe runoff dynamics and to estimate available streamflow for utilization in this study the equations of rc associated with its attributors of climate condition and catchment property were derived using the budyko framework the equations were used to estimate relationship between the rc and the attributors in the karst catchments in guizhou province of southwest china analysis in the selected 23 karst catchments demonstrates that the spatial distribution of rc is dominated by the catchment properties such as the catchment properties of geology slope and land use and land cover rather than climate condition of drought index correlation analysis indicates that the catchment with a large slope usually has a high value of rc and a large proportion of carbonate rock in a catchment reduces rc in the study area temporal increasing trend of rc during 1961 2000 was found for most catchments in the study area this increasing trend was primarily resulted from changes of catchment properties e g deforestation in large areas of guizhou province during the 1950s 1980s copyright 2013 john wiley sons ltd

conservation of soil moisture by different stone covers on alpine talus slopes lassen california abstract this study reports on the influence of stone covers with different clast sizes on the soil moisture of alpine talus slopes in lassen california fifteen four plot sets were sampled in the dry season july 1990 in sandy areas and in talus covered with pebbles cobbles or blocks between 2740 and 2775 m three depths 0 5 5 10 10 15 cm were sampled field moisture content increased gradually with depth in all soil profiles and also in plots covered by increasingly larger rocks surface soils in sand areas were very dry but under rocks had water contents 6 to 14 times greater differences among plots decreased with depth but subsoil samples in sand were still drier than those beneath any stone cover at similar depths blocks were most effective in conserving moisture water content below them was higher than even in deep 10 15 cm sand soils soil temperatures were recorded in sand and under blocks for an 11 day period minima were not significantly different but average maxima were 5 6 c lower under blocks than in sand which reached highs 4 4 c lower than the air differences in soil moisture among talus types are ascribed to lower evaporation losses under stones due to both disruption of capillarity by the coarse particles which prevented water flow to the talus surface and to their efficient reduction of maximum temperatures an irrigation experiment was conducted at 2110 m on a steep talus on the chaos crags from july 18 to aug 2 1993 four 100 75 cm plots with the same surface types than at lassen received 22 5 mm water moisture content was then periodically sampled watering produced similar water distributions among soil depths and talus types to those in lassen evaporation occurred quickly in bare soils due to high air and soil temperatures the sand surface was already dry 2 days after watering but stone covered plots remained moist until day 15 when soils under blocks still retained 77 97 of the water content percent by weight at the start of the test

modelling the hydrologic functions of a karst aquifer under active water management the lez spring a rainfall discharge model is applied to an aquifer characterized by active groundwater management the lez karst aquifer in the south of france groundwater is withdrawn by pumping in the main drain 400 m upstream from the main spring and 48 m below the aquifer overflow level a reservoir model was developed to characterize the functioning of this aquifer it is based on a conceptual model of the karst aquifer that takes into account flow through both the saturated zone and the unsaturated infiltration zone both rapid and slow flow in the infiltration zone and flow in the saturated zone are modelled since pumping withdraws groundwater from the main drain of the saturated zone modules characterizing various pumping practices are taken into account in the saturated zone reservoir the model simultaneously simulates spring discharge and water levels in the drain which characterize the saturated zone of the karst the groundwater reserves stored in the saturated zone can then be estimated the model can be used for water management since runoff and overflow from the aquifer feeding the lez river depend on the degree of saturation of the aquifer the model could be used for the flood management