role of oceans as biogenic sources of selenium the pathways leading to the volatilisation and atmospheric transfer of selenium from oceanic environments are poorly understood they may however affect the global distribution of selenium and its impact on marine and terrestrial ecosystems in this paper we describe the results of experiments which provide a reasonable estimate of the global selenium budget gaseous selenium compounds were determined in the north atlantic ocean during a spring bloom of phytoplankton species which are known to be a large source of atmospheric sulphur the results demonstrate that significant concentrations of gaseous selenium species occur in surface ocean waters and their production is closely linked to the gaseous sulphur species turnover selective uptake and biotransformation of dissolved selenium in seawater by phytoplankton is a major pathway for the production of gaseous selenium compounds in marine environments and their emission to the atmosphere it is therefore suggested that such a major selenium source supplies the terrestrial environment with selenium that can be used as an essential nutrient for animal and human life

groundwater recharge in arid areas induced by tropical cyclones lessons learned from gonu 2007 in sultanate of oman younger groundwater found in some omani aquifers is a result of recent recharge from cyclonic and storm events weyhenmeyer et al science 287 842 845 2000 young et al j appl geophys 57 43 61 2004 the analysis of the meteorological data in oman indicates an anomalous rainfall on a decadal interval whereas cyclones frequency is expected to increase due to global climatic changes the cyclone gonu has severely struck the eastern omani coasts in 2007 resulting in devastating floods huge volume of water 3 672 mm3 spread over the coastal plain calling for an assessment of potential groundwater recharge subsequent to this event the present study evaluates groundwater recharge with respect to gonu 2007 to assess the potential of recharge induced by such cyclones in the arid zones the hydrographs of several piezometers sited along the coastal plain in muscat province have been studied and variation in water table rise has been analyzed significant water table rise is indicated for areas with geological and structural settings favoring rapid infiltration of water yielding considerable groundwater mound whereas piezometers located in less favorable zones show minimum rise of water table however soon after the floods the aquifer hydrodynamics has readjusted to attain equilibrium and the groundwater mound dissipated the cumulative rise of the water table on an areal extent does not exceed a few centimeters indicating lesser volume of recharge comparatively recharge from frequent precipitation along favorable zones produces more significant recharge compared with cyclonic events where surface water residence time is shorter to allow for efficient infiltration

eolian deposition of trace elements onto taylor valley antarctic glaciers abstract the major ion and trace element chemistry in four 60 110 cm deep snow pits was examined from three antarctic taylor valley glaciers commonwealth canada and howard all located within 20 km of the ross sea taylor valley tv 77 30 s 163 15 e is part of the mcmurdo dry valleys mdv the largest ice free area in antarctica snow chemistry of these glaciers is strongly influenced by cross valley sw ne and ne sw winds that deposit eolian materials including mineral dust and soluble salts arsenic cd cu mo pb sb and sn in recent tv glacier snow are almost exclusively derived from eolian dust the relative magnitude of element variations with depth relate to the exposure of snow sites to prevalent winds eolian deposition is a primary source of these elements to canada glacier snow and supra and proglacial streams eolian processes are likely very important to the delivery and availability of nutrients and potentially toxic elements to dry valley antarctic ecosystems

water losses from irrigation canals abstract this paper investigates the water losses from a canal to an aquifer from field measurements large losses from canals have been identified even when the canal is lined the reasons for these losses are investigated by performing numerical model solutions for a series of examples with different conditions at the lower boundary of the aquifer at lateral boundaries and at the water table within the aquifer partial lining of a canal is shown to have little effect on the magnitude of the losses and total lining which contains defects is also ineffective the paper emphasises the need for detailed field work into the conditions within aquifers in the vicinity of canals

analytical solution for groundwater flow in an anisotropic sloping aquifer with arbitrarily located multiwells this paper presents a new analytical solution to describe the hydraulic head distribution and flow system in an anisotropic unconfined aquifer with a sloping bed and arbitrarily located multiwells under transient recharge unlike the existing analytical solutions for delineating the capture zones the solution presented in this study is easy and convenient to calculate flow field in some complicated systems and it can provide useful information for the pump and treat design in addition the presented solution may have the possible application in evaluating the sensitivity of hydrogeological parameters or estimating the hydraulic parameters when coupled with an optimization approach to analyze the aquifer data

determining long time scale hyporheic zone flow paths in antarctic streams in the mcmurdo dry valleys of antarctica glaciers are the source of meltwater during the austral summer and the streams and adjacent hyporheic zones constitute the entire physical watershed there are no hillslope processes in these systems hyporheic zones can extend several metres from each side of the stream and are up to 70 cm deep corresponding to a lateral cross section as large as 12 m 2 and water resides in the subsurface year around in this study we differentiate between the near stream hyporheic zone which can be characterized with stream tracer experiments and the extended hyporheic zone which has a longer time scale of exchange we sampled stream water from green creek and from the adjacent saturated alluvium for stable isotopes of d and 18 o to assess the significance and extent of stream water exchange between the streams and extended hyporheic zones over long time scales days to weeks our results show that water residing in the extended hyporheic zone is much more isotopically enriched up to 11 da nd 2 2 18 o than stream water this result suggests a long residence time within the extended hyporheic zone during which fractionation has occurred owing to summer evaporation and winter sublimation of hyporheic water we found less enriched water in the extended hyporheic zone later in the flow season suggesting that stream water may be exchanged into and out of this zone on the time scale of weeks to months the transient storage model otis was used to characterize the exchange of stream water with the extended hyporheic zone model results yield exchange rates generally an order magnitude lower 10 5 s 1 than those determined using stream tracer techniques on the same stream in light of previous studies in these streams these results suggest that the hyporheic zones in antarctic streams have near stream zones of rapid stream water exchange where fast biogeochemical reactions may influence water chemistry and extended hyporheic zones in which slower biogeochemical reaction rates may affect stream water chemistry at longer time scales copyright 2003 john wiley sons ltd

soil grain and water chemistry in relation to human selenium responsive diseases in enshi district china selenium deficiency keshan disease and toxicity diseases in humans occur within 20 km of each other in enshi district in china and have been linked to environmental levels of se low concentrations of se are associated with jurassic siltstones and sandstones whereas high concentrations occur in areas underlain by permian carbonaceous strata although these broad relationships between se in the environment and the human population have been established previously not all villages underlain by the carbonaceous strata suffer se toxicity problems and the precise controls on se distribution and availability have not been quantified in the present study soil grain drinking water and human hair samples are examined to determine the controls on se availability in 3 se environments in enshi district five low se and keshan disease villages 5 high se and no toxicity villages and 5 high se and toxicity villages were selected for the study results show that the majority of samples in the low se villages are deficient or marginal in se and that se availability to plants is inhibited by adsorption onto organic matter and fe oxyhydroxides in soil therefore remediation strategies involving the application of se fertiliser direct to the soil may not increase plant se levels as expected in the high se villages localised lithological variations result in considerable ranges in se concentrations in all sample types deficient and excessive levels of se are recorded in samples from the same village selenium bioavailability in the high se toxicity villages is controlled by the total soil se concentration and ph a greater proportion of the se is plant available in villages where the carbonaceous strata are interbedded with limestone villagers should be advised to avoid planting crops in these areas if possible

water tracks and permafrost in taylor valley antarctica extensive and shallow groundwater connectivity in a cold desert ecosystem water tracks are zones of high soil moisture that route water downslope over the ice table in polar environments we present physical hydrological and geochemical evidence collected in taylor valley mcmurdo dry valleys antarctica which suggests that previously unexplored water tracks are a significant component of this cold desert land system and constitute the major flow path in a cryptic hydrological system geological geochemical and hydrological analyses show that the water tracks are generated by a combination of infiltration from melting snowpacks melting of pore ice at the ice table beneath the water tracks and melting of buried segregation ice formed during winter freezing the water tracks are enriched in solutes derived from chemical weathering of sediments as well as from dissolution of soil salts the water tracks empty into ice covered lakes such as lake hoare resulting in the interfingering of shallow groundwater solutions and glacier derived stream water adding complexity to the geochemical profile approximately four orders of magnitude less water is delivered to lake hoare by any given water track than is delivered by surface runoff from stream flow however the solute delivery to lake hoare by water tracks equals or may exceed the mass of solutes delivered from stream flow making water tracks significant geochemical pathways additionally solute transport is two orders of magnitude faster in water tracks than in adjacent dry or damp soil making water tracks salt superhighways in the antarctic cold desert accordingly water tracks represent a new geological pathway that distributes water energy and nutrients in antarctic dry valley cold desert soil ecosystems providing hydrological and geochemical connectivity at the hillslope scale

groundwater flow to a horizontal or slanted well in an unconfined aquifer 1 new semianalytical solutions for evaluation of the drawdown near horizontal and slanted wells with finite length screens in unconfined aquifers are presented these fully three dimensional solutions consider instantaneous drainage or delayed yield and aquifer anisotropy as a basis solution for the drawdown created by a point source in a uniform anisotropic unconfined aquifer is derived in laplace domain using superposition the point source solution is extended to the cases of the horizontal and slanted wells the previous solutions for vertical wells can be described as a special case of the new solutions numerical laplace inversion allows effective evaluation of the drawdown in real time examples illustrate the effects of well geometry and the aquifer parameters on drawdown results can be used to generate type curves from observations in piezometers and partially or fully penetrating observation wells the proposed solutions and software are useful for the parameter identification design of remediation systems drainage and mine dewatering

assessment of effect of recharge from a check dam as a method of managed aquifer recharge by hydrogeological investigations check dams are often used as a method of managed aquifer recharge mar and are generally preferred in non perennial rivers for intentional storage of the water the objective of this study is to evaluate the efficacy of a check dam constructed as a mar initiative across arani river north of chennai india by long term hydrogeological investigations electrical resistivity survey and drilling of borehole helped to understand the subsurface geology water level and water quality measurements were carried out periodically from july 2010 to may 2012 groundwater occurs in unconfined condition in the alluvial formations extending up to a depth of about 50 m below the ground surface water table is at a depth ranging from 3 to 12 m below the ground level the electrical conductivity and concentration of major ion were less in water stored in the dam and hence the recharge of this water has led to improvement in groundwater quality rainfall recharge of this study area was estimated to be about 17 of annual rainfall about 63 of water stored in the check dam resulted in groundwater recharge this has led to an increase in groundwater level from 1 to 3 5 m until a distance of about 2 km the cost of 1 m3 of water stored by the check dam will be rs 1 20 the comparison of groundwater level water level in the check dam and water quality assisted in demarcating the areas benefited by the storage of water in the check dam thus the electrical conductivity and major ion concentration of water which are inexpensive rapid and easy to measure were used as a tool for understanding the area that is benefited by the water stored in the check dam the study brought out the efficiency of check dam as a method of mar in improving the groundwater recharge and groundwater quality

hydraulic head response of a confined aquifer influenced by river stage fluctuations and mechanical loading summary the response to river stage fluctuation of a drilled well penetrating a confined aquifer was simulated using a stream aquifer interaction algorithm because the confined aquifer is overlaid by a water table aquifer the algorithm was coupled with formulae used to correct the heads for mechanical loading the coupling of stream aquifer interaction and mechanical loading models was tried for the first time in this study the test site was a drilled well installed on the montalto uffugo aquifer located at the calabria university groundwater test field calabria region south of italy this aquifer comprises a 44 m thick sand bank bounded on bottom and top by clay layers and covered by a 7 m thick sandy conglomerate being adjacent to the mavigliano river overall the head changes caused by a river stage raise represented a contribution of 49 3 57 8 to the total head while mechanical loading accounted for the remaining 50 7 32 2 the loading was triggered by a sequence of short spaced rainfall events lasting for a total of 167 days which caused recharge to the unconfined aquifer thickening the water column by some 3 1 m

a solution of the nonlinear boussinesq equation for phreatic flow using an integral balance approach abstract an analytical solution of the nonlinear boussinesq equation is presented using the integral balance method the solution obtained is the same as that obtained by basak 1979 following a different approach

hydrogen uptake and diffusion in callovo oxfordian clay rock for nuclear waste disposal technology abstract the callovo oxfordian clay rich rock formation is currently considered as host rock barrier in the french geological repository facility for radioactive waste meuse haute marne after the closure of the facility hydrogen gas is expected to develop mainly from anaerobic corrosion of steel containers and other iron containing structures gas pressure build up could impact the safety of the repository it is therefore important to acquire in depth knowledge on the interaction between hydrogen gas and surrounding clay rock in terms of uptake ability and diffusion hydrogen uptake capacity was evaluated on dried clay rock samples i at 20 k to allow for hydrogen liquefaction and determine the maximal h 2 uptake of the clay and ii at typical pressure and temperature conditions expected to develop in the repository up to 363 k and a hydrogen pressure of 40 60 bar h 2 absorption on the dried raw callovo oxfordian start to saturate at about 30 40 bar and the average adsorption above 40 bar is about 0 1 in weight quasi elastic neutron scattering spectroscopy was used to study the diffusion mechanism of hydrogen gas in the clay rock at the microscopic scale and to determine hydrogen self diffusion coefficients in the dry samples in the temperature range 25 300 k neutron data suggested that hydrogen diffuses in the dry clay rock according to fick s law the findings reported in this work can help to better understand the behavior of h 2 in clay rock samples

recharge to aquifers with mixed boundaries abstract the problem of localized groundwater recharge from a strip basin to an aquifer bounded by stream and impermeable boundaries was solved by the use of extended finite fourier transforms the solution was evaluated by comparison with the method of images and with numerical and experimental results the existing expression for the inverse of the extended finite fourier cosine transform was corrected

solute and isotope geochemistry of subsurface ice melt seeps in taylor valley antarctica the mcmurdo dry valleys of antarctica are a polar desert region with watersheds dominated by glacial melt recent ground exploration reveals unusual surface fl ow seep features not directly supplied by glacial melt much of this seep water is potentially derived from permafrost snow patches refrozen precipitation accumulated in the subsurface buried glacier ice or even groundwater from the deep subsurface flow features that lack obvious glacier melt sources were identifi ed in archived aerial photographs of taylor valley this valley was surveyed for extant and extinct seeps and the locations of geomorphic features in fi active seeps were documented water samples from seeps were analyzed for major ions and stable isotopes of hydrogen and oxygen solute chemistry and isotopic signatures of seeps are distinct from those of nearby streams and glaciers with the seeps having elevated solute concentrations all but one seep had water isotopically heavier than water from nearby glaciers and streams suggesting that seep waters have been substantially modifi ed if they had been derived originally from the same meteoric sources that supply local glaciers and streams the seeps are important because they compose a previously overlooked component of the desert hydrological cycle seep features in the dry valleys are potential terrestrial analogs for the geologically young gullies observed on mars which are thought to be evidence of groundwater seepage and surface runoff

surface glaciochemistry of taylor valley southern victoria land antarctica and its relationship to stream chemistry we have analysed a series of surface samples from the alpine glaciers of taylor valley southern victoria land antarctica for their geochemical composition this was done to better establish the role of glaciochemical variation on the chemical composition of meltwater streams emanating from the glaciers the chemistry of the snow and ice changes with proximity to the ocean and with elevation of the glacier surface the aeolian transport of dry valley dust as indicated by both chemical and particulate matter variations is a major process affecting the overall glacier chemistry and the chemistry of the meltwaters streams originating on the western edges of the glaciers are more impacted by the aeolian input as they are in the direct path of the major regional wind direction our data strongly suggest that the variation in stream geochemistry in taylor valley is a result in part of the differences in chemical composition of glacier melt copyright 2003 john wiley sons ltd

stream aquifer interaction model with diffusive wave routing a practical approach to modeling the hydraulic interaction of a stream and aquifer via streambed leakage is based on the established u s geological survey usgs model modflow to represent flood wave propagation and the associated bank storage modflow s stream module is replaced by the muskingum cunge diffusive wave routing scheme the diffusive wave model closely approximates a dynamic model of a flood wave s speed shape and streambed leakage because the stream responds more rapidly to disturbances than the aquifer streambed leakage is calculated at the flood routing time scale in order to properly represent the stream aquifer coupling however both the relative magnitude and timing of aquifer response to a flood wave depend on the strength of this coupling we find discrepancies in both the flood wave and the streambed leakage when the wave and ground water motions are evaluated at different time scales these discrepancies are significant in the case of a strong stream aquifer coupling for which equal aquifer and flood routing time steps may be required wave diffusion and bank storage are shown to be comparable in magnitude and should therefore be included in stream aquifer interaction models diffusive wave routing more accurately represents wave propagation bed leakage and aquifer response if short aquifer time steps are taken and is preferable to the stream module for simulating short time transients however the stream module is useful for simulating large time frames if accurate modeling of the flood wave propagation is not required

the reactivity of carbonates in selected soils of southern spain the properties of many soils of arid and semiarid areas are influenced by the presence of carbonates this study was conducted to characterize the reactivity of carbonates in the surface horizons of 25 soils entisols inceptisols vertisols and alfisols of southern spain the samples were analyzed for calcium carbonate equivalent cce active calcium carbonate equivalent acce predominant carbonate mineralogy mg content particle size distribution psd of carbonates by sedimentation and by a ph stat acid dissolution method and surface area sa of carbonates by n2 adsorption and by 45ca exchange from the differences between intact and decalcified soil samples as well as by estimates from the psd described above the cces ranged from 70 to 778 g kg 1 of soil and the acces ranged from 48 to 285 g kg 1 dolomite was present in only eight samples and in the dolomite free samples calcite generally had mg ca mg ratio 0 03 the carbonate psd as determined by sedimentation differed from the psd calculated from the ph stat data with the latter method giving a much higher proportion of claysize carbonates the average sas of carbonates as estimated from the psd data were 0 49 m2 g 1 soil for the sedimentation method and 3 2 m2 g 1 for the ph state method the average sas determined by the n2 and the 45ca methods were 6 0 and 2 3 m2 g 1 respectively the average specific surface areas ssas of soil carbonate m2 g 1 cce were 1 5 7 5 8 8 and 22 for the sedimentation 45ca exchange ph stat and n2 methods respectively the low sa and ssa values from the sedimentation method were a consequence of the occurrence of porous aggregates which have considerably higher equivalent spherical diameters than the particles of which these aggregates are composed the ph stat and 45ca methods gave sa values of similar magnitude to each other probably because both methods are dependent on actual reactive surface area instead of aggregate size of the carbonate mass the higher values obtained by the n2 method might indicate that n2 is physisorbed on carbonate surfaces that are slowly reactive to acid attack or 45ca exchange the ph stat sa was highly correlated with acce which measures the reactivity of carbonates to oxalate to obtain a rapid estimate of the reactivity of soil carbonate the acce method because of its simplicity may be preferred

clay minerals trap hydrogen in the earth s crust evidence from the cigar lake uranium deposit athabasca abstract hydrogen h2 rich fluids are observed in a wide variety of geologic settings including gas seeps in serpentinized ultramafic rocks sub seafloor hydrothermal vents fracture networks in crystalline rocks from continental and oceanic crust and volcanic gases natural hydrogen sources can sustain deep microbial ecosystems induce abiotic hydrocarbons synthesis and trigger the formation of prebiotic organic compounds however due to its extreme mobility and small size hydrogen is not easily trapped in the crust if not rapidly consumed by redox reactions mediated by bacteria or suitable mineral catalysts it diffuses through the rocks and migrates toward the surface therefore h2 is not supposed to accumulate in the crust we challenge this view by demonstrating that significant amount of h2 may be adsorbed by clay minerals and remain trapped beneath the surface here we report for the first time h2 content in clay rich rocks mainly composed of illite chlorite and kaolinite from the cigar lake uranium ore deposit northern saskatchewan canada thermal desorption measurements reveal that h2 is enriched up to 500 ppm i e 0 25 mol kg 1 of rock in these water saturated rocks having a very low total organic content

transient infiltration from ephemeral streams a field experiment at the reach scale 1 an infiltration experiment at the stream reach scale was performed to estimate infiltration rates beneath an ephemeral losing stream during streamflow events at a time when the stream was dry a 7 m stream section was dammed upstream and downstream using metal sheets during a 5 day period water was pumped into the isolated section of the stream and the surface water level was maintained at three successive increasing stages the infiltration rate at each water level was thereby equal to the pumping rate required to maintain that water level the advantages of the method are that it samples a much greater area than traditional methods and provides information on infiltration through stream banks as well as through the streambed experimental results provide insight into transient infiltration and recharge processes beneath ephemeral streams although the experiment continued for 5 days infiltration during the first hour accounted for 19 of the total infiltration high transient infiltration rates were also observed following each increase in stream stage experimental infiltration rates were used to calibrate a two dimensional model developed within hydrus which was subsequently used to estimate infiltration associated with a natural flow event in the same stream reach during the natural flow event the total infiltration was 33 greater than would have been estimated assuming steady state infiltration rates dry antecedent moisture content controls the transient infiltration rate and hence increases the total infiltrated volume during flow events but it does not increase the aquifer recharge

environmental variability within the chinese desert loess transition zone over the last 20000 years the desert loess transition zone in northern china is sensitive to climate variability which is con trolled mainly by the relative strengths of the east asian summer and winter monsoons sandy loess layers found in the loess plateau and palaeosol sequences found in the sandy desert demonstrate latitudinal shifts of the southern desert margin over the last 20000 years stratigraphic investigations together with radiocarbon and some thermoluminescence dating show that during the last glacial maximum the desert margin was at its most southerly position 38 n during the early holocene it moved northward about three degrees in latitude 41 n at present the desert margin is again close to its most southerly position 38 219 n yet the northern boundary position of modern summer monsoon activity is placed at 41 459 n which is close to the estimated holocene optimum desert margin 41 n this situation cannot be explained from natural climate models hence an external driving mechanism needs to be considered and the most obvious one is that caused by human activity on the natural environment over the last 3000 years historical evidence tends to reinforce this consideration

weathering reactions and hyporheic exchange controls on stream water chemistry in a glacial meltwater stream in the mcmurdo dry valleys 1 in the mcmurdo dry valleys antarctica dilute glacial meltwater flows down wellestablished streambeds to closed basin lakes during the austral summer during the 6 12 week flow season a hyporheic zone develops in the saturated sediment adjacent to the streams longer dry valley streams have higher concentrations of major ions than shorter streams the longitudinal increases in si and k suggest that primary weathering contributes to the downstream solute increase the hypothesis that weathering reactions in the hyporheiczonecontrolstreamchemistrywastestedbymodelingthedownstreamincreasein solute concentration in von guerard stream in taylor valley the average rates of solute supplied from these sources over the 5 2 km length of the stream were 6 1 10 9 mol si l 1 m 1 and 3 7 10 9 mol k l 1 m 1 yielding annual dissolved si loads of 0 02 1 30 mol si m 2 of watershed land surface silicate minerals in streambed sediment were analyzed to determine the representative surface area of minerals in the hyporheic zone subject to primary weathering two strategies were evaluated to compute sediment surface area normalized weathering rates the first applies a best linear fit to synoptic data in order to calculate a constant downstream solute concentration gradient dc dx constant weathering rate contribution crc method the second uses a transient storage model to simulate dc dx representing both hyporheic exchange and chemical weathering hydrologic exchange he method geometric surface area normalized dissolution rates of the silicate minerals in the stream ranged from 0 6 10 12 mol si m 2 s 1 to 4 5 10 12 mol si m 2 s 1 and 0 4 10 12 mol k m 2 s 1 to 1 9 10 12 mol k m 2 s 1 these values are an order of magnitude lower than geometric surface area normalized weathering rates determined in laboratory studies and are an order of magnitude greater than geometric surface area normalized weathering rates determined in a warmer wetter setting in temperate basins despite the cold temperatures lack of precipitation and lack of organic material these results suggest that the continuous saturation and rapid flushing of the sediment due to hyporheic exchange facilitates weathering in dry valley streams index terms 1045 geochemistry low temperature geochemistry 1806 hydrology chemistry of fresh water 1625 global change geomorphology and weathering 1824 1886 1890 hydrology wetlands keywords hyporheic zone chemical weathering flow path antarctica stream

infiltration mechanism simulation of artificial groundwater recharge a case study at pingtung plain taiwan this paper discusses the artificial groundwater recharge effect of high infiltration basins for this purpose the hydrogeological parameters of the study area are collected to construct a conceptualized physical model the tough2 numerical simulation software is then used to simulate the infiltration behavior of an artificial recharge into an underground aquifer four wells mw 1 mw 2 mw 3 and mw 4 are observed at the field site after which the groundwater levels are compared with the simulation results it is found that good agreement exists between the observed and numerical data for mw 1 and mw 2 however the observed groundwater level in mw 3 is higher than the simulated level we also find that mw 3 is at the edge of the artificial recharge lake and that the high groundwater level may well be the result of a portion of the infiltration load following the well border into the well screen conversely the groundwater level in mw 4 is found to be lower than in the simulated well due to local permeability in the well location finally the numerical results predict that the groundwater level will attain a steady state at approximately 47 h after the onset of infiltration

recharge from an ephemeral stream following wetting front arrival to water table after the infiltration wetting front from a river bed of an ephemeral stream in flood reaches the shallow water table the rate of recharge which is also that of infiltration is affected by the development of a groundwater mound the effect is practically immediate if the water content behind the wetting front is close to saturation an approximate analytical solution is developed in that case which predicts the time dependence of the recharge rate comparison with experimental results in the laboratory shows that the solution is excellent in spite of the assumptions necessary in the derivations as long as the ratio of river width over depth to water table exceeds 2 and as long as the ratio of initial saturated thickness over depth to the water table exceeds 2 5 the analytical solution is essentially exact under most field conditions these ratios are largely exceeded consequently the predictive equation for the time dependence of the recharge is both quite simple to use and adequately accurate for field applications

water flow from a horizontal tunnel in an unsaturated zone flow from a horizontal tunnel in an unsaturated zone is an important factor in calculation of water loss from the conveying tunnel and in predicting the amount of water table build up this study has investigated the three dimensional unsaturated flow from a tunnel by using the linearized richards equation it superposes the point source solution along the tunnel axis to yield the line source solution for treating the tunnel surface as a saturated water content boundary this study first provides an empirical function to numerically calculate the flux distribution along the tunnel axis it then provides an analytical solution to calculate flow from the tunnel we find that the recharge rate from a horizontal tunnel decreases with time and gradually approaches a steady state rate the recharge increases with increasing tunnel length and radius and also with increasing the pore size distribution parameter of the soil the vertical downward recharge beneath the tunnel becomes constant and equals the total recharge from the tunnel at late time

on the horizontal well pumping tests in anisotropic confined aquifers a method that directly solves the boundary problem of flow to a horizontal well in an anisotropic confined aquifer is provided this method solves the point source problem first and then integrates the point source solution along the horizontal well axis to obtain the horizontal well solution the short and long time approximations of drawdowns are discussed and are utilized in the semilog analysis of the drawdown a closed form analytical solution of geometrical skin effect at the wellbore is derived type curves and derivative type curves of horizontal pumping wells are generated using the chow program this program also calculates the drawdown at any given observation well at any given time the horizontal well type curves are different from the vertical well type curves at early time reflecting the different nature of flow to a horizontal well and to a vertical well the horizontal well type curves converge to the vertical well type curves at late time showing the similar nature of flow to a horizontal well and to a vertical well at late time the sensitivity of the type curves and derivative type curves on monitoring well location aquifer anisotropy horizontal well depth and horizontal well length is tested these type curves and derivative type curves can be used in the matching point method for interpreting the pumping test data

analytic solutions for fresh groundwater lenses floating on saline water under desert dunes the kunin van der veer legacy revisited abstract a fully saturated lens of steady fresh groundwater floating in a homogeneous and isotropic desert sandy aquifer is analytically studied based on a hydrological model by kunin and interface solution by van der veer a static saline groundwater is beneath the lens a phreatic surface of moving fresh water inside the lens is partially recharged either naturally or by managed aquifer recharge from the vadose zone and partially exfiltrates to it a spatially focused recharge and intensive evapotranspiration preserve a steady downward upward topology of fresh water motion in terms of the 1 d dupuit forchheimer approximation in a horizontal in lens saturated flow a boundary value problem bvp for an ode for the strack potential is solved the shape of the water table and based on the ghijben herzberg assumption the interface are found the total volume of the positive pore pressure water flowing within the lens is evaluated constant infiltration and evaporation rates as well as evaporation linearly decreasing with depth of the water table counted from the ground surface are considered the case of 2 d flow is tackled by the toth model a triangular analytic element approximates a half of the flow domain and consists of an isobaric side and two no flow sides conformal mapping of this triangle onto a reference plane and solution of the dirichlet bvp in a half plane deliver the distribution of infiltration exfiltration intensity along the water table total flow rate and locus of the hinge point a mathematically more cumbersome approximation of the flow domain assumes the water table to be a tilted straight line but the interface to be found as a free boundary solution of the corresponding bvp uses a curvilinear triangle in the hodograph plane

stability of massive ground ice bodies in university valley mcmurdo dry valleys of antarctica using stable o h isotope as tracers of sublimation in hyper arid regions abstract to date studies of the stability of subsurface ice in the mcmurdo dry valleys of antarctica have been mainly based on climate based vapor diffusion models in university valley 1800 m a small glacier is found at the base of the head of the valley and adjacent to the glacier a buried body of massive ice was uncovered beneath 20 40 cm of loose cryotic sediments and sandstone boulders this study assesses the origin and stability of the buried body of massive ice by measuring the geochemistry and stable o h isotope composition of the ice and applies a sublimation and molecular diffusion model that accounts for the observed trends the results indicate that the buried massive ice body represents an extension of the adjacent glacier that was buried by a rock avalanche during a cold climate period the contrasting 18 o profiles and regression slope values between the uppermost 6 cm of the buried massive ice upward convex 18 o profile and s d 18o 5 1 and that below it progressive increase in 18 o and s d 18o 6 4 suggest independent post depositional processes affected the isotope composition of the ice the upward convex 18 o profile in the uppermost 6 cm is consistent with the ice undergoing sublimation using a sublimation and molecular diffusion model and assuming that diffusion occurred through solid ice the sublimation rate needed to fit the measured 18 o profile is 0 2 10 3 mm yr 1 a value that is more similar to net ice removal rates derived from 3 he data from cobbles in beacon valley till 7 0 10 3 mm yr 1 than sublimation rates computed based on current climate 0 1 0 2 mm yr 1 we suggest that the climate based sublimation rates are offset due to potential ice recharge mechanisms or to missing parameters particularly the nature and thermo physical properties of the overlying sediments i e temperature humidity pore structure and ice content grain size

effects of ph fluctuations on potentially toxic metals in the water and sediment of the dillon reservoir summit county colorado potentially toxic metals exist in many reservoirs of surface water and therefore require an understanding of their occurrence distribution and mobility the sediment accumulating at the bottom of the dillon reservoir colorado is contaminated with metals cu pb zn cd mo etc that are primarily sorbed to fe and al hydroxides present in the sediment the metals are derived from weathering of mineralized bedrock and mine tailings in the surrounding drainage basins sediment samples from the dillon reservoir were analyzed for major and trace elements and acidification experiments were performed to quantify the fraction of metals released from the sediment as a function of changes in ph the highest percentages of metals are released from the sediment at low ph with the exception of mo which has the highest percent released at near neutral ph in addition seasonal fluctuations in the concentrations of metals in the water of the dillon reservoir can be explained by changes in ph of as low as 0 2 ph units

the geochemistry of antarctic streams and their role in the evolution of four lakes of the mcmurdo dry valleys abstract major ion concentrations are reported for nineteen meltwater streams in the mcmurdo dry valleys antarctica and for the four lakes fed by these streams the most important solute acquisition processes for these flowing waters are dissolution of marine derived salts dissolution of calcite coatings derived from chemical weathering of parent rock and direct weathering of silicates although lakes joyce hoare and fryxell have undergone significant evaporative concentration the only simple salt which is predicted to form at present is calcite the shallow waters of all four lakes were supersaturated with respect to this mineral but were undersaturated with respect to other simple salts geochemical budgets however indicate that so4 k and mg in addition to ca and hco3 have been removed from some of these lakes over recent geological time bacterial sulfate reduction followed by precipitation of metal sulfides is likely to be a sink for sulfate sinks for mg and k are more problematic but may include formation of mgcalcites and in the case of k reverse weathering reactions the ages of the contemporary water columns as indicated by chloride budgets are relatively young and these lakes could have evolved their chemical compositions over a few thousand years of present stream flows it is not necessary to invoke trapped seawater or other salt sources to explain their evolution

water table rise in a semiconfined aquifer due to surface infiltration and canal recharge abstract a general solution to the fluctuation of water table for unsteady state flow in a semiconfined and finite aquifer with recharge from canals and surface infiltration is presented the flow is assumed to be one dimensional in a horizontal direction with the recharging canals at different elevations the laplace transformation method is employed in the solution a numerical example is given for a flow situation in a hypothetical finite aquifer bounded by two recharging canals under vertical infiltration giving water table changes with respect to time

artificial recharge of the phreatic aquifer in the upper friuli plain italy by a large infiltration basin to cope with the general reduction of water availability and increase the subsurface storage of high quality surficial waters an artificial recharge project is ongoing in northern italy within the warbo life project funded by eu warbo is aimed at implementing large scale use of artificial recharge in italy where water directives still strongly limit its application in this context the mereto recharge site was selected in the upper fruili plain where the water availability is guaranteed during winter period by the tagliamento and ledra rivers an infiltration basin about 5 5 m deep and 45 7 m2 wide was built at mereto in the early 2000s but the possibility of implementing the recharge has been allowed only very recently the site is characterized by an elevation of 105 m asl and the depth to the groundwater table averages 50 m below a few meter thick organic soil the aquifer is composed by coarse deposits with an estimated thickness of 100 m and an average vertical hydraulic conductivity on the order of 10 4 m s a 0 1 m3 s infiltration flow has been preliminary estimated corresponding to an infiltration rate of 60 cm h geophysical investigations electrical resistivity tomography high resolution seismic surveys together with infiltration and pumping tests have been carried out to characterize the vadose zone and the unconfined aquifer in the study area functional approaches and three dimensional 3d finite element numerical computations have been used to predict the effect of the artificial recharge the results of these investigations will greatly reduce the hydrogeological knowledge gaps and will be used to fine tune the recharge program and to define the monitoring concept this contribution aims to provide a methodology for the implementation of managed aquifer recharge programs using existing structures

water table fluctuation owing to time varying recharge pumping and leakage this paper presents an analytical solution of a 2 d linearized boussinesq equation to predict water table variation in a horizontal aquifer induced by time varying recharge and or withdrawal from any number of recharge basins pumping wells and leakage sites of different dimensions the rate of time varying recharge or withdrawal is approximated by series of line elements of different lengths and slopes depending on the nature of variation of recharge or withdrawal rate advantage of this approximation scheme is that any complex nature of recharge and or withdrawal rates for any number of recharge basins pumping wells and leakage sites and for any number of these operations can be approximated with more accuracy application of the solution in the prediction of water table variation in the presence of time varying recharging pumping and leakage is demonstrated with the help of an example problem the present analytical solution is validated by comparing its results with the corresponding numerical results obtained from modflow for the same example problem

occurrence of native selenium in yutangba and its environmental implications rare native se has been discovered in yutangba enshi city hubei province china where a sudden incidence of se poisoning occurred in the early 1960s it was first found in a small area where native se was produced on a large scale and was diverse in forms due to different formation mechanisms genetically native se can be divided into 3 categories the primary native se occurring in carbonaceous siliceous rocks and tiny se crystals formed in cracks of rocks during tectonic activities micro se crystals formed in the weathering processes of se rich rocks and larger se crystals derived from natural burning of stone coal on the subsurface of abandoned stone coal spoils the different forms of native se found in yutangba demonstrate that se can be activated transformed remobilized and enriched at special sites such as in the unsaturated subsurface zone or in the saturated zone this discovery of native se has not only resolved a long standing controversial question on modes of occurrence of se which has puzzled many researchers in china but has provided new possible evidence for the pathogenic explanation of the sudden prevalence of se poisoning in yutangba the research results also have important implications for studying the mineralogy ore geochemistry and environmental geochemistry of se

dissolved vanadium in rivers and estuaries abstract new measurements of dissolved vanadium in a variety of rivers and estuaries are presented here the data indicate that the average concentration of dissolved vanadium in major rivers entering the ocean is 15 nmol kg weathering rate and type of source rock rather than solution chemistry or anthropogenic influences appear to be the important factors in determining fluvial dissolved vanadium concentrations laboratory experiments suggest that in oxic waters vanadium is found predominantly in its most oxidized anionic form v v complexation with organic matter and formation of large colloidal species appear to be unimportant adsorption also appears to be a less important influence for vanadium than for some other trace elements such as zinc in estuaries vanadium behaves as a bioactive element showing a close correspondence with the distribution of phosphate the extent of estuarine vanadium removal is presently uncertain but may be low due to rapid remineralization of this element based on the river flux the oceanic residence time for dissolved vanadium is estimated to be 100 000 years

cation exchanged fe ii and sr compared to other divalent cations ca mg in the bure callovian oxfordian formation implications for porewater composition modelling abstract iron and sr bearing phases were thoroughly investigated by means of spectrometric and microscopic techniques in callovian oxfordian cox samples originating from the andra underground research laboratory url in bure france strontium was found to be essentially associated with celestite whereas fe was found to be distributed over a wide range of mineral phases iron was mainly present as fe ii in the studied samples 93 from mossbauer results most of the fe ii was found to be in pyrite sideroplesite ankerite and clay minerals iron iii if present was associated with clay minerals probably illite illite smectite mixed layer minerals and chlorite no fe iii oxy hydro xide could be detected in the samples strontianite was not observed either based on these observations it is likely that the cox porewater is in equilibrium with the following carbonate minerals calcite dolomite and ankerite sideroplesite but not with strontianite it is shown that this equilibrium information can be combined with clay cation exchange composition information in order to give direct estimates or constraints on the solubility products of the carbonate minerals dolomite siderite and strontianite as a consequence an experimental method was developed to retrieve the cation exchanged fe ii in very well preserved cox samples the very homogeneous cation exchange composition of the formation is completely in agreement with a homogeneous presence of calcite and dolomite minerals whose equilibrium reactions control part of the porewater composition amongst the broad range of values available for dolomite solubility products in thermodynamic databases the value of log kdolomite 3 57 is the most appropriate for the one present in the cox formation with regard to strontianite it appears that the equilibrium constant tabulated in the llnl database is not valid for natural clay systems the value given by busenberg et al used by most of the other available thermodynamic databases seems to be far more appropriate concerning fe ii and siderite ankerite equilibrium the measured fe ca ratio on the clay exchanger 0 01 could only be considered as a maximum value due to possible experimental bias leading to the following constraint for the solubility of the sideroplesite phase present in the cox fe0 7mg0 2ca0 1co3 h 0 7 fe2 0 2 mg2 0 1 ca2 hco 3 logksid cox this constraint is in agreement with the estimated solubility of this phase based on a solid solution model log ksid cox 0 23

water table rise due to infiltration from canals abstract analytical solutions are presented for transient water table profiles in finite unconfined aquifers due to infiltration occurring from a single canal or more than one canal the aquifer boundaries are assumed to be parallel to the alignment of the canal s and the lower impervious bottom is horizontal further the aquifer is assumed to be homogeneous and isotropic losses such as evapotranspiration are ignored likewise replenishment from other sources for example rainfall is also neglected

solute generation and transfer from a chemically reactive alpine glacial proglacial system the environs of the glacier de tsanfleuron switzerland was used as a study site to investigate the controls on the relative efficiency of solute generation and removal from glacial and proglacial environments here a 1500 m wide glacier forefield consists of a karstic limestone plateau flanked to the north by a till floored valley bedrocks and glacial debris are composed of chemically reactive pure and impure mesozoic and tertiary limestones with accessory pyrite spot sampling of ice snow and meltwaters in the late melt season was supplemented by systematic measurements of the main meltstream including during periods of rainfall and simple laboratory leaching and weathering experiments isotopic parameters were used to investigate water sources most meltwater and glacier ice samples lay close to a meteoric water line d 8 3 18o 14 defined by waters from small tributary streams heavy isotopic excursions of bulk meltwater chemistry were caused by rainfall events recovering within days to a 18o baseline around 12 permil no regular diurnal variations in 18 o were apparent the atmosphere is the source of cl and most na but the bulk of other solutes are generated in the environment ion loads of up to 1 meq l 1 are rapidly attained by calcite dissolution over periods of weeks to months pyrite oxidation generates sulphate and acidity that drives further calcite dissolution low water rock ratio weathering environments have characteristically high so42 mg2 sr2 and ratios of these species to calcium the characteristic cation ratios are influenced by non congruent calcite dissolution the ratio of sulphate to other species is highest where water rock contact times are highest although this relationship is complicated by spatial variations in pyrite abundance meltstream time series illustrate that 90 per cent of daily ion yields in fine weather are concentrated in the 12 h time period of higher discharge ion yields increase downstream mainly by a combination of dissolution of calcareous suspended sediment and input from tributaries and seepage from the till banks rainstorms lead to increased solute concentrations and resulting hourly fluxes can match daily fine weather ion fluxes excess nitrate appears to be largely sourced from the proglacial surface the capacity of the proglacial environment for yielding significant subsurface water as a result of the storm seems low unlike non glacial environments this implies that most of the excess solutes mobilized by storms comes from subglacial sources increased efficiency of yield of solutes from low water rock ratio subglacial weathering environments persists after the isotopic signature of the rainfall event has died away a simple conceptual model of the sources of water and solutes agrees with conclusions from attempts at hydrograph separation that mixing of water reservoirs of fixed solute composition cannot be used for quantitative descriptions of the system estimated annual solute yields 17 ton per km2 per m precipitation are high but cannot be readily expressed in purely areal terms because of likely significant losses to the underlying karstic system a tentative conclusion is that the proglacial environment is overall less efficient at producing solutes than the glacial environment but more information is required on processes in the early melt season to substantiate this statement copyright 1999 john wiley sons ltd

recharge from rectangular areas to finite aquifers abstract a generalized analytical solution is derived for the growth of groundwater mound in finite aquifers bounded by open water bodies in response to recharge from rectangular areas finite fourier transforms are used to solve the linearized differential equation of groundwater flow unlike earlier solutions the method presented here does not require the use of tables for evaluation of complicated functions the solution is evaluated by comparison with existing numerical and analytical results in stream aquifer systems similar to those described above application of the proposed solution is more realistic than using solutions available for infinite aquifers

reactivation of a cryptobiotic stream ecosystem in the mcmurdo dry valleys antarctica a long term geomorphological experiment abstract the mcmurdo dry valleys of antarctica contain many glacial meltwater streams that flow for 6 to 12 weeks during the austral summer and link the glaciers to the lakes on the valley floors dry valley streams gain solutes longitudinally through weathering reactions and microbial processes occurring in the hyporheic zone some streams have thriving cyanobacterial mats in streams with regular summer flow the mats are freeze dried through the winter and begin photosynthesizing with the onset of flow to evaluate the longer term persistence of cyanobacterial mats we diverted flow to an abandoned channel which had not received substantial flow for approximately two decades monitoring of specific conductance showed that for the first 3 years after the diversion the solute concentrations were greater in the reactivated channel than in most other dry valley streams we observed that cyanobacterial mats became abundant in the reactivated channel within a week indicating that the mats had been preserved in a cryptobiotic state in the channel over the next several years these mats had high rates of productivity and nitrogen fixation compared to mats from other streams experiments in which mats from the reactivated channel and another stream were incubated in water from both of the streams indicated that the greater solute concentrations in the reactivated channel stimulated net primary productivity of mats from both streams these stream scale experimental results indicate that the cryptobiotic preservation of cyanobacterial mats in abandoned channels in the dry valleys allows for rapid response of these stream ecosystems to climatic and geomorphological change similar to other arid zone stream ecosystems

groundwater flow in sloping aquifer under localized transient recharge analytical study abstractthis paper analyzes the groundwater flow system in an unconfined downward sloping aquifer of semi infinite extent in response to localized transient recharge the aquifer is in contact with a water body of constant water level at one end and receives localized transient recharge from a recharge basin of finite width the mathematical model is based on the boussinesq equation with dupuit forchheimer assumption in which the spatial coordinate of the recharge basin is treated as an additional parameter analytical solutions of the linearized boussinesq equation are obtained using the laplace transform technique by dividing the aquifer in a three zone system containing both dirichlet and neumann boundary conditions at the hypothetical interfaces upward and zero sloping cases are deduced from the main results by appropriately adjusting the slope parameter to assess the validity and efficiency of the linearization method the nonlinear boussinesq equation is also solved using a fully explicit predic

alluvial aquifer recharge enhanced by a natural dam feasibility assessment based on multidisciplinary characterization khuzestan southwest iran in the kushkak valley khuzestan southwest iran an anticlinal structure has partially impounded an ephemeral stream this natural impounded area has been chosen for an artificial recharge site due to its current rate of recharge capability to store water and favorable situation for the construction of man made barriers to stream flow the aquifer to be recharged is the kushkak unconfined aquifer which consists of medium to coarse grained alluvial deposits that overlie consolidated conglomerate rock in this semi arid area with infrequent relatively heavy falls of rain alluvial aquifer recharge can be an important process that sustains shallow over exploited groundwater bodies in this investigation a multidisciplinary approach including hydrometerological studies and a detailed hydrogeochemical survey have been carried out other essential prerequisite parameters for the scheme were also taken into account to determine the suitability of this location for groundwater artificial recharge the assessment has brought out that 1 the proposed reservoir will conserve a major part of the water being lost 2 annual runoff of about 0 27 mcm can be injected into the aquifer through recharge from impounded water 3 hydrochemical data from surface water and from the kushkak aquifer water demonstrates that dilution and change in compositional trend in the groundwater proximal to the impounded alluvial bed areas would be expected based on the infiltration capacity of this site and 4 cost benefit ratio of the project is 1 2 and it is assumed to recover the investment within six years

modelling of water table variation in response to time varying recharge from multiple basins using the linearised boussinesq equation a mathematical model is presented to describe the variations of the water table in an unconfined aquifer due to time varying recharge applied from four rectangular basins the model is developed by solving the linearised boussinesq equation using the extended finite fourier cosine transform the time varying recharge rate is approximated by a number of piecewise linear elements of different lengths and slopes depending on the nature of the variation in recharge rate application of this model for the prediction of water table fluctuations and in the sensitivity analysis of various controlling parameters on the aquifer response is demonstrated in an example

transmission losses infiltration and groundwater recharge through ephemeral and intermittent streambeds a review of applied methods summary aquifer recharge through ephemeral streambeds is believed to be a major source of groundwater recharge in arid areas however comparatively few studies quantify this streamflow recharge this review synthesizes the available field based aquifer recharge literature from arid regions around the world seven methods for quantifying ephemeral and intermittent stream infiltration and aquifer recharge are reviewed controlled infiltration experiments monitoring changes in water content heat as a tracer of infiltration reach length water balances floodwave front tracking groundwater mounding and groundwater dating the pertinent temporal and spatial scales as well as the advantages and limitations of each method are illustrated with examples from the literature comparisons between the methods are used to highlight appropriate uses of each field method with emphasis on the advantages of using multiple methods within a study in order to avoid the potential drawbacks inherent in any single method research needs are identified including quantitative uncertainty analysis long term data collection and analysis understanding of the role of riparian vegetation and reconciliation of transmission losses and infiltration estimates with actual aquifer recharge

transient water table rise with canal seepage and recharge abstract an analytical solution to the problem of water table rise in a finite length phreatic aquifer based on appropriate transformations is obtained the proposed solution is simpler than the available solution and for the selected illustrative numerical example gives fairly close results

bank storage characteristics of a finite aquifer due to sudden rise and fall of river level abstract unsteady seepage flow in a two dimensional water table aquifer is analysed for recession accretion due to a sudden rise or fall of water level in the adjoining river limiting solutions for long thin and short thick aquifers are deduced from the complete solution the long thin aquifer solution is similar to the usual one dimensional solution at small values of time the complete two dimensional solution is recommended for use because the one dimensional solution usually gives inaccurate results due to neglect of vertical motion implicit in the dupuit assumptions upon which the one dimensional solution is based

modeling of transient water table response to managed aquifer recharge a lagoon in muscat oman natural and anthropogenic conditions in the gulf countries lead to substantial changes in groundwater gw dynamics gw mound under a lagoon supplied by treated wastewater tww from a municipal sewage treatment plant stp in muscat oman is studied using analytical and numerical modeling techniques the water table mound in an unconfined aquifer laterally bounded by the sea receives recharge from a lagoon fed by a stp in a seasonally varying regime the onset and duration of the filling period and correspondingly infiltration from the lagoon bed is dictated by the wastewater processing and tww use following the period of recharge induced growth the gw mound decays when recharge ceases and the void space above the water table becomes available for future injection in the next annual cycle of infiltration and tww subsurface storage the green ampt model application illustrates that the first phase of the process vertical infiltration with front propagating from the lagoon bed to the regional flat water table is typically short several hours the second phase when tww gets in a direct hydraulic contact with gw is the longest and with a mound spreading to hundreds of meters during winter months no analytical solutions to this moving boundary value problem are known and approximate models based on the boussinesq approximation and its linearizations are utilized the hantush type drawup of the water table in the vicinity of the lagoon is studied by the watson analytical solution to the diffusion equation for a vertically averaged hydraulic head in an unbounded domain with an instantaneous jump of the head over a disk shaped zone this drawup is compared with modflow simulations which take into account a finite size of the flow domain catchment and discharge into the sea through a constant head segment the mishra guyonnet s formula assumes a spatially uniform flux from the lagoon bed disk in a model plain into a growing mound and is used for calculation of the total discharge which progressively decreases from the early stages of the green ampt infiltration to a theoretically zero value if the second phase lasts indefinitely long we assess characteristic times and phases of the mound dynamics during the rise and fall stages using regional hydrogeological parameters site geometry and typical patterns of wastewater disposal sensitivity analysis of the locus of the phreatic surface at a given instance and location is carried out with storativity hydraulic conductivity undisturbed aquifer thickness and lagoon radius as input variables for an example of an aquifer of saturated depth of 40 m undisturbed vadose zone thickness of 10 m saturated hydraulic conductivity of 10 m day effective porosity of 0 2 a circular lagoon size of 90 m and water depth there of 1 m we found that the infiltration front propagates to the water table in less than 0 2 days after 40 days of a continuous mound growth in a hypothetical piezometer located 400 m from the lagoon the water table drawup was in the range of 2 0 2 7 m if the aquifer hydraulic parameters and lagoon size are varied 20 from the average value this approach will permit to plan more detailed site investigation facilitate management decisions on the rate of water release to the lagoon and foresee waterlogged areas

analytical solutions for strip basin recharge to aquifers with cauchy boundary conditions abstract analytical solutions for groundwater recharge from strip basins to finite aquifers are presented the problem concerns the impact of either continuous or periodic seasonal recharge schemes on aquifers with a boundary condition of the third kind cauchy the solutions can be useful for assessing aquifer response as well as for calibrating numerical computer models

direct observations of aluminosilicate weathering in the hyporheic zone of an antarctic dry valley stream abstract this study focused on chemical weathering and bacterial ecology in the hyporheic zone of green creek a mcmurdo dry valley antarctica stream an in situ microcosm approach was used to observe dissolution features on the basal plane surface of muscovite mica four mica chips were buried in december 1999 and dug up 39 d later atomic force microscopy afm of the basal plane surfaces revealed small anhedral 10 a deep etch pits covering 4 of the surfaces from which an approximate basal plane dissolution rate of 8 3 10 18 mol muscovite cm 2 s 1 was calculated on the basis of the geometric surface area for the study period this is an integrated initial dissolution rate on a fresh surface exposed for a relatively brief period over the austral summer and should not be compared directly to other long term field rates the observation of weathering features on mica agrees with previous stream and watershed scale studies in the dry valleys which have demonstrated that weathering occurs where liquid water is present despite the cold temperatures afm imaging of mica surfaces revealed biofilms including numerous small

water table fluctuation in a sloping aquifer with transient recharge abstract an analytical solution of the linearized boussinesq equation with a complex transient recharge function is presented to describe the water table fluctuation in a sloping aquifer of finite width the solution is obtained by using an eigenvalue eigenfunction expansion method some previously known solutions for different recharge functions have been shown to be special cases of the present general solution applications of the solutions in prediction of the spatio temporal distribution of the water table in a ditch drainage system are illustrated with the help of synthetic examples

hydrologic characteristics of lake and stream side riparian wetted margins in the mcmurdo dry valleys antarctica water is a limiting factor for life in the mcmurdo dry valleys mdv antarctica the active layer seasonally thawed soil overlying permafrost accommodates dynamic hydrological and biological processes for 10 16 weeks per year wetted margins visually wetted areas with high moisture content adjacent to lakes and streams are potential locations of great importance in the mdv because of the regular presence of liquid water compared with the rest of the landscape where liquid water is rare at 11 plots four adjacent to lakes seven adjacent to streams soil particle size distribution soil electrical conductivity soil water content and isotopic signature width of the wetted margin and active layer thaw depth were characterised to determine how these gradients influence physicochemical properties that determine microbial habitat and biogeochemical cycling sediments were generally coarse grained in wetted margins adjacent to both lakes and streams wetted margins ranged from 1 04 to 11 01 m in average length and were found to be longer at lakeside sites than streamside average thaw depths ranged from 0 12 to 0 85 m and were found to be deepest under lake margins lake margins also had much higher soil electrical conductivity steeper topographic gradients but more gradual soil moisture gradients than stream margins patterns of soil water 18o and d distribution indicate capillary action and evaporation from wetted margins margin pore waters generally demonstrated isotopic enrichment with distance from the shore indicating evaporation of soil water lake margin pore waters were significantly more negative in dxs dxs d 8 18o than streamside pore waters indicating a longer history of evaporation there differences between lake and stream margins can be explained by the more consistent availability of water to lake margins than stream margins differences in margin characteristics between lakes and streams have important consequences for the microbial habitat of these margins and their functional role in biogeochemical cycling at these terrestrial aquatic interfaces copyright 2009 john wiley sons ltd

groundwater velocity in an unconfined aquifer with rectangular areal recharge three dimensional solutions for the hydraulic head and velocity components for transient groundwater flow in an unconfined compressible aquifer of finite thickness with a rectangular areal recharge source are analyzed using a linearized mathematical model the solution generalizes dagan s 1967 results which were obtained for an idealized aquifer of infinite thickness and hantush s 1967 results which were derived using the dupuit assumptions hydraulic head and velocity components are estimated by asymptotic methods for large times which are most appropriate for contaminant transport problems numerical analysis of the solution demonstrates spatial features of the velocity components in general and a transient effect of upward flow in particular similar to that found for circular sources zlotnik and ledder 1992 obtained formulas show that applicability of the dupuit assumption for computation of velocity components in an unconfined aquifer is limited to a far field zone given approximately by x 1 5x y 1 5y where x and y are the half width and half length respectively of the contaminant source

recharge to finite aquifers from strip basins abstract the problem of groundwater recharge from strip basins to finite aquifers is solved analytically by the method of finite fourier transforms both impermeable and recharge boundaries are considered the analytical solutions are evaluated by comparison with experimental results in sand tank models reported in the literature

an exact analytical solution for steady seepage from a perched aquifer to a low permeable sublayer kirkham brock s legacy revisited an analytical solution is obtained for steady 2 d potential seepage flow from a nonclogged and nonlined soil channel into a highly permeable porous layer with phreatic surfaces tapering toward a horizontal interface with a subjacent low permeable formation along this boundary a vertical component of the darcian velocity vector equals the formation saturated hydraulic conductivity the image of the physical flow domain in the hodograph plane is a circular polygon a triangle or digon in a limiting case of a phreatic jet impinging on the low permeable substratum the polygon is mapped onto an auxiliary half plane where the complex physical coordinate and complex potential are reconstructed by the polubarinova kochina method i e by solution of a riemann bvp the seepage flow rate from the channel free surfaces and a saturated water logged area are found for different thicknesses of the top layer channel widths and conductivity ratios of the two strata in particular the earlier results of brock kirkham and youngs which are based on a numerical solution dupuit forchheimer df approximation and approximate potential model are confirmed in the full 2 d models sufficiently far from the channel the phreatic surface and interface make a wedge for a sufficiently deep substratum three zones are analytically distinguished an almost vertical 1 d descending flow an almost wedge configured 1 d flow and an essentially 2 d zone in between where neither a standard infiltration theory nor df analysis are valid

analytical and experimental solutions for drainage of sloping lands with time varying recharge m j boussinesq s 1904 nonlinear partial differential equation for unsteady state flow of water through a phreatic aquifer resting on a sloping impervious barrier and receiving time varying recharge has been solved two patterns of recharge rates i e linearly increasing and exponentially declining with time were considered the initial conditions of the water table were taken at the drain level transformations were devised to transform the resulting approximate linearized boussinesq equation to the form of a one dimensional heat flow equation for each case of recharge pattern and analytical solutions for the height of the water table between parallel drains were obtained in the form of a convergent series the analytical solutions were experimentally verified with a hele shaw model a reasonably close agreement was found in the computed and observed phreatic surfaces the results showed that the analytical solutions presented herein can be used with reasonable accuracy for designing subsurface drainage in sloping phreatic aquifers

analytical study of capture time to a horizontal well we have investigated capture time through a horizontal well for several types of aquifers we have studied two scenarios in which wells are at the middle and at the bottom or the top of an aquifer we have obtained the closed form analytical solutions of capture times for these two scenarios in homogeneous confined aquifers for both isotropic and anisotropic cases we have discussed the applicability and the limitation of the analytical solutions the presence of confining boundaries in vertical direction constrains the vertical flow but enhances the horizontal flow the presence of anisotropy with a smaller vertical conductivity further limits the vertical flow and increases the horizontal flow we have conducted numerical simulations to obtain capture times and found that they were very close to the analytical solutions given the same conditions we have further analyzed the advantages and disadvantages of two different methods of simulating a horizontal well uniform flux and uniform head

a temporal stable isotopic δ18 o δd d excess comparison in glacier meltwater streams taylor valley antarctica in this paper we describe the importance of hyporheic dynamics within andersen creek and von guerard stream taylor valley antarctica from the 2010 11 melt season using natural tracers water collection started at flow onset and continued with weekly hyporheic zone sampling the water 18o and d values were isotopically lighter in the beginning and heavier later in the season d excess measurements were used as an indicator of mixing because an evaporative signature was evident and distinguishable between two primary end members glacier meltwater and hyporheic zone hyporheic zone influence on the channel water was variable with a strong control on streamwater chemistry except at highest discharges this work supports previous research indicating that von guerard stream has a large widespread hyporheic zone that varies in size with time and discharge andersen creek with a smaller hyporheic zone displayed hyporheic zone solute interaction through the influence from subsurface hypersaline flow overall the evolution of taylor valley hyporheic zone hydrology is described seasonally in mid december the hyporheic zone is a dynamic system exchanging with the glacier meltwater in the channel and with diminishing flow in january the hyporheic zone drains back into the channel flow also impacting stream chemistry this work adds new information on the role of hyporheic zone stream interaction in these glacier meltwater streams

simulating unsteady flow anabranching and hyporheic dynamics in a glacial meltwater stream using a coupled surface water routing and groundwater flow model 1 flooding affects ecosystems by transporting water and solutes across aquatic terrestrial interfaces removing nutrient and organic substrate limitations and spurring biogeochemical activity few studies have considered the influence of flooding on surface water groundwater interactions this research examines the temporally variable water storage and exchange in a stream in the mcmurdo dry valleys mdv of antarctica where diel flood pulses occur due to glacial melt several mdv streams display truncated discharge peaks suggesting water storage between the source glacier and the gauging station we tested the hypothesis that stream braids and subsurface water storage contribute to the difference between glacial melt and stream outflow hydrographs by constructing a coupled surface water routing and subsurface water flow model this model routes water into stream braids at high flows and allows this water to infiltrate and return to the stream via subsurface flow paths as flows recede our simulation demonstrates the importance of surface subsurface water interactions in controlling the hydrograph shape maximum simulated discharge was sensitive to storage parameters including aquifer depth and the flooding threshold while minimum discharge was sensitive to hydraulic conductivity subsurface storage volume varied by 38 over a diel cycle and stream subsurface exchange rates varied from 0 to 0 19 m3 h 1 m 1 with exchange from the stream to the subsurface during high flows and vice versa at low flows these results underscore how unsteady flow can increase hyporheic interactions and ecosystem productivity and provide support for maintaining natural stream morphology and flow regimes

metallogenic provinces geochemical provinces and regional geology what causes large scale patterns in low density geochemical maps of the c horizon of podzols in arctic europe the 2 mm fraction of 605 samples of the c horizon of podzols collected from an area of 188 000 km2 in the european arctic was analysed for more than 40 chemical elements the results were used to construct geochemical maps which showed clear regional distribution patterns notwithstanding the very low sample density of 1 site per 300 km2 some of these patterns fit established lithological boundaries others fit lineament structures in the area and underline the relative importance of certain tectonic directions some of which have not yet been delineated on existing geological maps some mark large scale hydrothermal events and related alteration finally some are connected with prominent known ore deposits occurring in the area however several large deposits and even famous metallogenic provinces fe ni cu are hardly or not at all reflected in the regional geochemical maps in their present definitions geochemical provinces and metallogenic provinces are thus not necessarily related special geochemical features can occur at very different scales the term geochemical province is so imprecise in terms of processes leading to regional scale geochemical features that it should be avoided low density geochemistry can be used to aid the interpretation of the geological evolution of large regions it can also be used to find prospective areas within such regions

diurnal hydrological physicochemical controls and sampling methods for minor and trace elements in an alpine glacial hydrological system summary we present diurnal i 0 45 and 0 1 m pore size filtered and ii operationally defined labile particulate associated major minor and trace element concentrations and fluxes in glacial outflow waters draining haut glacier d arolla switzerland we use speciation modelling phreeqci and water suspended sediment interaction experiments are utilised under conditions analogous to the subglacial channellised hydrological system in order to assess controls on and the most suitable sampling methods to investigate short term variations in the mode of major minor and trace element species export from a glacierised headwater catchment 0 45 m pore size filtered major ions sr and u are exported in glacial outflow waters predominately as mobile monovalent or divalent ions or as carbonate complexes and are controlled by hydrological variations over diurnal cycles exhibiting an inverse concentration with increasing meltwater discharge conversely 0 45 m pore size filtered concentrations of most minor and trace elements e g fe mn co ba and pb exhibit variations that are not strongly inter correlated with meltwater discharge or suspended sediment concentrations ssc over diurnal periods the use of 0 45 and 0 1 m pore size filter membranes indicates that significant colloidal material is not passing through the 0 45 m pore size filters and these unsystematic variations are not a result of colloid measurement speciation modelling applied to meltwaters and observations during water rock interaction experiments suggest that these unsystematic temporal variations reflect physicochemical controls this includes sorption and the oversaturation and precipitation of fe and al oxi hydroxides and the co precipitation of other species diurnal ph variations appear important in controlling such short term physicochemical controls which limits such species use for hydrological investigations the percentage of total elemental fluxes exported as the labile particulate associated flux paf for each minor and trace element changes dramatically between and during the diurnal cycles reflecting species specific sensitivity to hydrological and physicochemical controls hydrological interpretations of hydrochemical data must be made carefully when using chemical determinations by icp ms since we demonstrate that measurements will comprise of any material that passes through the filter this can lead to higher concentration measurements than if determined by ion chromatography which measures truly ionic dissolved species

advanced aquifer characterization for optimization of managed aquifer recharge managed aquifer recharge mar will play an increasingly important role in solving water scarcity the performance of mar systems depends primarily upon local hydrogeology greatest opportunities for improvement in the implementation of mar systems lie in the targeted application of conventional and advanced technologies to improve aquifer characterization surface geophysics e g ves tdem and seismic reflection and refraction generally provide low resolution but areal extensive data on subsurface hydrogeology times series of relative microgravity measurements have been used to map changes in both vadose and phreatic zone storage and to augment monitoring well systems surface nuclear magnetic resonance nmr has the potential to provide quantitative data on water filled porosity and pore size distribution and in turn an estimate of hydraulic conductivity standard borehole geophysical logging techniques can provide coarse scale data on aquifer heterogeneity advanced borehole logging techniques such as nmr microresistivity imaging and gamma ray spectroscopy have been used in mar projects in the usa and uae to provide fine scale petrophysical data e g porosity porosity types and pore size distribution groundwater modeling is used in mar investigations to evaluate system feasibility and to optimize system design and operation opportunities to improve groundwater modeling exist through the application of advanced reservoir simulation platforms that allow for the processing and integration of available lithological geophysical and aquifer testing data and their subsequent incorporation into groundwater flow models advanced groundwater modeling programs are available that allow for the simulation of complex aquifers such as dual porosity systems and variable density

a new model for simulation of collection and conveyance sections of qanat abstract in this paper a new numerical model has been developed for simulation of qanat aquifer system this model employs quasi 3d mixed form of richards equation and 1d fully hydrodynamic form of saint venant equations to simulate subsurface and overland flow respectively in order to handle non orthogonal grids subsurface flow module benefits from coordinate transformation technique using the above mentioned governing equations the presented model is able to simulate water flow inside both collection and conveyance sections of the gallery as well as dynamics of groundwater and vadose zone from impermeable bed rock to the soil air interface since measured data corresponding to the hydraulics of qanats is scarce the overland and subsurface modules have been validated with analytical numerical and experimental benchmarks in the literature subsequently the model was employed to simulate ten different hypothetical aquifer qanat systems with different properties including the depth of groundwater aquifer roughness of the gallery and saturated hydraulic conductivity of the gallery aquifer boundary and the influence of each the parameters was monitored on the outflow rate at the appearance point of each qanat furthermore the advance of water inside two initially dry galleries were simulated at different time levels up to steady state eventually the streamlines have been shown at the steady state for two qanat aquifer systems although the presented study sheds light on some aspects of qanat aquifer hydraulics the validation of the presented model with in lab or on field data remains ongoing for the future researches

two dimensional modelling of water table fluctuation in response to localised transient recharge abstract an analytical solution of the linearised boussinesq equation is presented and used to predict the spatio temporal variation of the water table in a finite aquifer system in response to a transient recharge from an overlying rectangular basin the boundary conditions of the finite aquifer are taken as fixed heads which would apply when the aquifer system is surrounded by open water bodies application of the solution is illustrated with the help of a numerical example the results would also have applications in studying stream aquifer interaction in the presence of transient recharge

steady groundwater flow in leaky multiple aquifer systems abstract the hydraulic properties of stratified formations usually vary from layer to layer within the area of influence of a pumped well drain or section of a river the subsoil can often be schematized into a limited number of aquifers each separated by less pervious layers a general method has been developed for the analytical solution of steady flow problems in leaky multiple aquifer systems comprising any number of aquifers this method has been used to investigate potential distributions in multilayered aquifers of infinite extent being pumped or recharged at a constant rate using completely penetrating wells and drains in one or more of the aquifers the same approach is applicable to groundwater flow problems with more complicated boundary conditions such as the influence of a wide river partially penetrating the leaky top layer the well flow solution has been applied to evaluate hydraulic properties of several aquifers and aquitards from pumping tests in a six layer leaky aquifer system in a general sense the method presented may be regarded as a combined analytical numerical technique

the occurrence and origin of selenium minerals in se rich stone coals spoils and their adjacent soils in yutangba china abstract several se bearing minerals have been identified in se rich stone coal spoils and their adjacent organic rich soils in yutangba of enshi china where human se toxicity occurred in the 1960s these minerals mainly include native se se 0 krutaite cuse 2 klockmannite cuse mandarinoite fe 2 seo 3 3 6h 2 o se bearing chalcopyrite cufe se s 2 and pyrite fe se s 2 the assemblage of native se krutaite klockmannite and se bearing pyrite and chalcopyrite is primarily present in the stone coal near a fault plane while the assemblage of native se and krutaite is found in the se rich carbonaceous mudstone and organic rich soils which are 60 m away from the stone coal exposure the assemblage of mandarinoite and native se is present in abandoned stone coal spoils where natural combustion occurred native se is quite extensive in the stone coal spoils and nearby soils derived from them the co occurrence of cu se minerals and native se indicates that these minerals could have formed under a relatively acidic and reducing environment below 220 c and suggests that cu could play a significant role in fixing reduced se ions in the acidic organic rich surface environment furthermore the occurrence of mandarinoite suggests that iron oxides constrain the geochemical behavior of se in oxidizing environments our observations provide new insights into the mechanisms of se fixation and accumulation during weathering of se rich rocks

water table fluctuations due to canal seepage and time varying recharge transient water table variation in an unconfined horizontal aquifer lying between two canals located at different elevations above the impermeable barrier and receiving time varying recharge is predicted by obtaining an analytical solution to the linearized boussinesq equation the proposed solution is for the generalized form of time varying recharge and has been obtained by applying an indigenously devised transformation to the flow governing equation the solution for constant rate of recharge a special case of the proposed solution is compared with the existing analytical solution and almost identical values of water table rise are obtained the effect of constant recharge exponentially decreasing recharge and a combination of constant and exponentially decreasing recharge on the water table rise is analyzed with the help of a numerical example

measuring thaw depth beneath peat lined arctic streams using ground penetrating radar in arctic streams depth of thaw beneath the stream channel is likely a significant parameter controlling hyporheic zone hydrology and biogeochemical cycling as part of an interdisciplinary study of this system we conducted a field investigation to test the effectiveness of imaging substream permafrost using ground penetrating radar gpr we investigated three sites characterized by low energy water flow organic material lining the streambeds and water depths ranging from 0 2 to 2 m we acquired data using a 200 mhz pulsed radar system with the antennas mounted in the bottom of a small rubber boat that was pulled across the stream while triggering the radar at a constant rate we achieved excellent results at all three sites with a clear continuous image of the permafrost boundary both peripheral to and beneath the stream our results demonstrate that gpr can be an effective tool for measuring substream thaw depth copyright 2005 john wiley sons ltd

enhancement of wadi recharge using dams coupled with aquifer storage and recovery wells wadi channel recharge to the underlying alluvial aquifer is naturally limited by the flashy nature of flood events evapotranspiration losses of water from the vadose zone and aquifer heterogeneity particularly low vertical hydraulic conductivity anthropogenic lowering of the water table in many wadi aquifers has also reduced the potential recharge by increasing the thickness of the vadose zone causing interflow water loss from surface emergence and evaporation a method to enhance recharge is to slow the flow within wadi channels by placement of dam structures thereby ponding water and increasing the vertical head gradient to create a more rapid rate of infiltration and percolation effectiveness of wadi dams to enhance aquifer recharge reduces over time due to mud deposition within the reservoir caused by storm events up to 80 of the water in old wadi reservoirs is lost to free surface evaporation before infiltration and recharge can occur one method to maintain or increase the rate of recharge is to convey clean water by gravity flow from the reservoir down gradient to artificially recharge the aquifer using existing wells this type of system is a low cost and low energy recharge method which could greatly enhance groundwater storage in wadi aquifers modeling results show that existing wells could store up to 1 000 m3 day under gravity feed conditions and up to 3 900 m3 day with the shut in of the well to produce a pressurized system

underground hydrogen storage in the uk to utilize the full potential of hydrogen energy in the uk a number of economic technical and environmental factors must be considered an important factor in replacing fossil fuels with hydrogen will be the practicality of storing a sufficient quantity to smooth out fluctuations in demand and provide a strategic reserve this paper investigates the potential for large scale underground hydrogen storage in the uk by considering the technical geological and physical issues of storage the locations of salt deposits legal and economic aspects in addition reference is made to the equations of state applicable to this type of storage the results of this investigation show that the uk has a number of potential locations where underground storage would provide a strategic reserve of hydrogen

water table fluctuations in an aquifer system owing to time varying surface infiltration and canal recharge a solution of the linearized boussinesq equation for predicting the transient position of the water table in an unconfined aquifer system which lies between two recharging canals at different elevations above the aquifer s base and receives time varying recharge from the overlying soils is presented the solution for the constant rate of recharge is shown as a special case of the present solution the effect of variation in the rate of recharge on the water table fluctuation is investigated with the help of an example

glacier meltwater hydrochemistry abstract glacierised areas present an ideal environment in which to study water rock interaction since chemical weathering rates are high and anthropogenic impacts are often minimal detailed investigations of meltwater quality variations have suggested the importance of these environments in estimates of terrestrial chemical erosion and global biogeochemical cycles most notably the role of meltwaters in co2 sequestration during episodes of deglaciation has attracted considerable attention since this may impact on climate at glacial interglacial timescales however there is still considerable uncertainty surrounding estimates of co2 drawdown by meltwaters which remains to be resolved water flow through glaciers exerts an important control on ice mass dynamics and influences the quantity and quality of water delivered to environments downstream of glacierised basins thus the study of the configuration and dynamics of subglacial drainage systems is important not only to enhance scientific understanding but also to allow effective water resource utilisation in glacierised headwater catchments bulk meltwater quality characteristics draining terrestrial ice masses also offer the potential to provide unique information on hydrological and hydrochemical processes operating in the inaccessible subglacial environment here significant advances have been made in understanding the controls on chemical weathering reactions based on the identification of key dissolved indicator species this has allowed water quality variations to be exploited as a tool for both subglacial hydrochemical and hydrological investigations as a result this area of glaciology has received considerable attention in recent years utilising an increasing range of dissolved ions and integrating field and laboratory studies however uncertainty still surrounds certain areas of meltwater quality science including the role of microorganisms in a system which to date has largely been viewed as abiotic a better understanding of the processes and rates of chemical weathering in glacierised environments has the potential to enhance our understanding of the environment and to facilitate the exploitation of water quality variations for both scientific and applied objectives in this paper the development and current state of meltwater quality science as a tool for investigating subglacial hydrology and geochemistry is detailed and problems and future directions identified this will hopefully stimulate wider interest in an important area of aquatic chemistry with significant applied implications

coupled effects of canal lining and multi layered soil structure on canal seepage and soil water dynamics ponding tests were conducted in the shiyang river basin in northwest china to assess canal leakage characteristics four anti seepage constructions concrete lining pebble lining clay lining plus compacted canal bed compacted canal bed only were performed on four canal sections which were situated in multi layered soils the canal sections were tested using a two stage approach first a stable water level was maintained followed by a stage where the water level in the canal section was permitted to drop the canal seepage rate and the soil water content near the canal bed were monitored during the stable and dropping stages soil texture bulk density and hydraulic conductivity were tested in each canal section and soil layer double ring infiltration tests were performed to investigate infiltration behaviour from the canal sections the saturated unsaturated flow model hydrus 2d was applied to simulate canal seepage and the local soil water response the simulation results compared well with the monitored data indicating that the model can reliably simulate canal seepage under these complex soil structures and different canal liners both experimental results and numerical modelling show that the clay lining plus compacted canal bed provides the best anti seepage performance followed by compacted canal bed only then pebble and concrete lining simulation results also predicted that the soil water content was discontinuous at the interface of distinct soil layers and that the range and form of wetting front varied greatly in the four canal sections with a larger wetted area for the more permeable canals simulations were performed to study the sensitivity on canal seepage of to the permeability of each soil lining layer and the lining effect on canal seepage the results confirmed by double ring infiltration tests indicated that the canal lining is not the only dominant factor affecting canal seepage the soil permeability can also influence the seepage greatly especially where there exists a low permeability layer e g compacted soil layer close to the canal

redox reaction of aqueous selenite with as rich pyrite from jiguanshan ore mine china reaction products and pathway the interaction of an as rich natural pyrite fes2 08as0 043 with aqueous se iv was investigated as a function of ph ferrous iron concentration and reaction time arsenic is often the most abun

diel stream geochemistry taylor valley antarctica unlike temperate and polythermal proglacial streams the proglacial streams in taylor valley tv antarctica are derived primarily from glacier surface melt with no subglacial or groundwater additions solute responses to flow reflect only the interaction of glacial meltwater with the valley floor surrounding the stream channel we have investigated the major minor and trace element 24 h variations of two proglacial melt streams andersen creek and canada stream originating from the canada glacier in tv antarctica both streams exhibited diel mid austral summer diurnal flow variation with maximum flow being more than 50 times the minimum flow dissolved 0 4 m major minor and trace solute behaviors through diel periods were strongly controlled by the availability of readily solubilized material on the valley floor and hyporheic biological exchanges anderson creek had generally greater solute concentrations than canada stream because of its greater receipt of eolian sediment andersen creek also acquired greater solute concentrations in the rising limb of the hydrograph than the falling limb because of dissolution of eolian material at the surface of the stream channel coupled with minimal hyporheic biological exchange conversely canada stream had less available eolian sediment but a greater hyporheic biological exchange which preferentially removed trace and major solutes in the rising limb and released them in the falling limb given the dynamic nature of discharge eolian and hyporheic biological processes solute loads in tv streams are difficult to predict copyright 2012 john wiley sons ltd