did a katian large igneous province trigger the late ordovician glaciation a hypothesis tested with a carbon cycle model abstract the ordovician is known as a period with high temperatures and high sea levels and a cooling event at the end of the period leading to the hirnantian glaciation and the first of the big five mass extinctions of marine life the cause of this cooling event remains unclear several authors correlate it with a drop in atmospheric p co 2 to a threshold permitting the ice accumulation on the gondwana supercontinent however what are the reasons of the atmospheric p co 2 decrease here we follow the hypothesis initiated by barnes 2004 that an ordovician superplume event occurred during the middle to late ordovician such an event would not only have a large impact on the ordovician biodiversification barnes 2004 but it would also be responsible for the climatic upheaval during the late ordovician by the emplacement of a low latitudinal continental basaltic province that had an impact on the atmospheric p co 2 there is no direct evidence of a superplume event or of basaltic traps and the present study is therefore a hypothetical modelling approach where we demonstrate with a numerical box model including carbon alkalinity and phosphorus cycles coupled with a 1d climate model energy balance model ebm francois and walker 1992 that such a scenario allows to explain both the mid ashgill katian global warming event known as the boda event fortey and cocks 2005 and the subsequent late ordovician hirnantian glaciation because silicate weathering is enhanced upon warm and wet climate we try to constrain the size and the latitudinal emplacement of the basaltic province leading to a sufficient consumption of atmospheric p co 2 to the threshold proposed by herrmann et al 2004 a b to initiate a glaciation on gondwana

simulation of groundwater exchange between an unconfined aquifer and a discrete fracture network with laminar and turbulent flows abstract in this study a new approach is developed to simulate groundwater flow through both an overlying unconfined aquifer and an underlying discrete fracture network the groundwater exchange between the aquifer and the fracture network including magnitude and direction is explicitly simulated based on the mass conservation which depends on a variety of parameters related to flow and network characteristics in the overlying unconfined aquifer we approximate the flow using the dupuit assumptions in the underlying fracture network we use the cubic law and forchheimer s law to iteratively simulate laminar or turbulent flow in individual fractures depending on the reynolds number explicitly separating laminar and turbulent flows in the fractures results in a system of nonlinear equations which is iteratively solved while the flow from the overlying unconfined aquifer is a small portion of the overall flow in the underlying fracture network incorrect use of the laminar or turbulent flow equation in the fractures can lead to significant errors in simulating the flow exchange as apertures increase both the portion of the total flowrate in the aquifer and the portion of the flow in the fractures coming from the aquifer decrease as the overall hydraulic gradient increases both the portion of the total flow in the aquifer and the portion of the fracture flow that comes from the aquifer increase the portion of the total flow in the aquifer increases with the aquifer thickness while the portion of fracture flow coming from the overlying aquifer decreases

development and application of an analytical model of stream aquifer interaction abstract a mathematical model to simulate stream aquifer interactions in an unconfined aquifer subjected to time varying river stage was developed from the linearized boussinesq equation using the principle of superposition and the concept of semigroups the mathematical model requires an estimate of three parameters to simulate ground water elevations transmissivity specific yield and recharge the solution has physical significance and includes terms for the steady state water level the steady state water level as influenced by a change in river stage a transient redistribution of water levels in the aquifer from the previous day and a transient change in water level caused by a change in river stage the mathematical model was tested using observed water table elevations at three locations across a 2 km wide alluvial valley aquifer the average absolute deviation between observed and simulated daily water levels was 0 09 m the difference in river stage over the test year was 4 9 m

changing tectonic controls on the long term carbon cycle from mesozoic to present tectonic drivers of degassing and weathering processes are key long term controls on atmospheric co2 however there is considerable debate over the changing relative importance of different carbon sources and sinks existing geochemical models have tended to rely on indirect methods to derive tectonic drivers such as inversion of the seawater 87sr 86sr curve to estimate uplift or continental basalt area here we use improving geologic data to update the representation of tectonic drivers in the copse biogeochemical model the resulting model distinguishes co2 sinks from terrestrial granite weathering total basalt weathering and seafloor alteration it also distinguishes co2 sources from subduction zone metamorphism and from igneous intrusions we reconstruct terrestrial basaltic area from data on the extent of large igneous provinces and use their volume to estimate their contribution to degassing we adopt a recently published reconstruction of subduction related degassing and relate seafloor weathering to ocean crust creation rate revised degassing alone tends to produce unrealistically high co2 but this is counteracted by the inclusion of seafloor alteration and global basalt weathering producing a good overall fit to mesozoic cenozoic proxy co2 estimates and a good fit to 87sr 86sr data the model predicts that seafloor alteration and terrestrial weathering made similar contributions to co2 removal through the triassic and jurassic after which terrestrial weathering increased and seafloor weathering declined we predict that basalts made a greater contribution to silicate weathering than granites through the mesozoic before the contribution of basalt weathering declined over the cenozoic due to decreasing global basaltic area

river stage tomography a new approach for characterizing groundwater basins received 19 june 2008 revised 16 february 2009 accepted 12 march 2009 published 9 may 2009 1 data from tomographic surveys make an inverse problem better posed in comparison to the data from a single excitation source a tomographic survey provides different coverages and perspectives of subsurface heterogeneity nonfully redundant information of the subsurface fusion of these pieces of information expands and enhances the capability of a conventional survey provides cross validation of inverse solutions and constrains inherently ill posed field scale inverse problems basin scale tomography requires energy sources of great strengths spatially and temporally varying natural stimuli are ideal energy sources for this purpose in this study we explore the possibility of using river stage variations for basin scale subsurface tomographic surveys specifically we use numerical models to simulate groundwater level changes in response to temporal and spatial variations of the river stage in a hypothetical groundwater basin we then exploit the relation between temporal and spatial variations of well hydrographs and river stage to image subsurface heterogeneity of the basin results of the numerical exercises are encouraging and provide insights into the proposed river stage tomography using naturally recurrent stimuli such as river stage variations for characterizing groundwater basins could be the future of geohydrology however it calls for implementation of sensor networks that provide long term and spatially distributed monitoring of excitation as well as response signals on the land surface and in the subsurface

on the causes of mass extinctions the temporal link between large igneous province lip eruptions and at least half of the major extinctions of the phanerozoic implies that large scale volcanism is the main driver of mass extinction here we review almost twenty biotic crises between the early cambrian and end cretaceous and explore potential causal mechanisms most extinctions are associated with global warming and proximal killers such as marine anoxia including the early middle cambrian the late ordovician the intra silurian intra devonian end permian and early jurassic crises many but not all of these are accompanied by large negative carbon isotope excursions supporting a volcanogenic origin most post silurian biocrises affected both terrestrial and marine biospheres suggesting that atmospheric processes were crucial in driving global extinctions volcanogenic atmospheric kill mechanisms include ocean acidification toxic metal poisoning acid rain and ozone damage and consequent increased uv b radiation volcanic darkness cooling and photosynthetic shutdown each of which has been implicated in numerous events intriguingly some of the most voluminous lips such as the oceanic plateaus of the cretaceous were emplaced with minimal faunal losses and so volume of magma is not the only factor governing lip lethality the missing link might be continental configuration because the best examples of the lip extinction relationship occurred during the time of pangaea many of the proximal kill mechanisms in lip extinction scenarios are also potential effects of bolide impact including cooling warming acidification and ozone destruction however the absence of convincing temporal links between impacts and extinctions other than the chicxulub cretaceous example suggests that impacts are not the main driver of extinctions with numerous competing extinction scenarios and the realisation that some of the purported environmental stresses may once again be driving mass extinction we explore how experimental biology might inform our understanding of ancient extinctions as well as future crises

modeling transient stream aquifer interaction with the non linear boussinesq equation and its analytical solution a new analytical solution of the non linear transient groundwater flow equation subject to time variable river boundaries was used to simulate stream aquifer interactions in an alluvial valley aquifer the differential equations were solved using the method of decomposition the mathematical model required relatively few parameters to simulate groundwater elevations hydraulic conductivity specific yield and recharge the model was physically based and could simulate the process of a flood wave propagation into an unconfined aquifer the model was tested using observed water table elevations at three locations across a 2 km wide alluvial valley aquifer the average daily deviation between observed and simulated water table elevations was approximately 0 09 m the transient redistribution of water in the aquifer was simulated well with the model the non linear form of the boussinesq equation was shown to better simulate cases when the transmissivity of the aquifer could not be assumed to be a constant

reducing the computational cost of unconfined groundwater flow in conjunctive use models at basin scale assuming linear behaviour the case of adra campo de dalias the optimization of conjunctive use management models with different competing demands several reservoirs and aquifers and a high interconnection among elements over long time horizons requires the use of computationally efficient groundwater flow models a review of conjunctive use models and some methods applied to reduce the computational cost of the groundwater flow model has been performed with special attention to the assumption of linear behaviour the effect of considering invariant transmissivity in a conjunctive use management model at the basin scale has been analyzed using as case study the adra campo de dalias system southeast of spain the system includes an unconfined aquifer not hydraulically connected to the river in which significant drawdown relative to the saturated thickness can appear the basin scale system also includes storage in a reservoir flows in several river segments and canals and a second simpler aquifer the management formulation seeks the best conjunctive operation of reservoir and aquifer to meet urban and irrigation demands while satisfying minimum flow and aquifer head constraints over a time horizon of several years the effect of the linear assumption has been studied by comparing and analyzing management model results obtained modeling the aquifer as confined and as unconfined groundwater flow is simulated in the optimization model using the response matrix method the optimization problem is solved using sequential linear programming slp in the unconfined case and using linear programming lp when confined behaviour is assumed although the drawdown are significant the difference in results is minor suggesting that the use of a linear assumption may be valid in many basin scale conjunctive management problems in which the aquifer is not hydraulically connected to the river system nevertheless the assumption should be tested if possible in each management problem with unconfined aquifers in which significant drawdown appears

recharge of aquifers by flood events in an arid region the process of aquifer recharge by flood events in an arid region was investigated as applied to the hazeva formation the karkom graben the wadi paran watershed israel the hydrological model was established as a complex system with due regard for groundwater and transmission losses of surface runoff it was based on a previously outlined hydrogeological model of the karkom graben and a model of transmission losses in arid watercourses under conditions of data deficiency proceeding from calculation of groundwater balances the contribution of surface runoff as a decisive balance component was confirmed the main characteristics of aquifer regimes such as changes in storage volume and groundwater level as well as lateral flow were all found to be dependent upon the net extraction rate i e pumpage discounting replenishment by flood events analysis and physical interpretation of model parameters enabled assessment of the influence of groundwater extraction on aquifer recharge this became apparent as increasing absorption capacity and recharge availability of the aquifer as a result of the groundwater abstraction copyright 2002 john wiley sons ltd

field experiments and numerical simulations of confined aquifer response to multi cycle recharge recovery process through a well summary shanghai is one of the cities suffering from land subsidence in china land subsidence has caused serious financial losses thus artificial recharge measures have been adopted to compensate the drawdown in shallow confined aquifers and thereby control land subsidence in this study a multi cycle recharge recovery field experiment was performed to investigate the response of a shallow confined aquifer to artificial recharge through a well in the experiment a series of recharge recovery cycles with different recharge volumes and durations with and without artificial pressure were performed the water levels monitored in the recharge and observation wells indicated the response of the aquifer to the multi cycle recharge recovery process meanwhile a finite difference method fdm numerical model was established and its parameters were obtained via a reversed numerical analysis on the experimental data the responses of the shallow confined aquifer to the multi cycle recharge recovery process were simulated in detail using the model the calculation results showed that the water level dropped significantly when the recharge ended moreover the efficiency of a multi cycle recharge was found to be higher than that of a concentrated one under the same recharge volume and time the relationship between recharge frequency and efficiency expressed as h 0 29498 f 0 40163 and r 2 0 97264 respectively was obtained through the fdm numerical simulation in the recharge intervals the optimal recharge efficiency was achieved when the water level rose to 40 of the peak

transient head development due to flood induced seepage under levees the purpose of this study was to predict the uplift force during floods on confining layers that overlay extensive horizontal confined aquifers that intersect a large river in response to the water level changes that occur with time in a flooding river transient flow of water through the confined aquifer was described by a diffusion type of equation with a boundary condition at the river in which the river head varied with time the transient head distribution developed from the unsteady flow model applied to the aquifer was compared with the hydraulic head distributions obtained from u s army corps of engineers steady state flow model and a finite element seepage model this study concluded that the transient flow model has the potential to analyze time lag in head development and to predict the seepage condition and heaving potential at various times and distances landside of a levee during a flood cycle but additional case histories are needed to justify widespread use of the model

time series analysis of large igneous provinces 3500 ma to present abstract we outline an efficient integrated wavelet a spectral and a cross spectral approach for the time series analysis of geologic data here these techniques are applied to a database of 154 large igneous provinces lips in order to test for cycles trends and abrupt changes in temporal distribution since 3500 ma the average frequency of events is relatively constant and supports an overall model of semicontinuous temporal emplacement of lips however several weak cycles were obtained in the analysis those of longest duration are a 170 m yr cycle from 1600 ma to present and in the late archean a 330 m yr cycle from about 3000 to 1000 ma a cycle decreasing in length from 730 to 550 m yr over the interval 3500 ma to present and a still weaker cycle increasing from 900 to 1000 m yr over the interval 2000 ma to present additional cycles of shorter duration include a 250 m yr cycle in the late archean a 230 m yr cycle in the phanerozoic a 105 m yr cycle in the early proterozoic an

groundwater surface water interaction in lake nasser southern egypt a cross sectional model based on the two dimensional groundwater flow equation of edelman was applied at seven transects distributed over four geological cross sections to estimate groundwater heads and recharge from or groundwater discharge to lake nasser the lake with a length of 500 km and an average width of 12 km was created over the period 1964 1970 the time for constructing the aswan high dam ahd the model constrained by regional scale groundwater flow and groundwater head data in the vicinity of the lake was successfully calibrated to timeseries of piezometeric heads collected at the cross sections in the period 1965 2004 inverse modeling yielded high values for the horizontal hydraulic conductivity in the range of 6 0 to 31 1 m day 1 and storage coefficient between 0 01 and 0 40 the results showed the existence of a strong vertical anisotropy of the aquifer the calibrated horizontal permeability is systematically higher than the vertical permeability 1000 1 the calibrated model was used to explore the recharge from or groundwater discharge to lake nasser at the seven transects for a 40 year period i e from 1965 to 2004 the analysis for the last 20 year period 1985 2004 revealed that recharge from lake nasser reduced by 37 compared to the estimates for the first 20 year period 1965 1984 in the period 1965 2004 seepage of lake nasser to the surrounding was estimated at 1 15 109 m3 year 1 this led to a significant rise of the groundwater table variance based sensitivity and uncertainty analysis on the edelman results were conducted applying quasi monte carlo sequences latin hypercube sampling the maximum standard deviation of the total uncertainty on the groundwater table was 0 88 m at toshka west of the lake the distance from the lake followed by the storage coefficient and hydraulic conductivity were identified as the most sensitive parameters copyright 2012 john wiley sons ltd

abrupt warming in the latest permian detected using high resolution in situ oxygen isotopes of conodont apatite from abadeh central iran abstract climate warming probably as a result of massive degassing of greenhouse gases from the siberian traps magmatism has often been acclaimed as a major cause of the end permian mass extinction indeed several studies have documented a sudden rise in seawater temperatures during the latest permian earliest triassic as evidenced by oxygen isotopic records measured on conodont apatite however whether such a rapid increase in seawater temperatures occurred before during or after the mass extinction remains controversial moreover the pattern of this rise in seawater temperatures and its timing relative to the latest permian earliest triassic carbon cycle disruption mass extinction as well as the siberian traps magmatism still need to be rigorously examined in various regions in this study we present high resolution oxygen isotopic records of conodont apatite 18oapatite from the upper permian lowermost triassic interval at the abadeh section central iran that are analyzed with in situ secondary ion mass spectrometry sims method the 18oapatite results from abadeh demonstrate a clear pattern consisting of three phases 1 from the lower wuchiapingian clarkina dukouensis zone to the end permian mass extinction horizon 18oapatite values are relatively stable fluctuating in the range of 18 28 20 15 with an average of 19 44 2 18oapatite value remains high as 19 26 at the mass extinction horizon above this horizon a sudden decrease occurs in the clarkina hauschkei zone and reaches a low value of 17 05 close to the permian triassic boundary 3 in the lowermost triassic 18oapatite values maintain a low baseline in the range of 16 92 17 39 with an average of 17 11 overall the most dramatic change in 18oapatite values i e a decrease of 2 converting into an abrupt warming of 10 c occurred above the mass extinction horizon and below the permian triassic boundary at abadeh the abadeh 18oapatite record is consistent with previous results documented in south china iran and armenia in terms of the timing and magnitude of a substantial warming and therefore represents a global signature if applying the high precision temporal framework established in the well dated meishan gssp section to abadeh the abrupt warming of 10 c took only a maximum duration of 37 kyr thousand years by projecting the carbon cycle change temperature rise mass extinction at the abadeh and meishan sections and the temporal evolution of the siberian traps magmatism onto a unified timescale the temporal correlation strongly suggests that the switch from dominantly extrusive eruptions to widespread sill intrusions is probably the most annihilating phase of the siberian traps magmatism and is temporally consistent with the end permian mass extinction

transient flow to a large diameter well in an aquifer with storative semiconfining layers the hantush theory of leaky aquifers with storge in the semiconfining layers is combined with large diameter well theory to produce equations that can be used in the analysis of pumped well and observation well data for stratified formations included in the equations are storage in the pumped well and a linear resistance to flow at the sand face or well bore skin three cases proposed by hantush are considered these depend upon whether the upper boundary of the overlying semiconfining layer or the lower boundary of the underlying semiconfining layer are constant head or no flow boundaries laplace transform solutions valid for the complete time domain are given for each of the three cases for the hydraulic head in the pumped well the aquifer and each of the semiconfining layers type cures obtained by numerical inversion are selected to illustrate the effects of well bore storage well bore skin and leakage although several dimensionless parameters are involved these parameters tend to influence the character of different portions of the type curves suggesting that unique matches are possible the type curves show that well bore storage in a large diameter well may completely obliterate effects of leakage derived from compressible storage in semiconfining layers for the purposes of aquifer testing it may be possible to reduce the magnitude of well bore storage in a large diameter well and thus reveal the presence of leaky semiconfining layers this may help to prevent erroneous interpretation of the well test data and incorrect evaluation of the aquifer parameters

paleosalinity determination in ancient epicontinental seas a case study of the t oae in the cleveland basin uk abstract the early jurassic toarcian oceanic anoxic event t oae was marked by deposition of organic rich sediments and a pronounced negative carbon isotope excursion across the northwest european sea nwes representing a signal that was stronger regionally than globally various models for the t oae have been proposed some focusing on general atmospheric oceanic controls to reflect its global character and others emphasizing local or regional factors to account for its strong expression in the nwes in this study we evaluate watermass dynamics of the early jurassic cleveland basin uk during the t oae using a combination of paleosalinity proxies b ga sr ba and s toc these proxies suggest that brackish conditions existed prior to onset of the t oae with a shift to nearly freshwater conditions during the t oae reflecting a large increase in terrestrial runoff due to a stronger hydrological cycle possibly combined with shallowing of the marginal sill of the cleveland basin through sea level fall following the t oae basinal salinity conditions first returned to brackish and then gradually shifted to fully marine this hydrographic history accounts for low mo concentrations in t oae sediments of the cleveland basin demonstrating control by watermass restriction and local rather than global aqueous mo drawdown these findings demonstrate the importance of local hydrographic controls on the sedimentary expression of the t oae the more general significance of this study is that it highlights the need for application of paired salinity and redox proxies in order to correctly interpret paleoenvironmental variations in marginal marine basins

aquifer response to surface water transience in disconnected streams 1 existing analytical solutions to determine aquifer response to a change in stream stage are inappropriate where an unsaturated zone exists beneath the stream as in the case of disconnected stream aquifer systems a better understanding of the relationship between aquifer response and transient stream stage in disconnected systems is therefore required as this would also aid in the field determination of the status of connection between the stream and aquifer we use a numerical model to examine transient stream stage and the corresponding water table response beneath disconnected streams the magnitude of head change in the water table level is a balance between the cumulative infiltration during a flow event and the rate at which the water can disperse laterally increases in wave duration stream width and streambed permeability result in greater infiltrated water volume and therefore a higher peak response at the water table conversely higher aquifer transmissivity and aquifer hydraulic conductivity allow the water to move laterally away from the stream faster resulting in a smaller head change below the stream lower unsaturated storage results in a greater and faster aquifer response because the unsaturated zone can fill more quickly under some combinations of parameters the magnitude of the disconnected head response is more than seven times greater than the change in stream stage driving streambed infiltration an effect which can never occur beneath a connected stream the results of this sensitivity analysis are compared to field data from a river in eastern australia to determine periods of disconnection where the change in aquifer head is greater than the change in stream stage disconnection between the stream and aquifer can be determined

biogeochemical constraints on the triassic jurassic boundary carbon cycle event 1 the end triassic mass extinctions represent one of the five most severe biotic crises in earth history yet remain one of the most enigmatic ongoing debate concerns the environmental effects of the central atlantic magmatic province camp eruptions and their linkage with the mass extinction event across the triassic jurassic boundary there is conflicting paleo evidence for changes in atmospheric pco2 during the extrusion of the camp basalts studies on sediments from european and pacific localities have however identified a substantial negative isotopic anomaly up to 3 5 across the tr j boundary providing an important indicator of changes in the operation of the ancient global carbon cycle we sought to explain the paleo evidence by utilizing a carbon cycle model for the hothouse world of the end triassic that emphasizes the chemical weathering of silicate and carbonate rocks and the ocean carbonate chemistry we find that volcanic co2 outgassing fails to fully account for either a sufficient rise in atmospheric pco2 indicated by the stomata of fossil leaves or the sedimentary isotopic fingerprint instead the scenario that best fits all of the geologic evidence is a positive feedback loop in which warming due to a buildup of volcanically derived co2 triggers destabilization of seafloor methane hydrates and the catastrophic release of ch4 palfy et al 2001 we calculate that this carbon cycle perturbation was huge involving the release of 8000 9000 gt c as co2 during the camp basaltic eruptions and 5000 gt c as ch4 in the model the initial isotopic excursion is assumed to take place over 70 kyr while complete reequilibration of the ocean atmosphere system with respect to co2 is accomplished over 700 1000 kyr our results thus provide a preliminary theoretical explanation for the bioevents estimated pco2 changes and isotopic excursions observed in marine and continental sediments at this time

exact analytical expressions for the piezometric profile and water exchange between stream and groundwater during and after a uniform rise of the stream level 1 we consider an archetypical problem relevant to a confined aquifer in contact with a stream the model problem consists of an idealized one dimensional region 0 x l where the left boundary at x 0 is held at a fixed piezometric head h0 and the right boundary s piezometric head at x l is increased from hl to h0 at a constant rate exact solutions for all times all points in the aquifer and for any possible constant rate of change of the right boundary piezometric head are presented for the piezometric head and the instantaneous flow rate an exact expression for the exchange volume at the groundwater stream interface for an arbitrary time is also provided this expression shows that there is a specific critical rising rate of the stream level above which the net exchange volume is into the aquifer and below which it is out of the aquifer the solution shows that regardless of the rise rate a certain water volume inversely proportional to the rise rate enters the aquifer

modification of canal flow due to stream aquifer interaction unsteady canal flow in an integrated canal flow groundwater flow system is analyzed by solving the coupled equations governing canal flow groundwater flow and the seepage between them analytical solu tions are obtained for the coupled system for small water level disturbances using fourier analysis methods and complex variables dimensionless parameter groups characterizing the aquifer the canal and the sediment layer are identified using the governing equations and the solution the influence in the aquifer and the semipermeable bottom sediment layer due to disturbances in canal flow is studied the analytical solutions are compared to numerical solutions obtained using the modflow model and the hydrologic simulation engine of the south florida regional simulation model results of the analysis are useful in determining the range of aquifer sediment and canal characteristics for which stream aquifer interaction is important the results can be used to determine the conditions for which the canal is hydraulically disconnected from the aquifer because of the sediment layer the analytical solution is useful to understand the propagation characteristics of small amplitude water level disturbances in the canal and the aquifer the characteristics studied include the amplitude decay constant and the speed the solution can be used to design benchmark problems that can be used to evaluate integrated canal flow groundwater flow models the results of the study can be used to estimate the space and time steps needed in the canal and the aquifer when simulating stream aquifer interaction as part of the overall effort to restore the everglades eco system in south florida and to meet its regional water man agement responsibilities the south florida water management district sfwmd sfwmd 1999 and other organizations have developed a number of mathematical models to simulate the water management system one important requirement of these models is the capability to simulate stream aquifer in teraction or stream wetland interaction a significant part of the south florida landscape is covered with a network of ca nals that extends for thousands of miles through wetlands ag ricultural areas and urban areas the behavior of water levels in the canals when areas adjacent to canals are subjected to water level changes is not completely understood the influ ences of the highly conductive surface aquifer and the less conductive bottom sediment layer of the canal on the overall hydrology are also not completely known these behaviors influence a significant part of south florida hydrology the current study provides a method to understand the basic pa rameters that govern the problem and to obtain an analytical solution stream aquifer and stream wetland interactions have previ ously been studied by a number of researchers the study by pinder and sauer 1971 was conducted by using a coupled numerical model for canal flow and 2d groundwater flow the objective was to study the influence of bank storage on the modification of flood waves the example used by pinder and sauer 1971 served as a benchmark test for integrated mod els such as modbranch swain and wexler 1996 and modnet walton et al 1999 these models consist of a modflow model mcdonald and harbaugh 1988 coupled with either the branch model schaffranek 1987 or the unet model hec 1996 the comparison between the so lution obtained by pinder and sauer 1971 and the solutions obtained using modbranch or modnet was not perfect 1

buffer effect on identifying transient streambed hydraulic conductivity with inversion of flood wave responses abstract determination of streambed hydraulic conductivity ksb and its variations over time are critical for quantifying exchange fluxes between surface water and groundwater previous studies have used flood wave response techniques frt to determine ksb or its transience excluding the streambed storage effect thus the estimated ksb may not be reliable in this study after improving a previous frt by substituting the gradient descent algorithm with an advanced and robust optimization method trust region reflective algorithm we have analyzed the influence of streambed storage effect on the estimation of time dependent ksb through successive inversion of flood wave responses the study shows that the streambed storage effect is not important for identifying the transience in the hydraulic properties of a relatively thin streambed e g several or dozens of centimeters but significant under estimation 1 2 orders of magnitude can be seen because of neglecting the streambed storage effect it is particularly true for a stream confined aquifer system if the streambed is composed of fine deposits e g silt clay with a thicker thickness greater than 1 m corresponding to low permeability but high storativity and the aquifer is characterized by relatively low permeability e g roughly 0 1 10 m d 1 and relatively low storativity roughly 1e 5 m 1 e g dense fine sands the new method in which streambed storage effect is incorporated can provide more reliable estimations of time dependent ksb for a stream confined aquifer system and it has been successfully applied to estimate the time dependent ksb of a reach of the arkansas river kansas usa

the timing and extent of the eruption of the siberian traps large igneous province implications for the end permian environmental crisis we present new high precision 40ar 39ar ages on feldspar and biotite separates to establish the age duration and extent of the larger siberian traps volcanic province samples include basalts and gabbros from noril sk the lower tunguska area on the siberian craton the taimyr peninsula the kuznetsk basin vorkuta in the polar urals and from chelyabinsk in the southern urals most of the ages except for those from chelyabinsk are indistinguishable from those found at noril sk cessation of activity at noril sk is constrained by a 40ar 39ar age of 250 3 1 1 ma for the uppermost kumginsky suite the new 40ar 39ar data confirm that the bulk of siberian volcanism occurred at 250 ma during a period of less than 2 ma extending over an area of up to 5 million km2 the resolution of the data allows us to confidently conclude that the main stage of volcanism either immediately predates or is synchronous with the end permian mass extinction further strengthening an association between volcanism and the end permian crisis a sanidine age of 249 25 0 14 ma from bed 28 tuff at the global section and stratotype at meishan china allows us to bracket the p tr boundary to 0 58 0 21 myr and enables a direct comparison between the 40ar 39ar age of the traps and the permo triassic boundary section younger ages 243 ma obtained for basalts from chelyabinsk indicate that volcanism in at least the southern part of the province continued into the triassic

numerical modeling the role of rubber dams on groundwater recharge and phreatic evaporation loss in riparian zones rubber dams have been widely built for their advantages in increase of flooding resources utilization in the north arid and semiarid plain regions of china rise in river water stage by the dams particularly during the drought periods increases lateral seepage of river water into groundwater and thus groundwater table and phreatic evaporation loss in the riparian zones in this study a riparian area of the baihe river in nanyang of henan province china was selected for investigation of influences of the river dams on the groundwater recharge and evaporation loss a hydraulic model hec ras was used for simulation of the river stage variations along the baihe river and a numerical groundwater model modflow was applied for simulation of groundwater dynamics and estimation of river flow seepage into aquifer and evaporation loss the results show that the dams increase river stages of 2 3 m during january 2000 december 2002 the increase in the captured groundwater recharge was 7 15 34 06 million m3 a and the increased phreatic evaporation loss occupies 10 of the increased recharge when four rubber dams were built

subduction history reveals cretaceous slab superflux as a possible cause for the mid cretaceous plume pulse and superswell events abstract subduction is a fundamental mechanism of material exchange between the planetary interior and the surface despite its significance our current understanding of fluctuating subducting plate area and slab volume flux has been limited to a range of proxy estimates here we present a new detailed quantification of subduction zone parameters from the late triassic to present day 230 0 ma we use a community plate motion model with evolving plate topologies to extract trench normal convergence rates through time to compute subducting plate areas and we use seafloor paleo age grids to estimate the thickness of subducting lithosphere to derive the slab flux through time our results imply that slab flux doubled to values greater than 500 km3 yr from 180 ma in the jurassic to 130 ma in the mid cretaceous subsequently halving again towards the cretaceous paleogene boundary largely driven by subduction zones rimming the pacific ocean basin the 130 ma spike can be attributed to a two fold increase in mid ocean ridge lengths following the break up of pangea and a coincident increase in convergence rates with average speeds exceeding 10 cm yr with one third of the total 230 0 ma subducted volume entering the mantle during this short 50 myr period we suggest this slab superflux drove a surge in slab penetration into the lower mantle and an associated increase in the vigour of mantle return flow this mid cretaceous event may have triggered or at least contributed to the formation of the darwin rise mantle superswell dynamic uplift of the south african plateau and the plume pulse that produced the ontong java hikurangi manihiki and kerguelen plateaus among others the models presented here contribute to an improved understanding of the time evolving flux of material consumed by subduction and suggest that slab superflux may be a general feature of continental dispersal following supercontinent breakup these insights may be useful for better understanding how supercontinent cycles are related to transient episodes of large igneous province and superswell formation and the associated deep cycling of minerals and volatiles as well as leading to a better understanding of tectonic drivers of long term climate and icehouse to greenhouse transitions

aquifer response to stream stage and recharge variations i analytical step response functions abstract laplace transform step response functions are presented for various homogeneous confined and leaky aquifer types and for anisotropic homogeneous unconfined aquifers interacting with perennial streams flow is one dimensional perpendicular to the stream in the confined and leaky aquifers and two dimensional in a plane perpendicular to the stream in the water table aquifers the stream is assumed to penetrate the full thickness of the aquifer the aquifers may be semi infinite or finite in width and may or may not be bounded at the stream by a semipervious streambank the solutions are presented in a unified manner so that mathematical relations among the various aquifer configurations are clearly demonstrated the laplace transform solutions are inverted numerically to obtain the real time step response functions for use in the convolution or superposition integral to maintain linearity in the case of unconfined aquifers fluctuations in the elevation of the water table are assumed to be small relative to the saturated thickness and vertical flow into or out of the zone above the water table is assumed to occur instantaneously effects of hysteresis in the moisture distribution above the water table are therefore neglected graphical comparisons of the new solutions are made with known closed form solutions

stream water infiltration bank storage and storage zone changes due to stream stage fluctuations abstract during a flood period stream stage increases induce infiltration of stream water into an aquifer subsequent declines in stream stage cause a reverse motion of the infiltrated water this paper presents the results of the water exchange rate between a stream and aquifer the storage volume of the infiltrated stream water in the surrounding aquifer bank storage and the storage zone the storage zone is the part of aquifer where groundwater is replaced by stream water during the flood modflow was used to simulate stream aquifer interactions and to quantify rates of stream infiltration and return flow modpath was used to trace the pathlines of the infiltrated stream water and to determine the size of the storage zone simulations were focused on the analyses of the effects of the stream stage fluctuation aquifer properties the hydraulic conductivity of streambed sediments regional hydraulic gradients and recharge and evapotranspiration et rates on stream aquifer interactions generally for a given stream aquifer system larger flow rates result from larger stream stage fluctuations larger storage volumes and storage zones are produced by larger and longer lasting fluctuations for a given stream stage hydrograph a lower permeable streambed an aquitard or an anisotropic aquifer of low vertical hydraulic conductivity can significantly reduce the rate of infiltration and limit the size of the storage zone the bank storage solely caused by the stage fluctuation differs slightly between gaining and losing streams short term rainfall recharge and et loss in the shallow groundwater slightly influence on the flow rate but their effects on bank storage in a larger area for a longer period can be considerable

water exchange and pressure transfer between conduits and matrix and their influence on hydrodynamics of two karst aquifers with sinking streams summary karst aquifers are heterogeneous media where conduits usually drain water from lower permeability volumes matrix and fractures for more than a century various approaches have used flood recession curves which integrate all hydrodynamic processes in a karst aquifer to infer physical properties of the movement and storage of groundwater these investigations typically only consider flow to the conduits and thus have lacked quantitative observations of how pressure transfer and water exchange between matrix and conduit during flooding could influence recession curves we present analyses of simultaneous discharge and water level time series of two distinctly different karst systems one with low porosity and permeability matrix rocks in southern france and one with high porosity and permeability matrix rocks in north central florida usa we apply simple mathematical models of flood recession using time series representations of recharge storage and discharge processes in the karst aquifer we show that karst spring hydrographs can be interpreted according to pressure transfer between two distinct components of the aquifer conduit and matrix porosity which induce two distinct responses at the spring water exchange between conduits and matrix porosity successively control the flow regime at the spring this exchange is governed by hydraulic head differences between conduits and matrix head gradients within conduits and the contrast of permeability between conduits and matrix these observations have consequences for physical interpretations of recession curves and modeling of karst spring flows particularly for the relative magnitudes of base flow and quick flow from karst springs finally these results suggest that similar analyses of recession curves can be applied to karst aquifers with distinct physical characteristics utilizing well and spring hydrograph data but information must be known about the hydrodynamics and physical properties of the aquifer before the results can be correctly interpreted

erosion of deccan traps determined by river geochemistry impact on the global climate and the 87sr 86sr ratio of seawater abstract the impact of the deccan traps on chemical weathering and atmospheric co2 consumption on earth is evaluated based on the study of major elements strontium and 87sr 86sr isotopic ratios of the main rivers flowing through the traps using a numerical model which describes the coupled evolution of the chemical cycles of carbon alkalinity and strontium and allows one to compute the variations in atmospheric pco2 mean global temperature and the 87sr 86sr isotopic ratio of seawater in response to deccan trap emplacement the results suggest that the rate of chemical weathering of deccan traps 21 63 t km2 yr and associated atmospheric co2 consumption 0 58 2 54 106 mol c km2 yr are relatively high compared to those linked to other basaltic regions our results on the deccan and available data from other basaltic regions show that runoff and temperature are the two main parameters which control the rate of co2 consumption during weathering of basalts according to the relationship f r f c 0 exp ea r 1 t 1 298 where f is the specific co2 consumption rate mol km2 yr rf is runoff mm yr c0 is a constant 1764 mol l ea represents an apparent activation energy for basalt weathering with a value of 42 3 kj mol determined in the present study r is the gas constant and t is the absolute temperature k modelling results show that emplacement and weathering of deccan traps basalts played an important role in the geochemical cycles of carbon and strontium in particular the traps led to a change in weathering rate of both carbonates and silicates in carbonate deposition on seafloor in sr isotopic composition of the riverine flux and hence a change in marine sr isotopic composition as a result deccan traps emplacement was responsible for a strong increase of atmospheric pco2 by 1050 ppmv followed by a new steady state pco2 lower than that in pre deccan times by 57 ppmv implying that pre industrial atmospheric pco2 would have been 20 higher in the absence of deccan basalts pco2 evolution was accompanied by a rapid warming of 4 c followed after 1 myr by a global cooling of 0 55 c during the warming phase continental silicate weathering is increased globally since weathering of continental silicate rocks provides radiogenic sr to the ocean the model predicts a peak in the 87sr 86sr ratio of seawater following the deccan traps emplacement the amplitude and duration of this spike in the sr isotopic signal are comparable to those observed at the cretaceous tertiary boundary the results of this study demonstrate the important control exerted by the emplacement and weathering of large basaltic provinces on the geochemical and climatic changes on earth

final remark on modeling transient stream aquifer interaction with the non linear boussinesq equation and its analytical solution by serrano s e workman s r 1998 journal of hydrology 206 245 255

link between cyclic eustatic sea level change and continental weathering evidence for aquifer eustasy in the cretaceous abstract cyclic fluctuations in global sea level during epochs of warm greenhouse climate have remained enigmatic because absence or subordinate presence of polar ice during these periods precludes an explanation by glacio eustatic forcing an alternative concept suggests that the water bearing potential of groundwater aquifers is equal to that of ice caps and that changes in the dynamic balance of aquifer charge versus discharge as a function of the temperature related intensity of the hydrological cycle may have driven eustasy during warm climates however this idea has long been neglected for two reasons 1 the large storage potential of subsurface aquifers was confused with the much smaller capacity of rivers and lakes and 2 empirical data were missing that document past variations in the hydrological cycle in relation to eustasy in the present study we present the first empirical evidence for changes in precipitation continental weathering intensity and evaporation that correlate with astronomically long obliquity forced sea level cycles during the warmest period of the cretaceous cenomanian turonian we compare sequence stratigraphic data with changes in the terrigenous mineral assemblage in a low latitude marine sedimentary sequence from the equatorial humid belt at the south tethyan margin levant carbonate platform jordan thereby avoiding uncertainties from land ocean correlations our data indicate covariance between cycles in weathering and sea level predominantly chemical weathering under wet climate conditions is reflected by dominance of weathering products clays in deposits that represent sea level fall aquifer charge discharge conversely preservation of weathering sensitive minerals feldspars epidote and pyroxenes in transgressive sediments reflects decreased continental weathering due to dryer climate aquifer discharge charge based on our results we suggest that aquifer eustasy represents a viable alternative to glacio eustasy as a driver of cyclic 3rd order sea level fluctuations during the middle cretaceous greenhouse climate and it may have been a pervasive process throughout earth history

reply to comment on analytical solutions of the nonlinear groundwater flow equation in unconfined aquifers and the effect of heterogeneity by sergio e serrano

three dimensional streamlines in dupuit forchheimer models an approximate method is presented for determining streamlines in three dimensions using two dimensional dupuit forchheimer models the latter models of horizontal flow which may comprise several aquifers are based on the assumption that the resistance to flow in the vertical direction is neglected this assumption does not preclude the occurrence of flow in the vertical direction vertical components of flow are determined in an approximate fashion by requiring continuity of flow the problem of leakage from a shallow pond above an unconfined aquifer is discussed as an example of determining streamlines in three dimensions the errors induced by the approximation are determined for a few idealized flow problems that can be solved exactly

permian ice volume and palaeoclimate history oxygen isotope proxies revisited abstract a high resolution oxygen isotope record based on 356 measurements of conodont apatite from several low latitudinal sections in south china usa and iran was composed in order to unravel permian palaeotemperature and ice volume history the conodont apatite 18 o record is compared to published brachiopod calcite 18 o records brachiopods and conodonts from different palaeocontinents show significantly different 18 o values suggesting differences in local climatic conditions e g evaporation precipitation ratio as a consequence secular changes in palaeotemperature and oxygen isotope composition of permian sea water cannot be reconstructed from records combined from different areas but have to be based on records from a specific area oxygen isotope analyses of different conodont taxa suggest that streptognathodus and hindeodus lived in near surface seawater and recorded surface water temperature whereas the habitat of gondolellid genera was variable depending on sea level with both near surface and deeper waters as potential life habitat the oxygen isotope record measured on conodonts from south china exhibits relative high values between 22 and 23 vsmow during the glaciated early permian translating into warm seawater temperature between 26 and 30 c assuming that the late palaeozoic ice volumes were comparable to the pleistocene glacial maxima in contrast to the earlier view that the late palaeozoic ice age lpia terminated in the late sakmarian the south china conodont apatite oxygen isotope record suggests waning of the ice sheets in the kungurian ice melting is indicated by a pronounced decrease in 18 o of 2 vsmow which is interpreted as reflecting the combined effect of climatic warming and glacial ice melting significant temperature fluctuations 4 c warming succeeded by 6 to 8 c cooling are observed during the guadalupian lopingian transition interpreted as combined climate changes induced by emeishan volcanism and changes in habitat depth of gondolellid conodonts oxygen isotope values increase to 22 vsmow in the changhsingian which suggests climate cooling and clarkina moving to deeper waters because of the changhsingian sea level rise across the permian triassic boundary 18 o values decrease from 22 to 19 vsmow parallel to the significant negative carbon isotope excursion and the eruption of the siberian traps the latter is pointing to a cause effect relationship as a consequence of the massive release of volcanic greenhouse gases derived from the siberian volcanism and related processes

application of the coupled model to the somme river basin summary hydrological modeling of the somme river basin situated in the north of france was made with special emphasis on the stream aquifer interaction due to immense groundwater storage in the chalk aquifer a damaging flood took place in the basin in spring 2001 to best represent the phenomena occurring in the basin the coupled model also known as modcou was selected to be applied to this particular basin the whole model structure consists of several components namely surface model groundwater model unsaturated zone model and the coupled model in order to run the surface model meteorological forcing land use and soil type data were acquired by using land use and soil type data production zones were obtained the surface model partitions the precipitation between surface runoff infiltration and actual evapotranspiration according to the parameters of production zones the unsaturated zone model computes the recharge of groundwater by using infiltration from the surface using a nash cascade model by using the groundwater model a steady state piezometric head distribution is obtained to serve as an initial condition to the coupled model the unsteady groundwater and surface flow simulations are carried out by the coupled model initially spatial information on the basin was extracted by using digital elevation model dem analysis after acquiring the necessary spatial data the surface and aquifer grids were generated by using nested grid generators which make refinement on the stream network and subcatchment boundaries in order to increase the accuracy of numerical solution a very detailed calibration was performed by following a step by step procedure in which the best fit in flow and piezometric head hydrographs was sought in the surface model concentration time and parameters of production zones are calibrated for coupled surface groundwater flows transmissivity specific yield and discharge coefficient and for flow in unsaturated zone storage constant were calibrated during the simulations intense and interrupted exfiltrations were observed over the basin two algorithms were developed in order to correct the issue caused by the coarse resolution of the dem 1 a fill algorithm was used to remove the sinks and obtain a smoother surface and 2 a correction procedure for river cell elevations is proposed to acquire continuous exfiltration along the stream network validation of the model was made using the discharges at two points on the somme namely hangest sur somme and peronne which had not been used in any stage of the modeling process and satisfactory results were obtained the groundwater behavior its effect on the surface flow and the flood of 2001 are satisfactorily represented

electrical and hydraulic vertical variability in channel sediments and its effects on streamflow depletion due to groundwater extraction summary the stratification of channel sediments and their vertical hydraulic conductivity kv are important hydrologic information in the analysis of stream aquifer interactions this paper describes the use of direct push technology to generate electrical conductivity ec logs and collect continuous sediment cores beneath river channels the techniques were applied to nine study sites along a 130 km reach of the platte river in southeast nebraska ec logs for the channel surface down to as much as 24 m below the channel surface indicate that the channel sediments in the western part of the reach consist predominantly of sand and gravel low kv silt clay layers occur in the rest of the reach these silt clay layers are either interbedded with sand and gravel or occur as a major unit within the channel sediments as a result the values of kv determined from the sediment cores can vary by four to five orders of magnitude in the same vertical profile of channel sediments at a number of sites the river channel is not lined by a low kv layer at the surface instead the kv values for the top part of channel sediments were consistently greater than kv values for sediments in deeper parts they show a decreasing tendency with the depth this paper also analyzes the effect of low kv layers within channel sediments on streamflow depletion induced by groundwater pumping simulation results suggest that the effectiveness of low kv layers on the calculation of streamflow depletion depends on their depth thickness vertical permeability the length along the channel and the width within the channel as well as the extension into the aquifer on both sides of the river a low kv layer present at the channel surface seems to be the most effective hydrologic feature in reducing the hydrologic connection of stream aquifer a 2008 elsevier b v all rights reserved

climate changes caused by degassing of sediments during the emplacement of large igneous provinces most mass extinctions during the last 500 m y coincide with eruptions of large igneous provinces lips the cretaceous tertiary extinction was synchronous with the deccan flood volcanism the permian triassic extinction with the eruption of the enormous siberian traps and the end guadalupian extinction with the emeishan volcanic province the causal link remains disputed however and many lips apparently had no significant impact on the biosphere here we show that a key control on the destructive consequences of lip emplacement is the type of sedimentary rock in basins beneath the flood basalts contact metamorphism around intrusions in dolomite evaporite coal or organic rich shale generates large quantities of greenhouse and toxic gases co 2 ch 4 so 2 which subsequently vent to the atmosphere and cause global warming and mass extinctions the release of sediment derived gases had a far greater impact on the environment than the emission of magmatic gases

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

response of sloping unconfined aquifer to stage changes in adjacent stream ii applications summary we convolve the system response functions of the linearised 1d equation of boussinesq extended for slope dupuit approximation derived in the companion paper of akylas and koussis akylas e koussis a d submitted for publication response of sloping unconfined aquifer to stage changes in adjacent stream i theoretical analysis and derivation of system response functions j hydrol and develop solutions for the interaction of a fully penetrating stream with a sloping unconfined aquifer taking also into account a low conductivity streambed layer these solutions give the aquifer stage and flow rate the flow exchange rate at the stream aquifer interface and the exchanged water volumes bank storage release the solutions are analytical when the flow inducing stream stage variations are common functions otherwise the convolution integral is evaluated numerically responses are compared for aquifers on positive negative and zero base slopes to a wave like change in the stage of the stream analytical and numerical convolution derived solutions are used to model the interaction of cedar river and its adjacent unconfined aquifer near cedar rapids iowa in the model the aquifer base is taken to be horizontal or inclined and the streambed clogged by a low conductivity sediment layer the model is verified against data not used in the calibration and is found to perform very well

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

groundwater dynamics due to general stream fluctuations in an unconfined single or dual porosity aquifer subjected to general areal recharge abstract analytical solutions of groundwater dynamics in an elongated aquifer subjected to general time dependent recharge are presented the lateral boundaries are specified heads with the head variations governed by general time dependent functions general recharge function was not considered in previous works of this kind both single and double porosity aquifers are considered the solution is obtained using fourier sine and laplace transformations followed by an inverse fourier laplace transform involving residue theorem and convolutional integral for the unconfined single porosity aquifer case the exact time domain solution is obtained using the residue theorem for the unconfined double porosity aquifer case the time domain head is calculated using the de hoog inverse laplace algorithm the presented solution can be used to estimate the hydraulic parameters of 1 groundwater head variation of a river basin aquifer subjected to general lateral head variation and recharge 2 groundwater head variation in a double porosity elongated fractured anticline 3 groundwater depletion of an elongated fractured anticline subjected to recharge due to rainfall or snowmelt to its adjacent alluvial aquifer in addition the presented solution can be utilized to optimize the irrigation pattern in a cropland between two trench drains to control the groundwater mound

the effects of large igneous provinces on the global carbon and sulphur cycles abstract the correlation between large igneous provinces lips extinction events and rapid climate change suggests that volcanism can have a detrimental impact on earth surface conditions changes in atmospheric and ocean chemistry particularly the climate sensitive carbon and sulphur cycles are among the most probable processes for inducing global environmental stress however the interactions and feedbacks between volcanism and these cycles are numerous and complex making the characterisation of the response to a lip challenging here we summarise the sources and sinks of carbon and sulphur from large scale volcanism and magmatism using information from modern and ancient systems for the sources we review the current understanding of volcanic emissions and explore the relative contributions and importance of magma derived degassing versus volatile release from sediments affected by igneous intrusions and lava in addition we explore the various ways in which lips can reduce atmospheric concentrations of these same elements the relative influences of each source and sink are in part determined by the mode of lip emplacement and eruption style along with the subsequent timescales of such effects we focus on a few key examples including the siberian traps the parana etendeka and the central atlantic magmatic province camp to demonstrate how the environmental impact can vary considerably with differing modes of emplacement lip duration and eruption styles in particular we show that the host rocks can have a dominant role as a source or sink of emissions depending on the lithologies affected by the lip emplacement

fully conservative coupling of hec ras with modflow to simulate stream aquifer interactions in a drainage basin this work describes the application of a methodology designed to improve the representation of water surface profiles along open drain channels within the framework of regional groundwater modelling the proposed methodology employs an iterative procedure that combines two public domain computational codes modflow and hec ras in spite of its known versatility modflow contains several limitations to reproduce elevation profiles of the free surface along open drain channels the drain module available within modflow simulates groundwater flow to open drain channels as a linear function of the difference between the hydraulic head in the aquifer and the hydraulic head in the drain where it considers a static representation of water surface profiles along drains the proposed methodology developed herein uses hec ras a one dimensional 1d computer code for open surface water calculations to iteratively estimate hydraulic profiles along drain channels in order to improve the aquifer drain interaction process the approach is first validated with a simple closed analytical solution where it is shown that a piccard iteration is enough to produce a numerically convergent and mass preserving solution the methodology is then applied to the groundwater surface water system of the choele choel island in the patagonian region of argentina smooth and realistic hydraulic profiles along drains are obtained while backwater effects are clearly represented

development and verification of a 3 d integrated surface water groundwater model summary coupled modelling of surface and subsurface systems is a valuable tool for quantifying surface water groundwater interactions in the present paper the 3 d non steady state navier stokes equations after reynolds averaging and with the assumption of a hydrostatic pressure distribution are for the first time coupled to the 3 d saturated groundwater flow equations in an integrated surface water groundwater model irene a finite difference method is used for the solution of the governing equations of irene a semi implicit scheme is used for the discretisation of the surface water flow equations and a fully implicit scheme for the discretisation of the groundwater flow equations the two sets of equations are coupled at the common interface of the surface water and groundwater bodies where water exchange takes place using darcy s law a new approach is proposed for the solution of the coupled surface water and groundwater equations in a simultaneous manner in such a fashion that gives computational efficiency at low computational cost irene is verified against three analytical solutions of surface water groundwater interaction which are chosen so that different components of the model can be tested the model closely reproduces the results of the analytical solutions and can therefore be used for analysing and predicting surface water groundwater interactions in real world cases

basaltic volcanism and mass extinction at the permo triassic boundary environmental impact and modeling of the global carbon cycle the siberian traps represent one of the most voluminous continental flood basalt provinces on earth the mass extinction at the end of the permian was the most severe in the history of life in the present paper these two major concurrent events that occurred are analysed and a geochemical model coupled with an energy balance model is used to calculate their environmental impact on atmospheric co2 oceanic 13c and marine anoxia the latitudinal temperature gradient is reduced relative to today resulting in warmer temperatures at high latitudes the warmer climate and the presence of fresh basaltic provinces increase the weatherability of the continental surfaces resulting in an enhanced consumption of atmospheric co2 through weathering first the eruption of the siberian traps is accompanied by a massive volume of 13c depleted co2 degassed from the mantle and added to the ocean through silicate weathering thus lowering marine 13c second the rapid collapse in productivity induces a strong decrease in the global organic carbon burial this too tends to increase the proportion of light carbon in the ocean these two effects can explain the low 13c values across the pt boundary and methane release need not be invoked to explain the 13c fluctuations it is proposed that the phosphorus cycle which drives primary production in the model plays an important role on the recovery of productivity and the 13c variations

the potential added value of regional climate models in south america using a multiresolution approach this paper aims to identify those regions within the south american continent where the regional climate models rcms have the potential to add value pav compared to their coarser resolution global forcing for this we used a spatial scale filtering method based on the wavelet theory to distinguish the regional climatic signal present in atmospheric surface fields from observed data cpc and trmm and 6 rcm simulations belonging to the cordex project the wavelet used for filtering was haar wavelet but a comparative analysis with daubechies 4 wavelet indicated that meteorological fields or regional indices were not very sensitive to the wavelet selected once the longer wavelengths were filtered we focused on analyzing the spatial variability of extreme rainfall and the spatiotemporal variability of maximum and minimum surface air temperature on a daily basis the results obtained suggest essential differences in the spatial distribution of the small scale signal of extreme precipitation between trmm and regional models together with a large dispersion between models while trmm and cpc register a large signal throughout the continent the rcms place it over the andes cordillera and some over tropical south america pav signal for surface air temperature was found over the andes cordillera and the brazilian highlands which are regions characterized by complex topography and also on the coasts of the continent the signal came specially from the small scale stationary component the transient part is much smaller than the stationary one except over la plata basin where they are of the same order of magnitude also the rcms and cpc showed a large spread between them in representing this transient variability the results confirm that rcms have the potential to add value in the representation of extreme precipitation and the mean surface temperature in south america however this condition is not applicable throughout the whole continent but is particularly relevant in those terrestrial regions where the surface forcing is strong such as the andes cordillera or the coasts of the continent

response of sloping unconfined aquifer to stage changes in adjacent stream i theoretical analysis and derivation of system response functions we study the interaction of a stream with a sloping unconfined aquifer that the stream is assumed to fully penetrate the analysis applies to flow in a vertical section considers the existence of a low conductivity streambed layer and the flow in the aquifer to be induced by variations of the stream stage invoking the dupuit assumption yields the 1 d boussinesq equation extended for a sloping base the boussinesq equation is linearised the derived flow model is critiqued and an objective procedure for determining the linearisation level is developed we solve the linear governing equation by the method of laplace transform with analytical inversion the horizontal aquifer case is treated in the zero slope limit the system response function is derived for the general case sloping aquifer sediment bed layer and for several specific cases and solutions are verified against known analytical results responses are contrasted for aquifers on positive negative and zero slopes to step changes in the stage of streams with and without a sediment bed layer the solutions give the aquifer stage and flow rate the flow exchange rate at the stream aquifer interface and the exchanged water volumes bank storage release

double porosity models for a fissured groundwater reservoir with fracture skin theories of flow to a well in a double porosity groundwater reservoir are modified to incorporate effects of a thin layer of low permeability material or fracture skin that may be present at fracture block interfaces as a result of mineral deposition or alteration the commonly used theory for flow in double porosity formations that is based upon the assumption of pseudo steady state block to fissure flow is shown to be a special case of the theory presented in this paper the latter is based on the assumption of transient block to fissure flow with fracture skin under conditions where fracture skin has a hydraulic conductivity that is less than that of the matrix rock it may be assumed to impede the interchange of fluid between the fissures and blocks resistance to flow at fracture block interfaces tends to reduce spatial variation of hydraulic head gradients within the blocks this provides theoretical justification for neglecting the divergence of flow in the blocks as required by the pseudo steady state flow model coupled boundary value problems for flow to a well discharging at a constant rate were solved in the laplace domain both slab shaped and sphere shaped blocks were considered as were effects of well bore storage and well bore skin resultsmore obtained by numerical inversion were used to construct dimensionless type curves that were applied to well test data for a pumped well and for an observation well from the fractured volcanic rock terrane of the nevada test site less

aquifer response to stream stage and recharge variations ii convolution method and applications abstract in this second of two papers analytical step response functions developed in the companion paper for several cases of transient hydraulic interaction between a fully penetrating stream and a confined leaky or water table aquifer are used in the convolution integral to calculate aquifer heads streambank seepage rates and bank storage that occur in response to stream stage fluctuations and basinwide recharge or evapotranspiration two computer programs developed on the basis of these step response functions and the convolution integral are applied to the analysis of hydraulic interaction of two alluvial stream aquifer systems in the northeastern and central united states these applications demonstrate the utility of the analytical functions and computer programs for estimating aquifer and streambank hydraulic properties recharge rates streambank seepage rates and bank storage analysis of the water table aquifer adjacent to the blackstone river in massachusetts suggests that the very shallow depth of water table and associated thin unsaturated zone at the site cause the aquifer to behave like a confined aquifer negligible specific yield this finding is consistent with previous studies that have shown that the effective specific yield of an unconfined aquifer approaches zero when the capillary fringe where sediment pores are saturated by tension extends to land surface under this condition the aquifer s response is determined by elastic storage only estimates of horizontal and vertical hydraulic conductivity specific yield specific storage and recharge for a water table aquifer adjacent to the cedar river in eastern iowa determined by the use of analytical methods are in close agreement with those estimated by use of a more complex multilayer numerical model of the aquifer streambank leakance of the semipervious streambank materials also was estimated for the site the streambank leakance parameter may be considered to be a general or lumped parameter that accounts not only for the resistance of flow at the river aquifer boundary but also for the effects of partial penetration of the river and other near stream flow phenomena not included in the theoretical development of the step response functions

transient solution for stream unconfined aquifer interaction due to time varying stream head and in the presence of leakage summary this paper presents new analytical solutions of a linearized boussinesq equation characterizing groundwater flow in a stream unconfined aquifer system due to transient seepage the aquifer is underlain by a horizontal leaky bed and interacts with an adjoining stream of varying water level through a semipervious vertical stream bank close form analytical expressions are derived to predict water head distribution flow rate and volumetric exchange of water in response to time dependent rise or drop in the stream water level comparison between analytical and numerical results shows satisfactory agreement the effects of the finite and semi infinite lengths of the domain are considered in detail certain asymptotic situations such as sudden rise or drop in the stream water level no flow condition at the aquifer s base and absence of vertical stream bank can be dealt with as limiting cases of main results an illustration of the new analytical approach is used to quantify the accretion recession of the bank storage due to variation in various aquifer parameters

atmospheric pco2 perturbations associated with the central atlantic magmatic province the effects of a large igneous province on the concentration of atmospheric carbon dioxide pco2 are mostly unknown in this study we estimate pco2 from stable isotopic values of pedogenic carbonates interbedded with volcanics of the central atlantic magmatic province camp in the newark basin eastern north america we find pre camp pco2 values of 2000 parts per million ppm increasing to 4400 ppm immediately after the first volcanic unit followed by a steady decrease toward pre eruptive levels over the subsequent 300 thousand years a pattern that is repeated after the second and third flow units we interpret each pco2 increase as a direct response to magmatic activity primary outgassing or contact metamorphism the systematic decreases in pco2 after each magmatic episode probably reflect consumption of atmospheric co2 by weathering of silicates stimulated by fresh camp volcanics

mediterranean flash flood transfer through karstic area karstic aquifers influence flash floods propagation in mediterranean countries near montpellier southern france discharge data are recorded on the coulazou river upstream and downstream of the aumelas causse two gauging stations are used to describe the hydrodynamics of this binary karstic system the first station characterizes the non karstic catchment area the second one is representative of the karstic part of the watershed records since april 2004 are used to understand how the river interacts with a karstic aquifer hydrograph analysis of three flash flood events is described corresponding discharge time series recorded at the two gauging stations are used to describe the modification of the hydrographs by auto and crosscorrelations analyses finally linear system analyses are used to provide the transfer functions of this binary karstic system according to the three flood events characteristics initial conditions volume spatial distribution of rainfall etc theses functions summarize the hydrodynamic behaviour of the system their shapes are indicative of the dynamics of the storage the release and the contribution to surface waters

multiply nested regional climate simulation for southern south america sensitivity to model resolution abstract results are reported from two 5 month long simulations for southern south america using the fifth generation pennsylvania state university ncar mesoscale model mm5 the periods of simulation correspond to may september 1997 and 1998 which were anomalously wet and dry winters for central chile respectively the model setup includes triply nested two way interacting domains centered over the eastern south pacific and the western coast of southern south america with horizontal grid intervals of 135 45 and 15 km boundary conditions are provided from ncep ncar reanalyzed fields the analysis focuses on two subregions of central chile 30 41 s region 1 32 35 s which is where the observed interannual precipitation differences are largest is topographically very complex with a mean height of the andes cordillera around 4500 m region 2 35 39 s has relatively smooth terrain as the mean height of the andes drops to 3000 m station precipitation and temperature data are used for model

wavelet analysis of simulated tropical convective cloud systems part i basic analysis abstract a wavelet analysis of a three dimensional 7 day explicit simulation of the tropical cloud systems in the global atmosphere research programme garp atlantic tropical experiment phase iii is performed three physically distinct regimes squall line nonsquall cloud cluster and scattered convection in a doubly periodic domain are analyzed using discrete meyer wavelets these wavelets are complete and facilitate the inversion of the decomposed modes the full wavelet spectra well characterize the spatial localization of each physical variable in particular the vertical velocity and the condensate fields the probability distribution of the wavelet coefficients is non gaussian despite the horizontal winds the temperature and humidity being closely gaussian in physical space this demonstrates the effectiveness of the wavelet basis for analyzing cloud system organization the full wavelet spectrum also selects a preferred spatial orientation of the convective organization in physical space a p

worldwide distribution of continental rock lithology implications for the atmospheric soil co2 uptake by continental weathering and alkalinity river transport to the oceans 1 the silicate rock weathering followed by the formation of carbonate rocks in the ocean transfers co2 from the atmosphere to the lithosphere this co2 uptake plays a major role in the regulation of atmospheric co2 concentrations at the geologic timescale and is mainly controlled by the chemical properties of rocks this leads us to develop the first world lithological map with a grid resolution of 1 1 this paper analyzes the spatial distribution of the six main rock types by latitude continents and ocean drainage basins and for 49 large river basins coupling our digital map with the gem co2 model we have also calculated the amount of atmospheric soil co2 consumed by rock weathering and alkalinity river transport to the ocean among all silicate rocks shales and basalts appear to have a significant influence on the amount of co2 uptake by chemical weathering

a semianalytical solution for the boussinesq equation with nonhomogeneous constant boundary conditions the boussinesq groundwater equation is widely used in hydrology to predict streamflow from an unconfined aquifer and derive the aquifer s saturated hydraulic conductivity and drainable porosity and to predict water table height in drainage engineering in this work we solve this equation in an unconfined horizontal aquifer for nonhomogeneous boundary conditions for the water table height the solution is found in the form of a taylor series that has a finite radius of convergence which is different for each initial condition we also present an expression for the flux boundary condition at the origin as a function of the depth of the adjoining stream that automatically satisfies the boundary condition at infinity and thus eliminates the need for a trial and error approach for the solution which is accurate to 10 7 in order to obtain an approximation for the water table height in the region where the series solution diverges first we computed a diagonal pade approximation from the series coefficients which converges in a larger interval than the series and then we matched it with a new asymptotic approximation for large values of the independent variable we found that the proposed matched solution is better suited to cases where the water head at the origin is close to the initial water head in the aquifer

applicability of analytical solutions to tidal propagation in circular islands abstract the propagation of tides into coastal aquifers is an important phenomenon in the migration of coastal contaminants for the representation of shoreline boundary conditions in regional scale groundwater models and for the estimation of aquifer properties based on tidal amplitude attenuation and or phase increase in this study an analytical solution to the propagation of tidal fluctuations in a radial flow field applicable to circular islands is compared to the existing straight coastline ferris solution the analytical solution is compared to numerical simulation using seawat of a simple harmonic ocean tide and its propagation within a circular island this represents the first attempt to combine a previous correction that allows seawat to simulate axisymmetric flow and a modification to seawat to create tidal boundary conditions bench testing the analytical solution against the numerical model confirms the numerical approach the circular island solution is compared to the ferris solution in terms of tidal amplitude decay and phase shift whereas amplitude decay from the ferris solution is valid only for near shore locations within circular islands the ferris solution produces reasonable phase lag estimates for typical aquifer diffusivities and for most locations within circular islands by comparing the ferris and circular island solutions we propose a correction factor to the ferris solution that allows it to be applied in circular boundary settings this extends the application of the widely applied ferris solution to a broader range of situations

time series analyses for karst river interactions assessment case of the coulazou river southern france summary in many karst systems throughout the world numerous karst features facilitate the exchange of water between the surface the vadose zone and the saturated zone of the aquifer these interactions play actually a prominent role in the ground and surface waters circulation this study aims at assessing karst river interactions by the way of flood hydrograph analysis and new tools for time series analysis in this field of research as in many others binary karst system the captured waters of the coulazou river travel through conduits and preferential flow paths in the vadose zone and join the saturated zone of the aquifer this river is an ephemeral river in a mediterranean context where rapid and intense floods occur each year this hydrologic behaviour is appropriate to study the transfer of a flood through a karst area the water level in caves the rainfall all over the karst aquifer catchment area the piezometric level within the karst aquifer and the discharge in the river upstream and downstream of the karst aquifer are measured in order to understand the karst river exchanges during a flood the modification of the surface flows in the river is treated as a linear time invariant system lti system correlation and spectral analyses are used to understand how the lti system dissipates or enhances the flood wave energy for several floods the frequency response function estimations are interpreted in term of flood wave modification through the karst area in this way according to the initial state of the karst river system the autogenic and or allogenic recharge of the aquifer may induce surge flows and a significant karst contribution to surface flows

a geoclim simulation of climatic and biogeochemical consequences of pangea breakup large fluctuations in continental configuration occur throughout the mesozoic while it has long been recognized that paleogeography may potentially influence atmospheric co2 via the continental silicate weathering feedback no numerical simulations have been done because of the lack of a spatially resolved climate carbon model geoclim a coupled numerical model of the climate and global biogeochemical cycles is used to investigate the consequences of the pangea breakup the climate module of the geoclim model is the foam atmospheric general circulation model allowing the calculation of the consumption of atmospheric co2 through continental silicate weathering with a spatial resolution of 7 5 long 4 5 lat seven time slices have been simulated we show that the breakup of the pangea supercontinent triggers an increase in continental runoff resulting in enhanced atmospheric co2 consumption through silicate weathering as a result atmospheric co2 falls from values above 3000 ppmv during the triassic down to rather low levels during the cretaceous around 400 ppmv resulting in a decrease in global mean annual continental temperatures from about 20 c to 10 c silicate weathering feedback and paleogeography both act to force the earth system toward a dry and hot world reaching its optimum over the last 260 myr during the middle late triassic in the super continent case given the persistent aridity the model generates high co2 values to produce very warm continental temperatures conversely in the fragmented case the runoff becomes the most important contributor to the silicate weathering rate hence producing a co2 drawdown and a fall in continental temperatures finally another unexpected outcome is the pronounced fluctuation in carbonate accumulation simulated by the model in response to the pangea breakup these fluctuations are driven by changes in continental carbonate weathering flux accounting for the fluctuations in area available for carbonate platforms the simulated ratio of carbonate deposition between neritic and deep sea environments is in better agreement with available data

hydrogeology of a complex champlain sea deposit quebec canada implications for slope stability the thick sequences of marine clayey deposits which blanket the st lawrence lowlands in south eastern canada are highly susceptible to landslides with 89 of the population of the province of que