assessing preferential flow through an unsaturated waste rock pile using spectral analysis 1 waste rock piles are an outcome of open pit and underground mining operations unprocessed low grade rock is disposed of in piles from several meters high to 100 m high waste rock piles may still contain sufficient concentrations of metals to be a potential source of pollution the evaluation of the potential risk involves properly characterizing flow through these piles under unsaturated conditions the main flow characteristic of the piles is the presence of a large range of grain and pore sizes based on data from an instrumented rock pile located in saskatchewan canada unsaturated flow through the pile is modeled as a linear system after separating a fast and a slow component water reaching the base of the pile is monitored by 16 contiguous zero tension lysimeters the fast component flowing through macropores is assumed to be released instantaneously while the slow component is simulated using a linear reservoir model that assumes the presence of an interconnected porous matrix an empirical transfer function tf is computed as the ratio of the spectra of signals between the output basal outflow and the input rainfall time series determination of a parametric transfer function model provides information on the characteristic time of water storage in the matrix and on the fraction of the water within each subsection of the experimental pile that is channeled through the macropores an analysis of the output signal at different support scales is performed indicating the nonlinearity of the macropore fraction scaling processes

the role of groundwater in the amazon water cycle 3 influence on terrestrial water storage computations and comparison with grace 1 we explore the mechanisms whereby groundwater influences terrestrial water storage tws in the amazon using grace observations and two contrasting versions of the leaf hydro flood hydrological model one with and the other without an interactive groundwater we find that first where the water table is shallow as in northwestern amazonia and floodplains elsewhere subsurface stores vadose zone and groundwater are nearly saturated year round hence river and flooding dominate tws variation where the water table is deep as in southeastern amazonia the large subsurface storage capacity holds the infiltrated water longer before releasing it to streams hence the subsurface storage dominates tws variation second over the whole amazon the subsurface water contribution far exceeds surface water contribution to total tws variations based on leaf hydro flood simulations 71 of tws change is from subsurface water 24 from flood water and 5 from water in river channels third the subsurface store includes two competing terms soil water in the vadose zone and groundwater below the water table as the water table rises the length of vadose zone is shortened and hence the change in groundwater store is accompanied by an opposite change in soil water store resulting in their opposite phase and contributions to total tws we conclude that the inclusion of a prognostic groundwater store and its interactions with the vadose zone rivers and floodplains in hydrological simulations enhances seasonal amplitudes and delays seasonal peaks of tws anomaly leading to an improved agreement with grace observations

dissolved organic matter and terrestrial lotic linkages in the central amazon basin of brazil we evaluate the hypothesis that decomposition and adsorption reactions operating in upland soils of headwater catchments control the concentration and composition of dissolved and fine particulate organic matter in rivers of the amazon basin in two contrasting first order catchments characteristic of the central amazon basin we analyzed plant litter soil groundwater and stream water chemistry our results indicate that clear and persistent differences exist in the concentration and elemental composition of dissolved organic matter dom in stream waters and groundwaters from the two catchments due mainly to corresponding differences in soil texture and chemistry within the more oxide and clay rich oxisols underlying terra firme forest groundwater dom concentrations were uniformly low 120 mc and c n ratios averaged 10 conversely within the oxide and clay deficient spodosols underlying campinarana forest groundwater dom concentrations were greatly elevated 3000 mc and c n ratios averaged near 60 we found that in the terra firme oxisol terrain the majority of dom contributions to the stream derived from the riparian zone while in the campinarana spodosol terrain upland groundwater contributions could account for the concentration and composition of dom in the stream the implications of our findings are that in the terra firme terrains which dominate the region upland soil profiles are not the site of definitive processes which impart compositional signatures to organic matter carried by the largest rivers of the amazon basin as was hypothesized instead we suggest that definitive reactions are focused primarily in the river corridor

susceptibility and predictability of conditions for preferential flow preferential flow in the field might be caused by various factors and is difficult to observe in situ this experimental study was designed to identify the combined effects of air entrapment surface desaturation suction head soil layering and water repellency hydrophobicity of the porous media on unstable preferential flow or fingering in the vadose zone the predictability of unstable flow was studied on the basis of two existing criteria for gravity fingering 1 a velocity criterion proposed by hill and parlange 1972 and 2 a pressure head criterion by raats 1973 and philip 1975 two dimensional transparent chambers 60 cm high 41 5 cm wide and 2 8 cm thick and 90 cm deep 74 5 cm wide and 1 8 cm thick were used to visualize water infiltration into a water wettable sand a water wettable loam differently layered sand and loam and a water repellent sand the results suggested that infiltration into the homogeneous sand and a sand over loam system without the effects of air entrapment and surface desaturation was unconditionally stable infiltration into the loam was also stable as observed in the limited chambers the flow was unconditionally unstable in a fine over coarse stratified sublayer and conditionally unstable in the homogeneous sand under the effects of air entrapment and surface desaturation in multiple layered systems infiltration flow was semiunstable fingers developed in the sand layer and were stabilized in the loam in the repellent sand the wetting front was unstable under low ponding conditions however it was stabilized when the ponding depth exceeded the water bubbling entry value of the hydrophobic medium both the velocity and pressure head criteria predicted fingering in the sand layers with the effects of gravity however the criteria failed to predict stable flow in the loam indicating that the capillary stabilizing effects on the flow need to be included in theoretical developments finally the observed width and speed of the fingers and the system flux were found to be always higher under air draining fingering conditions than with fingering under air confined conditions

observations of preferential flow during a liquid release experiment in fractured welded tuffs author s salve rohit abstract to better understand preferential flow in fractured rock we carried out an in situ field experiment in the exploratory studies facility at yucca mountain nevada this experiment involved the release of 22 m3 of ponded water at a pressure head of 0 04 m over a period of 7 months directly onto a 12 m2 infiltration plot located on a fractured welded tuff surface as water was released changes in moisture content were monitored along horizontal boreholes located in the formation 19 22 m below distinct flow zones varying in flow velocity wetted cross sectional area and extent of lateral movement intercepted the monitoring boreholes there was also evidence of water being diverted above the ceiling of a cavity in the immediate vicinity of the monitoring boreholes observations from this field experiment suggest that isolated conduits each encompassing a large number of fractures develop within the fractured rock formation to form preferential flow paths that persist if there is a continuous supply of water in addition in fractured welded tuffs the propensity for fracture matrix interactions is significantly greater than that suggested by existing conceptual models in which flow occurs along a section of fracture surfaces an overriding conclusion is that field investigations at spatial scales of tens of meters provide data critical to the fundamental understanding of flow in fractured rock

grace measurements of mass variability in the earth system monthly gravity field estimates made by the twin gravity recovery and climate experiment grace satellites have a geoid height accuracy of 2 to 3 millimeters at a spatial resolution as small as 400 kilometers the annual cycle in the geoid variations up to 10 millimeters in some regions peaked predominantly in the spring and fall seasons geoid variations observed over south america that can be largely attributed to surface water and groundwater changes show a clear separation between the large amazon watershed and the smaller watersheds to the north such observations will help hydrologists to connect processes at traditional length scales tens of kilometers or less to those at regional and global scales

constraints for flow regimes on smooth fracture surfaces 1 in recent years significant advances have been made in our understanding of the complex flow processes in individual fractures aided by flow visualization experiments and conceptual modeling efforts these advances have led to the recognition of several flow regimes in unsaturated individual fractures subjected to different initial and boundary conditions for an idealized smooth fracture surface the most important regimes are film flow rivulet flow and sliding of droplets the existence of such significantly dissimilar flow regimes has been a major hindrance in the development of self consistent conceptual models of flow for single fracture surfaces that encompass all the flow regimes the objective of this study is to delineate the existence of the different flow regimes in individual fracture surfaces for steady state flow conditions we developed physical constraints on the different flow regimes that satisfy minimum energy configurations which enabled us to segregate the wide range of fracture flux volumetric flow rate per fracture width into several flow regimes these are in increasing order of flow rate flow of adsorbed films flow of sliding drops rivulet flow stable film flow and unstable turbulent film flow the scope of this study is limited to wide aperture smooth fractures with the flow on the opposing sides of fracture being independent

remote sensing of floodplain geomorphology as a surrogate for biodiversity in a tropical river system madre de dios peru the complex floodplains of large rivers offer a striking example of how geomorphology by dictating patterns in the frequency and duration of soil saturation and surface flooding influences ecosystem structure and function this study draws on multiple sources of data from remote sensing together with ground observations and water sampling to distinguish floodplain ecosystems in the madre de dios river a tributary of the amazon river in peru this remote tropical river meanders across sub andean alluvial deposits in a tectonically active region and creates floodplain surfaces of varying ages including terraces that are above the reach of present day river floods data from landsat etm optical multispectral jers 1 l band radar and the shuttle radar topography mission c band interferometric digital elevation models were integrated in an object oriented image analysis approach to distinguish five classes of floodplain vegetation vegetation classes generally correspond with successional age and reflect the activity of the riverine meander belt stage data for the river show erratic fluctuations and an annual range exceeding 8 m but the maximum depth of floodplain inundation varied from 1 m close to the river to approximately 0 1 m on more elevated terraces the major ion composition of standing waters on the floodplain during the dry season indicated the importance of emergence of local groundwater in maintaining saturated soils particularly further from the river where backswamp vegetation is distinct and includes palm swamps thus a hydrological continuum exists from deep but sporadic river inundation near the river to constant soil saturation by groundwater emergence in distal backswamps reflecting the geomorphological origin and age of the floodplain deposits this hydrogeomorphic continuum results in fundamental ecological differences the exceptionally rich biodiversity of the sub andean region may be ascribed in part to the enhanced biodiversity associated with fluvial geomorphological features and thus conservation planning must account for the diverse landforms created by fluvial dynamics

conceptual model of the geometry and physics of water flow in a fractured basalt vadose zone a conceptual model of the geometry and physics of water flow in a fractured basalt vadose zone was developed based on the results of lithological studies and a series of ponded infiltration tests conducted at the box canyon site near the idaho national engineering and environmental laboratory the infiltration tests included one 2 week test in 1996 three 2 day tests in 1997 and one 4 day test in 1997 for the various tests initial infiltration rates ranged from 4 1 cm d 4 75 10 7 m s to 17 7 cm d 2 05 10 7 m s and then decreased with time presumably because of mechanical or microbiological clogging of fractures and esicular basalt in the near surface zone as well as the effect of entrapped air the subsurface moisture redistribution was monitored with tensiometers neutron logging time domain reflectrometry and ground penetrating radar a conservative tracer potassium bromide was added to the pond water at a concentration of 3 g l to monitor water flow with electrical resistivity probes and water sampling analysis of the data shows evidence of preferential flow rather than the propagation of a uniform wetting front we propose a conceptual model describing the saturation desaturation behavior of the basalt in which rapid preferential flow occurs through the largest vertical fractures followed by a gradual wetting of other fractures and the basalt matrix fractures that are saturated early in the tests may become desaturated thereafter which we attribute to the redistribution of water between fractures and matrix lateral movement of water takes place within horizontal fracture and rubble zones enabling development of perched water bodies

evaluation of new grace time variable gravity data over the ocean 1 monthly grace gravity field models from the three science processing centers csr gfz and jpl are analyzed for the period from february 2003 to april 2005 over the ocean the data are used to estimate maps of the mass component of sea level at smoothing radii of 500 km and 750 km in addition to using new gravity field models a filter has been applied to estimate and remove systematic errors in the coefficients that cause erroneous patterns in the maps of equivalent water level the filter is described and its effects are discussed the grace maps have been evaluated using a residual analysis with maps of altimeter sea level from jason 1 corrected for steric variations using the world ocean atlas 2001 monthly climatology the mean uncertainty of grace maps determined from an average of data from all 3 processing centers is estimated to be less than 1 8 cm rms at 750 km smoothing and 2 4 cm at 500 km smoothing which is better than was found previously using the first generation grace gravity fields

water saturation relations and their diffusion limited equilibration in gas shale implications for gas flow in unconventional reservoirs author s tokunaga tk shen w wan j kim y cihan a zhang y finsterle s abstract 2017 american geophysical union all rights reserved large volumes of water are used for hydraulic fracturing of low permeability shale reservoirs to stimulate gas production with most of the water remaining unrecovered and distributed in a poorly understood manner within stimulated regions because water partitioning into shale pores controls gas release we measured the water saturation dependence on relative humidity rh and capillary pressure pc for imbibition adsorption as well as drainage desorption on samples of woodford shale experiments and modeling of water vapor adsorption into shale laminae at rh 0 31 demonstrated that long times are needed to characterize equilibrium in larger 5 mm thick pieces of shales and yielded effective diffusion coefficients from 9 10 9 to 3 10 8 m2 s 1 similar in magnitude to the literature values for typical low porosity and low permeability rocks most of the experiments conducted at 50 c on crushed shale grains in order to facilitate rapid equilibration showed significant saturation hysteresis and that very large pc 1 mpa are required to drain the shales these results quantify the severity of the water blocking problem and suggest that gas production from unconventional reservoirs is largely associated with stimulated regions that have had little or no exposure to injected water gravity drainage of water from fractures residing above horizontal wells reconciles gas production in the presence of largely unrecovered injected water and is discussed in the broader context of unsaturated flow in fractures

time variable gravity from grace first results eleven monthly grace gravity field solutions are now available for analyses we show those fields can be used to recover monthly changes in water storage both on land and in the ocean to accuracies of 1 5 cm of water thickness when smoothed over 1000 km the amplitude of the annually varying signal can be determined to 1 0 cm results are 30 better for a 1500 km smoothing radius and 40 worse for a 750 km radius we estimate the annually varying component of water storage for three large drainage basins the mississippi the amazon and a region draining into the bay of bengal to accuracies of 1 0 1 5 cm

interannual variability of greenland ice losses from satellite gravimetry 1 using extended satellite gravity measurements from the gravity recovery and climate experiment grace here we show that ice losses in southeast greenland appear to have slowed down dramatically since late 2007 while those in the west especially northwest greenland show continued accelerations in recent years over the period april 2002 to november 2009 averaged ice loss rates in eastern greenland 120 31 gt yr are still significantly larger than those in the west 86 3 22 gt yr however the estimated ice loss rate from glaciers in northwest greenland has increased from 30 9 8 gt yr over the first few years 2002 2005 to 128 2 33 gt yr for the more recent period 2007 2009 while the loss rate in southeast greenland for the more recent period has become almost negligible down from 109 28 gt yr of just a few years ago the rapid change in the nature of the regional ice mass in southeast and northwest greenland in the course of only several years further reinforces the idea that the greenland ice sheet mass balance is very vulnerable to regional climate conditions the dramatic slow down of ice loss in southeast greenland observed by grace provides an independent verification of similar reports from other remote sensing data the observed significant interannual variability of greenland ice mass change suggests that it is very challenging to quantify greenland s long term ice mass change rates and some observed apparent accelerations might simply be a reflection of the interannual variability

a mechanistic model for water seepage through thick unsaturated zones in fractured rocks of low matrix permeability the theme developed in this paper is that water seepage in thick unsaturated zones in fractured rocks of low matrix permeability cannot be understood by considering spatial and temporal averages we suggest that most such seepage proceeds in an unsteady episodic manner in localized preferential pathways mechanisms are proposed and explored which permit water to flow relatively freely in networks of interconnected fractures in the presence of strong suction pressures from an unsaturated rock matrix imbibition into the rock matrix is reduced by limited wetted area the episodic nature of flow and possibly also by the presence of mineral coatings of low permeability on the fracture walls these effects and conditions combine to limit total imbibition rates to values less than saturated matrix hydraulic conductivity leaving the rock matrix in partially saturated conditions even as water is flowing freely in portions of the fracture network the proposed conceptual model is elaborated and substantiated with analytical estimates and numerical simulation studies mechanisms are demonstrated that can funnel distributed seepage into spatially localized preferential paths subsequent horizontal broadening from dispersive mechanisms is found to be a slow process for fractures of high intrinsic permeability the presence of an unsaturated rock matrix provides constraints on fracture matrix interface areas for imbibition and on the frequency of episodic deep seepage events further studies are needed to test the proposed model

tracer movement in a single fissure in granitic rock some experimental results and their interpretation radionuclide migration was studied in a natural fissure in a granite core the fissure was oriented parallel to the axis in a cylindrical core 30 cm long and 20 cm in diameter the traced solution was injected at one end of the core and collected at the other breakthrough curves were obtained for the nonsorbing tracers tritiated water and a large molecular weight lignosulphonate molecule and for the sorbing tracers cesium and strontium from the breakthrough curves for the nonsorbing tracers it could be concluded that channeling occurs in the single fissure a dispersion model based on channeling is presented the results from the sorbing tracers indicate that there is substantial diffusion into and sorption in the rock matrix sorption on the surface of the fissure also accounts for a part of the retardation effect of the sorbing species a model which includes the mechanisms of channeling surface sorption matrix diffusion and matrix sorption is presented the experimental breakthrough curves can be fitted fairly well by this model by use of independently obtained data on diffusivities and matrix sorption

movement of amazon surface water from time variable satellite gravity measurements and implications for water cycle parameters in land surface models 1 the large scale observations of terrestrial water storage from grace satellites over the amazon are analyzed with land surface model lsm outputs of runoff and soil moisture a simple yet effective runoff routing method based on a continuity equation is implemented to model horizontal transport of surface water within the amazon basin the grace observations are analyzed separately for soil moisture and surface water storages generated from runoff relying on their distinct spatial patterns being disperse for soil moisture and localized for surface water various effective velocities for storage transport are tested against the grace observations when the model runoff is routed with an uniform velocity of 30 cm s the annual variation of the resulting surface water storage is generally found to be larger than the satellite measurements and ground gauge data by a factor of 1 5 or higher the peak annual anomaly of surface water storage is observed around the midstream of the amazon main stem however the runoff routing simulations present the peak amplitude consistently around the delta downstream unless the increasing velocity in a downstream region is used as complements to the ground gauge data the satellite observations provide unique spatial information of water cycle parameters our analysis indicates possible shortcomings in the certain lsm mass transport scheme between atmosphere and land surface particularly the production of too large seasonal variations in runoff and maybe too little variations in evapotranspiration and the dynamic characteristics of surface water transport within the amazon basins

trichloroethene dnapl flow and mass distribution in naturally fractured clay evidence of aperture variability a cylindrical sample 0 5 m in diameter and length was obtained by excavation from 3 7 4 2 m depth below ground surface in a surficial deposit of fractured glaciolacustrine clay the sample was enclosed in a triaxial cell in a cold room to impose conditions close to field temperature and stress hydraulic testing using a hydraulic gradient of 2 provided a saturated hydraulic conductivity of 7 10 10 m s which is only slightly larger than the matrix hydraulic conductivity the cubic law provided a mean hydraulic aperture of 5 6 m for the four continuous vertical fractures in the sample a column of immiscible phase trichloroethene tce imposed incrementally at the top of the sample provided an entry pressure derived aperture equal to 17 m for a parallel plate fracture tce dense nonaqueous phase liquid dnapl that flowed through the sample produced dissolved phase diffusion haloes in the matrix that indicated the preferential fracture pathways these haloes indicated that dnapl flowed through only 5 15 of the visible oxidation stained fractures hence natural fractures had variable apertures along their length and the larger aperture regions provided channels for fluid flow using the hydraulic test results and applying the cubic law only to the aperture segments of confirmed dnapl flow an equivalent hydraulic aperture of 8 11 m was obtained which is greater than the conventional mean hydraulic aperture and smaller than the local aperture determined from the dnapl entry pressure these differences are large in the context of fluid flux which is proportional to the aperture cubed

effect of isolated fractures on accelerated flow in unsaturated porous rock 1 fractures that begin and end in the unsaturated zone or isolated fractures have been ignored in previous studies because they were generally assumed to behave as capillary barriers and remain nonconductive we conducted a series of experiments using berea sandstone samples to examine the physical mechanisms controlling flow in a rock containing a single isolated fracture the input fluxes and fracture orientation were varied in these experiments visualization experiments using dyed water in a thin vertical slab of rock were conducted to identify flow mechanisms occurring due to the presence of the isolated fracture two mechanisms occurred 1 localized flow through the rock matrix in the vicinity of the isolated fracture and 2 pooling of water at the bottom of the fracture indicating the occurrence of film flow along the isolated fracture wall these mechanisms were observed at fracture angles of 20 and 60 degrees from the horizontal but not at 90 degrees pooling along the bottom of the fracture was observed over a wider range of input fluxes for low angled isolated fractures compared to high angled ones measurements of matrix water pressures in the samples with the 20 and 60 degree fractures also demonstrated that preferential flow occurred through the matrix in the fracture vicinity where higher pressures occurred in the regions where faster flow was observed in the visualization experiments the pooling length at the terminus of a 20 degree isolated fracture was measured as a function of input flux calculations of the film flow rate along the fracture were made using these measurements and indicated that up to 22 of the flow occurred as film flow these experiments apparently the first to consider isolated fractures demonstrate that such features can accelerate flow through the unsaturated zone and should be considered when developing conceptual models

yucca mountain earth science issues at a geologic repository for high level nuclear waste abstract the nation has over 40 000 metric tonnes mt of nuclear waste destined for disposal in a geologic repository at yucca mountain in this review we highlight some of the important geoscience issues associated with the project and place them in the context of the process by which a final decision on yucca mountain will be made the issues include understanding how water could infiltrate the repository corrode the canisters dissolve the waste and transport it to the biosphere during a 10 000 year compliance period in a region the basin and range province that is known for seismic and volcanic activity although the site is considered to be dry a considerable amount of water is present as pore waters and as structural water in zeolites the geochemical environment is oxidizing and the present repository design will maintain temperatures at greater than 100 c for thousands of years geoscientists in this project are challenged to make unprecedented predictions about coupled thermal hydrol

approximate boundaries between different flow regimes in fractured rocks recent studies have shown how water films at near zero matric potentials on fracture surfaces could permit fast flow in unsaturated fractures the present work is aimed at delineating the ranges of conditions necessary to permit film flow the approximate matric potential needed to permit thickening of water films on fracture surfaces was estimated through correlating air entry matric potentials and permeabilities for a wide range of porous media an upper matric potential limit associated with saturating the fracture was related to the fracture aperture these two limits one dependent on matrix permeability and the other on fracture aperture delineate the matric potential range within which thick water films develop on fracture surfaces rocks with matrix permeabilities less than 10 14 m2 and fractures with apertures greater than 30 m permit some matric potential range over which thick water films can form highly transmissive films can develop on fracture surfaces only under near zero matric and pressure potentials

the role of contact angle on unstable flow formation during infiltration and drainage in wettable porous media 1 the impact of contact angle on 2 d spatial and temporal water content distribution during infiltration and drainage was experimentally studied the 0 3 0 5 mm fraction of a quartz dune sand was treated and turned subcritically repellent contact angle of 33 48 56 and 75 for s33 s48 s56 and s75 respectively the media were packed uniformly in transparent flow chambers and water was supplied to the surface as a point source at different rates 1 20 ml min a sequence of gray value images was taken by ccd camera during infiltration and subsequent drainage gray values were converted to volumetric water content by water volume balance narrow and long plumes with water accumulation behind the downward moving wetting front tip and negative water gradient above it tail developed in the s56 and s75 media during infiltration at lower water application rates the plumes became bulbous with spatially uniform water content distribution as water application rates increased all plumes in these media propagated downward at a constant rate during infiltration and did not change their shape during drainage in contrast regular plume shapes were observed in the s33 and s48 media at all flow rates and drainage profiles were nonmonotonic with a transition plane at the depth that water reached during infiltration given that the studied media have similar pore size distributions the conclusion is that imbibition hindered by the nonzero contact angle induced pressure buildup at the wetting front dynamic water entry value that controlled the plume shape and internal water content distribution during infiltration and drainage

nonlinear dynamics in flow through unsaturated fractured porous media status and perspectives 1 the need has long been recognized to improve predictions of flow and transport in partially saturated heterogeneous soils and fractured rock of the vadose zone for many practical applications such as remediation of contaminated sites nuclear waste disposal in geological formations and climate predictions until recently flow and transport processes in heterogeneous subsurface media with oscillating irregularities were assumed to be random and were not analyzed using methods of nonlinear dynamics the goals of this paper are to review the theoretical concepts present the results and provide perspectives on investigations of flow and transport in unsaturated heterogeneous soils and fractured rock using the methods of nonlinear dynamics and deterministic chaos the results of laboratory and field investigations indicate that the nonlinear dynamics of flow and transport processes in unsaturated soils and fractured rocks arise from the dynamic feedback and competition between various nonlinear physical processes along with complex geometry of flow paths although direct measurements of variables characterizing the individual flow processes are not technically feasible their cumulative effect can be characterized by analyzing time series data using the models and methods of nonlinear dynamics and chaos identifying flow through soil or rock as a nonlinear dynamical system is important for developing appropriate short and long time predictive models evaluating prediction uncertainty assessing the spatial distribution of flow characteristics from time series data and improving chemical transport simulations inferring the nature of flow processes through the methods of nonlinear dynamics could become widely used in different areas of the earth sciences

a model of water streaking down a wall rainwater streaking down a vertical wall exhibited the characteristics of fingered flow the wall serves as an analogy to film flow in a relatively smooth and wide aperture fracture a digital photograph of the wall suggests that the vertical distribution of water is heavy tailed a fractional order advection dispersion equation is used as a model

terrestrial water mass load changes from gravity recovery and climate experiment grace recent studies show that data from the gravity recovery and climate experiment grace is promising for basin to global scale water cycle research this study provides varied assessments of errors associated with grace water storage estimates thirteen monthly grace gravity solutions from august 2002 to december 2004 are examined along with synthesized grace gravity fields for the same period that incorporate simulated errors the synthetic grace fields are calculated using numerical climate models and grace internal error estimates we consider the influence of measurement noise spatial leakage error and atmospheric and ocean dealiasing aod model error as the major contributors to the error budget leakage error arises from the limited range of grace spherical harmonics not corrupted by noise aod model error is due to imperfect correction for atmosphere and ocean mass redistribution applied during grace processing four methods of forming water storage estimates from grace spherical harmonics four different basin filters are applied to both grace and synthetic data two basin filters use gaussian smoothing and the other two are dynamic basin filters which use knowledge of geographical locations where water storage variations are expected global maps of measurement noise leakage error and aod model errors are estimated for each basin filter dynamic basin filters yield the smallest errors and highest signal to noise ratio within 12 selected basins grace and synthetic data show similar amplitudes of water storage change using 53 river basins covering most of earth s land surface excluding antarctica and greenland we document how error changes with basin size latitude and shape leakage error is most affected by basin size and latitude and aod model error is most dependent on basin latitude

impactites of the yaxcopoil 1 drilling site chicxulub impact structure petrography geochemistry and depositional environment the impact breccias encountered in drill hole yaxcopoil 1 yax 1 in the chicxulub impact structure have been subdivided into six units the two uppermost units are redeposited suevite and suevite and together are only 28 m thick the two units below are interpreted as a ground surge deposit similar to a pyroclastic flow in a volcanic regime with a fine grained top unit 3 23 m thick nue ardente and a coarse breccia unit 4 15 m thick below as such they consist of a mlange of clastic matrix breccia and melt breccia the pyroclastic ground surge deposit and the two units 5 and 6 below are related to the ejecta curtain unit 5 24 m thick is a silicate impact melt breccia whereas unit 6 10 m thick is largely a carbonate melt breccia with some clastic matrix components unit 5 and 6 reflect an overturning of the target stratigraphy the suevites of units 1 and 2 were deposited after emplacement of the ejecta curtain debris reaction of the super heated breccias with seawater led to explosive activity similar to phreomagmatic steam explosion in volcanic regimes this activity caused further brecciation of melt and melt fragments the fallback suevite deposit of units 1 and 2 is much thinner than suevite deposits at larger distances from the center of the impact structure than the 60 km of the yax 1 drill site this is evidence that the fallback suevite deposit units 1 and 2 originally was much thicker unit 1 exhibits sedimentological features suggestive of suevite redeposition erosion possibly has occurred right after the k t impact due to seawater backsurge but erosion processes spanning thousands of years may also have been active therefore the top of the 100 m thick impactite sequence at yaxcopoil in our opinion is not the k t boundary

high resolution temperature measurements in the borehole yaxcopoil 1 mexico within the frame of the international continental deep drilling program icdp and as a part of the chicxulub scientific drilling project csdp high resolution temperature measurements were performed in the borehole yaxcopoil 1 yax 1 the temperature was logged to the depth of 858 m seven times between march 6 19 2002 starting 10 days after the hole was shut in and mud circulation ceased successive logs revealed only small temperature variations in time and space indicating a fast temperature recovery to almost undisturbed conditions prior to the first log from these logs a mean temperature gradient of 37 mk m was determined below the uppermost 250 m another temperature log was recorded on may 24 2003 15 months after the shut in to a depth of 895 m the obtained temperature profile is very similar to the 2002 profile with an insignificantly higher mean gradient below 250 m that may indicate a long term return to the pre drilling temperature the temperature in the uppermost part of the hole bears signs of considerable influence of a convective contribution to the vertical thermal heat transfer the depth extent of the convection seems to have deepened from 150 m in march 2002 to 230 m in may 2003 based on the observed temperature gradient and the rock types encountered in the borehole above 670 m the conducted heat flow is expected to be in the range 65 80 mw m2

laboratory investigation of matrix imbibition from a flowing fracture predicting fluid flow and transport behavior in unsaturated fractured rock is greatly simplified where matrix imbibition can be modeled as a linear function of the square root of time t1 2 however such treatment implicitly assumes homogenous matrix properties to investigate matrix heterogeneity effects we perform a simple experiment in which x ray imaging is used to measure the imbibition of water from a flowing fracture into a slab of volcanic tuff experimental results show matrix imbibition to follow a linear t1 2 relationship even though the saturated hydraulic conductivity of the tuff varies by over four orders of magnitude

liquid phase structure within an unsaturated fracture network beneath a surface infiltration event field experiment 1 we conducted a simple field experiment to elucidate structure i e geometry of the liquid phase water resulting from ponded infiltration into a pervasive fracture network that dissected a nearly impermeable rock matrix over a 46 min period dyed water was infiltrated from a surface pond while electrical resistance tomography ert was employed to monitor the rapid invasion of the initially dry fracture network and subsequent drainage we then excavated the rock mass to a depth of 5 m mapping the fracture network and extent of dye staining over a series of horizontal pavements located directly beneath the pond near the infiltration surface flow was dominated by viscous forces and the fracture network was fully stained with increasing depth flow transitioned to unsaturated conditions and the phase structure became complicated exhibiting evidence of fragmentation preferential flow fingers irregular wetting patterns and varied behavior at fracture intersections ert images demonstrate that water spanned the instrumented network rapidly on ponding and also rapidly drained after ponding was terminated estimates suggest that our excavation captured from 15 to 1 or less of the rock volume interrogated by our infiltration slug and thus the penetration depth from our short ponding event could have been quite large

influence of fracture intersections under unsaturated low flow conditions recent experimental evidence suggests that the capillary heterogeneity associated with fracture intersections can act to impose temporal and spatial structure on network scale flows a simple intersection between orthogonal fractures one horizontal and the other vertical has been shown to integrate unsaturated flows at low flows the intersection forms a capillary barrier that accumulates water in a growing pool eventually the retaining meniscus snaps discharging a pulse of water here we develop a mechanistic explanation for this observed behavior and experimentally consider three perturbations to the geometry of the simple orthogonal intersection two of the perturbations also act as capillary barriers while the third formed a capillary bridge across the intersection at low flow all of our experimental intersections imposed a temporal signal with the nature of that signal dependent on intersection geometry and participation by the horizontal fractures in dynamic storage at high flow a continuous fluid tendril spanned the system from inlet to outlet with water pooled above the intersection caused by a narrow fluid connection that restricted flow across the intersection results from all experiments suggest that pulsation is critically sensitive to small variations in the geometry of fracture intersections and storage in the horizontal fractures when combinedmore with dependency on supply rate this sensitivity can generate pulsation of flow across a wide range of time periods and discharge volumes less

unsaturated flow and transport through a fault embedded in fractured welded tuff 1 to evaluate the importance of matrix diffusion as a mechanism for retarding radionuclide transport in the vicinity of a fault located in unsaturated fractured rock we carried out an in situ field experiment in the exploratory studies facility at yucca mountain nevada this experiment involved the release of 82 000 l of water over a period of 17 months directly into a near vertical fault under both constant positive head at 0 04 m and decreasing fluxes a mix of conservative tracers pentafluorobenzoic acid pfba and bromide applied in the form of lithium bromide was released along the fault over a period of 9 days 7 months after the start of water release along the fault as water was released into the fault seepage rates were monitored in a large cavity excavated below the test bed after the release of tracers seepage water was continuously collected from three locations and analyzed for the injected tracers observations of bromide concentrations in seepage water during the early stages of the experiment and bromide and pfba concentrations in the seepage water indicate the significant effects of matrix diffusion on transport through a fault embedded in fractured welded rock

thermal instability of the fluid column in a borehole application to the yaxcopoil hole mexico observational evidence proved that even when a borehole is in fully stabilized conditions temperature data may exhibit certain unrest resembling irregular oscillations in the order of hundredths or in the extreme case even tenths of degree temperature was monitored in complicated hydrogeological conditions in the yaxcopoil 1 hole chicxulub impact structure mexico two experiments are reported a 20 day monitoring when a logger was located in the center of the high temperature gradient anomaly produced by the cold wave slowly propagating downwards and b simultaneous three loggers 18 day monitoring with loggers located above in and below the anomaly all observed temperature time series displayed intermittent oscillations of temperature with sharp gradients and large fluctuations over all observed time scales while the upper and lower records revealed quasi periodic temperature variations the central record shows fast temperature oscillations with strong up and down reversals all with amplitudes up to a few tenths of degree the observed temperature time series were processed by recurrence and recurrence interval quantification as well as by spectral analyses it is shown that fluid in a borehole subject to thermal gradient is stable as far as the gradient remains below a certain critical value at higher rayleigh numbers the periodic character of oscillations typical for quiescent regime is superseded by stochastic features this oscillatory convection occurs due to instability of the horizontal boundary layers in the specific case of the yaxcopoil hole the time series above and below the cold wave characterized by relatively lower temperature gradients between 20 and 50 mk m contain a clear low frequency component produced by tidal forcing this component dominates over the high frequency domain periods from 10 15 to 1 min which exhibit a scaling behavior this pattern conspicuously changes in the center part of the cold wave where the local temperature gradient exceeds 200 mk m and where tidal forcing composes only 3 of the signal

flow path visualization in a lignitic mine soil using iodine starch staining abstract a dye tracer visualization experiment was carried out in order to study the importance of preferential flow at forest reclaimed mine soils the objective was to evaluate iodine starch staining for the identification of flow paths in such soils for the commonly used dye tracer brilliant blue showed a poor contrast to the relatively dark lignitic mine soil the experimental site was located in the lusatian mining district northeast germany and afforested with pinus nigra at the experimental plot area of 250 130 cm 60 mm of iodide solution was applied at a rate of 7 5 mm h flow path visualization was conducted at 10 cm increments down to 150 cm soil depth the soil surface was powdered with starch and sprayed with a bleaching agent iodine starch staining indicated the tracer conducting soil regions stained soil sections were documented by photography as well as by manual tracing on transparent window films at each depth increment 25 core samples were taken at a regular grid of 25 25 cm for each core sample the amount of residual iodide was determined according to the visualized flow paths the iodide solution infiltrated into the mine soil at distinct points beneath a redistribution zone at 10 cm flow paths occurred as fingers which constricted the hydraulically active soil volume to about 15 and persisted down to a depth of 60 cm at one point to 150 cm only a part of the iodine starch stainings spatially coincided with the vertical iodide concentration for a closer relationship the analysis of the complete soil volume seems to be necessary iodine starch staining proved to be suitable for flow path visualization at dark lignitic mine soils under field conditions and seems to be feasible also for other dark soils at lignitic forest reclaimed mine soils fingered flow has to be considered in water and solute budgets

physics of gravity fingering of immiscible fluids within porous media an overview of current understanding and selected complicating factors abstract while gravity fingering of water in unsaturated sands has been demonstrated and studied under constrained laboratory conditions its significance under field conditions in the vadose zone is still under debate we review current understanding of the gravity fingering process as developed through linear stability analysis and laboratory experiments with respect to many complicating factors inherent in the field this understanding is deficient in determining the field conditions where gravity fingering can be expected and the behavior of the field scale fingering process when it occurs this deficiency is exemplified in the results we present of a field experiment conducted in a sandy alluvial deposit while simple extrapolation of current understanding of the process predicted instability fingers did not occur to begin to understand the influence of complicating factors inherent in the field we conducted several laboratory experiments that address three important complicating factors uniform and non uniform initial moisture content media heterogeneity and the presence of macropores and fractures these factors can fundamentally alter the gravity fingering process its scale of expression and under many field conditions suppress its occurrence entirely while the significance of gravity fingering of water in a wettable vadose zone is still inconclusive gravity fingering will likely play a significant role in water napl non aqueous phase liquid or water napl air systems as occur within the saturated and vadose zones respectively at many contaminated industrial sites to demonstrate this role the results of a simple experiment are presented

interpretation and mathematical modeling of temporal changes of temperature observed in borehole yaxcopoil 1 within the chicxulub impact structure mexico summary geothermal research of the chicxulub impact structure on the yucatan peninsula mexico included repeated temperature logs following 0 3 0 8 15 24 34 and 50 months after shut in of drilling operations at the 1 5 km deep yaxcopoil 1 borehole a gradual distortion of the linear temperature profile by a cold wave propagating downward from 145 m to 317 m was detected within the observational period of 49 months march 2002 april 2006 the amplitude of the cold wave was increasing with depth and time in the range of 0 8 1 6 c as an explanation of this unusual phenomenon the hypothesis of downward migration of a large volume of drilling mud reported lost during drilling within the overlying and cooler highly porous and permeable karstic rocks has been proposed the thermal effects of the migrating fluid have been evaluated by solving numerically the heat conduction convection equation in appropriate geothermal models the best coincidence between the observed data and the simulations was yielded by the model of the drilling mud migrating as a large body parameters of this model are constrained by the measured temperature logs relatively tightly i the vertical extent of the downward migrating fluid body is about 5 10 m possibly increasing within the observational period of 49 months by a factor of 2 ii the horizontal extent of the body must be at least 15 20 m i e by order s of magnitude larger than the diameter of the borehole iii the average speed of the migration is about 5 metres per month and iv the fluid must migrate through a highly porous rock 80 porosity or more this high porosity which is necessary for the model to fit the observed data and the observed relatively stable velocity of the migration indicate the existence of a well developed system of interconnected cavities down to more than 300 m about 150 m more than the deepest cave system known in yucatan yet

precise temperature monitoring in boreholes evidence for oscillatory convection part 1 experiments and field data temperature was monitored in two boreholes in kamchatka russia in years 2001 2003 ten min reading sampling interval was selected for the first half year run followed by shorter 12 days experiment with 5 s reading interval a similar experiment was repeated later in the test borehole sporilov prague czech republic where four temperature time series were performed with reading intervals varying from 1 to 20 s all temperature time series except the record from the bottom of the hole displayed intermittent non periodic oscillations of temperature of up to several hundredths of degree with sharp gradients and large fluctuations over all observed time intervals no such oscillation was detected at the bottom of the hole the spectral analysis revealed a high level of stochasticity in the measured signal calculated spectra showed band pass behavior without any definite peaks which might characterize certain periodicity local growth of the second moment technique revealed the presence of at least two distinct temperature forming processes one of them can be related to heat transfer in the structurally and compositionally complex subsurface the second process which presents the bulk of the measured signal probably reflects certain intra hole convection we hypothesized that the oscillatory regime of such convection is responsible for the stochastic nature of measured temperatures results of numerical modeling describing the fluctuation of water cells in a vertical slot support the idea of thermally unstable water column in a hole the instability of which produces a complex oscillation system model solutions and their discussion is presented in part ii of this work

transient simulations of flow and transport in the chalk unsaturated zone chalk is a fractured porous medium composed of matrix blocks bounded by interconnected fractures furthermore there are a number of commonly observed and apparently contradictory phenomena these include a fast water table response slow solute migration and very little solute dispersion to the authors knowledge no unified physically based numerical model has been able to reconcile all of these points in this paper these issues were addressed through the development of a transient dual permeability model of flow and transport the behaviour of the model was explored through a hypothetical scenario the one dimensional model featured a fixed water table at 10 m depth a recharge time series derived using the penman grindley model in conjunction with daily precipitation and monthly potential evaporation data from the kennet valley berkshire was applied at the top of the model a conservative solute that could be tritium chloride or nitrate was applied to the recharge for 1 year subsequent years involved the input of clean water the simulations suggested that although transient effects have been previously neglected overlying soil and gravelly chalk layers are likely to cause significant attenuating effects on flow such that most flow occurs through the matrix fracture flow was found to be episodic and infrequent and represented between 17 and 30 of the annual recharge

fracture matrix interaction in a fracture of finite extent 1 the behavior of a wetting front invading a fracture in an unsaturated porous matrix is of some importance for understanding infiltration and recharge processes contaminant transport and similar topics previous investigators have examined this problem and a number of models have been published in the literature it is however difficult to observe processes inside a fracture particularly in a field setting many models of fracture flow and fracture matrix interaction therefore lack an observable quantity and instead rely on comparisons with numerical simulations to test the validity of the theoretical constructs here a method is proposed that avoids this difficulty by analyzing flow in a finite fracture or fracture network the fracture is considered finite because after some interval of injecting water to the fracture at a constant rate the wetting front reaches the far end of the fracture and exits at a point where it can be monitored the discharge from the fracture constitutes an observable quantity and allows comparison with field or laboratory data a curve matching procedure is described by which parameters characterizing the fracture matrix system may be estimated and the method is demonstrated using output from a numerical simulation data from a laboratory experiment and data from two field tests

integrated deep drilling coring downhole logging and data management in the chicxulub scientific drilling project csdp mexico impact structures in the solar system are mainly recognized and explored through remote sensing and on earth through geophysical deep sounding to date a continuous scientific sampling of large impact craters from cover rocks to target material has only seldom been performed the first project to deep drill and core into one of the largest and well preserved terrestrial impact structures was executed in the winter of 2001 2002 in the 65 myr old chicxulub crater in mexico using integrated coring sampling and in situ measurements the combined use of different techniques allows a three dimensional insight and a better understanding of impact processes here we report the integration of conventional rotary drilling techniques with wireline mining coring technology that was applied to drill the 1510 m deep yaxcopoil 1 yax 1 well about 40 km southwest of mrida yucatn mexico during the course of the project we recovered approximately 900 m of intact core samples including the transitions of reworked ejecta to post impact sediments and that one from large blocks of tilted target material to impact generated rocks i e impact melt breccias and suevites coring was complemented by wireline geophysical measurements to obtain a continuous set of in situ petrophysical data of the borehole walls the data acquired is comprised of contents of a natural radioactive element velocities of compressional sonic waves and electrical resistivity values all the digital data sets including technical drilling parameters initial scientific sample descriptions and 360 core pictures were distributed during the course of the operations via internet and were stored in the icdp drilling information system http www icdp online org serving the global community of cooperating scientists as a basic information service

a probabilistic analysis of episodic preferential flow into superheated fractured rock the amount of water seeping into waste emplacement tunnels is important for the long term performance of the proposed geologic nuclear waste repository at yucca mountain nevada the repository site is located in thick partially saturated fractured tuff that will be heated to above boiling temperatures as a result of heat generation from the decay of nuclear waste since water infiltrating down towards the repository will be subject to vigorous boiling for a significant time period the superheated zone i e rock temperature above the boiling point of water may form an effective vaporization barrier that reduces the possibility of water arrival at emplacement drifts in this paper we analyze the behavior of episodic preferential flow events that penetrate down into the hot fractured rock zone and evaluate the impact of such flow behavior on the effectiveness of the vaporization barrier the characteristic features of episodic preferential flow are estimated from laboratory experiments and described by appropriate probability distributions a semi analytical solution is utilized to determine the complex flow processes in the hot rock environment the solution is applied at several discrete times after emplacement in order to cover the time period of strongly elevated temperatures at yucca mountain

surface zone flow along unsaturated rock fractures although fractures in rock are well recognized as pathways for fast percolation of water processes which permit fast flow along unsaturated fracture pathways remain to be identified and understood earlier aperture based models of flow in partially saturated fractures permit fast flow only through a continuous network of locally saturated segments film flow was recently identified as a mechanism capable of sustaining fast flow along truly unsaturated fractures when the matric potential is very close to zero another mechanism for fast flow along unsaturated fractures is introduced in this study surface zone flow which can be important when the permeability of the rock along fractures fracture skin is significantly greater than that of the bulk rock matrix in such systems the fracture surface zone provides low resistance pathways through which fast flow relative to the bulk matrix rock can occur even when the fractures are at very low water saturation initial experimental tests of surface zone fast flow were performed surface zone fast imbibition of water was measured on a welded tuff and a rhyolite however because 1 imbibition rates are also strongly influenced by rock wettability 2 these initially air dry rocks exhibited finite contact angles upon exposure to water and 3 we lack methods to reliably measure permeabilities of thin regions on rock surfaces quantification of permeability contrasts was not possible in these initial tests

penetration of liquid fingers into superheated fractured rock 1 water infiltrating down a fracture in unsaturated rock experiences complex fluid flow and heat transfer phenomena when entering above boiling rock temperature regions such conditions are expected for example after emplacement of heat generating nuclear waste in underground repositories a new efficient semianalytical method is proposed in this paper that simulates the flow processes of infiltration events subject to vigorous boiling from the adjacent hot rock it is assumed that liquid flow forms in localized preferential flow paths and that infiltration events are typically short in duration but large in magnitude relative to the average net infiltration the new solution scheme is applied to several test cases studying sensitivity to a variety of input parameters sample simulations are performed for conditions representative of the potential nuclear waste repository at yucca mountain nevada a characteristic parameter is introduced that provides a quick estimate of the relative significance of boiling at a given location of interest

hydrologic issues in arid unsaturated systems and implications for contaminant transport analysis of unsaturated flow and transport in arid regions is important not only in water resource evaluation but in contaminant transport as well partic ularly in siting waste disposal facilities and in remediat ing contaminated sites the water fluxes under consid eration have a magnitude close to the errors inherent in measuring or in calculating these water fluxes which makes it difficult to resolve basic issues such as direction and rate of water movement and controls on unsaturated flow the purpose of this paper is to review these issues on the basis of unsaturated zone studies in arid settings because individual techniques for estimating water fluxes in the unsaturated zone have limitations a variety of physical measurements and environmental tracers should be used to provide multiple independent lines of evidence to quantify flow and transport in arid regions the direction and rate of water flow are affected not only by hydraulic head gradients but also by temperature and air pressure gradients the similarity of water fluxes in a variety of settings in the southwestern united states indicates that vegetative cover may be one of the pri mary controls on the magnitude of water flow in the unsaturated zone however our understanding of the role of plants is limited most unsaturated flow in arid systems is focused beneath topographic depressions and diffuse flow is limited thick unsaturated sections and low water fluxes typical of many arid regions result in preservation of paleoclimatic variations in water flux and suggest that deep vadose zones may be out of equilib rium with current climate whereas water movement along preferred pathways is common in humid sites field studies that demonstrate preferential flow are restricted mostly to fractured rocks and root zones in arid regions results of field studies of preferential flow in humid sites generally restricted to the upper 1 2 m because of shallow water tables cannot be applied readily to thick vadose zones in arid regions

accelerated antarctic ice loss from satellite gravity measurements accurate quantification of antarctic ice sheet mass balance and its contribution to global sea level rise remains challenging gravity recovery and climate experiment data spanning the period april 2002 to january 2009 confirm earlier estimates of ice loss for antarctica and indicate that east antarctica started losing mass in about 2006

gravity driven infiltration instability in initially dry nonhorizontal fractures experimental evidence demonstrating gravity driven wetting front instability in an initially dry natural fracture is presented an experimental approach is developed using a transparent analog rough walled fracture to explore gravity driven instability three different boundary conditions were observed to produce unstable fronts in the analog fracture application of fluid at less than the imbibition capacity inversion of a density stratified system and redistribution of flow at the cessation of stable infiltration the redistribution boundary condition analogous to the cessation of ponded infiltration is considered in a series of systematic experiments gravitational gradient and magnitude of the fluid input were varied during experimentation qualitative observations imply that finger development is strongly correlated to the structure of the imbibition front at the onset of flow redistribution measurements of fingertip velocity are used to develop a first order relationship with fingertip length measured finger width is compared to theoretical predictions based on linear stability theory

a two state integral balance model for soil moisture and groundwater dynamics in complex terrain a dynamical model is devised for a hydrologic system where unsaturated and saturated storage serve as the principal control on rainfall runoff and where complex topography drainage area and variable depth of moisture penetration describe the flow geometry the model is formed by direct integration of the local conservation equation with respect to the partial volumes occupied by unsaturated and saturated moisture storage respectively this yields an integral balance model in just two state variables the relationship of the dynamical model to field data in complex terrain is found through a joint probability density for terrain features this serves as a volume weighting function to construct conditional averages for the state variables and fluxes over a specified range of terrain features the scale of averaging could range from hillslopes to river basins two examples of the joint probability of terrain features altitude and aspect are demonstrated for valley ridge and appalachian plateau digital elevation models the strategy of a dynamical model formed by conditional averages of state variables with respect to terrain features is proposed as a way of simplifying the dynamics while preserving the natural spatial and temporal scales contributing to runoff response the parametric form of the storage flux or constitutive relationships for the proposed model is determined from numerical experiments in a simple hillslope flow geometry the results show that a competitive relation exists between unsaturated and saturated storage except for the lowest precipitation rates saturation overland flow is proposed to be a storage feedback relation solutions to the integral balance model are presented in terms of the phase portrait which represents all possible solution trajectories in state space the timing and magnitude of peaks in the runoff hydrograph from pulse type input events demonstrate quick flow from near stream saturated storage saturation overland flow including rejected rainfall storage feedback and late time infiltration from upslope subsurface flow

development of slender transport pathways in unsaturated fractured rock simulation with modified invasion percolation 1 slender transport pathways have been found in laboratory and field experiments within unsaturated fractured rock here we consider the simulation of such structures with a modified form of invasion percolation mip results show that slender pathways form in fracture networks for a wide range of expected conditions can be maintained when subsequent matrix imbibition is imposed and may arise even in the context of primarily matrix flow due to the action of fractures as barriers to inter matrix block transport