statistical and hydrochemical methods to compare basalt and basement rock hosted groundwaters atherton tablelands north eastern australia multivariate analysis of physico chemical and chemical data has enabled differentiation among groundwaters sourced from different lithological formations in the atherton tablelands region of north eastern australia the main water resource is stored in basalt although basement rocks such as granite and metamorphics also contain variable amounts of water groundwater in the basalt is mostly mg ca na hco3 type with electrical conductivities less than 300 s cm and ph values from 6 5 to 8 5 some of the other groundwater is quite similar making the identification of hydrochemical facies difficult groundwater samples were grouped based on the results of a principal component factor analysis of the major dissolved constituents h4sio4 na ca2 mg2 and hco3 as well as ph and electrical conductivity based on this differentiation it was possible to identify the likely host rocks of groundwaters from unidentified lithological units define the basalt thickness and provide a better understanding of the groundwater resource principal component factor analysis has also been useful in identifying the likely hydrochemical processes controlling the composition of these groundwaters including the production of weak acids in the soil layers silicate mineral weathering ion exchange reactions evapotranspiration and the leaching of ions from organic matter supplementary material to this paper can be obtained by using the springer link server located at http dx doi org 10 1007 s00254 002 0667 z

avulsion processes at the terminus of low gradient semi arid fluvial systems lessons from the rio colorado altiplano endorheic basin bolivia abstract the rio colorado dryland river system in the southeast of the endorheic altiplano basin bolivia terminates on a very flat coastal plain at the edge of the salar de uyuni the world s largest salt pan with an area of ca 12 500 km 2 since the pleistocene the basin has experienced several lake expansion and contraction cycles in response to wetter and drier climate periods respectively at present the basin is in a dry climate period which results in a lake level lowstand and progradation of fluvial systems such as the rio colorado onto the former lake bottom the present field study of the terminus of the rio colorado shows that the river experiences a gradual downstream decrease of bankfull width and depth this bankfull decrease is caused by the combined effects of 1 extremely low gradient of the lake bottom and hence loss of flow energy and 2 downstream transmission losses due to high evaporation potential and river water percolation through the channel floor peak water discharge in seasonal short duration rain periods causes massive overbank flooding and floodplain inundation on satellite images the morphology of the river terminus has a divergent pattern and resembles a network of coeval sinuous distributary channels however field observations show that only one channel is active at low flow stage and at high flow stage an abandoned partially infilled channel may be active as well the active channel at its termination splits into narrow and shallow anastomosing streams before its demise on the lacustrine coastal plain the rest of the channels which form the divergent network are older sediment filled abandoned sinuous river courses with multiple random avulsion points these channel deposits together with extensive amalgamated crevasse splay deposits form an intricate network of fluvial sand deposits successive stages of progressively deeper crevasse channel incision into the floodplain are the result of waning stage return flow of floodwaters towards the main channel this results in increased crevasse channel width depth and length and redeposition of eroded lacustrine coastal plain sediment at the junction of the crevasse channel with the present day river a sedimentary model is proposed in which deep river bank incision by return flow in crevasse channels creates the preferential locus for river avulsion in a lowstand systems tract with little vertical accommodation increase the recurring avulsed river paths result in a thin but laterally extensive network of amalgamated channel fill point bar crevasse channel and crevasse splay deposits the resulting sedimentary architecture could easily be mistaken as produced by a distributary system of simultaneously active fluvial channels

event frequency and landscape stability on the floodplain systems of arid central australia abstract central australian floodplains contain landforms suggesting activity at three scales a set of large sand sheets sand threads and megaripple covered channels related to a few enormous floods the contemporary floodplain which consists of channels and levees floodouts unchannelled floodplains and floodbasins and erosion cell mosaics which result from local redistribution of sediment classical floodplain models do not fit these systems which behave more like low angle alluvial fans because they continue to accumulate sediment the sedimentary history of the central australian floodplains suggests that deposition in the last 10 000 years has been dominated by a few gigantic floods these events are not represented in the published slackwater deposit record but morphological evidence for them can be found in bedrock gorges as well as on floodplains since the last major flood channel levee systems have been growing slowly upwards and outwards and outwards from the mountain ranges away from these systems sediment supply is limited and the dominant process is local reworking this has intensified since the arrival of europeans 100 years ago and also as a result of increased flooding due to variations in rainfall

zonal flow stationary wave relationship during el nino implications for seasonal forecasting abstract an analysis of the northern hemispheric zonal mean flow anomalies during el nino is performed and the dynamical effect of such atmospheric flows on the wintertime climatological stationary waves over the pacific north american pna region is assessed only in the subtropical latitudes can one identify a statistically significant zonal flow anomaly during the el ni os of the historical record strong zonal flow anomalies in the midlatitudes are observed during individual el ni o events although these appear to be manifestations of chaotic atmospheric behavior the observational results are confirmed by gcm climate simulations using prescribed ssts for the 1982 93 period the principal sst forced zonal flow signal in these experiments is located on the equatorward flank of the subtropical jet using a linear diagnostic modes the authors find the climatological stationary waves over the pna region to be insensitive to zonal mean flow anomalies in the subtropics on the other hand zonal mean ano

water quality analysis of groundwater in crystalline basement rocks northern ghana hydrochemical data are presented for groundwater samples collected from fractured aquifers in parts of northern ghana the data was collected to assess the groundwater suitability for domestic and agricultural use results of the study reveal that the ph of the groundwater in the area is slightly acidic to slightly alkaline the electrical conductivity values total dissolved solids tds values and calcium magnesium and sodium concentrations in the groundwater are generally below the limit set by the who for potable water supply on the basis of activity diagrams groundwater from the fractured aquifers appears to be stable within the montmorillonite field suggesting weathering of silicate minerals an inverse distance weighting interpolator with a power of 2 was applied to the data points to produce prediction maps for nitrate and fluoride the distribution maps show the presence of high nitrate concentrations 50 194 mg l in some of the boreholes in the western part of the study area indicating anthropogenic impact on the groundwater elevated fluoride level 1 5 4 mg l higher than the who allowable fluoride concentration of 1 5 is recorded in the groundwater underlying the northeastern part of the study area more specifically bongo and its surrounding communities of the upper east region results of this study suggest that groundwater from the fractured aquifers in the area exhibit low sodicity low salinity s1 c1 low sodicity medium salinity s1 c2 characteristics united states salinity laboratory ussl classification scheme all data points from this study plot within the excellent to good category on a wilcox diagram groundwater in this area thus appears to provide irrigation water of excellent quality the hydrochemical results indicate that although nitrate and fluoride concentrations in some boreholes are high the groundwater in the study area based on the parameters analyzed is chemically potable and suitable for domestic and agricultural purposes

forms and processes of two highly contrasting rivers in arid central australia and the implications for channel pattern discrimination and prediction tooth s nanson g c 2004 forms and processes of two highly contrasting rivers in arid central australia and the implications for channel pattern discrimination and prediction geological society of america bulletin 116 7 8 802 816 rae2008

determinants of peak discharge in steep mountain catchments case of the rift valley escarpment of northern ethiopia peak discharge is an important hydrological parameter of mountain torrents however due to the flashy and destructive nature of their stream flows it is usually difficult to understand the hydrological behavior of steep mountain catchments through direct measurements of discharges in this study 332 daily peak discharge events from 11 steep 0 27 0 65 m m 1 catchments 0 4 25 km2 were measured in three rainy seasons 2012 2014 with the objective of analyzing runoff response of steep mountain catchments in the western rift valley escarpment of northern ethiopia seven rain gauges were installed at different altitudes 1623 2851 m a s l in and nearby the catchments event peak discharges were calculated using the manning s equation from daily measurements of maximum discharge height at 11 crest stage gauges percentages of land cover classes were detected from high resolution 0 6 m google earth imagery february 1 2014 morphometric characteristics of the catchments were computed both from aster digital elevation model dem and topographic maps correlation analysis between average daily precipitation pd and peak discharge qp showed strong positive relation r2 0 32 0 94 p 0 05 in all the catchments catchment specific peak discharge coefficient cp showed a strong decreasing relation with vegetation cover r2 0 85 p 0 01 relative distance of vegetation cover from the thalweg r2 0 55 p 0 01 combined index of vegetation cover and its relative distance from the thalweg r2 0 76 p 0 01 catchment length r2 0 37 p 0 05 and time of concentration r2 0 43 p 0 05 it was correlated positively with catchment slope gradient r2 0 37 p 0 05 and index of vegetation distribution r2 0 45 p 0 05 a stepwise multiple regression analysis revealed that 99 p 0 01 of the variability of catchment specific peak discharge coefficient in the catchments can be predicted by vegetation cover and infiltration number overall this study demonstrates that in reforesting steep mountain catchments where direct measurement of discharges using the conventional methods is difficult due to the flashy and destructive nature of the stream flows hydrological variability can easily be understood using simple measurements of daily precipitation and peak discharges further runoff response is determined by precipitation event and strongly by percentage of vegetation cover and its strategic location farther from the thalweg in the sloping sides of the catchments

comparison of lacustrine successions and their palaeohydrological implications in two sub basins of the triassic cuyana rift argentina fil benavente cecilia andrea consejo nacional de investigaciones cientificas y tecnicas centro cientifico tecnologico conicet mendoza instituto argentino de nivologia glaciologia y ciencias ambientales provincia de mendoza instituto argentino de nivologia glaciologia y ciencias ambientales universidad nacional de cuyo instituto argentino de nivologia glaciologia y ciencias ambientales argentina

maintenance of northern summer stationary waves in a gcm abstract the maintenance of northern summer stationary waves is studied with data from a 15 year integration of the general circulation model gcm experiment performed at the geophysical fluid dynamics laboratory the model has relatively high resolution rhomboidal 30 wavenumbers 9 vertical levels and simulates the summertime stationary waves reasonably well a steady linear baroclinic model is used to understand the various forcing mechanisms for the northern summer stationary waves the linear model response to global diabatic heating is found to play a dominant role in maintaining the summertime stationary waves in the gcm especially in the subtropics this response to diabatic heating shows a baroclinic structure in the vertical with a node at about 0 5 on the other hand stationary nonlinear interaction terms are found to be largely responsible for the extratropical equivalent barotropic stationary wave features it is hypothesized that this nonlinear interaction is a result of the therm

hydraulic parameters in the neoproterozoic aquifer of yaounde cameroon in this paper hydrological properties generally needed to improve all over the world the policy and then the sustainability of groundwater resources are also presented in the neoproterozoic terrane of yaounde cameroon for this purpose data collected from 150 boreholes realized in the study area were analysed statistically the transmissivity t and the specific flow q s have been deduced from the pumping tests interpretation using the jacob recovery method the average transmissivity is equal to 2 9 10 5 m2 s and the specific flow is equal to 0 26 m2 s wells depth d in general ranges from 41 to 80 m with an average of 57 m the empirical relationship between t and q s is t 0 0158 q s 1 01 with the determination coefficient r2 0 64 the weathered layer has a thickness h ranged from 2 6 to 63 3 m with an average of 16 8 m compared to other areas of the crystalline basement although in the middle of the equatorial forest the mean specific flow and the mean transmissivity in the neoproterozoic terrane of yaounde represent barely half values those parameters are of paramount importance in the groundwater management policy

flash flood and bedload dynamics of desert gravel bed streams comparatively little is known about the hydrology of desert flash floods despite the extent of the world s drylands there is even less known about their sedimentary behaviour and particularly about the movement of coarse material as bedload the results of an intense field monitoring programme carried out on an ephemeral gravel bed stream in the northern negev desert are presented in this semi arid setting flow duration analysis indicates that the channel is hydrologically active for 2 of the time or about seven days per year and that overbank flow can be expected for only 0 03 of the time about three hours per year multipeaked flood hydrographs are the norm reflecting many factors including the arrival of separate slugs of discharge from contributing subcatchments the passage of the initial flood bore is surprisingly slow but the rising limb of the flood hydrograph is rapid with a median time of rise of 10 minutes in keeping with expected flash flood behaviour bedload flux is high averaging 2 67 kg s 1 m 1 during the period that the channel carries flow this gives very high bedload sediment yield despite the infrequent and short duration of flood flows and matches the high yield of suspended sediment the relationship between bedload flux and boundary shear stress is simple in contrast with perennial gravel bed streams and the exponent of the log log relationship is 1 52 of great value is that the behaviour of the nahal eshtemoa corroborates a pattern established by the authors previously in a smaller tributary stream 1998 john wiley sons ltd

multiscale diagnosis of the north american monsoon system using a variable resolution gcm abstract the onset and evolution of the north american monsoon system during the summer of 1993 were examined from regional to large scales using the national aeronautics and space administration nasa goddard earth observing system geos stretched grid gcm the model s grid spacing for the dynamical core ranges from 0 4 0 5 in latitude longitude over the united states to about 2 5 3 5 at the antipode and the physical package is solved on an intermediate 1 1 uniform grid a diagnostic analysis of the monsoon s onset reveals the development of a positive potential temperature anomaly at the surface that favors a lower level cyclonic circulation while a negative potential vorticity pv anomaly below the tropopause induces an upper level anticyclonic circulation ignoring diabatic effects this pattern is consistent with the superimposition of idealized pv and anomalies as previously discussed in the literature the inclusion of the smaller scale features of the core monsoon in the mod

the east atlantic west russia ea wr teleconnection in the north atlantic climate impact and relation to rossby wave propagation large scale winter teleconnection of the east atlantic west russia ea wr over the atlantic and surrounding regions is examined in order to quantify its impacts on temperature and precipitation and identify the physical mechanisms responsible for its existence a rotated empirical orthogonal function analysis of the upper tropospheric monthly height field captures successfully the ea wr pattern and its interannual variation with the north atlantic oscillation nao as the first mode ea wr s climate impact extends from eastern north america to eurasia the positive negative ea wr produces positive negative temperature anomalies over the eastern us western europe and russia east of caspian sea with negative positive anomalies over eastern canada eastern europe including ural mountains northeastern africa and the middle east these anomalies are largely explained by lower tropospheric temperature advections positive negative precipitation anomalies are found over the mid latitude atlantic and central russia around 60 e where lower level cyclonic anticyclonic circulation anomaly is dominant eastern canada and western europe including the mediterranean region are characterized by negative positive precipitation anomalies the ea wr is found to be closely associated with rossby wave propagation wave activity fluxes show that it is strongly tied to large scale stationary waves furthermore a stationary wave model swm forced with vorticity transients in the mid latitude atlantic 40 n or diabatic heat source over the subtropical atlantic near the caribbean sea produces well organized ea wr like wave patterns respectively sensitivity tests with the swm indicate enhancement of ea wr like blocking over west of scandinavia when the mean state is modified to have a positive nao component that enhances upper level westerlies between 40 and 60 n

analysis of groundwater quality using water quality index and conventional graphical methods the volta region ghana conventional graphical and statistical methods were used with water quality indices to characterize the hydrochemistry of groundwater from the northern part of the volta region of ghana the objective was to determine the processes that affect the hydrochemistry and the variation of these processes in space among the three main geological terrains the buem formation voltaian system and the togo series that underlie the area and to determine the suitability of groundwater from the area for drinking purposes the q mode cluster analysis reveals three main water groups the groups established from the q mode hca appear to indicate different degrees of weathering which could further indicate varying levels of fracturing aquifer hydraulic properties r mode hca and factor analysis using varimax rotation and kaiser criterion were then applied to determine the significant sources of variation in the hydrochemistry this study finds that groundwater hydrochemistry in the area is controlled by the weathering of silicate and carbonate minerals as well as the chemistry of infiltrating precipitation mineral activity diagrams for the cao na2o al2o3 sio2 h2o and cao mgo al2o3 sio2 h2o systems plotted for the area indicate stability in the smectite field and attribute hydrochemistry to the weathering of silicate minerals silicate mineral weathering and the effects of precipitation appear to be pervasive among all the three main geological terrains whereas carbonate weathering is localized among the voltaian aquifers cation exchange does not appear to play a significant role in the hydrochemistry but mild water quality indices wqi were calculated for the samples using the concentrations of na ca2 mg2 cl no3 f and ec at the various sample locations the wqi values indicate that groundwater from the study area is of excellent quality for drinking purposes wqi values from groundwater samples are averagely higher than samples taken from surface water sources in the area this implies that geology has had an impact on the wqi of groundwater in the area

facies analysis of a probable large fluvial fan depositional system the upper triassic chinle formation at petrified forest national park arizona u s a abstract the upper triassic blue mesa member and the overlying sonsela member of the chinle formation consist of paleosol bearing alluvial strata whose characteristics vary markedly strata exposed within a 4 km2 study area at petrified forest national park were evaluated using sedimentologic stratigraphic paleopedologic and petrographic criteria to formulate potential depositional models that may account for varying alluvial deposition the study succession records a progressive up section increase in grain size increase in channel depth and width increase in lateral and vertical connectivity of channel deposits decrease in overbank preservation and crevasse splay and or sheetflood deposition and increase in overbank drainage mean annual precipitation from the calmag paleosol weathering proxy suggests precipitation averages approximately 1300 mm yr 1 3 m yr throughout the succession despite changing paleosol drainage these features are consistent with deposition in a progradational fluvial system such as a large fan or splay complex sediment accumulation rates in the study interval suggest decreased subsidence in the upper blue mesa member reduced rates of accommodation gain may have promoted progradation of the fluvial system an up section decrease in sandstone mineralogical maturity may be related to increasing sediment bypass in proximal fan positions or increased rates of erosion and sedimentation increasingly better drained paleosols are attributed to deposition in more upland positions during fan or avulsion complex progradation rather than changing climate

sediment flux dynamics as fingerprints of catchment rehabilitation the case of western rift valley escarpment of northern ethiopia variability in supply and entrainment of stream bedload particles during storm events is an important hydrogeomorphologic response of steep mountain streams to land management in their catchments because of difficulties in its measurement and absence of accurate measuring equipment bedload transport in mountain streams is however poorly understood this study focuses on analyzing bedload supply and entrainment in 11 streams of sloping 27 65 catchments 0 4 25 km2 in northern ethiopia which have experienced severe deforestation and degradation processes until the first half of the 1980s and considerable rehabilitation thereafter field measurements of the median diameter of the 10 coarsest bedload particles max10 moved in each event n 332 and stream bed particle sampling were carried out in three rainy seasons 2012 2014 event peak discharges were calculated from daily measurements by 11 crest stage gauges using manning s equation percentages of land cover classes in the catchments were detected from high resolution 0 6 m google earth imagery 1 february 2014 morphometric characteristics of the catchments were computed from an aster digital elevation model and topographic maps hydraulic competence analysis for entrainment of the average max10 was carried out using peak discharge stream power and critical shear stress approaches the supply of max10 was positively related to scar density on the surrounding slopes r2 0 50 p 0 05 and catchment area r2 0 36 p 0 05 while negatively related with total forest cover r2 0 63 p 0 05 or vegetation cover r2 0 58 p 0 05 a multiple regression analysis showed that 98 of the variability in max10 is explained by scar density and catchment area entrainment of max10 was positively related to peak discharge qp r2 0 60 p 0 01 stream power r2 0 71 p 0 01 strickler s roughness sn r2 0 86 p 0 01 and critical shear stress c with reference to d50 r50 r2 0 96 p 0 01 and with reference to d84 r84 r2 0 93 p 0 01 the relationships between event max10 and event qp in each catchment were also used to extrapolate the peak discharges that would have prevailed in the first half of the 1980s and the results showed huge reductions in peak discharges p 0 01 as a result of the reforestation interventions overall this study demonstrates that i the supply of bedload in steep tropical mountains is determined negatively by forest or vegetation cover and positively by the presence of scar networks in the sloping parts of the catchments and catchment size ii entrainment of the coarsest bedload particles is determined positively by peak discharge stream power stream bed roughness and most strongly by critical shear stress and iii in steep mountain streams where direct measurement of bedload movement is difficult yet simple in situ measurement of the coarsest bedload particles max10 supplied and entrained in each event helps for understanding the dynamics of sediment flux in relation to catchment rehabilitation

physical processes involved in the 1988 drought and 1993 floods in north america abstract an analysis of the spring summer 1988 drought and 1993 floods over north america reveals a reversal in the sign of anomalies in several fields large sea surface temperature anomalies of opposite signs existed in the tropical pacific with strong la nina conditions in 1988 and a mature el nino in 1993 the distribution of tropical convection in the convergence zones and associated latent heating of the atmosphere were correspondingly altered implying a large scale switch in the anomalous tropical heating and forcing of extratropical quasi stationary waves in the atmosphere influencing the subtropical jet stream over the north pacific and across north america in 1988 the jet stream and the closely related storm track of high frequency disturbances in the upper troposphere were displaced into canada well north of the normal location the farthest north of any year from 1979 to 1993 in 1993 a broader jet stream and the storm track were displaced well south of normal to a more springlike location a

channel geometry bed material and inferred flow conditions in ephemeral stream systems barrier range western n s w australia streams draining the barrier range uplands in arid western n s w are ephemeral and undergo rapid channel contraction away from the uplands as a consequence of transmission loss these processes are documented on the basis of surveys of channel form and bed material at sequential sites located along the contracting lowland reaches of two representative streams channel width and depth display considerable fluctuation downstream but cross sectional area and maximum bed surface grain size decline in a very regular manner flood discharge estimated from the channel capacity and predicted critical and mean flow velocities also declines regularly the trends are well fitted by log linear models and are reported in terms of a half distance the channel length in km over which the value of a morphometric parameter declines by 50 per cent rates of channel contraction and transmission loss are inferred to be inversely proportional to the volume of flow delivered from the upland section of the drainage basin unusual channel characteristics including extensive tree growth in the bed make application of ordinary flow equations difficult because friction factors cannot be estimated with confidence systematic changes in the nature of the bed surface in contracting streams such as those studied here also have implications for the application of critical velocity equations and highlight a need for further study of desert channels

use of statistical analysis to formulate conceptual models of geochemical behavior water chemical data from the botucatu aquifer in sao paulo state brazil water chemical data from the botucatu sandstone aquifer in the sao paulo state part of the parana basin brazil was evaluated using geochemical methods and two statistical analyses cluster analysis and factor analysis the results were used to develop a conceptual geochemical model in which three geochemical regions were identified and their chemical behavior was modeled the characteristic chemicals changing from the recharge area to the center of the basin are sio2 hco3 and ca2 na co32 and so42 the distribution of the chemicals is interpreted as controlled by different water rock interaction processes in the different regions in the recharge area dissolution of alkali feldspar minerals in the sandstone is the main reaction observed in the mid section of the basin calcite dissolution results in high calcium and bicarbonate concentration in the center of the basin leakage from underlying layers becomes the governing factor

characteristics of summer stationary waves in the northern hemisphere abstract summer stationary waves in the northern hemisphere are separated by a midlatitude transition zone into the subtropical monsoon regime with a vertical phase reversal and the subarctic regime with a vertically uniform structure the dynamics and maintenance mechanism of the subtropical stationary waves have been investigated in the context of monsoon circulation depicted in terms of streamfunction with 40 yr ecmwf re analysis era 40 the dynamic characteristics of stationary waves in the transition zone and the subarctic region are thus the focus of this study the dynamics and maintenance mechanism of these waves were explored with the streamfunction budget and the velocity potential maintenance equations stationary waves across the transition region consist of anticyclonic shear zones over the north pacific and north atlantic and a cyclonic shear zone in east eurasia these transition elements are linked to subtropical oceanic anticyclones and continental thermal lows at high latitudes a th

factors determining the extratropical response to equatorial diabatic heating anomalies abstract the steady linear response of a spherical baroclinic atmosphere to an equatorial diabatic heat source having a simple horizontal and vertical structure is examined this source is imposed upon representative zonally symmetric as well as zonally varying flows during the boreal winter two climatologies are considered one is a 6 year average of global observations analyzed at the european centre for medium range weather forecasts ecmwf the other is a 30 year average taken from a general circulation model gcm run at the geophysical fluid dynamics laboratory in princeton the extratropical response is found to be very sensitive to the basic state around which the governing primitive equations are linearized and in the case of the ecmwf climatology to the longitudinal position of the source with respect to the climatological waves there is also some sensitivity to the vertical level of maximum heating although again this is more evident in the case of the ecmwf basic state these results ar

anatomy and facies distribution of terminal lobes in ephemeral fluvial successions jurassic tordillo formation neuquen basin argentina in terminal fluvial fan systems characteristic proximal to distal variations in sedimentary architectures are recognized to arise from progressive downstream loss of water discharge related to both infiltration and evaporation this work aims to elucidate downstream trends in facies and architecture across the medial and distal zones of terminal fan systems which record transitions from deposits of channel elements to lobe like and sheet like elements this is achieved via a detailed characterization of ancient ephemeral fluvial deposits of the well exposed kimmeridgian tordillo formation neuquen basin argentina the fine sand prone and silt prone succession associated with the medial to distal sectors of the system has been studied to understand relationships between depositional processes and resulting architectures facies and architectural element analyses and quantification of resulting sedimentological data at multiple scales have been undertaken to characterize sedimentary facies facies transitions bed types architectural elements and larger scale architectural styles eight bed types with distinct internal facies transitions are defined and interpreted in terms of different types of flood events channelized and non channelized architectural elements are defined based on their constituent bed types and their external geometry the most common elements are terminal lobes which are composite bodies within which largely unconfined sandy deposits are stacked in a compensational manner a hierarchical arrangement of internal components is recognized proximal feeder channel avulsion events likely controlled the evolution of terminal lobe elements and their spatiotemporal shifts stratigraphic relations between architectural elements record system wide trends whereby a proximal sector dominated by channel elements passes downstream via a gradational transition to a medial sector dominated by sandy terminal lobe elements which in turn passes further downstream to a distal sector dominated by silty terminal lobe margin and fringing deposits this work enhances current understanding of the stratigraphic record of terminal fluvial systems at multiple scales and provides insight that can be applied to predict the facies and architectural complexity of terminal fluvial successions

spatial and temporal evolution of a terminal fluvial fan system the permian organ rock formation south east utah usa the recognition of terminal fluvial systems otherwise termed terminal fans or distributary fluvial fan systems preserved in the ancient rock record is based primarily on the recognition of facies characteristics indicative of a progressive downstream decrease in i fluvial discharge ii channel depth and width iii lateral and vertical connectivity of channel fill elements and iv evidence for channellized flow and a systematic increase in i evidence for sheetflood deposition ii aeolian and or playa deposits and iii channel bifurcation however despite these criteria having been applied previously to a variety of outcrop successions there is still no unifying facies model that adequately accounts for the complex stratigraphic architectural relationships expected for such systems based on the varied styles of fluvial activity and system interaction known from modern examples moreover few previous studies have given significant consideration to the long term temporal evolution of terminal fluvial fans these issues are addressed by this study of the permian leonardian artinskian organ rock formation of the paradox basin south east utah a detailed stratigraphic framework based on 84 sedimentary logs demonstrates proximal to distal variations in sedimentary style integration of these data with high resolution architectural panels depicting the geometry and facies characteristics of individual fluvial elements has enabled the development of a series of depositional models that account for both the spatial and temporal evolution of the system and which are representative of i initial progradation of the fluvial system into the paradox foreland basin ii retreat of the fluvial system and expansion of a distal aeolian dune system iii the final phase of fluvial progradation following aeolian dune deflation and iv the final retrogradation of the fluvial system back towards the hinterland

hydrochemical characterization of groundwater mixing in sedimentary and metamorphic reservoirs with combined use of piper s principle and factor analysis abstract a procedure to interpret hydrochemical data based on a combined use of factor analysis correspondence analysis and piper s classification principle is outlined and applied to the study of a multi reservoir hydrothermal system allevard located in the french western alps values of physico chemical parameters determined on 95 water samples related to a single point allevard spring and gathered from previous studies extending over several decades were submitted to this procedure the approach proved successful in differentiating groundwater masses of different hydrogeological origin which mix and discharge at the outlet of the system the statistical analysis supported by structural and isotopic information allowed formulation of a flow and mixing model in agreement with geological evidence and comprising near surface subsurface and deep subsystems

an assessment of the origin and variation of groundwater salinity in southeastern ghana groundwater from the major aquifers in southeastern part of ghana was sampled to determine the main controls on groundwater salinity in the area this paper uses multivariate statistical methods conventional graphical methods and stable isotope data to determine spatial relationships among groundwaters from the different hydrogeologic units in the area on the basis of salinity q mode hierarchical cluster analysis hca was used to spatially classify the samples whilst r mode factor analysis was used to reduce the dataset into two major principal components representing the sources of variation in the hydrochemistry analysis of the major chemical parameters suggests that the principal component responsible for salinity increment in the area is the weathering of minerals in the aquifers this factor is especially more significant in the upland areas away from the coast the second factor responsible for salinity in the area is the combined effects of seawater intrusion and anthropogenic activities this study finds that four major spatial groundwater groups exist in the area low salinity acidic groundwaters which are mainly derived from the birimian and togo series aquifers low salinity moderate to neutral ph groundwaters which are mainly from the voltaian buem and cape coast granitoids very high salinity waters which are not suitable for most domestic and irrigation purposes and are mainly from the keta aquifers and intermediate salinity groundwaters comprising groundwater from the keta basin aquifers with minor contributions from the other major terrains the major water type identified in this study is the ca mg hco3 type which degrades into predominantly na cl so4 more saline groundwaters toward the coast stable isotope data analyses suggest that groundwater in the voltaian aquifers is largely of recent meteoric origin the birimian and togo aquifers receive a component of recharge from the tributaries of the densu and volta rivers after the waters have undergone evaporative enrichment of the heavier isotopes in the keta basin recharge is mainly from precipitation but an observed enrichment of 2h and 18o isotopes is probably due to seawater and evaporative effects since the water table there is very shallow an analysis of the irrigation quality of groundwater from the six aquifers in the study area using sodium adsorption ratio and electrical conductivity suggests that most of the aquifers supply groundwater of acceptable quality for irrigation the only exception is the keta basin area where extremely high salinities and sar values render groundwater from this basin unsuitable for irrigation purposes

teleconnections associated with northern hemisphere summer monsoon intraseasonal oscillation the boreal summer intraseasonal oscillation bsiso has strong convective activity centers in indian i western north pacific wnp and north american na summer monsoon sm regions the present study attempts to reveal bsiso teleconnection patterns associated with these dominant intraseasonal variability centers during the active phase of ism a zonally elongated band of enhanced convection extends from india via the bay of bengal and philippine sea to tropical central pacific with suppressed convection over the eastern pacific near mexico the corresponding extratropical circulation anomalies occur along the waveguides generated by the north african asian jet and north atlantic north european jet when the tropical convection strengthens over the wnpsm sector a distinct great circle like rossby wave train emanates from the wnp to the western coast of united states us with an eastward shift of enhanced meridional circulation in the active phase of nasm large anticyclonic anomalies anchor over the western coast of us and eastern canada and the global teleconnection pattern is similar to that during a break phase of the ism examination of the evolution of the bsiso teleconnection reveals quasi stationary patterns with preferred centers of teleconnection located at europe russia central asia east asia western us and eastern us and canada respectively most centers are embedded in the waveguide along the westerly jet stream but the centers at europe and russia occur to the north of the jet induced waveguide eastward propagation of the iso teleconnection is evident over the pacific north america sector the rainfall anomalies over the elongated band near the monsoon domain over the indo western pacific sector have an opposite tendency with that over the central and southern china mexico and southern us providing a source of intraseasonal predictability to extratropical regions the bsiso teleconnection along and to the north of the subtropical jet provides a good indication of the surface sir temperature anomalies in the nh extratropics

facies architecture and palaeoenvironmental implications of the upper cretaceous santonian csehbanya formation at the iharkut vertebrate locality bakony mountains northwestern hungary abstract the csehbanya formation santonian exposed in the iharkut open pit bakony mountains hungary is made up of a cyclic alternation of conglomerate sandstone and variegated siltstone and clay deposited in a fluviolacustrine environment as a result of continuous excavation since 2002 it has yielded rich and diverse continental vertebrate and plant assemblages a facies and architectural analysis of the csehbanya formation at this location identified four main lithofacies associations with eight subtypes consisting of 1 lenticular sandstones representing river channels 2 conglomerates with sandstone coarse grained likewise representing channel deposits 3 heterolithic channel fill high density flash flow deposits 4 splay sandstones produced by crevasse splays 5 dark sandy siltstone small scale stagnant pool deposits with high organic content 6 greenish grey claystone deposits of shallow lakes and ponds 7 reddish moderately drained paleosols and 8 yellowish mottled hydromorphic paleosols the sedimentological investigations revealed that the terrestrial deposits exposed by the iharkut open pit were formed in an anastomosing fluvial system because i the alluvial architecture is characterized by large proportion of overbank deposits encasing the channel sandstone bodies ii the ribbon shaped sandstone bodies are dominant iii cross bedding and lateral accretion are almost completely absent in the channel fill deposits and iv the sandstone bodies are clearly isolated from each other embedded in floodplain sediments suggesting multiple co existing channels the most important vertebrate fossil site sz 6 was examined in special detail because it shows peculiar lithological features the layers richest in fossils unit 1 of sz 6 site are interpreted as a lag deposit formed during an episodic high density flash flood event representing a relatively short time interval i e probably within a single rainy season

a note on cluster bedform behaviour in a gravel bed river abstract the behaviour of cluster bedforms was investigated in the farma r central italy a study reach was surveyed and the three components of the pebble clusters occuring on the surface of a gravel bar were painted using different colours before and after each flood all the clusters were photographed and a comparison was made this simple methodology allowed the evolution of the painted clusters to be followed and also allowed a survey of the dislodgment of the clusters particles and the addition of new ones the experiment shows that the mobility of the wake grains is higher than that of the stoss particles a pebble cluster generally loses the wake grain first followed by the stoss pebbles the obstacel clast is commonly the last to be entrained and acts as a single particle after the wake and stoss particles have been dislodged different explanations of this unexpected behaviour are postulated and the interaction of pebble with bed armouring and bedload size distribution is discussed

discontinuous ephemeral streams abstract many ephemeral streams in western north america flowed over smooth valley floors before transformation from shallow discontinuous channels into deep arroyos these inherently unstable streams of semiarid regions are sensitive to short term climatic changes and to human impacts because hillslopes supply abundant sediment to infrequent large streamflow events discontinuous ephemeral streams appear to be constantly changing as they alternate between two primary modes of operation either aggradation or degradation may become dominant attainment of equilibrium conditions is brief disequilibrium is promoted by channel entrenchment that causes the fall of local base level and by deposition of channel fans that causes the rise of local base level these opposing base level processes in adjacent reaches are maintained by self enhancing feedback mechanisms the threshold between erosion and deposition is crossed when aggradational or degradational reaches shift upstream or downstream extension of entrenched reaches into channel fans tends to create continuous arroyos upvalley migration of fan apexes tends to create depositional valley floors with few stream channels less than 100 years is required for arroyo cutting but more than 500 years is required for complete aggradation of entrenched stream channels and valley floors discontinuous ephemeral streams have a repetitive sequence of streamflow characteristics that is as distinctive as sequences of meander bends or braided gravel bars in perennial rivers the sequence changes from degradation to aggradation headcuts concentrate sheetflow a single trunk channel conveys flow to the apex of a channel fan braided distributary channels end in an area of diverging sheetflow and converging sheetflow drains to headcuts the sequence is repeated at intervals ranging from 15 m for small streams to more than 10 km for large streams lithologic controls on the response of discontinuous ephemeral streams include 1 amount and size of sediment yielded from hillslopes 2 infiltration capacity of valley floor alluvium that influences both the unit stream power available for upstream headcut migration and the attenuation of flashy streamflow events by riparian vegetation in sheetflow reaches and 3 cohesiveness of alluvium which affects headcut and streambank morphology and rates of arroyo extension downcutting and widening initiation of arroyo cutting may be too complex to be attributed to a single cause such as change in mean annual precipitation or grazing by livestock but is most likely associated with a decrease in density of protective plant cover on hillsides and along valley floors relatively larger unit stream power makes downstream reaches more susceptible to initial entrenchment during floods than headwaters reaches and favors persistent arroyos entrenchment continues until an equilibrium longitudinal profile is briefly attained then channel widening occurs streambanks are undercut and aggradation begins

climatic versus halokinetic control on sedimentation in a dryland fluvial succession fluvial systems and their preserved stratigraphic expression as the fill of evolving basins are controlled by multiple factors which can vary both spatially and temporally including prevailing climate sediment provenance localized changes in the rates of creation and infill of accommodation in response to subsidence and diversion by surface topographic features in basins that develop in response to halokinesis mobilized salt tends to be displaced by sediment loading to create a series of rapidly subsiding mini basins each separated by growing salt walls the style and pattern of fluvial sedimentation governs the rate at which accommodation becomes filled whereas the rate of growth of basin bounding salt walls governs whether an emergent surface topography will develop that has the potential to divert and modify fluvial drainage pathways and thereby dictate the resultant fluvial stratigraphic architecture discerning the relative roles played by halokinesis and other factors such as climate driven variations in the rate and style of sediment supply is far from straightforward diverse stratigraphic architectures present in temporally equivalent neighbouring salt walled mini basins demonstrate the effectiveness of topographically elevated salt walls as agents that partition and guide fluvial pathways and thereby control the loci of accumulation of fluvial successions in evolving mini basins drainage pathways can be focused into a single mini basin to preserve a sand prone fill style whilst leaving adjoining basins relatively sand starved by contrast over the evolutionary history of a suite of salt walled mini basins region wide changes in fluvial style can be shown to have been driven by changes in palaeoclimate and sediment delivery style the triassic moenkopi formation of the south western usa represents the preserved expression of a dryland fluvial system that accumulated across a broad low relief alluvial plain in a regressive continental to paralic setting within south eastern utah the moenkopi formation accumulated in a series of actively subsiding salt walled mini basins ongoing evolution of which exerted a significant control on the style of drainage and resultant pattern of stratigraphic accumulation drainage pathways developed axial parallel to salt walls resulting in compartmentalized accumulation of strata whereby neighbouring mini basins record significant variations in sedimentary style at the same stratigraphic level despite the complexities created by halokinetic controls the signature of climate driven sediment delivery can be deciphered from the preserved succession by comparison with the stratigraphic expression of part of the system that accumulated beyond the influence of halokinesis and this approach can be used to demonstrate regional variations in climate controlled styles of sediment delivery

groundwater flow modeling and particle tracking for chemical transport in the southern voltaian aquifers groundwater is the major source of water supply for most uses in the rural settlements in ghana a groundwater flow model was calibrated for some aquifers of the southern voltaian sedimentary system under steady state conditions the objective was to determine estimates of the hydraulic conductivities of the different hydrostratigraphic units of the southern voltaian and the distribution of recharge from precipitation data on the stable isotopes of oxygen and hydrogen from the study area suggest that groundwater recharge in the area is from rainfall the calibrated steady state model suggests that aquifer hydraulic conductivities in the study area range from 1 19 to 6 3 m day hydrostratigraphic unit specific hydraulic conductivities are discussed the calibrated recharge ranges from 3 81e 05 m day to 6 0e 04 m day which represents 0 9 6 of the precipitation in the form of rainfall six distinct flowpaths have been defined using particle tracking the particle tracking simulation suggests travel times in the range of 380 to 5 199 years from recharge areas to discharge areas along the flowpaths identified a contaminant dropped at the recharge areas in the central sections of the model area would travel at these rates along the flowpaths assuming that advection is the dominant transport process inverse geochemical modeling indicates the dissolution of albite k feldspars and anorthite respectively along flowpaths i and iv the inverse modeling along flowpaths i and iv suggest the dissolution of albite k feldspar and anorthite respectively at 1 085e 06 3 16e 08 and 3 168e 07 mmol year

channel fill and sheet flood facies sequences in the ephemeral terminal river gash kassala sudan abstract detailed facies analysis of the river gash fluvial sediments on two dimensional profiles across and along the main channel has revealed a number of facies and two distinct types of sequences channel fill and sheet flood sequences it seems that each sequence type is produced by specific depositional event and both sequences represent two end members for suite of mixed sequences the facies and sequences show rapid lateral variability and they merge and interfinger with each other they also show partial to complete modification due to subsequent floods and stage variation it seems that the thick sediments of the river gash in the kassala area were produced in two phases first by braided channel aggradation and lateral migration second by both channelized and unchannelized sheet flood deposition deposits of these two phases contribute to the sediments of the present day gash fluvial basin in the kassala area the gash sediments show some similarities and differences to those of ephemeral and low sinuosity braided streams the predominance of sheet flood deposits is consistent with the ephemeral flashy high flow regime in the river gash the non conformity of the river gash depositional style with the braided model of fluvial deposition may be due to this semi arid terminal flashy character which has control on the depositional processes and patterns

northern hemisphere teleconnection patterns during extreme phases of the zonal mean circulation abstract regional climate anomalies associated with year to year changes in the tropospheric zonal mean zonal wind are examined this study focuses on the wintertime northern hemisphere extratropics and compares seasonal mean anomalies associated with to those associated with the el nino southern oscillation during the 1947 94 period dynamical model experiments indicate that a single zonal index characterized by out of phase anomalies at 35 and 55 n is of primary importance for zonal flow stationary wave interactions in the northern hemisphere extratropies such fluctuations in the zonal mean zonal flow are shown to occur independently of tropical sst variability consistent with earlier studies dynamical model experiments and regression analyses of the historical data indicate that such a zonal index explains a significant fraction of the wintertime stationary wave variability in several regions the principal centers of action reside within wave trains over the north pacific north american

fluvial processes and cyclicity in terminal fan deposits an example from the late devonian of southwest ireland abstract the gun point formation is a sandstone dominated sequence approximately 1 5 2 5 km thick which forms part of a major 6 km late devonian alluvial basin fill succession in southwest ireland it is interpreted as the deposits of a southerly flowing terminal fan system which operated under a semi arid climate the proximal zone was characterized by low sinuosity gravelly feeder channels which passed downstream into a medial zone dominated by a sandy braidplain further south in the distal zone phases of high energy flood activity were centred on transient low sinuosity ephemeral channels and were separated by more quiescent periods of shallow sheetflooding subaerial exposure and non deposition sedimentary parameters such as set thickness coset thickness channel sand body density and maximum sand body thickness all exhibit regular cyclic fluctuations with a periodicity of 160 180 m the cycles are interpreted as evidence of regular discharge variations which may have been a response to the 412 ka orbital eccentricity cycle a second periodicity of approximately 700 m has also been detected and is thought to reflect long term variations in basin subsidence

a new approach to a hydrochemical study of groundwater flow abstract a statistical approach based on a multivariate correlation of various hydrochemical parameters has been developed for the interpretation of groundwater flow lines of the vasilikon basin in the southern part of the central area of euboea island in greece water samples mainly from wells but also from boreholes were collected and analysed for 44 hydrochemical parameters from which the conductivity dissolved o2 ca mg chloride acid consuming capacity base consuming capacity si fe and as were selected for the evaluation after normalization of each parameter by z transformation to equalize the influence of parameters with small and large variations a classification of the sampling stations was obtained by cluster analysis by the use of the same z transformed data the degree of similarity of element concentration z transformed profiles between the central sampling points and the surrounding sampling points was investigated the resulting radially distributed correlation vectors were reduced to the main axis of an ellipse so that flow lines or trend of groundwater movements became visible the results of this method were also compared with hydrogeological observations of the vasilikon basin

using principal components analysis and na cl ratios to trace groundwater circulation in a volcanic island the example of reunion abstract the development of the limited groundwater resources of a remote tropical island in particularly rugged volcanic terrain requires a thorough understanding of the hydrogeology the cost of a classical approach by borehole investigations often precludes a reasoned approach resulting in a somewhat haphazard development of resources wuth varying success this paper describes the use of multivariate statistical analysis to trace groundwater circulation in volcanic terrains the method involves the use of principal components analysis pca based on both structural and hydrochemical parameters of 243 springs of reunion western indian ocean as a result we propose the use of na cl analysis in differentiating three types of volcanic aquifers this analysis is consistent with a geological and hydrogeological conceptual model developed from a combined hydrochemical and geological reconnaissance of 27 springs

a sedimentary model for early palaeozoic fluvial fans alderney sandstone formation channel islands uk abstract fluvial fans in the rock record are inferred based on critical criteria such as downstream grain size fining evidence for drainage fractionation along bifurcating channels increasing fluvial aeolian interaction in the basinward direction and radial palaeoflow dispersion since pre vegetation fluvial rocks often lack heterolithic alluvium and channelisation at the outcrop scale the recognition of pre silurian fluvial fans has so far not been straightforward this research proposes a sedimentary model for the alderney sandstone formation of channel islands uk so far considered as a fine record of early palaeozoic axial fluvial sedimentation here outcrop based and remote sensing analysis of the formation s type section reveal the interaction of fluvial and aeolian processes expressed by the alternation of compound fluvial bars enclosing macroform surfaces related to phases of perennial discharge fluvial sandsheets containing antidunal forms and soft sediment deformations related to seasonal i e flashy discharge and aeolian bedforms overlying thin stream flow deposits an up section increase in aeolian deposits is accompanied by the shrinking of fluvial bars and minor channel cuts suggesting that drainage was fractioned along smaller channels terminating into marginal aeolian environments together with a propensity towards more dispersed values of fluvial cross set thickness up section again due to discharge fractionation along intermittently active channels these features depict an aeolian influenced fluvial fan this work discusses a set of criteria for the identification of fluvial fans in pre vegetation environments in doing so it also explores possible parallels to modern environments and underscores the potential of integrated outcrop and remotely sensed observations on ancient fluvial rocks and modern sedimentary realms

channel reach morphology in mountain drainage basins a classification of channel reach morphology in mountain drainage basins synthesizes stream morphologies into seven distinct reach types colluvial bedrock and five alluvial channel types cascade step pool plane bed pool rime and dune ripple coupling reach level channel processes with the spatial arrangement of reach morphologies their links to hillslope processes and external forcing by confinement ripar ian vegetation and woody debris defines a process based framework within which to assess channel condition and response potential in mountain drainage basins field investigations demonstrate character istic slope grain size shear stress and roughness ranges for different reach types observations consistent with our hypothesis that alluvial channel morphologies reflect specific roughness configurations ad justed to the relative magnitudes of sediment supply and transport ca pacity steep alluvial channels cascade and step pool have high ratios of transport capacity to sediment supply and are resilient to changes in discharge and sediment supply whereas low gradient alluvial channels pool rime and dune ripple have lower transport capacity to supply ra tios and thus exhibit significant and prolonged response to changes in sediment supply and discharge general differences in the ratio of transport capacity to supply between channel types allow aggregation of reaches into source transport and response segments the spatial distribution of which provides a watershed level conceptual model linking reach morphology and channel processes these two scales of channel network classification define a framework within which to in vestigate spatial and temporal patterns of channel response in moun tain drainage basins

characterization of the groundwater flow regime and hydrochemistry of groundwater from the buem formation eastern ghana this study demonstrates the application of multivariate statistical methods in definition of groundwater recharge and discharge areas in a sedimentary basin in ghana q mode hierarchical cluster analysis hca was applied to 57 hydrochemical data from the buem formation in the northern part of the volta region in ghana r mode hca and r mode factor analysis were then applied to the same dataset to reveal the processes controlling the hydrochemistry of groundwater from this hydrogeological formation results of both the q and r mode analyses were backed by graphical methods the analyses revealed two major water types differentiated by salinity levels into four spatial groundwater associations the characteristics of the four groundwater types are discussed the recharge areas are characterized by cahco3 low salinity waters which evolve through rock water interactions to nahco3 high salinity waters in the discharge areas this study finds that the hydrochemistry of groundwater from this formation is mainly controlled by the weathering of minerals principally silicates in the aquifer matrix the effects of the chemistry of recharging precipitation are higher in the recharge areas while mineral weathering tends to be severe close to the discharge areas in the groundwater flow regime all the four spatial groundwater associations have low sodium content but salinity levels increase towards the discharge areas such that some of wells in the discharge areas may not be acceptable for irrigation on grounds of high salinities which might affect the osmotic potentials of plants copyright 2011 john wiley sons ltd

hydrogeological and hydrochemical characterization of the voltaian basin the afram plains area ghana in the afram plains area groundwater is the main source of water supply for most uses the area is underlain by aquifers of the southern voltaian sedimentary basin which are predominantly sandstones mudstones conglomerates and shale ordinary least squares regression analysis using 41 well test data from aquifers in the afram plains portion of the voltaian system reveals that transmissivity t exists in a non linear relationship with specific capacity sc the analysis reveals that t 0 769sc1 075 with r 2 0 83 for aquifers in the area the mudstone conglomerate aquifer in the area appears to be the most variable in terms of both specific capacity and transmissivity with transmissivity ranging from 0 18 to 197 7 m2 day and 0 5 and 148 5 m3 day m respectively horizontal fractures and joints resulting from secondary fracturing appear to be the main determinants of both transmissivity and specific capacity in the area phreeqc modeling and mineral stability diagrams indicate that groundwater quality in the afram plains area is controlled by the incongruent weathering of silicate minerals in the aquifers these processes concentrate calcium sodium magnesium potassium bicarbonate ion and quartz leading to calcite dolomite and aragonite supersaturation at most locations hierarchical cluster analysis performed on the raw chemical data reveals two main water types or facies the calcium sodium chloride bicarbonate facies and the magnesium potassium sulfate nitrate facies for the southern and northern sections of the afram plains area respectively

restoration of floodplain topography by sand splay complex formation in response to intentional levee breaches lower cosumnes river california restoration of sustainable geomorphic processes that create floodplain topography through development of sand splay complexes at intentional breaches is one method to promote variability in physical structure needed for habitat restoration the topography of splay complexes provides a range of floodplain elevations that creates local variability in i inundation duration and frequency and depth to ground water that influence riparian vegetation establishment and ii flow depth and velocity that create refuge for fish two intentional levee breaches along the lowland cosumnes river central valley ca were evaluated during water years 1999 and 2000 in order to document changes in morphology and relief associated with deposition of sandsplay complexes during the study period annual peak flow recurrence intervals ranged from 1 to 3 years and water flowed through the breaches for a minimum of 55 days during water year 1999 and 53 days during water year 2000 at the two study sites rapid vertical accretion and scour occurred within the first several years after intentionally breaching the levee at the accidental forest floodplain constructed in 1995 and at the corps breach floodplain constructed in 1997 splay complexes are organized into a variety of landforms including lateral levees and lobes separated by new floodplain channels maximum deposition measured on the splay surface is 0 36 m year while maximum scour in channels is 0 27 m year juxtaposition of floodplain splay deposition and adjacent channel scour creates relief ranging from 1 6 to 0 25 m that decreases with distance from the breach and that becomes more pronounced over time as higher magnitude floods scour channels in the old floodplain sediment and deposit new sand and silt onto the surface of the splay the ratio of splay complex height to depth of formative flow is estimated as 0 4 progradation of main and secondary splay channels takes place by down floodplain sand transport 25 m year maximum large wood recruited onto the floodplain through the breach promotes local scour and deposition that enhances topographic variability at one of the study sites initial grading of a low setback berm prior to opening the breach forced a change in floodplain flow direction and the geometry of the splay complex additionally progradation of the complex is arrested by an excavated pond that creates a sediment trap we present a conceptual model that describes the importance of floods in constructing and modifying sand splay complexes that create floodplain topography the potential habitat variability created as floodplain topography evolves is the linkage between physical and ecological processes that are critical for restoration d 2002 elsevier science b v all rights reserved

hydrogeochemical assessment of groundwater in isfahan province iran groundwater quality in five catchment areas in isfahan province of iran is assessed by measuring physicochemical parameters including major cation and anion compositions ph total dissolved solid electrical conductivity and total hardness for this purpose 567 piezometric well samples were collected in october 2007 the abundance of major ions in four of the catchment areas including gavkhuni ardestan salt lake and central iran desert basins is similar and follows cl so42 na hco3 ca2 mg2 k co32 trend while in the fifth basin karoon the trend changes into hco3 ca2 cl so42 mg2 na k co32 in general four water facies are determined and it is shown that alkali elements and strong acids are dominating over alkaline earth and weak acids statistical analysis including mann whitney u test indicate that physicochemical parameters in three of the five investigated basins gavkhuni ardestan and central iran desert cid are similar while karoon and salt lake basins display different characteristics the result indicate that groundwater west of the province is suitable for irrigation while in the central and eastern parts of the province the groundwater loses its quality for this purpose it is concluded that mineral dissolution and evapotranspiration are the main processes that determine major ion compositions

the regional forcing of northern hemisphere drought during recent warm tropical west pacific ocean la nina events northern hemisphere circulations differ considerably between individual el nino southern oscillation events due to internal atmospheric variability and variation in the zonal location of sea surface temperature forcing over the tropical pacific ocean this study examines the similarities between recent northern hemisphere droughts associated with la nina events and anomalously warm tropical west pacific sea surface temperatures during 1988 1989 1998 2000 2007 2008 and 2010 2011 in terms of the hemispheric scale circulations and the regional forcing of precipitation over north america and asia during the cold season of november through april the continental precipitation reductions associated with recent central pacific la nina events were most severe over north america eastern africa the middle east and southwest asia high pressure dominated the entire northern hemisphere mid latitudes and weakened and displaced storm tracks northward over north america into central canada regionally over north america and asia the position of anomalous circulations within the zonal band of mid latitude high pressure varied between each la nina event over the northwestern and southeastern united states and southern asia the interactions of anomalous circulations resulted in consistent regional temperature advection which was subsequently balanced by similar precipitation modifying vertical motions over the central and northeastern united states the spatial variation of anomalous circulations resulted in modest inter seasonal temperature advection variations which were balanced by varying vertical motion and precipitation patterns over the middle east and eastern africa the divergence of moisture and the advection of dry air due to anomalous circulations enhanced each of the droughts

anastomosing river deposits sedimentation rates and basin subsidence magdalena river northwestern colombia south america situated in a tectonically active foreland basin the magdalena river consists of vertically accreting levee confined channels and adjacent extensive wetlands which are interpreted as an anastomosing river sedimentary system equivalent rates of basin filling and subsidence average 3 8 mm yr 1 based on 18 14c dates from five bore holes drilled to depths of 55 m and sediment transport budgets from 35 years of measurement located in a savanna tropical climate anastomosing river deposits of the magdalena are remarkably similar to the anastomosing deposits of the upper columbia river in a temperate cold climate in western canada suggesting that climate is not a controlling factor of anastomosis the geometry of anastomosing channel fills in the magdalena consists of stratigraphically non uniform low sinuous narrow stringers of sand up to 30 m thick by 600 m wide a width depth ratio of 20 thin 1 2 m off channel crevasse splay sand sheets extend laterally up to 10 km distance when buried both sand deposits become encased by lacustrine or marsh mud to form stratigraphic traps while there are few modern anastomosing river systems as compared to braiding and meandering there may be a disproportionately large number of ancient anastomosed fluvial rock sequences due to the rapid rate of vertical accretion such a different depositional style and geometry of sand bodies have considerable significance in the interpretation of some ancient fluvial rock sequences because it provides an alternative to the meandered and braided river deposition models

warm season subseasonal variability and climate extremes in the northern hemisphere the role of stationary rossby waves abstractthis study examines the nature of boreal summer subseasonal atmospheric variability based on the new nasa modern era retrospective analysis for research and applications merra for the period 1979 2010 an analysis of the june july and august subseasonal 250 hpa meridional wind anomalies shows distinct rossby wave like structures that appear to be guided by the mean jets on monthly subseasonal time scales the leading waves the first 10 rotated empirical orthogonal functions reofs of the 250 hpa wind explain about 50 of the northern hemisphere wind variability and account for more than 30 60 of the precipitation surface temperature variability over a number of regions of the northern middle and high latitudes including the u s northern great plains parts of canada europe and russia the first reof in particular consists of a rossby wave that extends across northern eurasia where it is a dominant contributor to monthly surface temperature and precipitation variability and

is midlatitude convection an active or a passive player in producing global circulation patterns abstract the ability of persistent midlatitude convective regions to influence hemispheric circulation patterns during the northern hemisphere summer is investigated global rainfall data over a 15 yr period indicate anomalously large july total rainfalls occurred over mesoscale sized midlatitude regions of north america and or southeast asia during the years of 1987 1991 1992 and 1993 the anomalous 200 hpa vorticity patterns for these same years are suggestive of rossby wave trains emanating from the regions of anomalous rainfall in the midlatitudes results from an analysis of an 11 yr mean monthly 200 hpa july wind field indicate that in the climatological mean rossby waveguides are present that could assist in developing a large scale response from mesoscale sized regions of persistent convection in the midlatitudes this hypothesis is tested using a barotropic model linearized about the 200 hpa july time mean flow and forced by the observed divergence anomalies the model results are in qualit

the groundwater recharge regime of some slightly metamorphosed neoproterozoic sedimentary rocks an application of natural environmental tracers isotope data of precipitation and groundwater in parts of the voltaian basin in northern ghana were used to explain the groundwater recharge regime in the area groundwater recharge is an important parameter in the development of a decision support system for the management and efficient utilization of groundwater resources in the area it is therefore important to establish the processes and sources of groundwater recharge 18o and 2h data for local precipitation suggest enrichment relative to the global meteoric water line gmwl and indicate that precipitation takes place at a relative humidity less than 100 the groundwater data plot on an evaporation line with a slope of 5 suggesting a high degree of evaporative enrichment of the precipitation in the process of vertical infiltration and percolation through the unsaturated zone into the saturated zone this finding is consistent with the observation of high evapotranspiration rates in the area and ties in with the fact that significant clay fraction in the unsaturated zone limits vertical percolation and thus exposes the percolating rainwater to the effects of high temperatures and low humidities resulting in high evapotranspiration rates groundwater recharge estimates from the chloride mass balance cmb method suggest recharge in the range of 1 8 32 of the annual average precipitation in the form of rainfall the highest rates are associated with areas where open wells encourage significant amount of groundwater recharge from precipitation in the area in the northern parts of the study area groundwater recharge is lower than 12 the recharge so computed through the application of the cmb methodology takes on a spatial distribution akin to the converse of the spatial pattern of both 18o and 2h in the area as such the locations of the highest recharge are associated with the most depleted values of the two isotopes this observation is consistent with the assertion that low vertical hydraulic conductivities slow down vertical percolation of precipitation down to the groundwater water the percolating precipitation water thus gets enriched in the heavier isotopes through high evapotranspiration rates at the same time the amount of water that finally reaches the water table is considerably reduced copyright 2013 john wiley sons ltd

physical mechanisms of the 1993 summer floods abstract the physical mechanisms responsible for the onset and maintenance of the 1993 summer floods were examined using the localized eliassen palm flux diagnostics and solutions of a single level primitive equation model linearized about a meridionally varying basic state the unusually long persistent summer pattern is linked with the marked transient eddy activity in late may and june the feedback of eddies in the time mean flow caused a strengthening and eastward extension of the pacific jet and a strengthening of the jet over north america results from the model suggest that the summer pattern may be interpreted as that of a lee trough forced by the rocky mountains in the presence of a strong westerly mean flow maintained by the eddies upstream composites from cases similar to that of the 1993 summer exhibit strong low level southerly flow cast of the rockies and suggest that the low level jet may be an important mechanism to sustain the anomalous rainfall it is concluded that the effect of the

a case study on geochemical anomaly identification through principal components analysis supplementary projection abstract based on a case study in which a single geochemical anomaly was located in the vicinity of an abandoned mine in central portugal a recursive methodology for anomaly background separation was developed this methodology relies on the supplementary projection of each of the samples taken from a subset of anomaly candidates onto the axes provided by principal components analysis of the background subset the concept of anomaly intensity defined by the average of the distances from the original to the supplementary projections is the basis for final anomaly identification

maintenance of circulation anomalies during the 1988 drought and 1993 floods over the united states the large scale circulation anomalies associated with the 1988 drought and the 1993 floods are investigated with the national centers for environmental prediction reanalysis data and a linear stationary wave model the transient vorticity and thermal forcings are explicitly calculated and the diabatic heating is derived as a residual in the thermodynamic energy equation using the april june amj data for 1988 and june august jja data for 1993 the linear stationary wave model is able to reproduce the main features of the geopotential height anomaly for the two seasons when all forcings are included this provides a basis for further investigation of stationary wave response to different forcing mechanisms using the linear model within the linear model framework the linear model responses to different forcings are examined separately the results indicate that the 1988 anomaly over the united states is a result of both the diabatic heating and the transient vorticity and thermal forcings the large anticyclonic anomalies over the north pacific and canada are forced mainly by the diabatic heating the 1993 anomaly however is dominated by the response to transient vorticity forcing by further separating the linear model responses to regional diabatic heating anomalies in 1988 the results indicate that the western north pacific heating is entirely responsible for the anticyclonic center over the north pacific which causes the northward shift and intensification of the pacific jet stream the eastern north pacific heating cooling couplet is the most important for maintaining the north american circulation

rossby wave propagation and the rapid development of upper level anomalous anticyclones during the 1988 u s drought abstract the upper tropospheric circulation is investigated for the three months of april may and june 1988 during which the great plains region of the united states experienced one of its most severe droughts in history it is found that during this period the april june amj seasonal mean anomaly was not representative of the variability of 10 day low pass anomalies rather over north america large fluctuations on monthly and shorter timescales occurred with the dominant streamfunction anomalies not strongly anticyclonic until june in fact the amj anomaly was dominated by two episodes of rapidly developing intense anomalous anticyclones in early and late june examination of the daily 10 day low pass streamfunction anomalies at 300 mb suggests that propagating rossby waves originating in the west pacific played a dominant role in the initiation of these intense anomalous anticyclones numerical experiments with a linear time dependent barotropic model also support this hypothesis these result

drainage organization on the newly emerged dead sea bed israel abstract the organization of distributary drainage systems on the emerging coastal areas of the dead sea was studied following a rapid base level fall of 24 m during the period 1945 2002 which made the emerging pristine coastal zone a natural field laboratory photogrammetric digital elevation models were extracted to identify different emerged areas and to quantify erosion and deposition processes visual interpretation of orthophotos was used in order to recognize different drainage networks and to delineate the receding shoreline the remotely sensed data were backed by field surveys including measurement of longitudinal profiles the study demonstrates the spatial variability of runoff allocation from prograding fans to the emerging areas and the variable drainage responses three distinct environments were revealed on the emerged areas from the coast to the land deeply incised channels which are the main transmitters of the base level effect headward dendritic coalescing systems that are the reversal of the diverging channel system on alluvial fans and areas with unconfined sheet flowouts which are detached from base level control the threshold gradient of erosion on the emerged areas is 3 headward erosion was uncoupled with the lake level drop i e the rate of headward entrenchment increased with time despite an almost constant base level fall

anabranching rivers on the northern plains of arid central australia anabranching rivers are a widespread feature of the northern plains in the alice springs region of central australia but their unusual characteristics previously have not been described on the northern plains anabranching occurs on rivers transporting bedloads of coarse sand and gravel and is characterised by channels of variable size and shape which occur within a broader typically well defined channel train channels are separated by channel train ridges narrow flow aligned vegetated features or by wider islands ridges and islands are either depositional features formed in situ by accretionary processes or erosional features formed by excision from once continuous areas of floodplain vegetation plays a key role in the initiation survival and growth of depositional forms through its influence on flow sediment transport and ridge and island stability anabranching is also related to the influence of tributaries for some large rivers alternate from single thread to anabranching along their length in response to tributary inputs of water and sediment tributary inputs occur during flow events that are either independent from or in concert with floods in the trunk channel ridges and islands form in association with tributaries as a result of various hydrological depositional and erosional processes including irrigation of enhanced numbers of in channel trees and resulting lee side sediment accretion floodplain scour and the formation and maintenance of deferred junction tributaries the change from single thread to anabranching downstream of tributary junctions occurs in the absence of any significant change in channel gradient or degree of channel confinement on the northern plains anabranching appears to be a stable river pattern that helps to maintain the throughput of relatively coarse sediment in low gradient typically 0 0005 0 002 channels characterised by an abundance of within channel vegetation and subject to declining downstream discharges

dynamics of the stationary anomalies associated with the interannual variability of the midwinter pacific storm track the roles of tropical heating and remote eddy forcing abstract the leading mode of interannual variability of the midwinter pacific storm track is such that the storm track is weaker during the winters when the pacific jet is strong and stronger when the jet is weak in this paper experiments are conducted using a stationary wave model as well as an idealized global circulation model to explore the roles of anomalous tropical heating and eddy fluxes in forcing the observed pacific jet anomalies it is found that enhanced tropical heating over the region 60 e to the date line 25 s to 25 n acts to force a stronger and narrower pacific jet on average tropical heating may account for about one third of the strong jet anomaly but there is significant year to year variability moreover tropical heating does not appear to contribute to the weak jet anomaly much of the pacific jet anomalies are forced by anomalous eddy fluxes by examining the regional contributions from the pacific the atlantic and asia it is found that local eddy feedback over the paci

bedforms and sediment transport processes in the ephemeral streams of kobo basin northern ethiopia abstract bedforms and channel deposits architecture were studied in the ephemeral streams of the structural basin of kobo in northern ethiopia the froude numbers calculated at bankfull flow for a few of the study reaches are in agreement with the extensive occurrence of horizontal planar lamination small bedforms not previously reported in the literature are found and described as produced mainly by scouring rather than accretion processes equations to predict particle entrainment proved that large individual boulders standing scattered on the stream bed can be transported at bankfull flow for long distances direct inspection of the old alluvium and the modern channel deposits allow to identify a typical arrangement within a single bed consisting of divisions with specific characteristics this model of division association is explained in terms of vertical distribution of shear stress and compared with hyperconcentrated flow and traction carpet models in contrast with recent theories of flat asymmetrical bed waves progradation at froude numbers close to unity

splay formation along the lower reaches of ephemeral rivers on the northern plains of arid central australia abstract splays are common features of many rivers and deltas forming as a result of overbank flooding and sediment deposition but they have rarely been described from modern dryland settings this paper investigates splay formation along the lower reaches of ephemeral rivers on the northern plains of arid central australia here splays vary from small lobate or tongue shaped features 1 km long to larger elongate features up to 4 km long and are supplied with rare floodwater and sediment through well defined breaches in the upper parts of the main channel banks in proximal and medial parts splay channels are incised up to 2 m into pre splay fine grained floodplain sediments but remain elevated between 0 5 m and 2 m above the main channels only in the very distal parts are splay channels less deeply incised either grading into the floodplain surface or terminating as sediment lobes that are deposited upon the floodplain aerial photographs and field observations indicate that many splays develop rapidly during large floods and are modified during infrequent subsequent floods four main stages of splay development are proposed 1 aggressive overbank flow results in bank line breaching and channel scour on the floodplain but little sediment deposition 2 coarse bed sediment is diverted from the main channel preventing further deepening at the bank line breach and slowing channel scour 3 increasing coarse sediment transport through the bank line breach and scoured channels leads to the formation of distal sediment lobes 4 subsequent floods divert around these distal lobes sometimes leading to further channel scour and lobe formation on the northern plains splays contribute to downstream decreases in the discharge and size of the main channels and splay deposits form local accumulations of gravelly sand in the predominantly fine grained floodplain successions some splays ultimately may evolve into distributaries or anabranches the dominantly erosional bases of these splay channels contrast with typical descriptions of many humid region splays but they do not display any geomorphological or sedimentological features that are necessarily diagnostic of formation in a dryland setting

morphology and sediment dynamics of ephemeral stream terminal distributary systems in the kobo basin northern welo ethiopia channel morphology bedforms and sedimentary structures of the distributary systems of ephemeral streams in the structural basin of kobo northern ethiopia are analysed the basin is characterised by a semi arid monsoon affected climate most of the rivers originate in the western margin range and dry up in the middle of the basin where they form large distributary systems they show characteristics different from those of the terminal fans and floodouts previously reported in the literature no flow data are available but bankfull discharge for several study reaches has been obtained by field survey of a number of cross sections hydraulic geometry streambed gradient and bed material grain size distribution in both the main stems and the distributary channels two different types of terminal distributary systems have been identified bird foot and lobate the first type by far predominates in the kobo basin bird foot distributary systems were recognized to consist of five distinctive reach units while the lobate splays have a simpler morphology and are thought to evolve into the former more complex type a description of channel morphology bedforms and sedimentary structure distribution is given and these characteristics are compared to those of other similar depositional systems reported in the literature other features such as the lack of scour pockets around boulder particles scattered on the streambed surface and the interaction of individual large particles with massive or horizontal laminated sand on top of typical upward fining channel sequences are also highlighted

evidence for climate shifts in the 2 0ga upper makgabeng formation erg south africa abstract eolian ergs and associated environs are sensitive to short and long term climatic changes in one of the oldest erg deposits the 2 0 ga makgabeng formation vertical changes in facies associations reflect one of the earliest records of short term climatic shifts in a continental setting the makgabeng formation is separated into lower and upper erg deposits by a playa or saline pan deposit the lower erg deposit consists of dune sets with thin lenses of dry and deflationary interdune strata that transition vertically to thicker damp to wet interdune strata a laterally persistent playa deposit in the middle of the section consists of mudstone with deep and shallow penetrating mud cracks and subordinate siltstone and sandstone interbeds above this lower mudstone interval the playa strata are sandy overlying the playa deposit the upper erg deposit consists of thick eolian sets with thin lenses of dry interdune deposits grain size change near the top of the upper erg deposit corresponds with the appearance of fluvial sheet flood eolian cross beds sculpted by mass flows and thin playa deposits vertical stacking of facies associations demonstrates temporal shifts in precipitation and fluctuating water tables fluvial and playa deposits record high water tables whereas low water tables are reflected in the core erg the transition from a lower to higher water table is recorded by wet interdune interspersed within the dune strata toward the top of this interval rapid climatic amelioration occurred near the termination of the makgabeng erg resulting in impingement of ephemeral river systems development of playas and generation of massive sand flows this 2 0 ga erg demonstrates the impact of climate change on erg development resulting from shifts in monsoonal impingement through time

role of transients in the dynamics of east asian summer seasonal mean circulation anomalies a study of 1993 and 1994 abstract by using the national centers for environmental prediction reanalysis data and a nonlinear barotropic model the transient activities and the possible role of transient vorticity fluxes in the maintenance of east asian summer seasonal mean circulation anomalies associated with japan s extremely cool and wet summer of 1993 and hot and dry summer of 1994 are examined data analysis shows that the summertime atmospheric circulation and the transient activity anomalies exhibit nearly opposite patterns over east asia during these two years vorticity budget calculations indicate that the anomalies of transient activities in these two years produced strong transient vorticity flux forcing anomalies that are comparable in magnitude to the divergent forcing anomalies over east asia the nonlinear barotropic model when forced by the anomalous divergence and transient vorticity flux forcing together produces simulations that bear resemblance to the observed summertime seasonal mean circulation anomalies

geostatistical and geochemical analysis of surface water leakage into groundwater on a regional scale a case study in the liulin karst system northwestern china abstract the liulin karst system is typical of hydrogeological systems in northern china with a group of springs as the dominant way of regional groundwater discharge surface water leakage into groundwater has been observed in six sections of the rivers in the study area to extract hydrogeological information from hydrochemical data 29 water samples were collected from the system on a trilinear diagram most of the groundwater samples are clustered around the surface waters indicating the effect of leakage on their chemistry r mode factor analysis was made on seven variables na ca mg so 4 cl hco 3 and no 3 of the samples and three principal factors were obtained the f 1 factor is composed of ca mg and so 4 the f 2 of hco 3 and no 3 and the f 3 of na and cl these factors are then used as regionalized variables in ordinary kriging for unbiased estimates of the spatial variations of their scores considering regional hydrogeological conditions the hydrogeological implications of the spatial distribution of the factor scores as related to the effects of the surface leakage are discussed to evaluate the geochemical processes the geochemical modeling code netpath was employed the modeling results show that mixing commonly occurs in the system and dolomite dissolution is more important than calcite dissolution dedolomitization calcite precipitation and dolomite dissolution driven by anhydrite dissolution is locally important in the western flank of the system where the surface water leakage has the least effect

a sem cathodoluminescence study on weathering of quartz grains in faults central japan summary cathodoluminescence cl of quartz grains or particles was observed using a scanning electron microscope the quartz grains were collected from fault gouge and fault breccia within the atotsugawa fault central japan and the quartz particles were obtained by crushing parent rocks of the fault such as granite and gneiss in an iron bowl in comparison with particles from the parent rocks those from the fault showed the following differences cl inherited from the parent rock cl caused by faulting and cl modified by weathering or alterations of the fault these differences are attributed to the faulting and subsequent weathering the cl observations were in general agreement with secondary electron observations and it is recommended that both methods should be used in parallel

estimation of transmissivity from specific capacity data in fractured carbonate rock aquifer central jordan transmissivity of an aquifer is determined from pumping test analysis but due to the difficulty of performing such tests as well as the relatively high cost of these test it is often estimated from specific capacity data in this study an empirical relation is derived using 237 pairs of transmissivity and specific capacity values that are obtained from groundwater wells penetrating a fractured and karstified carbonate aquifer linear and logarithmic regression functions have been performed and it is found that the logarithmic relationship predicting transmissivity from specific capacity data has a better correlation r 0 95 than linear one r 0 84 this is logically true because both transmissivity and specific capacity are lognormally distributed the spatial distribution of transmissivity is also affected by the presence of fracturing and karstification phenomena within the aquifer matrix

hydro geochemical processes in an area with saline groundwater in lower shire river valley malawi an integrated application of hierarchical cluster and principal component analyses abstract our ability to adapt to changes in groundwater quality arising from a changing climate and or local pressures is dependent on comprehension of the governing controls of spatial variation in groundwater chemistry this paper presents results of an assessment of dominant hydro geochemical processes controlling groundwater chemical composition using an integrated application of hierarchical cluster analysis hca and principal component analysis pca of a major ion dataset of groundwater from lower shire river valley malawi the area is in the southernmost part of the western section of the east african rift system ears and has localised occurrence of saline groundwater hca classified samples into three main clusters c1 c3 according to their dominant chemical composition c1 dominant composition na cl median tds 3436 mg l 1 c2 dominant composition na hco 3 median tds 966 mg l 1 and c3 dominant composition alkali earths hco 3 median tds 528 mg l 1 these clusters were in turn described by the principal components pc1 pc3 and pc2 respectively resulting from the pca the results of the pca and geochemical interpretation suggest that the spatial variation of groundwater quality in the area is influenced by the following processes c3 samples result mainly from h 2 co 3 weathering of aluminosilicate minerals by percolating water supersaturated with co 2 in addition to aluminosilicate weathering c2 samples are influenced by the processes of cation exchange of ca 2 and mg 2 in the water for na on clay minerals and carbonate precipitation the increase in ionic strength of c2 samples is attributed to mixing with high tds groundwater in proximity with c2 samples the saline brackish c1 groundwater results from the processes of evaporation for samples with high water table close to the shire marshes and dissolution of cl and so 4 evaporative salts followed by mineralised seep from sedimentary karoo and cretaceous lupata sandstones

hydrochemical characteristics of aquifers near sutherland in the western karoo south africa the western karoo depends entirely on groundwater for domestic and agricultural use an understanding of the chemical evolution of the groundwater provides insight into the interaction of water with the environment and contributes to better resource management descriptive statistics correlation matrices and factor analysis together with stable isotope data were used to gain an understanding of the hydrochemical processes of the groundwaters in the fractured rocks around sutherland in the western karoo the main processes influencing the groundwater chemistry are salinisation mineral precipitation and dissolution cation exchange and human activity the stable isotope data indicate that the infiltration of evaporated water is partly responsible for the occurrence of saline subsurface waters the ionic oxygen and hydrogen stable isotope composition of the groundwaters suggests that the effects of localised topography are one of the overriding factors controlling the groundwater chemistry in higher lying areas ca hco3 2 type waters are prevalent while in topographical flat areas nacl type waters dominate in areas where water collects close to or at the surface saline soils are formed from these areas salts are leached to the subsurface during significant recharge periods these findings are important in that they contribute to the identification of suitable locations for developing groundwater resources that could yield a relatively better quality water q 2001 elsevier science b v all rights reserved

what can the grace seasonal cycle tell us about lake aquifer interactions abstract lake aquifer interactions have been the subject of investigation and debate for decades traditional investigation methods include measurement of water flux across the groundwater surface water interface application of heat and environmental tracer methods conducting numerical simulations of the water flow and mass balance based approaches we first review evaluate and describe the different approaches that have been applied for examining lake aquifer interactions and propose an additional complementary approach while the leakage from lakes and its slow movement through porous media laminar flow is well characterized by existing methods modeling the rapid and turbulent flow through preferred pathways faults karst remains a challenging task to better understand the nature and the full scale of the lake aquifer interactions and using lake nasser and the underlying dakhla subbasin of the nubian sandstone aquifer system nsas in the western desert of egypt area 0 66 106 km2 as a test site we examine model and correlate temporally and spatially the variations in gravity recovery and climate experiment terrestrial water storage gracetws solutions with precipitation lake levels area and water volume we review current grace applications in hydrology and present our novel approach findings include firstly large seasonal fluctuations peak nov dec trough july aug in lake nasser s surface water levels average annual fluctuations from 3 7 m to 7 5 m area average area 3622 km2 but up to 4530 km2 and volume annual average 13 4 km3 and up to 34 km3 are observed throughout years 2006 to 2015 these fluctuations are accompanied by an increase in gracetws average 50 13 mm yr up to 77 18 mm yr over lake nasser and by a progression of a front of increasing gracetws values 50 13 mm away from the lake reaching distances of up to 700 km some 3 to 5 months following peak lake level periods the areas witnessing the seasonal increase in gracetws display a progressive increase in phase and decrease in amplitude with distance from the lake secondly the negligible precipitation over the dakhla subbasin cannot account for the observed seasonal gracetws patterns and neither can the leakage signal from lake nasser thirdly overall similarities in the distribution of gracetws seasonal spatial patterns are observed during high lake level periods e g dec 2007 feb 2015 additional and more distant areas from lake nasser saw increases in gracetws and vice versa during low lake level periods e g july 2006 aug 2010 these observations are consistent with lake nasser being the main source of modern recharge for the dakhla subbasin and suggest a new conceptual model for the subbasin a slow groundwater flow through a porous matrix and a rapid groundwater flow along a network of faults fractures and karst topography across the matrix we suggest that the proposed conceptual model for the interaction between lake nasser and the dakhla subbasin could be applicable to aquifers of similar geologic climatic and hydrologic settings worldwide and that approaches similar to those advocated here could be used to investigate the validity of this suggestion

froude supercritical flow processes and sedimentary structures new insights from experiments with a wide range of grain sizes recognition of froude supercritical flow deposits in environments that range from rivers to the ocean floor has triggered a surge of interest in their flow processes bedforms and sedimentary structures interpreting these supercritical flow deposits is especially important because they often represent the most powerful flows in the geological record insights from experiments are key to reconstruct palaeo flow processes from the sedimentary record so far all experimentally produced supercritical flow deposits are of a narrow grain size range fine to medium sand while deposits in the rock record often consist of a much wider grain size distribution this paper presents results of supercritical flow experiments with a grain size distribution from clay to gravel these experiments show that cyclic step instabilities can produce more complex and a larger variety of sedimentary structures than the previously suggested backsets and scour and fill structures the sedimentary structures are composed of irregular lenses mounds and wedges with backsets and foresets as well as undulating planar to low angle upstream and downstream dipping laminae the experiments also demonstrate that the froude number is not the only control on the sedimentary structures formed by supercritical flow processes additional controls include the size and migration rate of the hydraulic jump and the substrate cohesion this study further demonstrates that froude supercritical flow promotes suspension transport of all grain sizes including gravels surprisingly it was observed that all grain sizes were rapidly deposited just downstream of hydraulic jumps including silt and clay these results expand the range of dynamic mud deposition into supercritical flow conditions where local transient shear stress reduction rather than overall flow waning conditions allow for deposition of fines comparison of the experimental deposits with outcrop datasets composed of conglomerates to mudstones shows significant similarities and highlights the role of hydraulic jumps rather than overall flow condition changes in producing lithologically and geometrically complex stratigraphy

downstream changes in dryland river channels the northern plains of arid central australia abstract many dryland rivers undergo marked downstream changes owing to factors such as infrequent floods flow transmission losses and typically few tributary inflows beyond the headwaters along the sandover bundey sandover bundey and woodforde rivers on the northern plains of arid central australia downstream channel changes are broadly similar in upland zones small rocky channels transporting sand and gravel gradually increase in size before entering piedmont zones where channels and narrow floodplains are confined by bedrock alluvial terraces or aeolian dunes in lower gradient lowland zones channels and floodplains remain confined and in the absence of tributary inflows channel cross sectional areas and discharges decrease downstream confining landforms are not present in floodout zones which results in splay formation increased floodplain widths and marked overall downstream decreases in cross sectional areas eventually channelised flow and bedload transport terminate although occasional large floods continue across extensive unchanneled alluvial surfaces termed floodouts these broad similarities apart downstream changes along the three rivers differ in detail the sandover is largely a single thread channel whereas many reaches of the sandover bundey and woodforde are anabranched on the small woodforde river downstream decreases in parameters such as cross sectional area and width are roughly linear on the larger sandover and sandover bundey downstream changes are more irregular particularly through the floodout zones where there are marked fluctuations in widths depths and bed slopes the irregular downstream changes typical of the lower reaches of these large rivers may be due to the reduced influence of vegetation on bankline stability and width adjustment relative to that of smaller rivers on the northern plains as in other drylands complex interactions between discharge sediment transport slope patterns of tributary drainage bank sediment type and vegetation result in variable patterns of downstream channel change