bed material transport estimated from the virtual velocity of sediment this study evaluates the possibility of determining bed material transport using the virtual rate of travel of individual particles dimensions of the active layer of the streambed and porosity and density of streambed material magnetically tagged stones and scour indicators were employed in carnation creek british columbia to quantify transport rates observations cover flows up to 36 m3 s 1 0 081 transport rates ranging from 0 090 to 9 7 kg s 1 0 12 13 2 m3 h 1 display a relatively sensitive trend with maximum stream power as expected error analysis indicates that uncertainty in virtual velocity covers the majority of sample variance an evaluation of the two measurement techniques used to delineate active layer dimensions magnetically tagged stones and scour indicators indicates that they yield comparable depths widths and transport rates over the range of flows observed issues for further study are discussed 1998 john wiley sons ltd

long term slowdown of river tracer pebbles generic models and implications for interpreting short term tracer studies 1 we propose generic approaches to modeling the reduction in mobility that occurs as tracer pebbles seeded on the surface are mixed to less active locations e g beneath the bed or high on bars or advected downstream to reaches with different shear stress or bed grain size advection slowdown which may be negligible is quantified using a regression equation relating virtual velocity to tracer and reach properties mixing slowdown which is always present is simulated using a markov model of exchanges between three stores and assumptions about relative mean velocities of tracers in each store the model can be calibrated from a full search on one date and at least a surface search on another date calibration to six reaches of allt dubhaig scotland in which tracers were mapped after 2 and 8 years suggests mixing took 3 5 years to approach equilibrium in five reaches and was still proceeding in one simulated slowdown through mixing is far greater than that through advection and goes much of the way to explaining the 50 observed reduction in virtual velocity over 8 years compared to 2 years implications for the design and comparison of tracer pebble experiments are considered

the elements and richness of particle diffusion during sediment transport at small timescales the ideas of advection and diffusion of sediment particles are probabilistic constructs that emerge when the master equation a precise probabilistic description of particle conservation is approximated as a fokker planck equation the diffusive term approximates nonlocal transport it looks upstream and downstream for variations in particle activity and velocities whose effects modify the advective term high resolution measurements of bed load particle motions indicate that the mean squared displacement of tracer particles when treated as a virtual plume primarily reflects a nonlinear increase in the variance in hop distances with increasing travel time manifest as apparent anomalous diffusion in contrast an ensemble calculation of the mean squared displacement involving paired coordinate positions independent of starting time indicates a transition from correlated random walks to normal fickian diffusion this normal behavior also is reflected in the particle velocity autocorrelation function spatial variations in particle entrainment produce a flux from sites of high entrainment toward sites of low entrainment in the case of rain splash transport this leads to topographic roughening where differential rain splash beneath the canopy of a desert shrub contributes to the growth of a soil mound beneath the shrub with uniform entrainment rain splash transport often described as a diffusive process actually represents an advective particle flux that is proportional to the land surface slope particle diffusion during both bed load and rain splash transport involves motions that mostly are patchy intermittent and rarefied the probabilistic framework of the master equation reveals that continuous formulations of the flux and its divergence the exner equation represent statistically expected behavior analogous to reynolds averaged conditions key topics meriting clarification include the mechanical basis of particle diffusion effects of rarefied conditions involving patchy intermittent motions and effects of rest times on diffusion of tracer particles and particle borne substances this article is protected by copyright all rights reserved

the cause of advective slowdown of tracer pebbles in rivers implementation of exner based master equation for coevolving streamwise and vertical dispersion tracer pebbles are often used to study bed load transport processes in gravel bed rivers models have been proposed for their downstream dispersion and also for vertical dispersion but not for the combined effects of downstream and vertical movement here we use the exner based master equation to characterize the transient coevolution of streamwise and vertical advection diffusion of tracer pebbles under equilibrium transport conditions no net aggradation or degradation the coevolution of streamwise and vertical dispersion gives rise to behavior that can differ markedly from that associated with purely streamwise processes with no vertical exchange one example is streamwise advective slowdown particles that are advected downward into zones where the probability of reentrainment becomes asymptotically small are essentially trapped and can no longer participate in streamwise advection as a result the mean streamwise velocity of the tracer plume declines in time qualitative and quantitative comparisons with two field experiments show encouraging agreement despite the simplified boundary conditions in the model

long term bedload mobility in gravel bed rivers using iron slag as a tracer abstract bedload dispersion is evaluated in gravel bed rivers using slag elements from ironworks established along rivers in the ardenne region between the fourteenth and the nineteenth centuries large quantities of slag were dumped close to these rivers or even directly into the channels for centuries slag elements were dispersed in the bedload and transported by floods of varying importance consequently slag may be considered as a reliable tracer to analyze bedload dispersion over several centuries the size of slag elements was studied along 16 ardenne rivers the longitudinal size trend of the largest slag particles allows the effective competence of these rivers to be determined between 19 and 129 mm for rivers where specific stream power for the bankfull discharge ranges between 20 and 134 w m a direct relationship doesn t exist between these two parameters as the size of slag elements must be considered with regard to the d 50 of the bed selective transport was analyzed directly downstream of the input sites the sorting distance varies from river to river and depends on the velocity of the coarse elements introduced into the river since the inception of the iron industry downstream of two metallurgic sites the slag propagation fronts were located as the periods of activity at these sites are known from historical studies the virtual velocity of bedload movement in these rivers was estimated to be 2 4 km century

enhanced sediment delivery in a changing climate in semi arid mountain basins implications for water resource management and aquatic habitat in the northern rocky mountains the delivery and transport of sediment through mountain rivers affects aquatic habitat and water resource infrastructure while climate change is widely expected to produce significant changes in hydrology and stream temperature the effects of climate change on sediment yield have received less attention in the northern rocky mountains we expect climate change to increase sediment yield primarily through changes in temperature and hydrology that promote vegetation disturbances i e wildfire insect pathogen outbreak drought related die off here we synthesize existing data from central idaho to explore 1 how sediment yields are likely to respond to climate change in semi arid basins influenced by wildfire 2 the potential consequences for aquatic habitat and water resource infrastructure and 3 prospects for mitigating sediment yields in forest basins recent climate driven increases in the severity and extent of wildfire suggest that basin scale sediment yields within the next few years to decades could be greater than the long term average rate of 146 t km 2 year 1 observed for central idaho these elevated sediment yields will likely impact downstream reservoirs which were designed under conditions of historically lower sediment yield episodic erosional events massive debris flows that dominate post fire sediment yields are impractical to mitigate leaving road restoration as the most viable management opportunity for offsetting climate related increases in sediment yield however short term sediment yields from experimental basins with roads are three orders of magnitude smaller than those from individual fire related events on the order of 101 t km 2 year 1 compared to 104 t km 2 year 1 respectively for similar contributing areas suggesting that road restoration would provide a relatively minor reduction in sediment loads at the basin scale nevertheless the ecologically damaging effects of fine sediment material

empirical relationships between elevation and the stable isotope composition of precipitation and surface waters considerations for studies of paleoelevation change a compilation of 68 studies from throughout many of the world s mountain belts reveals an empirically consistent and linear relationship between change in elevation and change in the isotopic composition of precipitation along altitudinal transects the isotopic composition of precipitation decreases linearly with increasing elevation in most regions of the world except in the himalayas and at elevations 5000 m there are no significant differences in isotopic lapse rates from most regions of the world 0 28 permil 100 m except at the extreme latitudes where isotopic lapse rates are higher given information on past changes in the isotopic composition of precipitation preserved in pedogenic or authigenic minerals this global isotopic lapse rate can be used to place numerical constraints on the topo graphic development of some ancient mountain belts or plateaus there are many complicating factors that can confound interpretation of paleoel evation change based on stable isotopes and many of these are unique to specific mountain belts or time periods relevant to all stable isotope based paleoelevation change studies is the temperature dependent isotope fractionation between a pedo genic or authigenic mineral and the water from which it forms in cases where isotopic proxy minerals are sampled from localities where temperature will change simulta neously with elevation change the apparent change in the isotopic composition of precipitation may be dampened by several permil this suggests that samples taken from the rainshadow side of an emerging orographic barrier may be more likely to preserve isotopic changes resulting from mountain uplift than samples taken from atop a rising mountain range or plateau

sedimentary bed evolution as a mean reverting random walk implications for tracer statistics sediment tracers are increasingly employed to estimate bed load transport and landscape evolution rates tracer trajectories are dominated by periods of immobility waiting times as they are buried and reexcavated in the stochastically evolving river bed here we model bed evolution as a random walk with mean reverting tendency ornstein uhlenbeck process originating from the restoring effect of erosion and deposition the ornstein uhlenbeck model contains two parameters a and b related to the particle feed rate and range of bed elevation fluctuations respectively observations of bed evolution in flume experiments agree with model predictions in particular the model reproduces the asymptotic t 1 tail in the tracer waiting time exceedance probability distribution this waiting time distribution is similar to that inferred for tracers in natural gravel streams and avalanching rice piles indicating applicability of the ornstein uhlenbeck mean reverting model to many disordered transport systems with tracer burial and excavation

field evidence for rapid downstream fining of river gravels through selective transport doubts have been expressed about the ability of either abrasion or sorting to explain strong downstream fining of river gravels we describe pronounced fining over a short distance in a scottish river that has no human disturbance or lateral input of water and sediment measured abrasion rates are far too small to explain observed downstream fining but bed load trap measurements and the dispersion of magnetic tracer pebbles in six subreaches both show sorting during transport the observed downstream fining is also simulated well by a numerical sediment routing model using hydraulic and transport laws consistent with our field measurements the geomorphological cause of the strong fining is slope reduction above a local base level control in this common situation the development of downstream fining is part of the river9s tendency to minimize downstream variation in bed load transport rates and can proceed far more rapidly than the major aggradation otherwise required for equilibration

hydrological and isotopic characterization of river water groundwater and groundwater recharge in the heihe river basin northwestern china we used hydrochemistry and environmental isotope data 18o d tritium and 14c to investigate the characteristics of river water groundwater and groundwater recharge in china s heihe river basin the river water and groundwater could be characterized as ca2 mg2 hco3 so42 and na mg2 so42 cl types respectively hydrogeochemical modelling using phreeqc software revealed that the main hydrogeochemical processes are dissolution except for gypsum and anhydrite along groundwater flow paths from the upper to middle heihe reaches towards the lower reaches dolomite and calcite tend to precipitate the isotopic data for most of the river water and groundwater lie on the global meteoric water line gmwl or between the gmwl and the meteoric water line in northwestern china indicating weak evaporation no direct relationship existed between recharge and discharge of groundwater in the middle and lower reaches based on the isotope ratios d excess and 14c values on the basis of tritium in precipitation and by adopting an exponential piston flow model we evaluated the mean residence time of shallow groundwater with high tritium activities which was around 50 years a furthermore based on the several popular models it is calculated that the deep groundwaters in piedmont alluvial fan zone of the middle reaches and in southern part of the lower reaches are modern water whereas the deep groundwaters in the edge of the middle reaches and around juyan lake in the lower reaches of heihe river basin are old water copyright 2010 john wiley sons ltd

numerical simulation of downstream fining by selective transport in gravel bed rivers model development and illustration a numerical model has been developed for the routing of gravel sized sediment along a river channel which is free to adjust both its long profile and surface texture hydraulic calculations use a step backwater approach and sediment transport is predicted with the method of parker 1990a which uses a low degree of size selectivity exchange of sediment between the surface and subsurface is described using the modified exner equation of parker and sutherland 1990 the model is applied to an idealized channel based on the highly concave allt dubhaig scotland in which fining by particle wear is minor the rapid downstream fining observed in this river is closely matched by model predictions after a time equivalent to 102 years under the present flow regime of the river the evolution of the fining pattern during the model run and associated changes in sediment transport and bed aggradation are described it is concluded that strong profile concavity can force rapid downstream fining even though bed load transport is only slightly size selective this run of the model serves as a basis for testing of the sensitivity of downstream fining to alternative choices of parameter values and boundary conditions which are summarized here and will be described in a subsequent paper

coarse sediment transport in a bedrock channel with complex bed topography 1 independent lithologic and structural controls in fluvial bedrock systems interact with coarse sediment transport processes to play a key role in bedrock incision processes such as abrasion during a 3 year study on the ocoee river in the blue ridge province of the southern appalachians usa we used painted tracer clasts to measure coarse sediment transport dynamics and address whether different scales of morphologic variability in bedrock channels lead to coarse sediment transport processes that differ from alluvial channels at the reach scale folded metasedimentary units are exposed in the channel bed and appear as linear bedrock ribs that vary in amplitude and orientation to flow under similar flow conditions for which size dependent transport has been observed in alluvial channels dimensionless shields stress within 1 5 2 0 times the dimensionless critical shear stress transport distance was a significant function of grain size where bedrock ribs were longitudinal to flow reach 1 and reach 2 however transport distance was not size dependent where bedrock ribs were oblique to flow reach 3 at different intrareach scales the variables characterizing the local bedrock topography and sediment architecture were the best predictors of transport distance in all three reaches therefore bed load transport processes may be influenced by bed forms in bedrock streams bedrock ribs but at potentially smaller scales than bed forms in alluvial channels the strong influence of bedrock ribs on coarse sediment transport suggested that coarse sediment transport processes are controlled by different factors in bedrock channels only when bedrock ribs cross the channel at a high angle to the flow

hydrogeochemical and isotopic study of the kumho river korea implications for anthropogenic and seasonal effects the geochemical and isotopic compositions of river water are controlled by different factors the seasonal and spatial variations in the geochemical composition d 18o and 15n no3 of the kumho river were investigated to reveal the geochemical processes occurring at different seasons the kumho river which runs through different geologic terrains with different land use characteristics is the largest tributary of the nakdong river the longest river in south korea the data varied significantly according to the land use and the season each monitoring station showed the lowest concentrations of various ions during july the rainy season due to the increase of precipitation rate the ionic concentrations gradually increased downstream by the mineral weathering and anthropogenic activity at the upper regions of the river ca and hco3 which are closely associated with mineral weathering were the most dominant cation and anion respectively the relatively high si concentration of the headwater samples caused by the weathering of volcanic rocks also showed the importance of weathering in the upper regions mainly composed of volcanic rocks the downstream regions of the kumho river are mainly influenced by sedimentary rocks at the lower reaches of the river especially near the industrial complexes in daegu the third largest city in korea na cl and so4 became the dominant ions indicating that the anthropogenic pollution became more important in regulating the chemical composition of the river the increasing ca mg na k hco3 ratio downstream also indicates that the anthropogenic effects became more important as the river flows downstream the isotopic compositions of d and 18o indicate that the river waters were significantly affected by evaporation during may and july but the evaporation effect was relatively low during october the isotopic composition of 15n no3 increased downstream also confirming that anthropogenic effects became more significant at the lower reach of the river and near daegu

unequal mobility of gravel and sand in weakly bimodal river sediments bed load was trapped during flood events over a 20 month period at the lower end of the allt dubhaig a small river in scotland with rapid downstream fining of gravel bed material on a slowly aggrading concave long profile the channel bed near the trap is predominantly gravel with a secondary sand mode total transport in each event depended mainly on peak shear stress rather than duration over a threshold bed load was mainly sand in smaller events bimodal in intermediate events and mainly gravel in the biggest floods mean and maximum grain diameter both increased with peak shear stress but in different ways analysis of fractional transport rates and maximum grain size in relation to peak shear stress suggests that gravel transport is slightly size selective but sand transport is close to equal mobility the slight selectivity in gravel transport is consistent with previous field studies of near equilibrium unimodal beds and supports assumptions made in the numerical model of hoey and ferguson 1994 which successfully simulates the observed amount of downstream fining over the 2 5 km upstream of the bed load trap

stable isotopes in the source waters of the yamuna and its tributaries seasonal and altitudinal variations and relation to major cations water samples from the yamuna and its tributaries one of the major river systems draining the himalaya have been analysed for their stable oxygen and hydrogen isotopes during three seasons summer monsoon and post monsoon the data show clear seasonal and altitudinal variations waters from higher altitudes and those collected during monsoon season are characterized by relatively depleted isotopic composition regression analysis of d 18 o data of samples collected during summer and monsoon seasons shows that the slope of the best fit lines are nearly identical to those of precipitation at new delhi for the same period the similarity in their slopes suggests that the isotopic composition of precipitation contributing water to these rivers are reasonably well preserved in both monsoon and non monsoon seasons however during the non monsoon period both rainfall and river waters carry signatures of evaporation the deuterium excess in river waters during the three seasons though overlap with each other the values during october are higher this can be understood in terms of recycled moisture contributions to precipitation the altitude effect for 18 o in these waters is determined to be 0 11 per 100 m a factor of about two less than that reported for the ganga source waters from similar altitudinal range the variability in altitude effects in rivers draining the himalaya seems to be controlled by the amount effect associated with the monsoon the significant spatial variability in altitude effect in these river basins which are a few hundred kilometers apart suggests that reconstruction of palaeoelevation in the himalaya based on 18 o altitude gradients would depend critically on its proper assessment in the region this study has established a relationship between total cation abundance and 18 o in waters of the yamuna mainstream total cations corrected for cyclic components double for a 1 4 km decrease in altitude as the yamuna flows downstream

stable isotope ratios in precipitation and their relationship with meteorological conditions in the kumaon himalayas india summary for the first time environmental isotopic 2h 18o 3h data predominantly based on precipitation samples in the kumaon himalayas india have been used to understand the influence of various meteorological factors governing rainout processes in the region further the data are also used to understand the orographic effects in precipitation and to estimate the altitude effect in stable isotopic ratios in precipitation etc the interpretation of the isotopic data revealed that the source of moisture for winter october february and summer may precipitation in the kumaon himalayas is mainly from the western disturbances whereas for the remaining period the source is monsoonal southwest the 2 18o relationship in the local precipitation during the monsoon season shows a distinct seasonal effect with a slope of 7 6 the winter and summer precipitation samples measured higher environmental 3h compared to southwest monsoon samples thus indicating continental evaporated moisture there is wide range of altitude effects 18o variation per 100 m elevation 0 30 july august 0 57 september with the mean altitude effect being 2 61 and 0 36 per 100 m elevation for 2h and 18o respectively these values are different from that reported earlier for the region based on the isotopic compositions of springs rivers samples the altitude effect in successive precipitation is basically a temperature dependent phenomenon and is explained on the basis of adiabatic cooling related rainout process dry adiabatic lapse rate moist adiabatic lapse rate and saturated adiabatic lapse rate for moist air mass the altitude effect is found to be more reliable in case of 2 as deuterium is least affected by secondary evaporation the effect of secondary evaporation has been observed on the true altitude effect secondary evaporation of rainfall increases the oxygen isotopic ratios and the increase is directly proportional to the vertical distance travelled by the raindrops through air

soil n alkane δd vs altitude gradients along mount gongga china the altitude effect on the isotopic composition of precipitation and its application to paleoelevation reconstruction using authigenic or pedogenic minerals have been intensively studied however there are still no studies on variations in biomarker d along altitude transects to investigate its potential as a paleoelevation indicator although it has been observed that d of higher plant lipid may record changes in precipitation d dp here we present d values of higher plant derived c27 c29 and c31n alkanes from surface soil along the eastern slope of mount gongga china with great changes in physical variables and vegetation over a range from 1000 to 4000 m above sea level the weighted mean d values of these n alkanes dwax show significant linear correlations with predicted dp values r2 0 76 with an apparent isotopic enrichment ewax p of 137 9 indicating that soil dwax values track overall dp variation along the entire altitudinal transect leaf dwax is also highly correlated with mountain altitude by a significant quadratic relationship r2 0 80 evapotranspiration is found declining with altitude potentially lowering dwax values at higher elevations however this evapotranspiration effect is believed to be largely compensated by the opposing effect of vegetation changes resulting in less varied ewax p values over the slope transect this study therefore confirms the potential of using leaf dwax to infer paleoelevations and more generally to infer the d of precipitation

the relation between particle path length distributions and channel morphology in gravel bed streams a synthesis abstract the path length downstream displacement over a given time period of individual bed particles in gravel bed rivers is central to morphological methods for measuring bed load transport rate and is also fundamental to understanding the bed load transport process and the development of channel morphology previous studies of particle movement using tracers report predominantly strongly positively skewed frequency distributions of path length with modes close to the point of entrainment however gravel bed rivers often have regularly spaced erosion scour pools and deposition channel bars sites that are several channel widths apart and it is reasonable to expect that particle path length would reflect this morphological scale at least during flows large enough to create and modify the morphology here we synthesize and re analyze results from published bed load tracing experiments in gravel bed rivers to identify the variety of possible path length distributions for differing channel morphology channel dimensions bed particle size and particle mobility i e flow magnitude and to look for occurrences of path length coinciding with the length scale of the morphology the results show that path length distributions may be positively skewed symmetrical and uni bi or multi modal and may include modes that coincide with known or expected pool bar spacing primary path length modes equivalent to possible pool bar spacing are more probable at higher non dimensional bed shear stress from which it is inferred that both particle mobility and channel morphology exert an influence on particle path lengths and that particle movement is unlikely to be stochastic except at relatively low particle mobility existing data are inadequate for more than a preliminary analysis of this problem consequently there is a need for new data collected explicitly and systematically to confirm these preliminary results isolate the effect of the several variables that influence the characteristics of path length frequency distributions and identify the conditions under which path length coincides with the length scale of the dominant morphology

using passive integrated transponder pit tags to investigate sediment transport in gravel bed rivers abstract in gravel bed rivers measuring the displacement of individual grains by fluid flow is essential in order to understand sediment transport processes and to investigate changes in channel morphology we present preliminary results of a new technique that traces pebble movements by inserting 23 mm passive integrated transponders pit into individual clasts because each pit has its own signal identification this technique is ideal for tracking the individual movements of episodically transported particles in gravel bed rivers two hundred and four tagged particles were inserted into a 130 m long reach of a gravel bed river with a 2 slope and a bed material with a d50 of 70 mm the b axis size of the tagged particles ranged from 40 mm to 250 mm recovery percentages after two competent floods were 96 and 87 clearly demonstrating the effectiveness of this new technique buried particles can be recovered at a depth of 0 25 m pit tags are also suited for long term studies over several years

virtual rate and mean distance of travel of individual clasts in gravel bed channels travel distances in gravel bed rivers of tagged particles of various sizes are related to excess stream power estimated for peak discharge mean distance of movement irrespective of grain size is weakly correlated with stream power especially near the threshold of movement there may be several reasons for the weak correlation including variable effects of bed structure varying magnitudes of sediment mobilizing events and sampling problems grain size itself is of marginal significance the virtual rate of travel calculated using total time for which the flow is larger than that needed to initiate clast movement also bears a weak relation to the excess stream power over the period better results are obtained by relating the virtual rate of travel to the first peak of the flow event only this implies that the initial seeding of the tagged particles dominates the observations nonetheless an underlying general relation is indicated by the data which are derived from a wide range of flow regime types

stable isotopic variations in modern herbivore tooth enamel plants and water on the tibetan plateau implications for paleoclimate and paleoelevation reconstructions stable isotope analyses of fossil teeth and other authigenic minerals have been used to reconstruct the paleoenvironment and paleoelevation of the tibetan plateau the accuracy of such reconstructions is limited by the lack of a comprehensive modem comparative database from the region we analyzed the carbon and oxygen isotopic compositions delta c 13 and delta o 18 values of tooth enamel from modem herbivores the delta c 13 values of gasses and the delta o 18 values of water samples collected from various elevations within the tibetan plateau to examine their relationships with modem environment elevation the delta c 13 values of enamel samples from horses yaks and goats display a narrow range of variation with a mean of 10 7 1 4 parts per thousand n 301 indicating that these modem herbivores were feeding predominantly on c3 plants consistent with the current dominance of c3 vegetation in the region some of the samples have delta c 13 values between 7 3 and 10 parts per thousand although these higher delta c 13 values could suggest consumption of some c4 plants by the animals the lack of significant seasonal delta c 13 variations within individual teeth indicates that these higher enamel delta c 13 values are due to consumption of c3 plants experiencing water stress and or some cam plants rather than c4 plants our data show that the conservative cut off delta c 13 value for a pure c3 diet within the tibetan plateau should be 8 parts per thousand for modem herbivores and 7 parts per thousand or even 6 5 parts per thousand for fossils if the region was as and in the past as today in contrast to the small intra tooth delta c 13 variations within individual teeth serial enamel samples display large intra tooth delta o 18 variations reflecting seasonal variations in the delta o 18 of meteoric water the mean delta o 18 values of tooth enamel from yaks and horses show a strong correlation with water delta o 18 values confirming that the delta o 18 of tooth enamel from obligate drinker generally tracks the 6180 of meteoric water unfortunately elevation alone cannot explain most of the variance in the delta o 18 of precipitation and tooth enamel suggesting that quantitative reconstruction of the paleoelevation of the tibetan plateau using re constructed delta o 18 values of paleo meteoric water from fossil enamel or other oxygen bearing minerals is not warranted for a given environment horses have the lowest enamel delta o 18 values while goats display the highest enamel delta o 18 values among the species studied the large inter species delta o 18 variations are likely due to differences in physiology and diet drinking behavior of the animals this underscores the importance of species specific studies when interpreting delta o 18 data of fossil mammalian teeth in a stratigraphic sequence as a record of paleoclimate changes c 2008 elsevier b v all rights reserved

predicting paleoelevation of tibet and the himalaya from δ18o vs altitude gradients in meteoric water across the nepal himalaya the 18o value of meteoric water varies with elevation providing a means to reconstruct paleoelevation if the 18o values of paleowater are known in this study we determined the 18o values of water 18omw from small tributaries along the seti river and kali gandaki in the nepal himalaya we found that 18omw values decrease with increasing altitude for both transects 18omw vs altitude along the kali gandaki in west central nepal fit a second order polynomial curve consistent with increasing depletion of 18o with increasing elevation as predicted by a rayleigh type fractionation process this modern 18omw vs altitude relationship can be used to constrain paleoelevation from the 18o values of miocene pliocene carbonate 18oc deposited in the thakkhola graben in the southern tibetan plateau paleoelevations of 3800 480 m to 5900 350 are predicted for the older tetang formation and 4500 430 m to 6300 330 m for the younger thakkhola formation these paleoelevation estimates suggest that by 11 ma the southern tibetan plateau was at a similar elevation to modern

δ18o and δd systematics in the surficial waters of the gaula river catchment area kumaun himalaya india abstract the 18 o and d measurements of surface waters streams springs lakes and precipitation from the gaula river catchment area of kumaun himalaya are reported the d and 18 o values are positively correlated as has been the case with waters from several other regions the lake waters are found to be enriched in 18 o and d compared with the neighbouring regions owing to evaporation estimates of mean total evaporation during the dry season range from 10 to 25 spring water samples collected from various altitudes from 915 m to 2150 m display variations in values showing an altitude effect of 0 1491 per 100m elevation

using h and o isotopic data for estimating the relative contributions of rainy and dry season precipitation to groundwater example from cheju island korea abstract a comparison of deuterium excess or d values of precipitation and groundwater at cheju island korea indicates that unlike in many temperate climates precipitation during the whole year contributes to groundwater recharge this in turn suggests that evapotranspiration effects are minimal consistent with the fact that the island contains highly permeable volcanic rocks overlain by thin soils this hypothesis is contrary to current water budget models that ascribe a significant role to evapotranspiration processes three coastal springs and several streams and ponds throughout the island have enriched 18 o and d values that plot off the local meteoric water line and have relatively high cl concentrations this relationship is suggestive of seawater mixing for the coastal springs and evaporation for the streams and ponds this database thus provides a useful means for evaluation of groundwater resources of the island

entrainment displacement and transport of tracer gravels the mass and size distribution of grain entrainment per unit bed area may be measured by replacing a volume of the bed with tracer gravels and observing the mass difference before and after a transport event this measure of spatial entrainment is relevant to any process involving size selective exchange of sediment between transport and bed and may be directly used in calculations of sediment transport rate using an elementary relation for fractional transport components presented here this relation provides a basis for evaluating tracer data collected by different methods and may be used to provide physical insight regarding the expected behaviour of tracer grains the variation with grain size of total displacement length l ti depends on the degree of mobilization of the individual fractions on the bed surface l ti is independent of d i for smaller fully mobile sizes and decreases rapidly with d i for larger fractions in a state of partial transport in which a portion of the surface grains remain immobile through the flow event the boundary between fully and partially mobile grain sizes increases with flow strength these inferences are supported by values of l ti calculated from flume experiments and provide a physical explanation for a summary relation between l ti and d i based on field data 1997 john wiley sons ltd

the effects of low magnitude flow conditions on bedload mobility in a steep mountain stream abstract the transport of coarse material strongly controls the stability and evolution of mountain fluvial systems but despite this bedload dynamics are not yet fully understood especially in mountain streams in this sense particular attention was paid on the bedload magnitude volume expressed at event scale and on the long term while few studies were focused on when and how the transport of the coarse material occurs the aim of this work was to investigate the bedload mobility in the rio cordon a mountain stream characterized by cascade and step pool morphologies with a rough streambed here the critical conditions for initiation of motion transport distance and virtual velocity expressed by the coarse streambed material were assessed and their relationships with hydraulic forcing conditions and grain size were analyzed to this end a monitoring program based on bedload tracing was maintained over 7 years allowing to analyze the bedload mobility during persistent high frequency low magnitude flow conditions to investigate the bedload mobility 250 tracers were released between 2011 and 2012 and their propagation along study site was monitored until 2018 overall 14 tracer inventories were realized determining 1697 tracer localizations during the study period the bedload dispersion resulted well described by the peak discharge magnitude qp qp and p c while no significant relationships were observed with duration of competent flow tover and effective runoff volume er transport distance and tracer grain size were negatively correlated whereas virtual velocity increased with increasing particle size in this sense the propagation velocity seems to be affected by the high frequency flows that on the one hand triggered mobilization of the coarser tracers only through limited and impulsive events and on the other hand favored a slowdown on the finer particles due to bedforms disturbance compared to other study sites the rio cordon exhibited accentuated threshold conditions with lower transport distance and virtual velocity confirming that steep mountain streams are generally influenced by a reduced transport efficiency due to protruding bedforms and macro roughness that cause a pronounced energy dissipation interestingly such condition seems to have progressively reduced from under to near bankfull flows the results were compared to the bedload mobility observed in the rio cordon during 1993 1998 enabling to quantitatively assess how the bedload dispersion varied between a setting of stable armouring layer with protruding bedforms 2012 2018 and a partial alteration of these 1993 1998 an evident difference was observed in terms of transport distance while critical conditions did not significantly change lastly the long term bedload tracing investigation highlighted that a certain legacy on the transport efficiency was produced by the persistent high frequency flow conditions over the study period a general decrease of transport distance was observed that could be explained by a progressive stabilization of streambed material previous studies suggested that such condition can be interrupted by high magnitude low frequency floods

vertical mixing of coarse particles in gravel bed rivers a kinematic model burial of transported material in gravel bed rivers was examined using several hundred magnetically tagged particles burial depth of individual particles varies with no simple relation to particle size distributions of burial depth of particles were examined by considering observed burial depth of individual size groups of all mobile particles and of all tagged particles including static ones simple single peak flow events yielded exponential distributions of burial depth of mobile particles distributions with secondary peaks were obtained from large and multipeak events season long results were skew peaked with a tendency toward uniformity an m layer model is developed to account for the variation of frequency of burial depth of particles based on the assumptions that the burial depth of particles in a simple event is exponentially distributed and the proportion of particles which change vertical position from a given layer is constant from event to event the model is elaborated for varying mixing rates varying scour depths and variable behavior of different size classes after many events the material is uniformly distributed throughout all layers in conformity with field experience

evaporative fractions and elevation effects on stable isotopes of high elevation lakes and streams in arid western himalaya summary isotopes of oxygen and hydrogen in water from streams snow and lakes were used to model the ratio of evaporation to total inflow e i of four high elevation lakes in closed basins in the indian himalaya air temperature and relative humidity h data from meteorological stations and global climate grids gmao merra were used as input to the model a second model of the volume of inflow during snowmelt constrained the magnitude of seasonal variability in isotopic composition similar to other areas of the himalaya elevation was a strong determinant of isotopic composition of stream water suggesting that heavier isotopes rain out at lower elevations deuterium excess d in stream water suggests that summer precipitation originating from the bay of bengal rather than winter precipitation from central asia is the dominant source of precipitation for the largest and deepest lakes 15 m e i was 77 87 and 18 50 for two shallow lakes

mobility of river tracer pebbles over different timescales 1 tracer pebbles are widely used to learn about gravel transport along rivers movement over short times and distances is dominated by factors controlling entrainment relative particle size and shear stress movement at longer scales also involves depositional factors burial and reexposure and exchange between channels bars and other depositional environments we mapped mixed size tracers in six reaches of a small scottish river after 2 and 8 years to investigate differences in relative and absolute mobility and infer the importance of burial and exchange patterns of relative mobility according to size and shear stress both within and between reaches did not change significantly some local bunching of tracers was apparent in both surveys with redistribution from pools into riffles and bars the main change was that virtual velocities were 50 lower and estimated gravel fluxes were also lower in the longer term this slowdown is attributed to vertical mixing giving decreased mobility as surface seeded tracers become buried long term storage in bars and other less active parts of the system and in this channel advection of tracers downstream onto a finer bed giving higher relative size

the concept of transport capacity in geomorphology the notion of sediment transport capacity has been engrained in geomorphological and related literature for over 50 years although its earliest roots date back explicitly to gilbert in fluvial geomorphology in the 1870s and implicitly to eighteenth to nineteenth century developments in engineering despite cross fertilization between different process domains there seem to have been independent inventions of the idea in aeolian geomorphology by bagnold in the 1930s and in hillslope studies by ellison in the 1940s here we review the invention and development of the idea of transport capacity in the fluvial aeolian coastal hillslope debris flow and glacial process domains as these various developments have occurred different definitions have been used which makes it both a difficult concept to test and one that may lead to poor communications between those working in different domains of geomorphology we argue that the original relation between the power of a flow and its ability to transport sediment can be challenged for three reasons first as sediment becomes entrained in a flow the nature of the flow changes and so it is unreasonable to link the capacity of the water or wind only to the ability of the fluid to move sediment secondly environmental sediment transport is complicated and the range of processes involved in most movements means that simple relationships are unlikely to hold not least because the movement of sediment often changes the substrate which in turn affects the flow conditions thirdly the inherently stochastic nature of sediment transport means that any capacity relationships do not scale either in time or in space consequently new theories of sediment transport are needed to improve understanding and prediction and to guide measurement and management of all geomorphic systems

water balance of the indus river basin and moisture source in the karakoram and western himalayas implications from hydrogen and oxygen isotopes in river water 1 stable isotope measurements of hydrogen and oxygen for surface waters from the indus river basin irb together with historical records for river discharge annual precipitation and groundwater levels are used to assess water balance for the basin the indus river presently drains 53 km3 yr 1 or roughly one eighth of the 398 km3 water that annually falls on the basin in the form of rain and snow with the remainder returned to the atmosphere by evapotranspiration monthly samples for the indus river close to its mouth for the water year march 1994 to february 1995 show a tight correlation in d and 18o space the slope of the linear regression is 7 5 which is not significantly different from the slopes of the local meteoric water lines lmwl 7 3 and 7 1 this observation argues against significant loss of water by direct evaporation from river surfaces or from soils in hydrologic continuum with surface waters an upper limit for evaporation from poorly drained soils is calculated to be 10 km3 yr 1 or only 2 5 of the annual precipitation flux groundwater storage in the entire canal command area received a maximum of 23 km3 yr 1 or 5 8 of the annual precipitation during the early stages of irrigation but modern recharge is probably balanced by discharge to rivers and well exploitation transpiration by natural vegetation and crops annually returns 83 of the precipitation flux and constitutes the largest pathway for the loss of water from the basin deuterium excess d excess in the irb ranges between 4 and 28 with values for 95 of the sample population exceeding 10 the indus main channel close to its mouth varies in d excess between 12 and 20 during low and high water stands respectively with a discharge weighted average of 18 these values are distinctly higher than the long term average for the indian monsoon 8 and reflect contributions from water vapor originating in the mediterranean 22 or other inland seas using these end member compositions and the discharge weighted average d excess isotope balance calculations require that up to 72 of the indus discharge close to its mouth must be derived from the mediterranean end member and implies that bulk of the indus discharge is the result of delayed runoff from the karakoram and the himalayas

slope induced changes in channel character along a gravel bed stream the allt dubhaig scotland changes in channel character along a small river in the scottish highlands are described using measurements in seven reaches over a 3 km length with no significant tributaries but a decline in slope from 0 02 to o ooo15 because of local baselevel control this decline in slope is associated with rapid downstream fining of the gravel bed followed by an abrupt transition to a sand bed the channel pattern alters progressively rather than abruptly in the sequence 1 near braided 2 meandering with active point bar chutes 3 meandering with active outer bank talweg 4 stable equiwidth sinuous the changes in channel pattern and hydraulic geometry are predicted better by rational approaches based on critical shear stress or other physical cdncepts than by purely empirical discriminant or trend equations measurements in five reaches confirm a downstream decrease in shear stress and the amount and calibre of bedload it is argued that the downstream changes in channel character in this stream are induced by profile concavity inherited from deglacial conditions are typical of many streams in mountainous areas and can be understood in terms of slope induced changes in hydraulic properties

stable isotope paleoaltimetry a critical review stable isotope paleoaltimetry makes use of systematic trends in the distribution and isotopic composition of modern precipitation with climate and topography and of the potential to estimate the isotopic composition of paleoprecipitation from authigenic in situ formed minerals to illustrate the usefulness as well as potential limitations of this method we review 1 processes controlling the isotopic composition of modern precipitation 2 stable isotope data from modern precipitation across regions of high topography and 3 stable isotope data from authigenic minerals that have been used to infer paleotopography from this we conclude that stable isotope studies of authigenic minerals can permit useful inferences on paleotopography with uncertainties that critically depend on a detailed understanding of local to global scale paleoclimate during the time interval of interest

reconstructing the paleotopography of mountain belts from the isotopic composition of authigenic minerals the paleorelief of mountain belts can be estimated from the 18 o value of authigenic minerals development of relief during mountain building often creates lee side rain shadows in which precipitation is depleted in 18 o and d the magnitude of this rain shadow effect is strongly correlated to relief a compilation of 18 o data from surface waters throughout the globe shows a linear relationship between net elevation change and 18 o r 2 0 79 through the use of this relationship we investigated the timing and magnitude of elevation change in the southern alps of new zealand and the sierra nevada of california the 18 o values of kaolinites from new zealand show an 6 decrease in the early pliocene that corresponds to an 2 km elevation change in the southern alps the 18 o of smectites from the sierra nevada show little change since 16 ma suggesting that these mountains have been a long standing topographic feature

the nature and controls on downstream fining within sedimentary links abstract at scales of 100 to 102 km grain size change in gravelly alluvial systems is characterized by punctuated downstream fining significant lateral sediment inputs define a sequence of sedimentary links within which fluvial processes produce fining trends using a new set of surface grain size data eighteen such links along two canadian gravel bed rivers are examined negative exponential functions are found to be most appropriate for describing within link grain size changes development of a pragmatic means of predicting grain size is then pursued by searching for a means to relate model diminution coefficients to link attributes consideration of lithologically differentiated fining trends indicates that lithology plays an insignificant role in controlling fining rate examination of within link longitudinal profiles indicates a reasonable relation between fining rate and the rate of change of channel slope the predictive value of this relation is limited by the regional nature of the data upon which it is based and the relative difficulty of obtaining accurate gradient information however as previously noted for alluvial fans although for different reasons channel gradient is correlated with link length and a reasonable predictive tool is apparent in a relation between link length and diminution rate the validity of the derived relation cannot be tested for want of a suitable data set several lines of evidence indicate that abrasion is unimportant as a fining mechanism on these rivers and it is argued that this may be typical of sedimentary links fining rate must then be a function of the efficiency with which sorting processes operate and it is suggested that this efficiency is dependent on aggradation rates associated with the lateral sediment influxes at the head and terminus of individual links

transport of tracer gravels on a coastal california river abstract tracer gravels can provide information about the transport of coarse gravels not sampled by standard sampling methods white dolomite fragments emplaced as riprap on the carmel river monterey county california were entrained by progressively higher flows in 1981 1982 and 1983 and were transported progressively further following the 1981 flow tracer gravel concentration decreased exponentially downstream after the 1982 flows and again after the 1983 flows the distribution of gravels reflected channel morphology not an exponential downstream decrease peak concentrations corresponded to locations of major gravel bars while tracer concentration decreased overall in the downstream direction its distribution suggested movement by discrete jumps from bar to bar rather than continuous movement calculation of bedload transport rates for rocks 45 mm by spatial integration of tracer data yields bedload transport rates of about 3 5 of the total bedload flux measured by helley smith sampler 5 5 km downstream the spatial integration method is not strictly applicable here because injection of tracer was not instantaneous and channel form is quite irregular nonetheless it is notable that results by this method are compatible with sampled transport rates downstream the results of this study show the dominant influence of channel morphology on tracer gravel distribution reflecting the importance of in channel storage sites in coarse sediment movement this effect and the low recovery rate reported for tracer gravels in the literature are reason for caution in using short term tracer gravel studies to compute rates of coarse bedload flux however tracer studies can be profitably used to provide data on the movement of coarse particles unmeasured by helley smith samplers

trouble with diffusion reassessing hillslope erosion laws with a particle based model 1 many geomorphic systems involve a broad distribution of grain motion length scales ranging from a few particle diameters to the length of an entire hillslope or stream studies of analogous physical systems have revealed that such broad motion distributions can have a significant impact on macroscale dynamics and can violate the assumptions behind standard local gradient flux laws here a simple particle based model of sediment transport on a hillslope is used to study the relationship between grain motion statistics and macroscopic landform evolution surface grains are dislodged by random disturbance events with probabilities and distances that depend on local microtopography despite its simplicity the particle model reproduces a surprisingly broad range of slope forms including asymmetric degrading scarps and cinder cone profiles at low slope angles the dynamics are diffusion like with a short range thin tailed hop length distribution a parabolic convex upward equilibrium slope form and a linear relationship between transport rate and gradient as slope angle steepens the characteristic grain motion length scale begins to approach the length of the slope leading to planar equilibrium forms that show a strongly nonlinear correlation between transport rate and gradient these high probability long distance motions violate the locality assumption embedded in many common gradient based geomorphic transport laws the example of a degrading scarp illustrates the potential for grain motion dynamics to vary in space and time as topography evolves this characteristic renders models based on independent stationary statistics inapplicable an accompanying analytical framework based on treating grain motion as a survival process is briefly outlined

large scale relocation of two decades of northern california seismicity using cross correlation and double difference methods 1 we simultaneously reanalyzed two decades 1984 2003 of the digital seismic archive of northern california using waveform cross correlation cc and double difference dd methods to improve the resolution in hypocenter locations in the existing earthquake catalog generated at the northern california seismic network ncsn by up to three orders of magnitude we used a combination of 3 billion cc differential times measured from all correlated pairs of events that are separated by less than 5 km and 7 million p wave arrival time picks listed in the ncsn bulletin data were inverted for precise relative locations of 311 273 events using the dd method the relocated catalog is able to image the fine scale structure of seismicity associated with active faults and revealed characteristic spatiotemporal structures such as streaks and repeating earthquakes we found that 90 of the earthquakes have correlated p wave and s wave trains at common stations and that 12 are colocated repeating events an analysis of the repeating events indicates that uncertainties at the 95 confidence level in the existing network locations are on average 0 7 km laterally and 2 km vertically correlation characteristics and relative location improvement are remarkably similar across most of northern california implying the general applicability of these techniques to image high resolution seismicity caused by a variety of plate tectonic and anthropogenic processes we show that consistent long term seismic monitoring and data archiving practices are key to increase resolution in existing hypocenter catalogs and to estimate the precise location of future events on a routine basis

virtual velocity of tracers in a gravel bed river using size based competence duration virtual velocity vi of river gravels is commonly used to determine sediment transport rates and gravel dispersion dynamics virtual velocity is calculated from tracer gravel step length data as the distance travelled divided by the duration of competence however no allowance is usually made for differences in competence duration according to grain size in this investigation vi of gravel tracer clasts for the river rede northumberland uk is calculated using a method that takes into consideration an approximation of size based competence duration although scaled transport distance data compared favourably to past studies it was the comparatively smaller clasts that tended to have lower vi in comparison to coarser clasts because of their longer competence duration contrasting with previously published research the key findings of the study serve as proof of concept and should be adopted in future studies that focus upon vi estimation

tracer pebble movement along a concave river profile virtual velocity in relation to grain size and shear stress over 1400 tracer pebbles 16 256 mm in diameter were tracked for 2 years in six reaches of allt dubhaig scotland a small gravel bed river along which shear stress and bed surface grain size decrease toward a local base level pebble movement was size selective both within and between reaches within reaches the decrease in mean travel distance with increasing grain size is strongest in the coarse tail of the size distribution particle shape has a minor secondary effect a nondimensional grain velocity averaged over the duration of competent flow is used to compare different size classes and reaches over 90 of its variance is explained by relative grain size and reach shields stress the pattern of size selectivity is consistent with single event tracer results elsewhere bedload trap data from our distal reach and the concept of partial mobility it provides a mechanism for strong downstream fining by selective transport and deposition along rivers in which stress declines toward base level the nondimensional prediction equation for grain velocity may be of use in other rivers but requires testing

modern precipitation stable isotope vs elevation gradients in the high himalaya comment on a new approach to stable isotope based paleoaltimetry implications for paleoaltimetry and paleohypsometry of the high himalaya since the late miocene by david b rowley et al earth planet sci lett 188 2001 253 268

bedload a granular phenomenon bedload the transport of sediment remaining in contact with the stream bed has mainly been studied from the perspective of the correlation between fluid driving forces and the responding sediment flux yet grain grain interactions are important and bedload should also be considered as a granular phenomenon we review progress made recently in the study of granular flows especially on segregation and rheology that better illuminates the nature of bedload granular flows may exhibit gas like or fluid like flow or quasi solid deformation all three conditions might be duplicated in bedload understanding of intense bedload transport occurring continuously in a layer several grains deep typical of sand beds might greatly benefit from results in granular physics as illustrated by grain inspired bedload results however processes restricted to the surface of the bed when particles move intermittently and the bed becomes structured while characteristic in gravel bed channels are not well addressed in granular physics mutual study of these phenomena may benefit both physics and fluvial geomorphology we intend therefore to contribute to an enhanced dialogue between granular physics and bedload science communities copyright 2010 john wiley sons ltd

linking fluvial bed sediment transport across scales 1 we present a new random walk model for bed load sediment transport that explains the scale dependency generally observed in transport rates and captures the transient anomalous dispersion often seen in rivers particles alternate between mobile and resting phases with a tempered stable probability distribution for both particle step length and resting time tempered fractional mobile immobile differential equations model the ensemble average of particle dynamics the model is tested against data from three sediment dispersion experiments using tempering in both space and time the new model is able to capture the full range of observed ensemble particle dynamics the random walk model illuminates the physical meaning of all transport parameters in the mobile immobile equations and explains transitions between observed super diffusive sub diffusive and regular diffusive ensemble particle dynamics by explicitly predicting the effects of spatial and temporal averaging on particle dynamics this method can be used to link observations of fluvial sediment dynamics across scales this approach is also generally applicable to a wide variety of geophysical and ecological dynamics such as ecological dispersal pathogen transmission in rivers nutrient export from watersheds and large scale geomorphodynamics associated with infrequent phenomena such as avalanches and turbidity currents