strontium and carbon isotope constraints on carbonate solution interactions and inter aquifer mixing in groundwaters of the semi arid murray basin australia abstract strontium and carbon isotopes are used to study the effect of carbonate mineral dissolution and inter aquifer mixing on the chemical evolution of groundwater from the murray group limestone aquifer in semi arid se australia the 87 sr 86 sr ratio of groundwater evolves from 0 7097 at the basin margin to a less radiogenic value of 0 7084 about 250 km down gradient which is similar to the 87 sr 86 sr ratio of the aquifer carbonate matrix the concomitant increase in 13 c dic sr ca and mg ca ratios in the groundwater along a 250 km transect suggests that incongruent dissolution of high mg calcite controls the carbonate geochemistry in this aquifer further down gradient the groundwater is characterized by a relatively more radiogenic 87 sr 86 sr ratio caused by upward leakage and mixing with more radiogenic groundwater from the renmark group sand aquifer a mixing model using 87 sr 86 sr ratio suggests that the fraction of water that contribute to the murray group aquifer through upward leakage from underlying renmark group aquifer ranges from 15 to 85

factors controlling hydro sedimentary response during runoff events in a rural catchment in the humid spanish zone abstract in galicia nw spain studies on the suspended sediment ss transported in river catchments are scarce using a dataset comprising three hydrological years 2004 05 2006 07 in the corbeira catchment nw spain the relationships between rainfall runoff and ss are analysed at event scale the catchment was instrumented to measure rainfall water level and ss in the stream several event rainfall discharge and ss concentration and load and pre event rainfall and discharge variables were calculated for all the events analysed correlation matrices were developed using these data discharge characteristics and rainfall depth showed good correlations with ss concentration and load suspended sediment and discharge relationships were also examined in most of the events the ss peak preceded peak discharge clockwise hysteresis implying that zones near the stream are the main sediment source areas

hydraulic geometry river sediment and the definition of bedrock channels a growing literature deals with bedrock channels erosion processes within them and their role in landscape evolution formal definitions currently in use classify channels as bedrock when alluvial cover is discontinuous or thin this is equated with a physical property of the flow using up to date erosion laws and descriptions of channel dynamics we show that existing definitions are difficult to apply and may lead to conflicting classifications we propose the definition a bedrock channel cannot substantially widen lower or shift its bed without eroding bedrock applied to channels in taiwan this leads to a different classification than previous definitions by analysing at a station hydraulic geometry of these channels we show that the classification exposes different controls of sediment effects on dynamics of channels classified as alluvial and bedrock

geomorphic response detection and quantification in a steep forested torrent abstract extreme events such as flash floods and debris flows are frequent phenomena that occur in steep torrential catchments these kinds of events can cause notable geomorphic changes repeated terrestrial laser scanning tls surveys were performed in a steep forested catchment of the kuzlovec torrent drainage area 0 7 km2 in central slovenia where a 200 m long section of the torrent was scanned in 2013 2014 and 2015 the main aim of this study was to perform the geomorphic response detection in the torrent due to hydro meteorological events of different magnitudes after applying several pre processing steps digital terrain models dtms with a cell resolution of 5 cm were produced the geomorphic change detection was performed using the dtm of difference approach dod several above average flow events occurred in the period from 2013 to 2015 some of them can be regarded as floods the 2014 august extreme flash flood that was initiated by the rainfall event with a return period exceeding 100 years where maximum 1 minute rainfall intensities were up to 288 mm h led to erosion rates of an order of magnitude higher than average annual erosion rates moreover the analysis of the geomorphic changes shows that the august 2014 flash flood caused intense sediment transport processes that resulted in the changes at the location of the main stream channel thalweg and reduced channel roughness the unit stream power for the scanned section of the torrent was assessed to be approximately 500 w m2 during this extreme event this is above the thresholds that were suggested to differentiate between the situations where significant geomorphic changes can occur and the situations where geomorphic changes are not notable

sediment output and effective discharge in two small high mountain catchments in the bavarian alps germany abstract sediment output solid and dissolved load from two small alpine rivers partnach and lahnenwiesgraben in the bavarian alps was measured during three summer field seasons from 2001 2003 there is high spatial variability of sediment output between the catchments and a high temporal variability between observation periods sediment transport in the partnach river reintal is dominated by solute load whereas the lahnenwiesgraben river transports a much greater proportion of solid load this difference can mainly be explained by the different lithologies of the systems the reintal catchment is dominated by massive triassic limestone in the lahnenwiesgraben catchment in addition to limestones unconsolidated rocks marls and mudstone layers are significant furthermore large rockslide dams in the partnach valley isolate large parts of the reintal catchment from solid load output the components of fluvial sediment transport were where possible calculated by using flow duration curves and rating curve techniques in the lahnenwiesgraben event specific rating curves were used to determine suspended load on the broad database of 55 measured flood events in the lahnenwiesgraben a good correlation r pearson 0 9 between event peak discharge and suspended load of the event was established effective discharge was calculated for the different types of sediment load solid and dissolved and total load in the reintal effective discharge for total load is found in low flow classes close to mean discharge because sediment output is dominated by dissolved load which has its maximum efficiency at low and moderate discharges in the lahnenwiesgraben most work is done by discharges much higher than mean discharge during extreme individual flood events

the evidence for paraglacial sedimentation and its temporal scale in the deglacierizing basin of small river glacier canada abstract spatially sampled suspended sediment data from extra channel surfaces of different ages during rainfall events were used to infer the timescale of landscape adjustment to little ice age lia deglacierization at small river glacier canada surface ages were determined by aerial photograph interpretation turbidimeters were installed in three ephemeral channels on young mature and old surfaces and their response to rainfall events of different magnitudes recorded results showed young ice proximal surfaces exposed since 1977 were increasingly vulnerable to mobilization during rainfall events a suspended sediment response from old surfaces exposed since 1910 was recorded for only three events with 5 and 30 year return periods the intensity and duration of rainfall events therefore had to increase in magnitude to mobilize sediment on surfaces of increasing maturity hysteresis in the channel suspended sediment response further confirmed the dependence of surface response on rainfall event magnitude the rapid temporal decline in surface response indicated that surface armoring or sediment exhaustion is stabilizing surfaces within decades of exposure from the lia maximum ca 1910 at small river glacier however further perturbation for example by glacial advance or extreme climatic events would likely modify the pattern of suspended sediment yields by changing terrain surface mobilization thresholds and reconfiguring channel sediment stores we therefore suggest that it is difficult to determine when paraglacial sedimentation ceases to influence suspended sediment yields and therefore significantly limiting the usefulness of the term to describe the period of suspended sediment yield adjustment following deglacierization

relationships among rainfall runoff and suspended sediment in a small catchment with badlands abstract the araguas catchment of the central spanish pyrenees has been monitored since 2004 to study weathering erosion and the hydrological and sediment response to rainfall events in order to understand the hydromorphological dynamics of a badland area in a relatively humid environment this small catchment 0 45 km2 shows highly active processes of physical and chemical weathering related to seasonal variations in temperature and moisture erosion and sediment transport are widely studied in badlands within mediterranean environments because they represent the dominant sediment source to obtain information about suspended sediment and discharge a gauging station was installed within the araguas catchment during the summer of 2005 the aim of this work is to determine the relationships among rainfall runoff and suspended sediment in this badland area towards this goal we analyze the relationships between suspended sediment concentration and discharge during rainfall events from a hydrological viewpoint the araguas catchment reacts to all rainfall events with torrential flow being the most characteristic hydrological response the results obtained between october 2005 and april 2007 reveal extremely high concentrations of suspended sediment with values frequently exceeding 100 g l 1 and reaching a maximum of 1200 g l 1 three different types of hysteretic loops were observed clockwise 22 events 28 counter clockwise 27 events 34 and figure eight 12 events 15 moreover 23 of events were classified as complex hysteretic loops and removed from the analysis due to their complexity clockwise hysteretic floods are characterized by their long duration and the highest hydrological and sedimentological responses counter clockwise hysteretic floods are characterized by their short duration and moderate hydrological and sediment responses finally figure eight hysteretic floods are related to multiple peaks in suspended sediment coinciding with oscillations in discharge associated with the highest rainfall intensities within each event and moderate hydrological and sediment responses

constraints on water reservoir lifetimes from catchment wide 10be erosion rates a case study from western turkey the functionality and retention capacity of water reservoirs is generally impaired by upstream erosion and reservoir sedimentation making a reliable assessment of erosion indispensable to estimate reservoir lifetimes widely used river gauging methods may underestimate sediment yield because they do not record rare high magnitude events and may underestimate bedload transport hence reservoir lifetimes calculated from short term erosion rates should be regarded as maximum values we propose that erosion rates from cosmogenic 10be which commonly integrate over hundreds to thousands of years are useful to complement short term sediment yield estimates and should be employed to estimate minimum reservoir lifetimes here we present 10be erosion rates for the drainage basins of six water reservoirs in western turkey which are located in a tectonically active region with easily erodible bedrock our 10be erosion rates for these catchments are high ranging from 170 to 1040 t km2 yr when linked to reservoir volumes they yield minimum reservoir lifetimes between 25 5 and 1650 360 years until complete filling with four reservoirs having minimum lifespans of 110 years in a neighboring region with more resistant bedrock and less tectonic activity we obtain much lower catchment wide 10be erosion rates of 33 to 95 t km2 yr illustrating that differences in lithology and tectonic boundary conditions can cause substantial variations in erosion even at a spatial scale of only 50 km in conclusion we suggest that both short term sediment yield estimates and 10be erosion rates should be employed to predict the lifetimes of reservoirs

hysteresis in suspended sediment to turbidity relations due to changing particle size distributions 1 turbidity t is the most ubiquitous of surrogate technologies used to estimate suspended sediment concentration ssc the effects of sediment size on turbidity are well documented however effects from changes in particle size distributions psd are rarely evaluated hysteresis in relations of ssc to turbidity ssc t for single stormflow events was observed and quantified for a dataset of 195 concurrent measurements of ssc turbidity discharge velocity and volumetric psd collected during five stormflows in 2009 2010 on yellow river at gees mill road in metropolitan atlanta georgia regressions of ssc normalized turbidity t ssc on concurrently measured psd percentiles show an inverse exponential influence of particle size on turbidity that is not constant across the size range of the psd the majority of the influence of psd on t ssc is from particles of fine silt and smaller sizes finer than 16 m this study shows that small changes in the often assumed stability of the psd are significant to ssc t relations changes of only 5 m in the fine silt and smaller size fractions of suspended sediment psd can produce hysteresis in the ssc t rating that can increase error and produce bias observed ssc t hysteresis may be an indicator of changes in sediment properties during stormflows and of potential changes in sediment sources trends in the psd time series indicate that sediment transport is capacity limited for sand sized sediment in the channel and supply limited for fine silt and smaller sediment from the hillslope

stratification in the northern bering sea in early summer of 2017 and 2018 abstract we investigated spatial and interannual variation in the physical environment in the northern bering sea focusing on stratification which is one factor affecting biological production in arctic subarctic regions in particular we analyzed in situ data obtained onboard the training ship oshoro maru in early summer in 2017 and 2018 we found that stratification in the areas just north of st lawrence island around 64 5 n and west of 168 5 w and south southwest of st lawrence island was significantly weaker in 2018 than in 2017 these results are consistent with the extremely low sea ice extent present in the winter of 2017 2018 which would have resulted in less freshwater being supplied to the surface layers and a warmer and less saline bottom water conversely stratification was as strong in 2018 as in 2017 in the area close to the alaska mainland including the bering strait area suggesting that the alaskan coastal water dominates stratification in this area in early summer moreover we found that the weakly stratified water column in the bering strait area stratified quickly shortly after the occurrence of strong northerly winds likely because of the ekman transport of warm and low salinity alaskan coastal water from the east

late holocene covariability of the southern westerlies and sea surface temperature in northern chilean patagonia abstract the climate of chilean patagonia is strongly influenced by the southern westerlies which control the amount and latitudinal distribution of precipitation in the southern andes in austral summer the southern westerly wind belt swwb is restricted to the high latitudes it expands northward in winter which results in a strong precipitation seasonality between 35 and 45 s here we present a new precipitation seasonality proxy record from quitralco fjord 46 s where relatively small latitudinal shifts of the swwb result in large changes in precipitation seasonality our 1400 yr record is based on sedimentological and geochemical data obtained on a sediment core collected in front of a small river that drains the patagonian andes which makes this site particularly sensitive to changes in river discharge our results indicate fe al and ti al values that are low between 600 and 1200 ce increasing at 1200 1500 ce and high between 1500 and 1950 ce increasing fe al and ti al values reflect a decrease in mean sediment grain size from 30 to 20 m which is interpreted as a decrease in seasonal floods resulting from an equatorward shift of the swwb our results suggest that compared to present day conditions the swwb was located in a more poleward position before 1200 ce it gradually shifted towards the equator in 1200 1500 ce where it remained in a sustained position until 1950 ce this pattern is consistent with most precipitation records from central and southern chile the comparison of our record with published regional sea surface temperature sst reconstructions for the late holocene shows that equatorward shifts of the swwb are systematically coeval with decreasing ssts and vice versa which resembles fluctuations over glacial interglacial timescales we argue that the synchronicity between sst and swwb changes during the last 1400 years represents the response of the swwb to temperature changes in the southern hemisphere

variation in suspended sediment concentration during storm discharges in three small streams in upper osun basin central western nigeria the suspended sediment concentration response of three small streams draining quartzites and quartz schists in south western nigeria to storms of varying magnitude are presented a total of 1468 water samples from 62 storm responses with peak stream discharge values ranging from 80 to 120 l s 2 were analysed and storm and suspended sediment concentration hydrographs and hysteresis loops were used to depict the response patterns the six different types of responses identified include the single and multiple discharge peak rises with sediment lead and lag and also the mixed response patterns both valley slope and channel erosion constituted important sources of suspended sediment however sediment availability exhaustion and flushing effects determined the variation in the different response types

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

hydroclimatic and channel snowpack controls over suspended sediment and grain size transport in a high arctic catchment temporal variability in suspended sediment delivery processes was studied during three seasons in a 7 9 km2 catchment at cape bounty melville island nunavut in the canadian high arctic discharge was controlled primarily by the magnitude of snowmelt with limited inputs from ground ice melt and precipitation years with greater snowpack non linearly increased sediment yield and resulted in seasonal counter clockwise hysteresis while a year with low snowpack resulted in reduced sediment yield and clockwise hysteresis and indicates that sediment was increasingly available after the onset of streamflow in addition to the event scale hysteresis observed during the nival discharge peak diurnal clockwise hysteresis was observed during all three seasons and suggests daily exhaustion of sediment supplies these results indicate that the channel snowpack plays a primary role over sediment accessibility during the nival discharge peak similarly grain size analysis of suspended material in the river showed that the coarsest mean grain size was transported during the early phase of peak nival discharge and indicates that isolated sources of coarse material were being accessed by high velocity flow snowpack is present through the peak nival period and conditions sediment availability by isolating channel sediments from high energy flow these results indicate sediment delivery characteristics in small high arctic catchments reflect complex interactions with channel snowpack and disproportionate responses to flow conditions that differ from glacial and temperate settings copyright 2008 john wiley sons ltd

tracing sediment sources during floods using diffuse reflectance infrared fourier transform spectrometry drifts a case study in a highly erosive mountainous catchment southern french alps summary in mountainous catchments large quantities of sediment are exported within very short periods leading to numerous environmental problems e g reservoir siltation the origin of suspended sediment during two distinct floods was determined by conducting an original fingerprinting method coupling diffuse reflectance infrared fourier transform spectroscopy drifts and a chemometric technique i e partial least squares pls analysis samples of the potential sediment sources were collected in badland areas developed on various substrates i e molasse marly limestones black marls and gypsum in the galabre 20 km 2 catchment located in the french southern alps drifts spectra provided a way to discriminate between the different potential sediment sources furthermore the use of mid infrared spectra allowed the direct quantification of the gypsum proportion in sediment this contribution was systematically null at the catchment outlet because of the rapid dissolution of gypsum in the river a pls model was then constructed to estimate the contribution of the three other potential sources to the sediment flux during the floods this model was developed and validated using a set of 45 experimental samples that were prepared in the laboratory in order to contain various proportions of the three remaining sources by introducing drifts spectra into the pls model we could predict the proportions of those sources in the mixed experimental samples with a confidence interval of ca 10 the model was then applied to the sediment collected during the two selected floods in order to outline their origin black marls provided the highest contribution of sediment during both events but the analysis also revealed a significant contribution of molasse results also showed the remobilisation of sediment originated from molassic substrates that deposited on the riverbed during a preceding event opportunities for improvement and further use of this method as an alternative or rapid complementary sediment fingerprinting technique are finally discussed

strontium isotope evidence on the history of oilfield brines mediterranean coastal plain israel abstract the isotopic composition of sr in oil field brines from the mediterranean coastal plain was determined in 18 drillholes 13 of which are oil producing wells the brines are characterized by salinities ranging from 35 to 93 g l tds sr from 28 to 350 mg l sr ca molar ratios from 0 011 to 0 053 and 87 sr 86 sr ratios from 0 7075 to 0 7090 e a 0 7081 0 0004 2 the brines are classified into two groups 1 a mavqi im group brines with relatively high 87 sr 86 sr ratios 0 7087 and 0 7090 sampled from elastics dolomites and anhydrites of upper miocene age 2 b heletz group brines with relatively low 87 sr 86 sr ratios 0 7075 to 0 7081 sampled from sandstones and dolomites of lower cretaceous age equations were derived to show the relations between 87 sr 86 sr ratio of the brines and the processes through which they evolved dolomitization and dissolution reprecipitation it is suggested that both groups of brines originated from mediterranean evaporated seawater during the messinian desiccation the strontium isotope composition of the seawater is reflected in that of both groups of brines the mavqi im group containing the original 87 sr 86 sr ratio 0 7088 the heletz group evolved later on through exchange reactions of those primary brines with a carbonate sequence of cretaceous age and consequently new 87 sr 86 sr ratios 0 7078 could have been developed the effect of the dissolution reprecipitation reactions on the carbonate rocks is estimated to be very slight only around 1 by weight

discharge and suspended sediment patterns in a small mountainous watershed with widely distributed rock fragments summary understanding and quantifying sediment loads is important in watersheds with highly erodible materials which will eventually cause environmental and ecological problems within this context suspended sediment ss transport and its temporal dynamics were studied in a small mountainous watershed with sloping lands containing rock fragments in subtropical china soils containing rock fragments with many macro pores have a high permeability rate over a 7 year period the mean runoff coefficient of this watershed was 0 65 overall 30 flood events were monitored and accounted for 95 5 27 3 17 1 of the total ss load precipitation and total discharge respectively over a 5 year period the presence of rock fragments in soils can affect soil loss when comparing the soil loss in the studied watershed with that of other watersheds under similar climatic conditions rock fragments negatively affect soil loss however an extreme event occurred on 14 august 1990 and the sediment load exhibited a phenomenon called small deposits towards lump withdrawal which resulted in a soil loss of 20 499 t 4 6 times the mean yearly soil loss this event exhausted most of the ss s stored by the rock fragments on the slope and channel following this event the mean ss concentration ssc of the 11 events was 1 05 kg m 3 and the mean ssc of the 18 previous events was 1 75 kg m 3 twelve variables were separated using the classical hydrograph separation method partial least squares regression plsr was used to determine the highly co related variables of the discharge the results indicated that plsr could explain runoff well the relationship between discharge and ssc was highly scattered during 24 flood events three types of hysteresis loops were observed clockwise 17 events figure eight 3 events and complex 4 events

hydrogeomorphic linkages of sediment transport in headwater streams maybeso experimental forest southeast alaska hydrogemorphic linkages related to sediment transport in headwater streams following basin wide clear cut logging on prince of wales island southeast alaska were investigated landslides and debris flows transported sediment and woody debris in headwater tributaries in 1961 1979 and 1993 widespread landsliding in 1961 and 1993 was triggered by rainstorms with recurrence intervals 24 h precipitation of 7 0 years and 4 2 years respectively occurrence distribution and downstream effects of these mass movements were controlled by landform characteristics such as channel gradient and valley configuration landslides and channelized debris flows created exposed bedrock reaches log jams fans and abandoned channels the terminus of the deposits did not enter main channels because debris flows spread and thinned on the unconfined bottom of the u shaped glaciated valley chronic sediment input to channels included surface erosion of exposed till rain splash sheet erosion and freeze thaw action and bank failures bedload sediment transport in a channel impacted by 1993 landslides and debris flows was two to ten times greater and relatively finer compared with bedload transport in a young alder riparian channel that had last experienced a landslide and debris flow in 1961 sediment transport and storage were influenced by regeneration of riparian vegetation storage behind recruited woody debris development of a streambed armour layer and the decoupling of hillslopes and channels both spatial and temporal variations of sediment movement and riparian condition are important factors in understanding material transport within headwaters and through channel networks copyright 2004 john wiley sons ltd

strontium in rainwater from israel sources isotopes and chemistry abstract eighteen rain samples from israel have been analyzed for their chemical composition and87sr 86sr ratios the sr isotopic ratios lie in the range 0 7078 and 0 7092 and the sr concentrations vary from 1 10 4 to 9 10 4 meq sr l soluble salts in rainwater are inherited from three major natural sources seaspray recent marine minerals and mineral dust eroded from rock outcrops and soil a mixing model is formulated to apply the chemical composition of rain cl and sr2 and its isotopic87sr 86sr ratio for the identification and estimation of the sr sources all the samples fall within the mixing space predicted by the model for the three end members mentioned above the data indicate that the most important non seaspray source contributing dissolved salts to the rains in israel comprises a mixture of senonian to eocene chalk and its weathering products and recent marine minerals from local and imported sources most of the samples 67 contain 50 or more non seaspray sr i e sr dissolved from dust or recent marine minerals whereas 56 of the samples display87sr 86sr ratios lower than 0 7090 the rest represent mixtures of seaspray and recent marine minerals

the combined use of 87sr 86sr and carbon and water isotopes to study the hydrochemical interaction between groundwater and lakewater in mantled karst abstract the hydrochemical interaction between groundwater and lakewater influences the composition of water that percolates downward from the surficial aquifer system through the underlying intermediate confining unit and recharges the upper floridan aquifer along highlands in florida the 87sr 86sr ratio along with the stable isotopes d 18o and 13c were used as tracers to study the interaction between groundwater lakewater and aquifer minerals near lake barco a seepage lake in the mantled karst terrane of northern florida upgradient from the lake the 87sr 86sr ratio of groundwater decreases with depth mean values of 0 71004 0 70890 and 0 70852 for water from the surficial aquifer system intermediate confining unit and upper floridan aquifer respectively resulting from the interaction of dilute oxygenated recharge water with aquifer minerals that are less radiogenic with depth the concentrations of sr2 generally increase with depth and higher concentrations of sr2 in water from the upper floridan aquifer 20 35 g l relative to water from the surficial aquifer system and the intermediate confining unit result from the dissolution of sr bearing calcite and dolomite in the eocene limestone dissolution of calcite 13c 1 6permil is also indicated by an enriched 13cdic 8 8 to 11 4 in water from the upper floridan aquifer relative to the overlying hydrogeologic units 13cdic groundwater downgradient from lake barco was enriched in18o and d relative to groundwater upgradient from the lake indicating mixing of lakewater leakage and groundwater downgradient from the lake the 87sr 86sr ratio of groundwater and aquifer material become less radiogenic and the sr2 concentrations generally increase with depth however sr2 concentrations are substantially less than in upgradient groundwaters at similar depths the lower sr2 concentrations result from the influence of anoxic lakewater leakage on the mobility of sr2 from clays based on results from mass balance modeling it is probable that cation exchange plays the dominant role in controlling the 87sr 86sr ratio of groundwater both upgradient and downgradient from lake barco even though groundwater from the three distinct hydrogeologic units displays considerable variability in sr concentration and isotopic composition the dominant processes associated with the mixing of lakewater leakage with groundwater as well as the effects of mineral water interaction can be ascertained by integrating the use of stable and radiogenic isotopic measurements of groundwater lakewater and aquifer minerals

suspended sediment load during floods in a small stream of the dolomites northeastern italy abstract suspended sediment load was analyzed in a small high gradient stream of the eastern italian alps which was instrumented to measure discharge and sediment transport the ratio of suspended to total sediment yield and the relations between sediment concentration and water discharge were analyzed for seven floods which occurred from 1991 to 1996 in summer and autumn from june to october different patterns of hysteresis in the relation between suspended sediment and discharge were related to types and locations of active sediment sources the within storm variation of particle size of suspended sediment during a major flood indicates a coarsening of transported material for increasing discharge an analysis of grain size has shown that erosion areas on hillslopes were the main sources of suspended load

relationships between suspended sediment concentrations and discharge in two small research basins in a mountainous mediterranean area vallcebre eastern pyrenees abstract the relationships between suspended sediment concentrations and discharge were studied at the can vila 0 56 km2 and ca l isard 1 32 km2 sub basins of the vallcebre research area eastern pyrenees during a period of 5 years that included 67 events of diverse magnitude abandoned agricultural fields and forests are the main land use in the can vila basin whereas the ca l isard basin is mainly forested though there are also some heavily eroded landscapes badlands the most frequent events were of a single discharge peak although double and multiple peaked events were also recorded clockwise positive hysteretic loops occurred in both catchments mainly during the wet seasons when precipitation was of moderate intensity average of 18 mm h 1 and baseflow before the event was rather high average for ca l isard 8 1 l s 1 km 2 and for can vila 11 76 l s 1 km 2 the bulk of stream discharge came from saturated areas whereas sediments came mainly from the stream channels counter clockwise negative hysteretic loops were much more frequent in the ca l isard basin mainly in summer when rainfall intensity was high average of 32 5 mm h 1 and baseflow was low average for ca l isard 0 94 l s 1 km 2 and for can vila 0 73 l s 1 km 2 most of the water and sediment came from the badlands eight shaped loops occurred in transition periods mainly in the ca l isard basin

suspended sediment transport response to upstream wash load supply in the sand bed reach of the upper yellow river china summary wash load is a major component of suspended sediment transport in the sand bed reach of the upper yellow river china this wash load sediment originates from the loess region with the high runoff mainly originating from the rock mountains of its upstream basin these characteristics result in a mismatch between water and sediment sources and a low probability of high runoffs meeting high suspended sediment concentration ssc flows as a result higher runoff with lower ssc levels hr ls and lower runoff with higher ssc values hs occur whose sscs do not follow the typical power form for flow discharges c i q where c i and q are ssc and flow discharge respectively here we modify the traditional power form with an upstream wash load supply function c 1 to satisfy the relation between the water and wash load sediment concentrations in water sediment mismatched cases c i q c 1 where c is an input flow s ssc using the daily flow discharges and sscs of nine typical hr ls flows and 18 hs flows in our study reach from 1960 to 2012 we find that changes in response to input flow conditions and downstream transport distances when the downstream transport distance is between 360 and 663 5 km varies between 0 3 and 0 6 in a hs input flow condition while in the hr ls input flow case tends to be greater than 0 6 between 0 74 and 0 65 the entrainment rate of an hr ls flow and the deposition rate of an hs flow appear to be asymmetrically balanced establishing a primary mechanism for channel aggradation and upward fining of floodplains in our study reach

currents and transport on the eastern bering sea shelf an integration of over 20 years of data abstract more than 20 years of data from moorings satellite tracked drifters and hydrographic surveys are integrated to provide a comprehensive view of currents and transport on the eastern bering sea shelf the major sources of water onto the eastern bering sea shelf are north pacific water flowing through unimak pass and bering slope water flowing onto the shelf usually via the canyons that intersect the shelf break absolute geostrophic transport through unimak pass varies from an average of 0 25 106 m3 s 1 sv in the warm months to 0 43 sv in the cold months flow along the 50 m isobath is weak with a transport of 13 months and from amukta pass to bering strait via the bering slope current is 8 months consequently the source of most of the heat transported into the arctic through bering strait is a result of air sea interactions local to the northern bering sea analysis of the currents and water properties on the southern shelf indicates that 50 of the shelf water is exchanged with slope water during october january each year this exchange elevates the october mid shelf average nitrate level from 6 m to 14 16 m by the end of january

drivers of erosion and suspended sediment transport in three headwater catchments of the mexican central highlands quantifying suspended sediment exports from catchments and understanding suspended sediment dynamics within river networks is important especially in areas draining erodible material that contributes to the siltation of downstream reservoirs and to the degradation of water quality a one year continuous monitoring study of water and sediment fluxes was conducted in three upland subcatchments 3 0 9 3 and 12 0 km2 located within the cointzio basin in the central volcanic highlands of mexico michoacan state two subcatchments generated high sediment exports i e huertitas 900 1500 t km 2 y 1 and potrerillos 600 800 t km 2 y 1 whereas the third subcatchment was characterized by a much lower sediment yield i e la cortina 30 t km 2 y 1 such disparities in subcatchment behaviours were associated with the presence of severely gullied areas in huertitas and potrerillos rather than with rainfall erosivity indices an adapted classification of hysteretic patterns between suspended sediment concentration ssc and discharge was proposed because 42 of flood events contributing to 70 of sediment export were not discriminated by the classical clockwise anticlockwise typology this new classification allowed the identification of relationships in the hydrosedimentary responses of successive floods a stream transport capacity limit was also detected during hydrograph recession phases overall hydrosedimentary processes proved to be seasonally dependent sediment export was repeatedly limited by the stream transport capacity during the first part of the rainy season whereas a channel minimum erosivity threshold was frequently reached at the end of the season

bedload transport in the instrumented catchment of the rio cordon part ii analysis of the bedload rate abstract sediment transport is monitored by a specially designed instrumentation installed on a steep mountain streams the rio cordon the variability of bedload rate and yield reflects the variability in flow discharge bedload and flow data for ordinary low peak flow floods and exceptional sediment transport events are used to test the range of application of the bedload equations proposed for high gradient streams such equations overestimate bedload rate for ordinary events while their reliability increases when used to predict high bedload transport rates like those recorded during the exceptional flood that affected rio cordon on september 14 1994 the best agreement between computed and measured values of cumulated bedload volumes is found by using the bagnold bagnold r a 1956 the flow of cohesionless grains in fluids philos trans r soc london 249a 235 297 smart and jaeggi smart j m jaeggi m n r 1983 sediment transport on steep slopes mitteil 64 versuchsanstalt fur wasserbau hydrologie und glaziologie eth zurich switzerland 191 pp and rickenmann rickenmann d 1991 hyperconcentrated flow and sediment transport at steep slopes j hydraul eng zurig 117 11 1419 1439 formulas the schoklitsch equation schoklitsch a 1962 handbuch des wasserbaues 3rd edn springer wien also provides good estimations for instantaneous bedload rates at high sediment transport intensity and unlimited sediment supply conditions the formal type of the last equation is still valid and can be calibrated for low intensity bedload rates

spatial scale dependence of sediment dynamics in a gullied rolling loess region on the loess plateau in china sediment dynamics is still imperfectly understood especially at spatial scale in the highly erodible region of the loess plateau and few studies have been heretofore conducted using 5 year continuous water and sediment records three plots and three basins in the gullied rolling loess region were selected and sediment dynamics at spatial scale was studied results showed that the floods where the peak discharge qp did not come earlier than the sediment peak were predominant in slope zones occupying 90 and 70 of the total for the mao slope and for the entire slope respectively however in basins most of the sediment peaks cp lagged behind qp implying that slope zone was the main origin of sediment more than 50 of the events presented clockwise hysteresis loops in the mao slope area while almost all the events had anticlockwise hysteresis loops in basins this can be attributed to less occurring frequency of hyperconcentrated flow as well as its instability in slope zones compared to those in the basins within these contexts gravitational erosion made the highest sediment concentration c in tuanshangou basin and median developing status of c discharge c q relationships in the entire slope area this study provides insights into the protection of slope surface and disruption of the development of hyperconcentrated flow to reduce soil loss

effect of seasonal snow cover on suspended sediment runoff in a mountainous catchment summary the effect of snow cover and snowmelt on suspended sediment ss runoff at a mountainous catchment in the temperate zone was investigated the observation was carried out from march 1999 to may 2002 3 years at an experimental catchment with the area of 0 347 km 2 ranging from 280 m to 618 m above mean sea level with average stream gradient of 1 4 it was concluded that the snow accumulation and ablation process in the catchment had a significant impact on ss runoff characteristics especially during the snow melting period it was estimated that more than 60 of the annual ss load flowed out during the snow melting period because of the enhanced water discharge the daily average ss flux during the snow melting period was calculated to be 2 54 g s 1 km 2 corresponding to a 6 7 times greater ss flux than that during other periods the c q relation analysis in each runoff event revealed a dynamic change in the ss runoff mechanism during the snow melting period strong clockwise hysteresis in c q relation in the early stage of the snow melting period may be explained by consumption of the bed load by the first flush followed by quick depletion of the material on the stream bed due to suppression of further ss supply by thick snow cover counterclockwise hysteresis in c q relation was observed only in the late stage of the snow melting period ss production at steep slopes beside the stream by avalanches and surface soil slides induced by an abundance of meltwater was considered to be one of the main causes of the counterclockwise loops it would be hypothesized that exposure of other steep slopes or bluffs in the catchment apart from the stream and stream bank failure by repeating surges of the stream water stage could also be other possible ss sources causing counterclockwise hysteresis in the late snow melting period

temporal variability of suspended sediment sources in an alpine catchment combining river rainfall monitoring and sediment fingerprinting influence of the rainfall regime on erosion and transfer of suspended sediment in a 905 km 2 mountainous catchment of the southern french alps was investigated by combining sediment monitoring rainfall data and sediment fingerprinting based on geochemistry and radionuclide concentrations suspended sediment yields were monitored between october 2007 and december 2009 in four subcatchments 22 713 km 2 automatic sediment sampling was triggered during floods to trace the sediment origin in the catchment sediment exports at the river catchment outlet 330 pm 100 t km 2 yr 1 were mainly driven 80 by widespread rainfall events long duration low intensities in contrast heavy local and short duration storms generated high peak discharges and suspended sediment concentrations in small upstream torrents however these upstream floods had generally not the capacity to transfer the sediment down to the catchment outlet and the bulk of this fine sediment deposited along downstream sections of the river this study also confirmed the important contribution of black marls up to 70 to sediment transported in rivers although this substrate only occupies c 10 of the total catchment surface sediment exports generated by local convective storms varied significantly at both intra and inter flood scales because of spatial heterogeneity of rainfall however black marls marly limestones contribution remained systematically high in contrast widespread flood events that generate the bulk of annual sediment supply at the outlet were characterized by a more stable lithologic composition and by a larger contribution of limestones marls quaternary deposits and conglomerates which corroborates the results of a previous sediment fingerprinting study conducted on riverbed sediment

comparison of warm and cold years on the southeastern bering sea shelf and some implications for the ecosystem the southeastern middle shelf of the bering sea has exhibited extreme variability in sea ice extent temperature and the distribution and abundance of species at multiple trophic levels over the past four decades from 1972 2000 there was high interannual variability of areal extent of sea ice during spring march april in 2000 this shifted to a 5 year 2001 2005 period of low ice extent during spring which transitioned to a 4 year 2007 2010 period of extensive sea ice high low areal extent of sea ice in spring was associated with cold warm water column temperatures for the following 6 7 months the ocean currents also differed between warm and cold years during cold years the monthly mean currents over the shelf were largely westward while in warm years the direction of currents was more variable with northward flow during december february and relatively weak flow during the remainder of the year the types and abundance of zooplankton differed sharply between warm and cold years this was especially true during the prolonged warm period 2001 2005 and cold period 2007 2010 and was less evident during the years of high interannual variability during the warm period there was a lack of large copepods and euphausiids over the shelf however their populations rebounded during cold period small crustacean zooplankton taxa did not appear to vary between and warm and cold years for both walleye pollock and pacific cod year class strength recruitment was low during the prolonged warm period but improved during the following cold period year class strength did not appear to vary as a function of warm and cold years during the period of high year to year variability also recruitment of arrowtooth flounder a predator of pollock and cod did not appear influenced by the warm or cold years finally the distribution and relative abundance of fin whales appeared to differ in warm and cold years with fewer whales on the southeastern middle shelf during warm years

step pool evolution in the rio cordon northeastern italy the principle that formative events punctuated by periods of evolution recovery or temporary periods of steady state conditions control the development of the step pool morphology has been applied to the evolution of the rio cordon stream bed the rio cordon is a small catchment 5 km2 within the dolomites wherein hydraulic parameters of floods and the coarse bedload are recorded detailed field surveys of the step pool structures carried out before and after the september 1994 and october 1998 floods have served to illustrate the control on step pool changes by these floods floods were grouped into two categories the first includes ordinary events which are characterized by peak discharges with a return time of one to five years 1 8 5 15 m3 s 1 and by an hourly bedload rate not exceeding 20 m3 h 1 the second refers to exceptional events with a return time of 30 50 years a flood of this latter type occurred on 14 september 1994 with a peak discharge of 10 4 m3 s 1 and average hourly bedload rate of 324 m3 h 1 step pool features were characterized primarily by a steepness parameter c h ls s the evolution of the steepness parameter was measured in the field from 1992 to 1998 the results indicate that maximum resistance conditions are gradually reached at the end of a series of ordinary flood events during this period bed armouring dominate the sediment transport response however following an extraordinary flood and unlimited sediment supply conditions the steepness factor can suddenly decrease as a result of sediment trapped in the pools and a lengthening of step spacing the analogy of step spacing with antidune wavelength and the main destruction and transformation mechanism of the steps are also discussed copyright 2001 john wiley sons ltd

shifts in the physical environment in the pacific arctic and implications for ecological timing and conditions abstract the northern bering sea and chukchi sea represent the gateway from the pacific to the arctic this contiguous marine system encompasses one of the largest continental shelves in the world and serves as the sole point of connection between the north pacific and arctic ocean this region has unique attributes and complex dynamics driven by the convergence of distinct water masses dynamic currents advection between pacific and arctic systems and important latitudinal gradients relevant to stratification and water mass structure water temperature and seasonal ice cover many processes and interactions in the region appear to be changing with important implications for both hydrography and ecology our analyses access remote and local data sources in us and russian waters to characterize oceanographic conditions and analyze the implications of dramatic shifts in recent years previously this region appeared resistant to trends apparent elsewhere in the greater arctic now the pacific arctic also appears to be in rapid transition the conditions observed in 2017 2019 are unprecedented we note important shifts in the phenology and magnitude of physical variables including sea ice extent concentration and duration as well as extreme reduction in the extent and intensity of the related bering sea cold pool we also note distinct regional dynamics in sea surface temperature in the bering chukchi system distinguishing western eastern and northern areas of the bering sea specifically our analyses distinguish the northern bering sea as an important transition zone between the pacific and arctic with higher frequency variability in sea surface temperature anomalies our results suggest that the strength and position of the aleutian low may be linked to warm and cold phases in the bering sea and has an important role in large scale circulation while cold winds out of the north are necessary to form ice in the northern bering sea strong winds may be associated with weak sea ice as wind action may break ice and enhance vertical mixing counteracting enhanced sea ice production from the advection of cold air research in this important region is complicated by international borders but may be enhanced through international collaboration this analysis represents an attempt to integrate data across russian and us waters to more fully represent system wide processes to contrast regional trends and to better understand physical interactions

seasonal patterns of suspended sediment transport in an abandoned farmland catchment in the central spanish pyrenees the suspended sediment response of a small catchment subjected to farmland abandonment and subsequent plant recolonization was studied in relation to its hydrological functioning the analysis of data over a seven year period demonstrated that suspended sediment yield was greatly influenced by the occurrence of intense low frequency events greater amounts of suspended sediment were exported during spring when the catchment was hydrologically more active rainfall intensity and baseflow at the start of a flood event had a strong influence on the sediment response suggesting that several hydrological processes were active within the catchment ssc suspended sediment concentration q hysteretic loop analysis at the event scale aided understanding of the sedimentological and hydrological behaviour of the catchment during the study period the ssc q loops showed a high degree of seasonality and two main patterns strongly related to catchment wetness were distinguished when the catchment was dry mainly during summer and the beginning of autumn the predominant process was infiltration excess runoff over sparsely vegetated areas close to the main channel under these conditions floods exhibited a counter clockwise hysteretic loop and were characterized by a small streamflow response short duration and high ssc under wet conditions mainly during winter and spring saturation excess runoff was increasingly dominant over vegetated areas under these conditions floods exhibited a clockwise hysteretic loop and were characterized by a larger streamflow response longer duration and higher suspended sediment yield the lower ssc during the falling stage of the hydrograph is likely to be due to dilution effects related to the contribution of clean water resulting from enlargement of the saturated areas together with an increase in the baseflow discharge copyright 2009 john wiley sons ltd

estimation of sea ice production in the bering sea from amsr e and amsr2 data with special emphasis on the anadyr polynya

temporal variation of suspended sediment transport in the koga catchment north western ethiopia and environmental implications event sediment transport and yield were studied for 45 events in the upstream part of the 260 km2 agricultural koga catchment that drains to an irrigation reservoir discharge and turbidity data were collected over a period of more than a year accompanied by grab sampling turbidity was very well correlated with the sediment concentrations from the samples r 0 99 which allowed us to estimate the temporal patterns of sediment concentrations within events the hysteresis patterns between discharge and sediment concentrations were analysed to provide insight into the different sediment sources anticlockwise patterns are the dominant hysteresis patterns in the area suggesting smaller contributions of suspended sediment from the river channels than from the hillslopes and agricultural areas complicated types of hysteresis patterns were mostly observed for long events with multiple peaks for a given discharge sediment yields in august and september when the catchment was almost completely covered with vegetation were much smaller than during the rest of the rainy season the hysteresis patterns and timing suggest that the sediment availability from the agricultural areas and hillslopes affects sediment yields more strongly than does peak discharge two distinct types of sediment rating curves were observed for the season when the agricultural land was covered with vegetation and when it was not indicating the dominating contribution of land use cover to sediment yields in the catchment the rate of suspended sediment transport in the area was estimated as 25 6 t year 1 ha 1 copyright 2013 john wiley sons ltd

controls on δ 34 s and δ 18 o of dissolved sulfate in aquifers of the murray basin australia and their use as indicators of flow processes the usefulness of stable isotopes of dissolved so4 34s and 18o to study recharge processes and to identify areas of significant inter aquifer mixing was evaluated in a large semi arid groundwater basin in south eastern australia the murray basin the distinct isotopic signatures in the oxidizing unconfined murray group aquifer and the deeper reducing renmark group confined aquifer may be more sensitive than conventional chemical tracers in establishing aquifer connections 34s values in the unconfined murray group aquifer in the south and central part of the study area decrease along the hydraulic gradient from 20 8 to 0 3 the concomitant increasing so4 cl ratios as well as relatively low 18oso4 values suggest that vertical input of biogenically derived so4 via diffuse recharge is the predominant source of dissolved so4 to the aquifer further along the hydraulic gradient towards the discharge area near the river murray 34s values in the unconfined murray group aquifer increase and so4 cl ratios decrease due to upward leakage of waters from the confined renmark group aquifer which has a distinctly low so4 cl and high 34s 14 9 56 4 relatively positive 34s and 18oso4 values and low so4 cl in the renmark group aquifer is typical of so4 removal by bacterial reduction the s isotope fractionation between so4 and hs of 24 estimated for the confined aquifer is similar to the experimentally determined chemical fractionation factor for the reduction process but much lower than the equilibrium fractionation 70 even though the confined groundwater residence time is 300 ka years mapping the spatial distribution of 34s and so4 cl of the unconfined murray group aquifer provides an indicative tool for identifying the approximate extent of mixing however the poorly defined end member isotopic signatures precludes quantitative estimates of mixing fractions

defining conditions for bulking and debulking in lahars through measurements at semeru volcano east java we define the conditions under which bulking entrainment of sediment and pore water and debulking dilution and sedimentation occur in rain triggered volcanic floods lahars two observation sites were installed 510 m apart along the curah lengkong river 11 5 km southeast of semeru s summit this 30 m wide box valley with a gravel and lava base represents a real world flume analogy pore pressure sensors provided stage measurements a broad band seismograph gave insight into sediment content and frictional collisional behavior video cameras were used to measure surface velocities and direct bucket samples were taken eight rainfall induced lahars were recorded lasting 1 3 h with heights of 0 5 2 m peak velocities of 3 7 m s and discharges of 25 250 m3 s flows ranged from typical 40 wt sediment to coarse and dense hyperconcentrated flows 50 60 wt sediment multiple distinct flow packets occurred within the complex lahars and were used to determine internal changes between sites from the multiparameter data set at each site volumetric bulking and wave shortening due to portions of the lahar accelerating toward the flow front are identified initial debulking of lahars between sites may reflect drainage into the dry substrate estimates of discharge and volume at each site lead to the quantification of bulking and debulking by these actively flowing lahars along the channel reach from this we observe that bulking can be localized to certain parts of lahars resulting in intraevent increases in peak discharge that are greater than what would occur if bulking was evenly distributed throughout the flow such data are essential for the development of numerical descriptions and hazard models for mass flows

anti clockwise hysteresis in suspended sediment concentration during individual storms holbeck catchment yorkshire england abstract analysis of the flow sediment hysteresis shape may assist in determining the sediment source area in a small basin a clockwise hysteresis occurs when sediment is derived from the bed and banks of the channel or areas adjacent to the channel whereas an anti clockwise hysteresis occurs when the upper part of the slopes is the sediment source area

from soil aggregates to riverine flocs a laboratory experiment assessing the respective effects of soil type and flow shear stress on particles characteristics particles eroded from hillslopes and exported to rivers are recognized to be composite particles of high internal complexity their architecture and composition are known to influence their transport behaviour within the water column relative to discrete particles to date hillslope erosion studies consider aggregates to be stable once they are detached from the soil matrix however lowland rivers and estuaries studies often suggest that particle structure and dynamics are controlled by flocculation within the water column in order to improve the understanding of particle dynamics along the continuum from hillslopes to the lowland river environment soil particle behaviour was tested under controlled laboratory conditions seven flume erosion and deposition experiments designed to simulate a natural erosive event and five shear cell experiments were performed using three contrasting materials two of them were poorly developed and as such can not be considered as soils whilst the third one was a calcareous brown soil these experiments revealed that soil aggregates were prone to disaggregation within the water column and that flocculation may affect their size distribution during transport large differences in effective particle size were found between soil types during the rising limb of the bed shear stress sequence indeed at the maximum applied bed shear stress the aggregated particles median diameter was found to be three times larger for the well developed soil than for the two others differences were smaller in the falling limb suggesting that soil aggregates underwent structural changes however characterization of particles strength parameters showed that these changes did not fully turn soil aggregates into flocs but rather into hybrid soil aggregate floc particles copyright 2013 john wiley sons ltd

erosion rates on different timescales derived from cosmogenic 10 be and river loads implications for landscape evolution in the rhenish massif germany we determined erosion rates on timescales of 101 104 years for two catchments in the northeastern rhenish massif in order to unravel the quaternary landscape evolution in a variscan mountain range typical of central europe spatially averaged erosion rates derived from in situ produced 10be concentrations in stream sediment of the aabach and mohne watersheds range from 47 6 to 65 14 mm ka and integrate over the last 9 13 ka these erosion rates are similar to local rates of river incision and rock uplift in the quaternary and to average denudation rates since the mesozoic derived from fission track data this suggests that rock uplift is balanced by denudation i e the landscape is in a steady state short term erosion rates were derived from suspended and dissolved river loads subsequent to 1 correcting for atmospheric and anthropogenic inputs 2 establishing calibration curves that relate the amount of suspended load to discharge and 3 estimating the amount of bedload the resulting solid mass fluxes suspended and bedload agree with those derived from the sediment volume trapped in three reservoirs however resulting geogenic short term erosion rates range from 9 to 25 mm ka and are only about one third of the rates derived from 10be model simulations in combination with published sediment yield data suggest that this discrepancy is caused by at least three factors 1 phases with higher precipitation and or lower evapotranspiration 2 rare flood events not captured in the short term records and 3 prolonged periods of climatic deterioration with increased erosion and sediment transport on hillslopes

major and trace element partition and fluxes in the rhone river dissolved and particulate major and trace element concentrations and suspended particulate contents were determined during three years on the lower rhone river france from subsurface water samples collected about twice a month and more regularly during flood events dissolved elements can be grouped into two sets showing similar relationship between concentration and water discharge related to dilution process and to local and diffuse inputs of dissolved elements in the rhone basin the variation of no 3 na and cl na ratios and the absence of correlation between no 3 and the enrichment in cl show that rhone river is not highly affected by fertilizer applications compared to other large french rivers seine and loire rivers in particulate phase ca sr u pb bi cd sb and zn displayed high enrichment factors over shale composition lead bi cd and zn enrichment could be related to the anthropogenic inputs while ca sr and u enrichment was explained by lithological composition of the rhone basin dominated by carbonate rocks distribution coefficients of elements kd are relatively stable with however some variations with increasing spm concentrations these variations were attributed to local and diffuse inputs and to a higher contribution of carbonate bedrock in the rhone basin during flood events dissolved and particulate major and trace elements and suspended particulate matter spm fluxes of the rhone river to the mediterranean sea were estimated for the period 2001 2003 spm and particulate element fluxes were highly dependent on flood events 69 to 91 of the annual fluxes were exported in less than 12 of the time rhone river inputs were the principal source of particulate elements except for cd and zn in the northwestern mediterranean sea while the major part of dissolved elements were carried out by atmospheric inputs except dissolved as for which rhone river contributed to more than 50 of the input to the marine system

river loads and modern denudation of the alps a review this paper presents the first comprehensive analysis of sediment and dissolved load across an entire mountain range we investigate patterns and rates of modern denudation of the european alps based on a compilation of data about river loads and reservoir sedimentation from 202 drainage basins that are between ca 1 to 10 000 km2 large the study basins cover about 50 of the total area of the alps modern glaciated basins have the highest sediment yields of up to 7000 t km 2 a 1 which are on average 5 to 10 times higher than in non glaciated basins likewise sediment yield and glacial cover are positively correlated instead relief is a relatively weak predictor of sediment yield the strong glacial impact in the correlations is due to glacier recession since the 19th century as well as due to glacial conditioning during repeated quaternary glaciations which have produced the strong transient state of the alpine landscape we suggest that this is the major cause for ca 3 fold enhanced denudation of the western compared to the eastern alps chemical denudation rates are highest in the external alps dominated by carbonate sedimentary rocks where they make up about one third of total denudation the high rates cannot be explained without anhydrite dissolution we estimated that only 45 of the sediments mobilized in headwaters are exported out off the alps most sediments being trapped in artificial reservoirs the total amount of sediment annually trapped within the alps equates to 43 mt when corrected for sediment storage we obtain an area weighted mean total denudation rate for the alps of about 0 32 mm a 1 the pre dam rate might be as high as 0 42 mm a 1 in total ca 35 plus 23 mt of mass are exported each year out of the alps as solids and solutes respectively these rates are not enough to out pace modern rock uplift nevertheless pattern of sediment yield across the alps coincides roughly with the intensity of glacial conditioning and modern rock uplift supporting the hypothesis of an erosion driven uplift of the alps

hydrologic controls on wash load sediment concentrations within a low ordered ephemeral watershed summary this study explores the influence of rainfall and runoff production on wash load sediment transport in a low order ephemeral watershed in southeast arizona wash load concentrations measured at the watershed outlet generally decreased throughout a runoff event and were better correlated with the rainfall intensity and the rainfall volume that fell within the 6 min the watershed s time of concentration before the sediment concentration was measured than with the runoff discharge the difference between the rainfall volume per unit time and the runoff discharge was primarily due to infiltration and transmission losses processes that reduce runoff volume but do not appear to affect the wash load concentration within the runoff infiltration and transmission losses are significant in this watershed and vary considerably in space and time but are generally described by an inverse relationship between the runoff coefficient and drainage area runoff coefficients vary amongst runoff events and are correlated to the peak rainfall intensity during each event results indicate that wash load concentrations are set by the sediment entrainment processes occurring on the hillslopes e g rainsplash hortonian overland flow and do not greatly fluctuate as water is routed through the watershed this suggests that wash load concentration may be better predicted by metrics of rainfall than flow discharge in certain environments using rainfall as a predictor of wash load could be useful for estimating sediment fluxes in semiarid regions where flow discharge is often difficult to monitor and sediment transport concentrations can be high i e 10 000 mg l 1

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

interpreting sediment delivery processes using suspended sediment discharge hysteresis patterns from nested upland catchments south eastern australia in this study suspended sediment concentration ssc and discharge q hysteresis patterns recorded at the outlets of two nested upland catchments in south eastern australia were examined detailed monitoring of sediment flux was undertaken in a 1 64 km2 sub catchment located within a 53 5 km2 catchment for which sediment yield was measured and the extent of incised channels mapped the analysis of ssc q hysteresis patterns was supplemented by these additional datasets to contribute to the explanation of observed patterns clockwise ssc q hysteresis loops with the suspended sediment peak leading the discharge peak were recorded most frequently at both sites this was attributed to initial rapid delivery of sediment from channel banks the dominant sediment source in the sub catchment and probably also for the catchment in conjunction with remobilization of in channel fine sediment deposits sediment exhaustion effects were considered to enhance clockwise hysteresis with reduced ssc on the falling limb of event hydrographs pronounced exhaustion effects were observed on some multi rise events with subsequent flow peaks associated with much reduced sediment peaks to compare ssc q hysteresis patterns between the two catchments a dimensionless similarity function sf was derived to differentiate paired event hysteresis patterns according to the extent of pattern similarity this analysis coupled with the other datasets provided insight into the function of erosion and sediment delivery processes across the spatial scales examined and indicated the dependency of between scale suspended sediment transfer on defined flow event scenarios quantitative measures of event ssc q hysteresis pattern similarity may provide a mechanism for linking the timing and magnitude of process response across spatial scales this may offer useful insights into the between scale linkage of dominant processes and the extent of downstream suspended sediment delivery copyright 2009 john wiley sons ltd

sea ice and water column structure on the eastern bering sea shelf abstract seasonal sea ice is a defining characteristic of the eastern bering sea shelf and plays a critical role in determining the vertical structure of temperature and salinity over this shelf ice movement relative to local winds ice composition and the impact of both arrival and retreat of ice on the water column at four mooring sites over the middle shelf are examined ice forms primarily in coastal regions and is advected over the southern and outer shelves ice drift from satellite data for two representative years 2003 and 2007 was 2 of local ncep wind speed and oriented 44 to the right of the winds r 2 0 25 measurements from 30 ice cores collected in 2006 2009 gave an average salinity of 5 62 0 88 and an average nitrate concentration of 0 99 0 83 m time series data collected at the biophysical moorings in the bering sea 1995 2012 were used to explore the evolution of the water column under ice at the northern mooring m8 the water column had mixed and cooled to 1 c prior to the arrival of ice little melt occurred after ice arrival at the other three moorings the ocean temperature was 2 4 c when ice arrived resulting in extensive melt melting ice freshened and cooled the upper water column resulting in stratification which persisted for 10 25 days wind induced water column mixing occurred more slowly under the ice than in ice free waters an estimated 1 4 m of ice melted with the first arrival of ice at the three southern moorings where the latent heat of fusion accounted for approximately half the observed cooling during ice retreat there appeared to be little ice melt around the southern two moorings but an estimated 0 8 m at m5 and m8 the extent of ice melt sets up the water column for the following summer

high flow events and sediment transport in small streams in the tertiary basin area in piedmont northwest italy rainfall peak discharges and suspended sediment transport were surveyed for 280 events in three small 0 8 to 10 km2 catchments in a hilly area derived from neogene marls silts and sands under similar hydrological input conditions stream flow behaviour and sediment delivery differed considerably from one catchment to another depending on topography lithology land use and especially sediment availability analytical treatment of data showed a good fit between sediment yield and peak flow discharge less good although still significant was the correlation between sediment concentration and discharge values for different flow stages rainfall peak basin lag time and rainfall discharge showed poor or no correlation mainly due to strong variations in rainfall distribution sediment concentration in the catchments varied enormously according to season from zero up to 334 g 1 1 sediment yield was 160 900 tonnes km 2 yr 1 in the two major catchments and over 5200 tonnes km 2 yr 1 in the headwater catchment stressing the importance of small tributaries not only in inducing floods in downstream channels but also in sediment supply

assessment of intermediate fine sediment storage in a braided river reach southern french prealps this paper presents a field investigation on river channel storage of fine sediments in an unglaciated braided river the bes river located in a mountainous region in the southern french prealps braided rivers transport a very large quantity of bedload and suspended sediment load because they are generally located in the vicinity of highly erosive hillslopes consequently these rivers play an important role because they supply and control the sediment load of the entire downstream fluvial network field measurements and aerial photograph analyses were considered together to evaluate the variability of fine sediment quantity stored in a 2 5 km long river reach this study found very large quantities of fine sediment stored in this reach 1100 t per unit depth 1 dm given that this reach accounts for 17 of the braided channel surface area of the river basin the quantities of fine sediment stored in the river network were found to be approximately 80 of the mean annual suspended sediment yields ssys 66 200 t year 1 comparable to the ssys at the flood event scale from 1000 t to 12 000 t depending on the flood event magnitude these results could explain the clockwise hysteretic relationships between suspended sediment concentrations and discharges for 80 of floods this pattern is associated with the rapid availability of the fine sediments stored in the river channel this study shows the need to focus on not only the mechanisms of fine sediment production from hillslope erosion but also the spatiotemporal dynamics of fine sediment transfer in braided rivers copyright 2010 john wiley sons ltd

suspended sediment behavior in a coastal dry summer subtropical catchment effects of hydrologic preconditions abstract variation in fluvial suspended sediment discharge behavior is generally thought to be the product of changes in processes governing the delivery of sediment and water to the channel the objective of this study was to infer sediment supply dynamics from the response of suspended sediment behavior to antecedent hydrologic factors the salinas river california is seasonally active moderately sized and potentially susceptible to lasting impacts of hydrologic event history because of aridity high discharge variability and in channel terminating flows forty five years of suspended sediment data from the lower salinas and 80 years of hydrologic data were used to construct hydrologic descriptors of basin preconditioning and to test the effects of these preconditions on suspended sediment behavior hydrologic precondition factors including change in mean daily discharge and increasing elapsed time since the last moderate discharge event 10 20 times mean discharge q mean were found to have significant positive effects on discharge corrected fine suspended sediment concentrations conversely increased elapsed time since the last low discharge event 0 1 0 4 times q mean and the sum of low flow conditions over interannual time scales were found to cause significant negative trends in fine suspended sediment concentration residuals suspended sand concentrations are suppressed by increased elapsed time after threshold discharges of 0 1 2 and 5 100 times q mean and increased low to no flow days over time scales from 1 to 2000 days current and previous year water yield and precipitation magnitudes correlate positively with sand concentration addition of fine sediment from lower salinas hillslope or channel sources on the rising limb of the hydrograph is the major mechanism behind an overall positive hysteretic pattern which was forensically supported by the annual occurrence of in channel suspended sediment deposition by early season channel terminating flows and by the flushing function of moderate hydrologic events found in this study the importance of hillslope and or channel fine sediment contributions proximal to the lower salinas are further highlighted by the lack of control exerted by upper subbasin water provenance on fine suspended sediment concentration while sand behavior is differentiated by upper basin water provenance investigation of suspension of bed sized sediment showed that the channel bed could exert significant effects on fine and sand sized suspended sediment dynamics but this mediation for fine sediment was most likely small in terms of decadal scale sediment budgets the magnitude of the effects of hydrologic variables on sediment dynamics remains uncertain but the factors identified here may play a significant role in water quality if not long term sediment flux to the ocean

three decades of monitoring in the rio cordon instrumented basin sediment budget and temporal trend of sediment yield this paper investigates nearly 30 years of monitoring of sediment fluxes in an instrumented alpine basin rio cordon italy the collected bedload and suspended sediment transport data allows sediment dynamics to be analyzed at different time scales ranging from short single event to long term three decades the rio cordon monitoring station has been operating since 1986 continuously recording water discharge bedload and suspended load at the flood event scale a good relationship was found between peak discharges qpeak and sediment load bedload and suspended load the inter annual sediment yields were analyzed also assessing the contribution of the single floods to the total sediment budget the annual suspended load ranges from 10 to 2524 t yr 1 while the bedload varies from 0 to 1543 t yr 1 the higher annual yields were recorded in the years when large floods occurred highlighting that the sediment budget in the rio cordon is strongly controlled by the occurrence of high magnitude events investigation of the seasonal suspended load contribution demonstrated that from 1986 to 1993 most fine sediments were transported during the snowmelt summer seasons while autumn and snowmelt were the dominant seasons contributing to sediment yield in the periods 1994 2002 and 2003 2014 respectively the mean annual sediment yield from 1986 to 2014 is equal to 103 t km 2 yr 1 and overall bedload accounts for 21 of the total sediment yield the ratio between the sediment transport and the effective runoff of the events allowed the temporal trends of transport efficiency to be inferred highlighting the existence of periods characterized by different sediment availability in particular despite no significant changes in the hydrological variables i e rainfall nearly a decade 1994 2002 with high transport efficiency appears to have occurred after an exceptional event recurrence interval 100 years this event affected the sediment availability at the basin and channel bed scales and provided a legacy influencing the sediment dynamics in the basin over the long term by increasing the transport efficiency for approximately a decade this work benefits from the long lasting monitoring program undertaken in the rio cordon and is the product of long term data series the quasi unique dataset has provided detailed evidence of sediment dynamics over about three decades in a small alpine basin also enabling the effects triggered by an exceptional event to be analyzed

kinetic and mineralogic controls on the evolution of groundwater chemistry and 87sr 86sr in a sandy silicate aquifer northern wisconsin usa abstract substantial flowpath related variability of 87sr 86sr is observed in groundwaters collected from the trout lake watershed of northern wisconsin in the extensive shallow aquifer composed of sandy glacial outwash groundwater is recharged either by seepage from lakes or by precipitation that infiltrates the inter lake uplands 87sr 86sr of groundwater derived mainly as seepage from a precipitation dominated lake near the head of the watershed decreases with progressive water chemical evolution along its flowpath due primarily to enhanced dissolution of relatively unradiogenic plagioclase in contrast 87sr 86sr of groundwater derived mainly from precipitation that infiltrates upland areas is substantially greater than that of precipitation collected from the watershed due to suppression of plagioclase dissolution together with preferential leaching of sr from radiogenic phases such as k feldspar and biotite the results of a column experiment that simulated the effects of changing residence time of water in the aquifer sand indicate that mobile waters obtain relatively unradiogenic sr whereas stagnant waters obtain relatively radiogenic sr nearly the entire range of strontium isotope composition observed in groundwaters from the watershed was measured in the experimental product waters the constant mobility of water along groundwater recharge flowpaths emanating from the lakes promotes the dissolution of relatively unradiogenic plagioclase perhaps due to effective dispersal of clay mineral nuclei resulting from dissolution reactions in contrast episodic stagnation in the unsaturated zone along the upland recharge flowpaths suppresses plagioclase dissolution perhaps due to accumulation of clay mineral nuclei on its reactive surfaces differences in redox conditions along these contrasting flowpaths probably enhance the observed differences in strontium isotope behavior this study demonstrates that factors other than the calculated state of mineral saturation must be considered when attempting to simulate chemical evolution along flowpaths and that reaction models must be able to incorporate changing contributions from reacting minerals in the calculations

distinctive spring phytoplankton bloom in the bering strait in 2018 a year of historically minimum sea ice extent abstract under climate change the bering chukchi continental shelves have experienced drastic sea ice loss breaking the minimum sea ice extent record in 2018 in this paper we report a distinctive spring phytoplankton bloom in the bering strait based on year round mooring observations during 2016 2018 a near bottom fluorescence sensor mounted on a mooring and satellite observations indicate that despite the early sea ice retreat in spring of 2018 mid april the spring phytoplankton bloom was not observed for more than 20 days after sea ice retreat in contrast in 2017 when sea ice retreat did not occur as early as it did in 2018 early may the bloom and sea ice retreat occurred in tighter synchrony mooring 2016 2018 and satellite observations 2003 2011 2013 2018 suggest that an open water bloom rather than an ice edge bloom occurred in the bering strait in the spring of 2018 early sea ice retreat apparently provided unfavorable conditions for an ice edge bloom due to weak sunlight and winter like weather mid winter sea ice loss was promoted by unusual southerly winds bringing in warm water from the south for the bering strait the end of april is a reference date for sea ice retreat that distinguishes between an open water bloom and an ice edge bloom which is approximately one month later than that in the southeastern bering sea

variations in the strontium isotopic composition of seawater during the neogene the authors report 261 strontium isotopic analyses of well preserved planktonic foraminifers from three deep sea drilling project sites 519 588 and 607 these samples cover the period from 24 ma to present with an average of approximately one sample per 100 ka the combination of high sample density and uniformity of analytical procedures has produced a well defined record of changes in the sup 87 sr sup 86 sr of seawater during the neogene the record can be viewed as a series of essentially linear segments with slopes ranging from as high as 6 times 10 sup minus 5 m y to as low as 0 m y the times associated with major inflections in the curve do not appear to correspond to simple geologic phenomena such as eustatic cycles but are probably controlled by a combination of tectonic and climatic factors that influenced the abundance and isotopic composition of terrestrial strontium input to the oceans the strontium isotopic data are consistent with a progressive increase in the chemical weathering rates of the continents during the neogene probably related to repeated glaciations increased exposure of continents by lowered sea level and increased continental relief resulting from high rates of tectonic uplift

climate scale modelling of suspended sediment load in an alpine catchment debris flow rio cordon northeastern italy abstract pulsing storms and prolonged rainfall can drive hydrological damaging events in mountain regions with soil erosion and debris flow in river catchments the paper presents a parsimonious model for estimating climate forcing on sediment loads in an alpine catchment rio cordon northeastern italian alps hydroclimatic forcing was interpreted by the novel clismssl climate scale modelling of suspended sediment load model to estimate annual sediment loads we used annual data on suspended solid loads monitored at an experimental station from 1987 to 2001 and on monthly precipitation data the quality of sediment load data was critically examined and one outlying year was identified and removed from further analyses this outlier revealed that our model underestimates exceptionally high sediment loads in years characterized by a severe flood event for all other years the clismssl performed well with a determination coefficient r2 equal to 0 67 and a mean absolute error mae of 129 mg y 1 the calibrated model for the period 1986 2010 was used to reconstruct sediment loads in the river catchment for historical times when detailed precipitation records are not available for the period 1810 2010 the model results indicate that the past centuries have been characterized by large interannual to interdecadal fluctuations in the conditions affecting sediment loads this paper argues that climate induced erosion processes in alpine areas and their impact on environment should be given more attention in discussions about climate driven strategies future work should focus on delineating the extents of these findings e g at other catchments of the european alpine belt as well as investigating the dynamics for the formation of sediment loads

temporal dynamics of suspended sediment transport in a glacierized andean basin abstract suspended sediment transport can affect water quality and aquatic ecosystems and its quantification is of the highest importance for river and watershed management suspended sediment concentration ssc and discharge were measured at two locations in the estero morales a chilean andean stream draining a small basin 27 km2 hosting glacierized areas of about 1 8 km2 approximately half of the suspended sediment yield 470 t year 1 km 2 was transported during the snowmelt period and half during glacier melting the hysteresis patterns between discharge and ssc were calculated for each daily hydrograph and were analysed to shed light on the location and activity of different sediment sources at the basin scale during snowmelt an unlimited supply of fine sediments is provided in the lower and middle part of the basin and hysteresis patterns tend to be clockwise as the peaks in ssc precede the peak of discharge in daily hydrographs instead during glacier melting the source of fine sediments is the proglacial area producing counterclockwise hysteresis it is suggested that the analysis of hysteretic patterns over time provides a simple concept for interpreting variability of location and activity of sediment sources at the basin scale

rainfall runoff and suspended sediment delivery relationships in a small agricultural watershed of the three gorges area china abstract following construction of the three gorges dam many farmers resettled in surrounding mountain areas and cultivated marginal lands which are mostly on steep slopes with soil of poor structure in general high soil loss rates occur during intense storms therefore soil erosion is a major environmental problem in the three gorges area tga of china understanding and quantifying sediment load is important for sustainable agriculture and the environment in this region this paper analyzes the relationships between rainfall runoff and sediment transport in the wangjiaqiao watershed strong seasonal and monthly variability in sediment load was found sediment was strongly transported during summer months a period when frequent flood events of high magnitude and intensity occurred analysis of the relationships between precipitation discharge and sediment transport at an individual event scale showed significant correlations between total precipitation peak discharge total water yield maximum 30 min rainfall intensity and sediment related variables stepwise multiple regression analysis revealed that rainfall amount is the major cause of runoff while events producing a large discharge in a short time play an important role in inducing severe soil erosion during 40 flood events three different types of hysteretic loops were observed clockwise 28 events 70 figure eight 5 events 12 5 and complex 7 events 17 5 the results of this study confirm the complex and heterogeneous nature of sediment response in the wangjiaqiao watershed

vertical accretion sand proxies of gaged floods along the upper little tennessee river blue ridge mountains usa abstract understanding environmental hazards presented by river flooding has been enhanced by paleoflood analysis which uses sedimentary records to document floods beyond historical records bottomland overbank deposits e g natural levees floodbasins meander scars low terraces have the potential as continuous paleoflood archives of flood frequency and magnitude but they have been under utilized because of uncertainty about their ability to derive flood magnitude estimates the purpose of this paper is to provide a case study that illuminates tremendous potential of bottomland overbank sediments as reliable proxies of both flood frequency and magnitude methods involve correlation of particle size measurements of the coarse tail of overbank deposits 0 25 mm sand from three separate sites with historical flood discharge records for the upper little tennessee river in the blue ridge mountains of the southeastern united states results show that essentially all floods larger than a 20 probability event can be detected by the coarse tail of particle size distributions especially if the temporal resolution of sampling is annual or sub annual coarser temporal resolution 1 0 to 2 5 year sample intervals provides an adequate record of large floods but is unable to discriminate individual floods separated by only one to three years measurements of 0 25 mm sand that are normalized against a smoothed trend line through the down column data produce highly significant correlations r 2 values of 0 50 to 0 60 with p values of 0 004 to

temporal changes in suspended sediment transport in a gullied loess basin the lower chabagou creek on the loess plateau in china suspended sediment dynamics are still imperfectly understood especially in the loess hilly region on the loess plateau with strong temporal variability where few studies heretofore have been conducted using a dataset up to eight years long in the lower chabagou creek the variability in suspended sediment load at different temporal scales within flood variability monthly seasonal and annual is analyzed in this paper the results show that on the within flood scale most of the sediment peaks lag behind peak discharges implying that slope zones are the main sediment source area independent of the occurring sequences of the peaks of sediment and discharge all the events could present an anti clock wise hysteresis loop resulting from the abundant material and the influence of hyperconcentrated flows on suspended sediment concentration at monthly and seasonal scales there is a store release process i e sediment is prepared in winter spring and late autumn and exported in summer and early autumn at the annual scale the high variability in concentration and sediment yield are highly correlated with water yield resulting from the number and magnitude of floods recorded yearly and almost all the suspended load is transported during these events copyright c 2008 john wiley sons ltd

when does bedload transport begin in steep boulder bed streams the paper presents the results of field measurements of critical conditions for bedload motion conducted in the rio cordon a steep boulder bed stream in the italian alps under conditions of high reynolds numbers and low relative submergence poorly explored before two methods have been used to determine threshold of motion the displacement of marked clasts and the flow competence approach which uses the largest grain size diameter transported by each flood event the high values of confirm the great relevance of non bedload effective shear stresses in step pool streams given by the additional form drag associated with this morphology relative submergence effects on the dimensionless critical shear stress have been quantified by considering the relative submergence ratio rh d84 and the major effect of relative size on the mobility of each particle in steep widely graded bed mixtures has been evaluated finally the dimensionless critical unit discharge has also been adopted in the regression equations as the critical hydraulic parameter because it may represent an easier parameter to use than the critical shear stress for steep rough mountain rivers copyright 2006 john wiley sons ltd

environmental impacts on walleye pollock gadus chalcogrammus distribution across the bering sea shelf abstract adult and juvenile age 1 walleye pollock gadus chalcogrammus were sampled by the us noaa alaska fisheries science center summer bottom trawl survey in 2010 2017 2018 and 2019 in the northeastern and southeastern bering sea with profiles of temperature collected concurrently similarly the russian research institute of fisheries and oceanography pacific branch collected adult and juvenile pollock and temperature profiles on summer bottom trawl surveys in the northwestern bering sea results from these surveys show that adult pollock abundance in recent years 2017 2018 2019 has increased in northern regions of the bering sea shelf in both the us and russian sectors lower abundances compared to historic means were observed in southern regions of the shelf suggesting the pollock moved directionally from the south to the north we relate changes in pollock distribution in recent intermediate 2017 and warm low ice years 2018 2019 to a prior cold high ice year 2010 and describe how these observations relate to our longer time series we link temperature data from bottom trawl surveys us and russian sea ice indices retreat timing and extent as well as model based estimates of ocean circulation to changes in pollock distribution and examine potential environmental factors driving the observed changes changes in sea ice and bottom temperature e g reductions in ice extent and shrinking of the cold pool and changes in circulation stronger northward currents over the northeastern shelf in warmer years particularly in 2018 led to changes in distributions of adult and age 1 pollock adult pollock were concentrated north of st lawrence island and had larger longitudinal distributions in warm years 2017 2019 whereas they had a more southerly and narrow distribution over the outer shelf in the cold year 2010 age 1 pollock had higher densities over the inner eastern shelf in 2017 2019 compared to 2010 northward flow around st lawrence island particularly in the spring alternated between stronger flow on the west side of the island in 2010 and 2017 and stronger flow on the east side of the island in 2018 and 2019 variations in flow may have impacted the location of prey and movement of feeding pollock to the chukchi sea size structure comparisons between nw ne and se sections of the bering sea shelf suggest that movement of fish between us and russian waters may have been highest in 2019 one of the two warmest years and lowest in 2010 the coldest year spatial comparisons of distributions and size structure across the bering sea help provide a comprehensive view of factors affecting the movement of this highly important commercial fish species

87sr 86sr as a tracer of groundwater discharge and precipitation recharge in the glacial lake agassiz peatlands northern minnesota a contrast in the 87sr 86sr ratio of atmospherically derived sr 0 710 and sr from regional bedrock 0 730 allows quantification of the proportions of precipitation recharge and groundwater discharge into peat columns of bogs and fens in the glacial lake agassiz peatlands two contrasting bog fen pairs were studied the lost river peatland located over a regional groundwater discharge zone and the red lake peatland situated atop a hydrologic divide where recharge is expected to occur bog pore waters consist of 90 100 precipitation in the upper 2 m below which they mix with groundwater adjacent fens consist mostly of groundwater ranging from 30 near the surface to 100 with depth at the red lake peatland mixing relations suggest an additional sr source that may be peat mineralization distinct 87sr 86sr and ca sr ratios for groundwater discharging into bog and fen sites are indicative of distinct groundwater sources and are likely indicative of flow paths at two different length scales

the role of earthquakes and climate in the formation of diamictic sediments in a new zealand mountain lake we used itrax xrf magnetic susceptibility grain size and micro ct scanning to provide a facies classification for a late holocene sediment sequence from lake chappa ai in the southern alps new zealand the record contained multiple diamictic layers and our objective was to determine the environmental significance of these deposits clast fabric analysis indicated that the diamicts comprise dropstones transported to the centre of the lake by ice rafting diamicts belonging to facies 1 represent rock falls onto lake ice triggered by earthquakes that produced mmi modified mercalli intensity 8 shaking in the catchment mmi 8 earthquakes may need to occur when the lake has ice cover to produce facies 1 diamicts mmi 8 earthquakes in the ice free season or mmi 7 8 earthquakes may also result in an increased flux of large 1 mm clasts to the centre of the lake but may not produce a facies 1 diamict more work is required to establish the role of climate related processes on the formation of non facies 1 diamicts in lake chappa ai climate change may directly lead to diamict formation by changing lake ice cover and facilitating transport of large clasts by anchor ice or increasing the likelihood of rain on snow events in the spring changing ice cover conditions will also affect how mountain lakes record past earthquake events lakes that are ice free will not produce earthquake diamicts and lakes that have perennial ice cover may produce a single diamict representing multiple earthquakes if the lake becomes ice free a reduction in the duration of winter ice cover will also decrease the probability of capturing primary rockfall deposits from earthquakes additional data such as a diatom or chironomid record from lake chappa ai may help to resolve the contribution of climate processes to diamict formation we should consider the lake chappa ai record as an indicator of minimum earthquake activity until we can disentangle the effects of climate change on non facies 1 diamict formation this study highlights the multiple mechanisms that can lead to diamict formation in mountain lake sediments these processes should always be considered before attributing the presence of diamict deposits to ice rafted debris in a pro glacial lake this is particularly true in seismically active settings where earthquake triggered rockfalls may lead to diamict formation

effect of forest harvesting on hydrogeomorphic processes in steep terrain of central japan abstract forest harvesting activities affect various hydrogeomorphic processes in forest terrain including increases in occurrence of mass movements i e landslides and debris flows and changes in sediment transport rate in channels thus the influence of harvesting on these processes needs to be assessed to protect aquatic ecosystems in steep terrain with frequent mass movement relationships between rainfall magnitude and frequency of mass movements associated with forest harvesting are needed to develop improved strategies for disaster prevention we examined the effects of forest harvesting on the frequency of mass movements in the steep sanko catchment central japan using aerial photographs for six different years covering 1976 to 2003 we also investigated the spatial distribution of sediment stored in the system as well as sediment transport rate in selected subcatchments by field surveys landslides occur during moderate rainfall events return period of daily rainfall 25 years after harvesting the occurrence of mass movements substantially altered the volume of sediment storage in the channel that links sediment supply from hillslopes with sediment yield downstream however the volume and spatial distribution of sediment deposits in headwater channels were not clearly related to forest age because of the redistribution and evacuation of sediment by debris flows bedload transport rate was highly affected by sediment storage volume whereas suspended sediment concentration was affected by the area of exposed sediment along channels that was carved by debris flows thus the effect of harvesting on hydrogeomorphic processes cannot be estimated simply by the elapsed time after forest harvesting rainfall magnitude and the history of mass movements need to be considered to better understand these linkages

particle size characteristics of suspended sediment in hillslope runoff and stream flow this study examines the particle size characteristics of hillslope soils and fluvial suspended sediments in an agricultural catchment samples of surface runoff and stream flow were collected periodically and analysed for the size distributions of the effective undispersed sediment this sediment was subsequently dispersed and the ultimate size distributions determined the median effective particle size of stream suspended sediment was considerably coarser than the median ultimate particle size indicating that most of the load included a substantial proportion of aggregates moreover the proportion of fine material i e silt and clay increased and the proportion of sand sized material decreased with increasing discharge this decrease in sediment size with increased flow which is contrary to the traditional assumption of a positive discharge particle size relationship is thought to reflect i the influx of silt and clay predominantly the former originating on the catchment slopes and brought to the stream by overland flow along vehicle wheelings roads and tracks and ii erosion of fine material from the channel bed and banks during large storms however the proportion of sand sized sediment increased during the rising limb of the hydrograph as a result of the entrainment of coarser source material from the valley floor during overbank flooding the stream suspended sediment was finer than the catchment soils and considerably finer than material eroding from the catchment slopes during storms the degree of clay and silt enrichment in the suspended sediments was largely the result of preferential deposition of the coarser fraction during the transport and delivery of sediment from its source to basin outlet the data from this study confirm that a significant mode of sediment transport in fluvial systems is in the form of aggregates and that the dispersed sediment size distribution is inappropriate for determining the transportability of sediment by flow 1997 by john wiley sons ltd

flood stratigraphies in lake sediments a review abstract records of the frequency and magnitude of floods are needed on centennial or millennial timescales to place increases in their occurrence and intensity into a longer term context than is available from gauged river flow and historical records recent research has highlighted the potential for lake sediment sequences to act as a relatively untapped archive of high magnitude floods over these longer timescales abyssal lake sediments can record past floods in the form of coarser grained laminations that reflect the capacity for river flows with greater hydrodynamic energy to transport larger particles into the lake this paper presents a framework for investigating flood stratigraphies in lakes by reviewing the conditioning mechanisms in the lake and catchment outlining the key analytical techniques used to recover flood records and highlighting the importance of appropriate field site and methodology selection the processes of sediment movement from watershed to lake bed are complex meaning relationships between measureable sedimentary characteristics and associated river discharge are not always clear stratigraphical palaeoflood records are all affected to some degree by catchment conditioning fluvial connectivity sequencing of high flows delta dynamics as well as within lake processes including river plume dispersal sediment focussing re suspension and trapping efficiency with regard to analytical techniques the potential for direct e g laser granulometry and indirect e g geochemical elemental ratios measurements of particle size to reflect variations in river discharge is confirmed we recommend care when interpreting fine resolution geochemical data acquired via micro scale x ray fluorescence xrf core scanning due to variable down core water and organic matter content altering x ray attenuation we also recommend accounting for changes in sediment supply through time as new or differing sources of sediment release may affect the hydrodynamic relationship between particle size and or geochemistry with stream power where these processes are considered and suitable dating control is obtained discrete historical floods can be identified and characterised using palaeolimnological evidence we outline a protocol for selecting suitable lakes and coring sites that integrates environmental setting sediment transfer processes and depositional mechanisms to act as a rapid reference for future research into lacustrine palaeoflood records we also present an interpretational protocol illustrating the analytical techniques available to palaeoflood researchers to demonstrate their utility we review five case studies of palaeoflood reconstructions from lakes in geographically varied regions these show how lakes of different sizes and geomorphological contexts can produce comprehensive palaeoflood records these were achieved by consistently applying site validated direct and proxy grain size measurements well established chronologies validation of the proxy process interpretation and calibration of the palaeoflood record against instrumental or historical records