interpolation of an intertidal digital elevation model from heighted shorelines a case study in the western wash abstract a method of interpolating a spatiotemporal digital elevation model dem of an intertidal zone from a set of heighted shorelines is described the heighted shorelines are obtained by the water line method using remote sensing and hydrodynamic modelling this enables an intertidal dem to be constructed over a large area relatively quickly as well as frequent subsequent updating of the dem to detect changes the dem may be used for studying sediment transport in the intertidal zone and for the development of improved hydrodynamic models the spatiotemporal interpolator is based on universal block kriging and its results are illustrated using data from the wrangle flats area of the western wash u k for a kriging block size of 50 m 50 m 1100 days an average block height estimation standard deviation of 14 3 cm is achieved using shorelines from 33 images collected over the period 1992 1994 this height accuracy is compared with those obtained from dems constructed from beach transect data and is shown to be an improvement over the transect dem accuracies away from transects the construction of dems of improved accuracy 13 cm from combined shoreline and beach transect data using cokriging is discussed ways in which the shoreline accuracies may be improved are also considered

tide surge interaction in the meghna estuary most severe conditions abstract a numerical model with a 1 120 resolution is used in studying 1 the effects of tide surge interaction and 2 the effects of cyclone landfall on the noakhali cox s bazar coast of bangladesh i on the time deviation of the surge arrival from the landfall time of a cyclone and ii on the duration of the maximum surge the present study found that the tide surge interaction in the meghna estuary shows in general the progressive wave nature of the local tide if the peak of the maximum surge coincides with the tidal peak near the landfall the surge propagates toward the north faster than when the surge peak coincides with the tidal trough cyclones that make landfall before the arrival of the tidal peak produce higher but shorter duration surges than those that make landfall after the arrival of the tidal peak if the landfall time of the cyclone is kept fixed the surge peaks are found to arrive earlier and to be of shorter duration with i an increase in the propagation speed of the cyclon

upward recharge through groundwater depression cone in piedmont plain of north china plain summary whether a recharge was induced by groundwater depression cones is a crucial issue for water resource management in the north china plain shallow groundwater had been over pumped since 1970s and many groundwater depression cones formed the groundwater depression cone daceying machang occurred even in the piedmont plain in the area water levels of deep and shallow groundwater were observed since 2005 and field survey was conducted in the dry season 2010 the upward recharge induced by the depression cone is verified based on water level records major ions 2 h 18 o and kinds of statistical analyses since august 2006 the water level of the deep groundwater ascended by 1 9 mm d high correlations r 0 86 s 0 67 between the water level series of shallow and deep groundwater were found by two distinct correlation analyses only in the center of depression cone further the reversion of hydraulic gradient of the depression cone occurred in dry seasons since september 2008 hydro geochemical features of the shallow groundwater are consistent with deep groundwater in the center of depression cone which was demonstrated by the fuzzy c means clustering based on principal components and paired t test respectively it is concluded that the deep groundwater recharged the shallow groundwater from the center of the depression cone as a result the groundwater mixture occurred that improves the quality of the shallow groundwater seasonally changed flow of shallow groundwater enhanced the mixture the persistent overpumping of shallow groundwater and the large elevation difference around 1200 m between the recharge zone and the discharge point of deep groundwater facilitate the upward recharge

a storm surge prediction model for the northern bay of bengal with application to the cyclone disaster in april 1991 abstract a numerical model for simulating and predicting tides and storm surges in regions that include areas of open sea combined with estuarine channels and intertidal banks is described the model makes use of modified depth averaged equations with a numerical scheme in which the solution of 1d equations for narrow channels 2d equations for the open sea and an approach to modeling inundation are combined within a unified framework this simplifies the construction of realistic models for complex coastal areas and deltas the model is applied to the northern shelf of the bay of bengal and the ganges delta including the coast of bangladesh devastated by a cyclone surge in april 1991 in which about 140 000 people died hindcast and forecast simulations of this event using forcing derived from a semianalytical cyclone model with data supplied by the joint typhoon warning center jtwc are described it is shown that the timing of cyclone landfall and its coincidence with high tide determine the area

rate and historical change of direct recharge from precipitation constrained by unsaturated zone profiles of chloride and oxygen 18 in dry river bed of north china plain quantifying of direct recharge derived from precipitation is crucial for assessing sustainability of well irrigated agriculture in the north china plain the land use is dominated by groundwater irrigated farmland where the direct recharge derived from precipitation and irrigation to characterize the mean rate and historical variance of direct recharge derived from precipitation unsaturated zone profiles of chloride and d18o in the dry river bed of the beiyishui river were employed the results show that archival time scale of the profile covers the duration from 1980 to 2002 corresponding to depths from 5 to 2 m which is indicated by matching the d18o peaks in the isotope profile with the aridity indexes gained by instrumental records of annual precipitation and annual potential evaporation using the chloride mass balance method the mean rate of the direct recharge corresponding to the archival time scale is estimated to be 3 8 0 8 mm year 1 which accounts for about 0 7 of the long term average annual precipitation further the direct recharge rates vary from 2 1 to 6 8 mm year 1 since 1980 despite the subhumid climate the estimate of recharge rates is in line with other findings in semiarid regions the low rate of direct recharge is considered as a result of the relative dry climate in recent decades in dry river bed unsaturated zone profiles of chloride and d18o combined with instrumental records could offer valuable information about the direct recharge derived from precipitation during droughts copyright c 2011 john wiley sons ltd

paleoclimatic interpretation of the past 30 ka from isotopic studies of the deep confined aquifer of the north china plain abstract the 18 o and d values in the deep confined aquifer beneath the north china plain which is located at 112 30 e 119 30 e and 34 46 n 40 25 n reflect differences in paleoclimatic conditions between the holocene and the late pleistocene groundwater samples whose 14 c ages are between 12 and 25 ka b p have ranges of 9 4 to 11 7 for 18 o and 76 to 85 for d values these very negative 18 o and d values reflect the cold and arid climate in the last glacial period the temperature estimated in this period is 6 9 c cooler than that of the present the entire ranges of 18 o and d values for samples with 14 c dating from 7 ka b p to present are 7 7 to 10 2 and 63 to 73 respectively the greater 18 o and d enrichments of these samples indicate a period of relatively humid and warm climate in the holocene however the wide ranges of 18 o 9 0 to 11 1 and d 66 to 80 values for samples with 14 c age ranging from 12 to 7 ka b p imply an unstable climatic condition of rapidly increasing temperature which marks the transition from the pleistocene to the holocene

measurement of recent intertidal sediment transport in morecambe bay using the waterline method abstract an illustration of how sediment transport may be measured over a large dynamic intertidal area at reasonable cost and spatiotemporal resolution using the waterline method employing remote sensing and hydrodynamic modelling is presented areas and volumes of accretion and erosion were measured in the study area of morecambe bay in north west england over the period 1992 97 tidal asymmetry is considered to be the dominant agent of sediment movement in the bay with waves being of secondary importance waterlines i e land sea boundaries were extracted from 31 synthetic aperture radar images of the bay covering a substantial fraction of the tidal range heights were attached to the waterlines using water elevations from nested hydrodynamic tide surge models interpolation in space and time was carried out to produce a continuous spatiotemporal height map of the intertidal zone height maps with a spatial resolution of about 50 m and height accuracy of about 40 cm were constructed over an area of about 350 km 2 strong temporal decorrelation in the bay limited the height accuracy achievable differences between height maps for 1992 94 and 1995 97 allowed sediment volume changes to be extracted the intertidal region showed a loss of 16 1 4 5 10 6 m 3 over the period almost all the change being due to a significant decrease between mean sea level and the low water mark changes were also measured in three of the main river estuaries within the bay the leven kent and lune these included movement of the leven north east by about 2 km cutting into cartmel wharf accretion seaward of grange over sands and changes in the low water channels at the mouth of the lune these changes could be used to validate sediment transport models of the bay

characterising deep vadose zone water movement and solute transport under typical irrigated cropland in the north china plain understanding the dynamics and mechanisms of soil water movement and solute transport is essential for accurately estimating recharge rates and evaluating the impacts of agricultural activities on groundwater resources in a thick vadose zone 0 15 m under irrigated cropland in the piedmont region of the north china plain soil water content matric potential and solute concentrations were measured based on these data the dynamics of soil water and solutes were analysed to investigate the mechanisms of soil water and solute transport the study showed that the 0 15 m vadose zone can be divided into three layers an infiltration and evaporation layer 0 2 m an unsteady infiltration layer 2 6 m and a quasi steady infiltration layer 6 15 m the chloride nitrate and sulphate concentrations all showed greater variations in the upper soil layer 0 1 m compared to values in the deep vadose zone below 2 m the average concentrations of these three anions in the deep vadose zone varied insignificantly with depth and approached values of 125 242 and 116 mg l the accumulated chloride sulphate and nitrate was 2179 113 1760 383 and 4074 421 kg ha respectively the soil water potential and solute concentrations indicated that uniform flow and preferential flow both occurred in the deep vadose zone and uniform flow was the dominant mechanism of soil water movement in this study the piston like flow velocity of solute transport was 1 14 m yr and the average value of calculated leached nitrate nitrogen was 107 kg ha yr below the root zone the results can be used to better understand recharge processes and improve groundwater resources management this article is protected by copyright all rights reserved

late pleistocene precipitation δ18o interpolated across the global landmass global water cycles ecosystem assemblages and weathering rates were impacted by the 4 c of global warming that took place over the course of the last glacial termination fossil groundwaters can be useful indicators of late pleistocene precipitation isotope compositions which in turn can help to test hypotheses about the drivers and impacts of glacial interglacial climate changes here a global catalog of 126 fossil groundwater records is used to interpolate late pleistocene precipitation 18o across the global landmass the interpolated data show that extratropical late pleistocene terrestrial precipitation was near uniformly depleted in 18o relative to the late holocene by contrast tropical 18o responses to deglacial warming diverged late pleistocene 18o was higher than modern across india and south china but lower than modern throughout much of northern and southern africa groundwaters that recharged beneath large northern hemisphere ice sheets have different holocene pleistocene 18o relationships than paleowaters that recharged subaerially potentially aiding reconstructions of englacial transport in paleo ice sheets global terrestrial late pleistocene precipitation 18o maps may help to determine 3 d groundwater age distributions constrain pleistocene mammal movements and better understand glacial climate dynamics

evidence for periods of wetter and cooler climate in the sahel between 6 and 40 kyr bp derived from groundwater 1 concentrations of noble gases stable isotopes and 14c in samples from the continental terminal groundwaters of niger provide evidence for more humid and cooler climate phases in west africa in the holocene and the late pleistocene during humid phases even within the holocene the soil temperature was up to 5 5 c cooler than today which is partly attributed to atmospheric cooling but also to a change in the relationship between air and soil temperature due to increased vegetation intense rainfall events and increased groundwater recharge are consistently indicated by stable isotope data and excess air concentrations i e the component of dissolved atmospheric gases in excess of solubility equilibrium this finding encourages the use of excess air as an additional humidity related climate indicator

use of multiple age tracers to estimate groundwater residence times and long term recharge rates in arid southern oman abstract multiple age tracers were measured to estimate groundwater residence times in the regional aquifer system underlying southwestern oman this area known as the najd is one of the most arid areas in the world and is planned to be the main agricultural center of the sultanate of oman in the near future the three isotopic age tracers 4 he 14 c and 36 cl were measured in waters collected from wells along a line that extended roughly from the dhofar mountains near the arabian sea northward 400 km into the empty quarter of the arabian peninsula the wells sampled were mostly open to the umm er radhuma confined aquifer although some were completed in the mostly unconfined rus aquifer the combined results from the three tracers indicate the age of the confined groundwater is 100 ka in the central section north of the mountains and up to and one ma in the empty quarter the 14 c data were used to help calibrate the 4 he and 36 cl data mixing models suggest that long open boreholes north of the mountains compromise 14 c only interpretations there in contrast to 4 he and 36 cl calculations that are less sensitive to borehole mixing thus only the latter two tracers from these more distant wells were considered reliable in addition to the age tracers 2 h and 18 o data suggest that seasonal monsoon and infrequent tropical cyclones are both substantial contributors to the recharge the study highlights the advantages of using multiple chemical and isotopic data when estimating groundwater travel times and recharge rates and differentiating recharge mechanisms

simulation of storm surge wave currents and inundation in the outer banks and chesapeake bay during hurricane isabel in 2003 the importance of waves 1 this paper investigates the effects of waves on storm surge currents and inundation in the outer banks and chesapeake bay during hurricane isabel in 2003 through detailed comparison between observed wind wave surge and inundation data and results from an integrated storm surge modeling system ch3d ssms ch3d ssms which includes coupled coastal and basin scale storm surge and wave models successfully simulated measured winds waves storm surge currents and inundation during isabel comprehensive modeling and data analysis revealed noticeable effects of waves on storm surge currents and inundation among the processes that represent wave effects radiation stress outside the estuaries and wave induced stress outside and inside the estuaries are more important than wave induced bottom stress in affecting the water level maximum surge was 3 m while maximum wave height was 20 m offshore and 2 5 m inside the chesapeake bay where the maximum wave induced water level reached 1 m significant waves reached 3 5 m and 16 s at duck pier north carolina and 1 6 m and 5 s at gloucester virginia at duck wave effects accounted for 36 cm or 20 of the peak surge elevation of 1 71 m inside the chesapeake bay wave effects account for 5 10 of observed peak surge level a two layer flow is found at kitty hawk north carolina during the peak of storm surge owing to the combined effects of wind and wave breaking higher surge elevations result when the 3 d surge model instead of the 2 d surge model is coupled with the 2 d wave model owing to its relatively lower bottom friction wave heights obtained with 3 and 2 d surge models show little difference

changes in flow and chemistry of groundwater heavily affected by human impacts in the baiyangdian catchment of the north china plain to identify impacts of air pollution sewage drainage agricultural production over pumping and reservoir storage on groundwater a field survey was conducted in the baiyangdian catchment of the north china plain major ions and water isotopes were measured results show that hydrological processes and hydrogeochemical evolution of shallow groundwater were greatly disturbed by human activities excessive pumping resulted in significant declines of groundwater levels over the study area this also induced infiltration of surface water into groundwater a groundwater depression cone was the conflux center of groundwater surrounded by recharge zones including alluvial fans and surface water in alluvial plain pumping almost was the only way to discharge groundwater emission of so x and no x contributed at least 11 of rock weathering by dissolving into infiltrating precipitation surface waters containing sewage replenished ambient groundwater with an average mixing ratio of 74 17 due to groundwater level drawdown as a result groundwater had elevated concentrations of na and so4 2 with na exchanged into aquifer sediments about 29 16 of na was exchanged from groundwater into soil matrix agriculture nitrate was high only in the recharge zones the most important result is that the transformation of the study area from a place rich in water resource into an area lack of water just took several decades with the joint action of the heavily human activities our study also indicates that shallow groundwater could sensitively respond to and record environmental changes

an integrated forecast system over the mediterranean basin extreme surge prediction in the northern adriatic sea abstract a previsional system for the forecast of the state of the mediterranean sea and of surges in the northern adriatic sea has been designed and tested the system consists of a limited area model the bologna limited area model bolam which computes high resolution pressure and surface wind fields to serve as the input of a wave model wam and of a shallow water model two dimensional princeton ocean model pom 2d results of two case studies are presented chosen to test the ability of the system to predict extreme surge events originating from cyclonic circulation over the mediterranean basin the two case studies cover the periods 4 9 october 1998 and 11 22 november 1996 comparison with observed buoy data shows that the results of the wam simulations forced by the wind fields obtained from the high resolution bolam model are significantly better than those obtained using a lower resolution forcing from the ecmwf analyses two domains corresponding to the entire mediterranean basin and to th

tidal dynamics in channels single channels intricate networks of tidal channels such as are found in fjordic barrier island and branching estuarine systems are often at risk from contaminant inputs and can be important as spawning grounds or migration pathways for marine organisms these intricate systems are rarely spatially resolved in regional scale numerical tidal models and the setting up of a specific detailed numerical model for the purpose of rapidly assessing the likely tidal behavior of such geometrically complex systems carries a high overhead as a first step we describe a simple not published before algorithm which permits rapid assessment of the linear tidal dynamics in a single tidal channel the method will be extended to channel networks in a companion article the method needs only a minimum of input data namely 1 the forcing tidal elevation amplitude and phase at the entrances of the channel directly exposed to the open sea and 2 the length and depth of the channel the performance of the method is tested against observations in the menai straits uk by applying the case of a single channel forced at either end with friction

departures from the local inverse barometer model observed in altimeter and tide gauge data and in a global barotropic numerical model sea level data from the topex poseidon altimeter satellite and from subsets of the global tide gauge and bottom pressure recorder networks have been employed to study the worldwide distribution of departures from the simple local inverse barometer lib model from a combination of measurement techniques the lib model was found to provide a reasonable representation of the data within 5 10 outside of the tropics for timescales from several days to several weeks for most locations however several parts of the southern ocean and other higher latitude areas were seen from the altimetry to contain significant departures across the range of timescales accessible for study by the technique within the tropics the response of sea level to air pressure forcing was observed to be typically 50 of that of the lib model at timescales of several days with considerable spatial variation and to approximate the lib model more closely at timescales of several weeks a coarse grid global barotropic numerical model was found to reproduce qualitatively the global average response as a function of frequency to simulate many of the characteristics of the spatial variation of the response and to demonstrate the relative importance of air pressure and wind forcing at different timescales data sets from the permanent service for mean sea level and u k meteorological office were used to investigate lib departures at intraseasonal and longer timescales along continental coastlines and at ocean islands increasingly large departures were observed along many parts of the world coastline as timescales increased from months to seasons

identification of he sources and estimation of he ages in groundwater of the north china plain abstract dissolved helium concentrations and 3 he 4 he ratios were measured for 18 groundwater samples collected from the quaternary confined aquifers in the north china plain ncp the dissolved helium concentrations ranged from 1 10 7 to 1 10 6 cm 3 stp g 1 in the 14 samples from the central plain but was approximately two orders of magnitude higher between 6 10 6 and 9 10 5 cm 3 stp g 1 in 4 samples from the coastal plain based on these concentrations and the corresponding 3 he 4 he ratios varying from 0 09 to 0 55 r a where r a is the 3 he 4 he ratio of air the dissolved helium in groundwater in the central plain was identified to be primarily a mixture of atmospheric helium with radiogenic helium and a representative radiogenic helium ratio was estimated to be 0 035 r a despite the high fraction of terrigenic 4 he in the samples from the coastal plain their 3 he 4 he ratios were found to be significantly above this radiogenic value ranging between 0 20 and 0 37 r a indicating the presence of a mantle derived he component in this area about 2 4 mantle helium was estimated to be present in the groundwater of the coastal plain which probably is associated with the regional cangdong fault and tectonic activities based on the radiogenic he component 4 he ages of the groundwater in the central plain were calculated by assuming either pure in situ production or an external helium flux j 0 of 4 7 10 8 cm 3 stpcm 2 a 1 the estimated 4 he ages fall between 9 5 and 51 4 ka and are comparable to the 14 c ages suggesting that the results of 4 he dating are reasonable and can be an effective tool to estimate groundwater residence times under suitable conditions

downstream patterns of bed material grain size in a large lowland alluvial river subject to low sediment supply 1 a new data set of bimodal subaqueous channel bed sediments was analyzed for longitudinal patterns in grain size it yielded two interesting observations 1 separate fining trends in d50 exist for gravel and fines that overlap for 175 river kilometers and 2 this overlap in fining trends results in a protracted nonabrupt gravel to sand transition these suggest bed patchiness that is interpreted in the context of inherent grain size bimodality localized hydraulic sorting due to spatially heterogeneous and low sediment supply and local deviations in channel gradient the data also show that tributaries have a minor impact on main stem downstream fining due to basin shape and tectonic history in addition subaqueous channel sediments were observed to be finer than nearby sediments collected from exposed bars which may indicate a narrow active zone of transport where bars are disconnected from sediment movement this research has implications for bed material collection and theories of downstream fining

stable isotope geochemistry of dissolved chloride in relation to hydrogeology of the strongly exploited quaternary aquifers north china plain deep quaternary groundwater is the main source for industrial domestic and agricultural water supply in the north china plain ncp there is currently a regional decline of groundwater levels deterioration of water quality and environmental geological problems induced by increasing exploitation of the ncp quaternary aquifer system to trace sources and transport processes of dissolved cl in a regional aquifer system and to reveal hydrogeological characteristics of quaternary complexes 37cl 18o and d and chemical compositions including f cl br of the deep groundwater sampled from the northern flow system of the ncp were measured along the west east groundwater flow paths the measured 37cl values decreased from 0 39 to 2 22 smoc along the groundwater flow direction with increasing cl concentrations marine aerosol input via rainfall is the main source of cl in the deep groundwater near the recharge areas and subsequent evaporation evapotranspiration appears to be responsible for cl accumulation mixing of recharge water with water of high cl and low 37cl accounts for the pattern of 37cl and cl concentration observed in aquifer 3 along the west east transect the water with high cl and low 37cl is likely from pore water released from compacted clays induced by over exploitation of deep groundwater suggesting that clay is a dominant subsurface source of cl for groundwater where a regional depression cone is present in the quaternary aquifers the groundwater of aquifer 4 in the huang hua depression is potentially mixed with an upward flux of cl from the neogene aquifer through subvertical faults diffusion and ion filtration are two mechanisms invoked to explain the highly negative 37cl data for groundwater of aquifer 4 in the yanshan haixing areas which provides new insight into solute migration and the hydraulic relationship in the strongly exploited groundwater system this study using the conservative solute cl provides additional important information for further investigations of the geochemistry of a wide range of reactive solutes in the quaternary aquifer system so guiding water resource management

interconnectivity between volume transports through arctic straits arctic heat and freshwater budgets are highly sensitive to volume transports through the arctic subarctic straits here we study the interconnectivity of volume transports through arctic straits in three models two coupled global climate models one with a third degree horizontal ocean resolution higem1 1 and one with a twelfth degree horizontal ocean resolution hadgem3 and one ocean only model with an idealized polar basin tenth degree horizontal resolution the two global climate models indicate that there is a strong anti correlation between the bering strait throughflow and the transport through the nordic seas a second strong anti correlation between the transport through the canadian artic archipelago caa and the nordic seas transport and a third strong anti correlation is found between the fram strait and the barents sea throughflows we find that part of the strait correlations is due to the strait transports being coincidentally driven by large scale atmospheric forcing patterns however there is also a role for fast wave adjustments of some straits flows to perturbations in other straits since atmospheric forcing of individual strait flows alone cannot lead to near mass balance fortuitously every year idealized experiments with an ocean model nemo3 6 that investigate such causal strait relations suggest that perturbations in the bering strait are compensated preferentially in the fram strait due to the narrowness of the western arctic shelf and the deeper depth of the fram strait

a comparative study of storm surge and wave setup in the east china sea between two severe weather events abstract the coastal regions of the east china sea are frequently threatened by the increased sea level induced by intense tropical cyclones in this study a coupled wave circulation model adcirc swan is used to investigate the spatial and temporal characteristics of storm surges and wave setup heights in the southeastern coastal area of china during two severe weather events with different tracks typhoon saomai which made direct landfall and the bypassing typhoon chan hom by definition the storm surge is attributable to the wind forcing while the wave setup results from the wave radiation stress the simulated sea levels agree well with the observations with improved results when the wave setup was considered the simulation results showed clearly different spatial patterns depending on the track type the maximum storm surge resulted from the cumulative effect of the local onshore wind forcing occurring on the right side of the typhoon saomai track and the left side of the typhoon chan hom track significant surge levels along the coast on the left side of the typhoon track were well observed in both cases resulting from the coastal trapped shelf waves the saomai track type is more likely to cause extremely high storm surges along the coast due to the stronger cumulative effect of the onshore wind forcing the maximum wave setup was governed by the swell and slope of the sea floor the locations of the maximum wave setup and surge level were spatially close during typhoon saomai but they were separated during typhoon chan hom

estimating groundwater recharge using deep vadose zone data under typical irrigated cropland in the piedmont region of the north china plain summary groundwater recharge can be accurately estimated by understanding the soil water flow process in the deep vadose zone in this study soil water content and soil matric potential were measured in situ in the deep vadose zone 8 m under typical irrigated cropland in the piedmont region of the north china plain and were used to analyze the soil water dynamics and calibrate a transient matric flow model using the calibrated model the long period average groundwater recharge was estimated and the influences of the lower boundary depth and time scale length of study period on the recharge were assessed the study showed that the response time of the water table with a buried depth of 42 m to water input might be no more than 1 year because the velocity of the wetting front could be as high as 0 13 m day below the root zone however the lag time could be more than 15 years because of the slower velocity of the soil water displacement the variation in the recharge flux with depth was significant over shorter time scales therefore for more representative estimated recharge with a maximum deviation less than 20 from the 38 year mean value research should be conducted over a long period 12 years however the average annual recharge showed almost no change with depth at the 38 year scale and a depth of 2 m below ground surface could be used as an interface for estimating recharge at the 38 year scale the simulated annual recharge at a depth of 2 m ranged from 59 mm to 635 mm with a mean value of 200 mm the variation in water input precipitation and irrigation was the main reason for the variation in annual recharge at the depth of 2 m this approach improves our understanding of the recharge process in the deep vadose zone in this region and the results of this work could aid development of effective groundwater resources management

using major ions and stable isotopes to characterize recharge regime of a fault influenced aquifer in beiyishui river watershed north china plain a thorough understanding of recharge is usually a prerequisite for effective groundwater management the recharge regime remains unrevealed in the piedmont plain of the north china plain where is considered as the main recharge zone of the quaternary aquifer to characterize the recharge regime a case study is presented in the piedmont plain of the beiyishui river watershed the piedmont plain consists of proluvial fan and alluvial fan plain and groundwater quality in the two parts is distinct total dissolved solids and isotopic compositions are higher in the groundwater of proluvial fan than the groundwater of the alluvial fan plain local precipitation only recharges the groundwater in the proluvial fan fracture water ascending along a buried normal fault and lateral inflow from the proluvial fan feed the unconfined aquifer in the alluvial fan plain the runoff of the beiyishui river seeps in the streambed of upper reaches and then overflows seasonally in middle reach the recharge from middle reach to the aquifer is negligible in addition the fracture water originates from precipitation in the mountainous area with an average elevation about 500 m and discharges to the overlaying aquifer the contribution of fracture water to the aquifer was estimated to be 77 9 in the alluvial fan plain area due to the mixture in the aquifer major ions leached from soil of the proluvial fan are diluted and the hydrochemical pattern is changed from ca mg hco3 so4 to ca mg hco3 it is considered that fracture water is the major recharge source of the unconfined aquifer and the variation of precipitation in mountainous area would primarily affect the recharge this paper also shows the hydrological efficiency of buried normal fault as preferential flow

model simulations of the gulf of maine response to storm forcing 1 the storm response of the gulf of maine georges bank region was investigated using the dartmouth three dimensional nonlinear finite element coastal ocean circulation model called quoddy with uniform density and quadratic bottom stress a suite of model hindcast experiments were conducted for the 4 8 february 1987 period that featured a strong nor easter the model was forced at the open ocean boundaries by the m2 semidiurnal tidal sea level and in the interior by realistic surface wind stresses and in some cases atmospheric pressure the reference model run with just tidal and wind stress forcing and a time space constant bottom drag coefficient cd of 0 005 captured 65 of the observed detided low pass filtered or subtidal sea level variance of a representative array of coastal and bottom pressure stations in the gulf however there remained large unexplained model observed sea level differences particularly during the storm model sensitivity testing to a realistic range of constant cd values did not improve model results significantly however results of a model run in which atmospheric pressure forcing derived through linear interpolations of regional measurements was added to wind stress forcing captured 82 of the observed subtidal sea level variance

impact of coarse sediment supply from hillslopes to the channel in runoff dominated dryland fluvial systems sediment supply from hillslopes to channels is an important control on basin functioning and evolution however current theoretical frameworks do not adequately consider processes of runoff driven hillslope sediment supply which affect river channels spatially and temporally mountainous dryland basins exhibit an important manifestation of these processes because their debris mantled hillslopes produce coarse sediment and because rainfall is delivered as infrequent high intensity short duration rainstorms this paper combines field measurements and modeling to explore runoff driven coarse sediment supply from hillslopes to the channel and assesses a range of plausible storms on the longitudinal patterns of sediment load and its caliber over a dryland basin reach our results show that modeled sediment load and its grain size distribution are determined by the nonlinear interaction between rainfall characteristics and hillslope attributes resulting in longitudinal fluctuations in sediment supply the relative magnitude and location of which varies between storms results suggest that long hillslopes are most sensitive to rainfall and they exhibit large variations in supplied sediment load and grain size for different runoff characteristics short and steep hillslopes are less sensitive to rainfall variations as gradient effects dominate over the role of length in modulating runoff accumulation furthermore the signal of the median fraction d50 of modeled sediment supplied by the hillslope is preserved in the coarse fraction of the measured in channel grain sizes d90 finally we propose a simple index which provides new insights into the effectiveness of different rainstorms in terms of the impact of hillslope sediment supply on the channel

hindcasting coastal sea levels in morecambe bay a method of variational data assimilation by means of an adjoint model is used to improve the boundary conditions for a high resolution depth averaged two dimensional non linear hydrodynamic model of morecambe bay the modelled region contains a large inter tidal area and has an unusually high tidal range the assimilation procedure is robust and effective in reducing model error this system performs considerably better than the previous simple method used for assimilating data into the same numerical model height errors as low as 10 cm root mean square can be achieved

transient response in longitudinal grain size to reduced gravel supply in a large river 1 the first extensive dataset on subaqueous bed material grain size in a large river subject to reduced sediment supply is investigated alongside bathymetry modeled flow and sediment flux results suggest that following sediment supply decline and a shift to a finer sediment supply the gravel sand transition gst in fluvial systems extends and subsequently migrates upstream the non abrupt 125 km gst in the sacramento river corresponds with a hump in the long profile indicating recent downstream redistribution of sediment that impacts grain sizes the hump is composed of sediments winnowed from upstream gravel beds that accumulate downstream where slope declines this increases local sorting values and coarse sediment flux rates in the gst leading to further gravel loss by burial and net efflux thus in a transient response to sediment supply changes whether anthropogenic or natural the gst extends upstream as a longitudinally patchy bed modulated by bedload sheet transport that favors the loss of gravel

a two dimensional tidal model for the mediterranean sea the tidal propagation in the mediterranean sea is described through a high resolution two dimensional hydrodynamic model forced by the equilibrium tide and the incoming tide at the strait of gibraltar the four most significant constituents m2 s2 k1 and o1 are included in the model good agreement with a set of 63 coastal gauges is achieved the significance of the equilibrium tide and the forcing at the open boundary is investigated the incoming wave from the strait of gibraltar is important in tuning the tides in the whole of the mediterranean for the north aegean sea the solution without the forcing at gibraltar results in a doubling of the amplitudes of the semidiurnal tides the estimated energy dissipation due to bottom friction is 8 8 108 w the major area of dissipation is the gulf of gabes energy fluxes through the major straits are calculated

construction of an inter tidal digital elevation model by the water line method progress in the development of a method for constructing a digital elevation model dem of an inter tidal zone using remote sensing and hydrodynamic modelling is described the method allows the construction of an inter tidal dem over large areas relatively quickly as well as frequent subsequent monitoring of the dem to detect changes and is particularly suited to sar satellite data because of the all weather day night capability of sar the resulting dem may be used for the development of improved hydrodynamic models and for studying sediment mass transport in the inter tidal zone

a sensitivity analysis of the waterline method of constructing a digital elevation model for intertidal areas in ers sar scene of eastern england abstract a sensitivity analysis of the waterline method of constructing a digital elevation model dem of an intertidal zone using remote sensing and hydrodynamic modelling is described variation in vertical height accuracy as a function of beach slope is investigated using a set of nine ers synthetic aperture radar sar images of the humber wash area on the english east coast acquired between 1992 and 1994 waterlines from these images are heighted using a hydrodynamic tide surge model and interpolated using block kriging on 1 500 slope beaches an average block height estimation standard deviation of 18 22 cm is achieved this rises to 27 cm on 1 100 slope beaches and 32 cm on 1 30 slope beaches the average heighting error at different slopes is decomposed into components due to waterline heighting error inadequate sensor resolution and interpolation inaccuracy it is shown that at 1 500 slope waterline heighting error and interpolation inaccuracy are the main error sources whilst at 1 30 slope errors due to inadequate sensor resolution become dominant the ability of the technique to generate intertidal dems for almost the entire coastal zone in a complete ers sar scene covering 100 100 km is demonstrated

temperature variability beneath ronne ice shelf antarctica from thermistor cables thermistor cables have been deployed at two sites beneath ronne ice shelf antarctica one site is to the east of a submarine ridge that delineates the eastern boundary of the ronne depression and the other is 100 km to the north above the eastern slope of the depression long records from the cables up to 22 months indicate a large difference in the temperature variability at the two sites being an order of magnitude greater in the ronne depression site 2 although the records appear otherwise similar there is no significant correlation between them the high variability in the site 2 record has allowed the construction of a simple descriptive model of the local oceanographic regime winter freezing in the open water north of the ice front generates western shelf water wsw a type of high salinity shelf water which travels southwest beneath the ice shelf appearing at site 2 as a slope trapped current at the bottom of the water column baroclinic instability in the flow manifests itself in the site 2 temperature record as oscillations on time scales of 5 to 15 days the disturbances cause a periodic east west advection of water masses across the ronne depression site 2 is on the eastern slope of the depression where the wave induced eastward motion forces ice shelf water to rise resulting in periodic ice platelet formation in the water column as surmised from conductivity temperature depth measurements at the site the depth of the wsw layer decreases by 40 to 60 m during a 100 day period starting some 4 months after the beginning of the summer assuming an absence of significant wsw production during the summer the 4 month delay implies a minimum average speed of wsw flow of about 0 02 m s 1 the wsw flux into the ronne depression is estimated at 3 105 m3s 1

mobilization of coarse surface layers in gravel bedded rivers by finer gravel bed load 1 additions of sand to gravel beds greatly increase the mobility and flux of gravel however it is not known how additions of finer gravel to coarser gravel beds will affect the mobility of bed material here we examine the effect of fine gravel pulses on gravel bed material transport and near bed flow dynamics in a series of flume experiments bed material refers exclusively to sediment in the channel prior to the pulse introduction the observations indicate that fine sediment pulses tend to migrate downstream in low amplitude waves as the waves pass over the gravel bed the interstitial pockets in the bed material surface fill and coarse gravel particles are entrained this increases bed material transport rates and causes a distinct shift from a selective mobility transport regime where particles coarser than the bed material median 8 mm make up 30 of the load to an equal mobility transport regime where bed materials coarser than 8 mm and finer than 8 mm are transported in equal proportions the only possible source for this coarser bed load material is the sediment bed suggesting that portions of the coarse surface layer are being mobilized observations of near bed velocity and turbulence suggest that fine gravel pulses cause fluid acceleration in the near bed region associated with a reduction in the level of turbulence produced at the sediment boundary this accelerated fluid at the bed increases drag exerted on coarse surface layer particles promoting their mobilization our findings suggest that in general finer bed sediment not just sand can mobilize coarser sediment and that expressions for the influence of sand on bed mobility need to be generalized on the basis of grain ratios

characterizing the recharge regime of the strongly exploited aquifers of the north china plain by environmental tracers 1 we employed environmental tracers 3h 3he noble gases stable isotopes 18o and 2h to study groundwater recharge and residence times in the strongly exploited north china plain aquifer system in the area of shijiazhuang the capital of the hebei province groundwater in the unconfined parts of the piedmont plain contains tritium down to depths of about 100 m and exhibits 3h 3he ages of less than 40 years 3h 3he ages correlate well with sampling depth but less so with distance along a transect from the mountains in the west through the recharge area in the piedmont plain indicating a minor role of lateral inflow compared to spatially distributed recharge the increase of groundwater age with increasing thickness of the saturated zone combined with the steady groundwater table descent over the last decades implies an effective recharge rate of around 0 3 m yr mostly due to infiltration of precipitation and irrigation water despite the recycling of irrigation water a water balance deficit remains causing depletion of the aquifers anthropogenic modifications of the natural recharge regime appear to be reflected by a trend of increasing stable isotope ratios in groundwater of the last decades

wave set up in the storm surge along open coasts during typhoon anita abstract wave set up in storm surges is studied using a numerical model for coasts in tosa bay japan open to the pacific ocean simulation models employing only atmospheric pressures and winds as external forces are unable to properly simulate open coast storm surge heights such as those due to typhoon anita 1970 however the present study shows that a numerical model incorporating wave induced radiation stresses as well as wind stresses and pressure gradients is able to account for the open coast surge heights there is a maximum contribution of 40 by the radiation stresses to the peak sea level rises this study also evaluates the effects of the tides including the tides improves the agreement between the predicted water surface elevations and the observations the difference in predictions between one way coupling from wave to surge models and two way coupling of the surge and wave models is found to be small

coastal trapping and funneling effects on storm surges in the meghna estuary in relation to cyclones hitting noakhali cox s bazar coast of bangladesh abstract studies are described that use a fine resolution numerical model and incorporate the islands and detailed bottom topography of the meghna estuary they show that depending on the characteristics of the atmospheric cyclone and the astronomical tide storm surges can be coastal trapped in the meghna estuary and propagate like edge waves along the coastline causing widespread devastation and enormous loss of life and property the funneling effect of the narrowing estuary acts strongly on the pressure response and predominantly in the region north of sandwip island the combination of coastal trapping and the funneling effect results in the widespread nature of the surges in the meghna estuary the widespread nature of the surges is directly proportional to the wind inflow angle and to the radius of maximum cyclonic wind but inversely proportional to the angle of crossing of the cyclone as made with the coastline the cyclone striking the noakhali chittagong coast produces more widespread surges th

14c age reassessment of groundwater from the discharge zone due to cross flow mixing in the deep confined aquifer abstract in a groundwater flow system the age of groundwater should gradually increase from the recharge zone to the discharge zone within the same streamline however it is occasionally observed that the groundwater age becomes younger in the discharge zone in the piedmont alluvial plain and the oldest age often appears in the middle of the plain a new set of groundwater chemistry and isotopes was employed to reassess the groundwater 14c ages from the discharge zone in the north china plain ncp carbonate precipitation organic matter oxidation and cross flow mixing in the groundwater from the recharge zone to the discharge zone are recognized according to the corresponding changes of hco3 or dic and 13c in the same streamline of the third aquifer of the ncp the effects of carbonate precipitation and organic matter oxidation are calibrated with a 13c mixing model and dic correction but these corrected 14c ages seem unreasonable because they grow younger from the middle plain to the discharge zone in the ncp the relationship of cl content and the recharge distance is used to estimate the expected cl content in the discharge zone and ln a14c cl is proposed to correct the a14c in groundwater for the effect of cross flow mixing the 14c ages were reassessed with the corrected a14c due to the cross flow mixing varying from 1 25 to 30 58 ka and the groundwater becomes older gradually from the recharge zone to the discharge zone the results suggest that the reassessed 14c ages are more reasonable for the groundwater from the discharge zone due to cross flow mixing

sustainability of groundwater usage in northern china dependence on palaeowaters and effects on water quality quantity and ecosystem health a synthesis of groundwater ages recharge rates and information on processes affecting groundwater quality in northern china highlights the major challenges faced for sustainable management of the region s groundwater direct recharge rates range from hundreds of millimetres per year in the north china plain to tens of millimetres per year in the loess plateau to less than 4 mm year in the arid northwest recharge rates and mechanisms to deep semiconfined and confined aquifers are poorly constrained however on the basis of available data these are likely to be mostly negligible severe groundwater level declines 0 53 m year have occurred throughout northern china in the last three to four decades particularly in deep aquifers radiocarbon dating stable isotope and noble gas data show that the most intensively extracted deep groundwater is palaeowater recharged under different climate and land cover conditions to the present reservoir construction has reduced surface runoff in mountain front areas that would naturally recharge regional quaternary aquifers in many basins in combination with intensive irrigation practices this has resulted in the main recharge source shifting from surface runoff and mountain front recharge to irrigation returns this has reduced infiltration of fresh recharge at basin margins and rapidly increased nitrate concentrations and overall mineralisation in phreatic groundwater over wide areas in some cases to 400 mg l and 10 g l respectively in some basins there is evidence that poor quality shallow water has leaked into deep layers 200 m via preferential flow mixing with palaeowaters stored in semiconfined aquifers high concentrations of naturally occurring fluoride and arsenic locally 8 5 and 4 mg l respectively have recently lead to the abandonment of numerous supply wells in northern china creating further pressure on stressed water resources increasing water demand from direct and indirect consumption poses major challenges for water management in northern china which must consider the full water cycle copyright c 2012 john wiley sons ltd

spatial and temporal variability in the stable isotope systematics of modern precipitation in china implications for paleoclimate reconstructions the stable isotopic composition of materials such as glacial ice tree rings lake sediments and speleothems from low to mid latitudes contains information about past changes in temperature t and precipitation amount p however the transfer functions which link 18op to changes in t or p d 18op dt and d 18op dp can exhibit significant temporal and spatial variability in these regions in areas affected by the southeast asian monsoon past variations in 18o and d of precipitation have been attributed to variations in monsoon intensity storm tracks and or variations in temperature proper interpretation of past 18op variations here requires an understanding of these complicated stable isotope systematics since temperature and precipitation are positively correlated in china and have opposite effects on 18op it is necessary to determine which of these effects is dominant for a specific region in order to perform even qualitative paleoclimate reconstructions here we evaluate the value of the transfer functions in modern precipitation to more accurately interpret the paleorecord the strength of these transfer functions in china is investigated using multiple regression analysis of data from 10 sites within the global network for isotopes in precipitation gnip 18op is modeled as a function of both temperature and precipitation the magnitude and signs of the transfer functions at any given site are closely related to the degree of summer monsoon influence 18op values at sites with intense summer monsoon precipitation are more dependent on the amount of precipitation than on temperature and therefore exhibit more negative values in the summer in contrast 18op values at sites that are unaffected by summer monsoon precipitation exhibit strong relationships between 18op and temperature the sites that are near the northern limit of the summer monsoon exhibit dependence on both temperature and amount of precipitation comparison with simple linear models 18op as a function of t or p and a geographic model 18op as a function of latitude and altitude shows that the multiple regression model is more successful at reproducing 18op values at sites that are strongly influenced by the summer monsoon the fact that the transfer function values are highly spatially variable and closely related to the degree of summer monsoon influence suggests that these values may also vary temporally since the southeast asian monsoon intensity is known to exhibit large variations on a number of timescales annual to glacial interglacial and the magnitude and sign of the transfer functions is related to monsoon intensity we suggest that as monsoon intensity changes the magnitude and possibly even the sign of the transfer functions may vary therefore quantitative paleoclimate reconstructions based on 18op variations may not be valid

a record of temperature and monsoon intensity over the past 40 kyr from groundwater in the north china plain abstract the well known temperature dependence of noble gas solubilities in water enables the determination of absolute paleotemperature records from radiocarbon dated groundwater an advantage of the noble gas paleothermometer is that noble gas temperatures ngts can directly be related to stable isotope ratios from the same groundwater archive in order to calibrate the stable isotope thermometer over long time scales our record from heavily used aquifers of the north china plain constitutes a unique combined ngt and stable isotope data set from the region affected by the east asian monsoon in addition to providing a reliable estimate for the glacial interglacial temperature change the data enable the separation of the effects of temperature and precipitation monsoon strength on the stable isotopes although the record extends from modern waters to near the limit of the radiocarbon dating range at about 40 kyr bp the last glacial maximum is not represented probably because arid conditions limited groundwater recharge during that period the coldest observed period at about 30 kyr bp was 4 6 1 2 c cooler than the holocene whereas ngts show no systematic variation during the holocene the 18 o values increased by about 1 between the early and late holocene a similar increase of 18 o has been observed before in speleothems and ascribed to decreasing monsoon strength in response to decreasing insolation during the holocene our results confirm that the holocene trend in stable isotopes is not related to temperature in contrast 18 o and ngt are correlated within the pleistocene group of samples indicating a 18 o ngt slope of 0 18 0 05 c 1 similar to the temperature effect in modern precipitation of the region thus of the overall increase of 18 o by about 2 between 30 kyr bp and the late holocene about half is due to a temperature increase whereas the other half is due to a decrease of monsoon strength