Estimation of groundwater recharge rates using soil-water isotope profiles: a case study of two contrasting dune types on Langeoog Island,Germany     

Post  V. E. A.  Zhou  T.  Neukum  C.  Koeniger  P.  Houben  G. J.  Lamparter  A.  &#;im&#;nek  J. 《Hydrogeology Journal》2022,30(3):797-812

Hydrogeology Journal - The creation of artificial dunes for coastal protection may have important consequences for freshwater lenses in coastal aquifers. The objective of this study was to compare...  相似文献   

The first field-based descriptions of pumping-induced saltwater intrusion and upconing     

Georg Houben  Vincent E. A. Post 《Hydrogeology Journal》2017,25(1):243-247

Development of the ideas about the equilibrium between freshwater and saline water has received considerable attention in the literature, but little has been written so far about the earliest scientific works about well salinization. Based on a review of the literature from the second half of the 19th century and the early 20th century, this historical note explores how insights into groundwater abstraction and saltwater intrusion developed, and examples of the earliest field studies are provided. Fundamental research was driven by the need for increasing water supply, but the progress of science did not lead to sustainable management practices everywhere. Research outcomes were shared between scientists of different countries, marking the beginning of coastal hydrogeology as a scientific specialization in the first decade of the 20th century.  相似文献   

Electrical conductivity as a proxy for groundwater density in coastal aquifers     

Post VE 《Ground water》2012,50(5):785-792

Groundwater density is an important parameter in the interpretation of flow patterns. This paper investigates the relationship between electrical conductivity (EC) and groundwater density in coastal aquifers and evaluates the suitability of the UNESCO 1980 equation of state, developed for the world's oceans, for determining the density of groundwater based on its EC. To achieve this aim, a dataset of groundwater samples from four different types of coastal aquifers was collected. It is found that the density of a sample can be estimated to a good approximation on the basis of its EC using the UNESCO 1980 equation of state. Deviations from the equation of state were found to be due to the changes in EC and the density caused by geochemical reactions, such as the dissolution of carbonates, degradation of organic carbon, cation exchange, and sulfate loss. Owing to these deviations, the UNESCO 1980 equation of state may underestimate the density by up to 1.5 kg/m(3). The effect of this uncertainty on the correction terms applied to the hydraulic head required for a proper interpretation of groundwater flow patterns and rates is quantified. It was found that the fresh water head may be wrong by centimeters to a few decimeters. From this it is concluded that, unless the purpose of a groundwater investigation requires great accuracy, the equation of state provides an efficient and inexpensive way to estimate density from EC.  相似文献   

Spatial Periodic Boundary Condition for MODFLOW     

Tariq Laattoe  Vincent E.A. Post  Adrian D. Werner 《Ground water》2014,52(4):606-612

Small‐scale hyporheic zone (HZ) models often use a spatial periodic boundary (SPB) pair to simulate an infinite repetition of bedforms. SPB's are common features of commercially available multiphysics modeling packages. MODFLOW's lack of this boundary type has precluded it from being effectively utilized in this area of HZ research. We present a method to implement the SPB in MODFLOW by development of the appropriate block‐centered finite‐difference expressions. The implementation is analogous to MODFLOW's general head boundary package. The difference is that the terms on the right hand side of the solution equations must be updated with each iteration. Consequently, models that implement the SPB converge best with solvers that perform both inner and outer iterations. The correct functioning of the SPB condition in MODFLOW is verified by two examples. This boundary condition allows users to build HZ‐bedform models in MODFLOW, facilitating further research using related codes such as MT3DMS and PHT3D.  相似文献   

Local air temperature tolerance: a sensible basis for estimating climate variability     

Olavi Kärner  Piia Post 《Theoretical and Applied Climatology》2016,126(3-4):575-583

The customary representation of climate using sample moments is generally biased due to the noticeably nonstationary behaviour of many climate series. In this study, we introduce a moment-free climate representation based on a statistical model fitted to a long-term daily air temperature anomaly series. This model allows us to separate the climate and weather scale variability in the series. As a result, the climate scale can be characterized using the mean annual cycle of series and local air temperature tolerance, where the latter is computed using the fitted model. The representation of weather scale variability is specified using the frequency and the range of outliers based on the tolerance. The scheme is illustrated using five long-term air temperature records observed by different European meteorological stations.  相似文献   

Kinetic analysis of cation exchange in birnessite using time-resolved synchrotron X-ray diffraction     

Christina L. Lopano  Peter J. Heaney  Jeffrey E. Post 《Geochimica et cosmochimica acta》2011,75(14):3973-3981

In this study, we applied time-resolved synchrotron X-ray diffraction (TRXRD) to develop kinetic models that test a proposed two-stage reaction pathway for cation exchange in birnessite. These represent the first rate equations calculated for cation exchange in layered manganates. Our previous work has shown that the substitution of K, Cs, and Ba for interlayer Na in synthetic triclinic birnessite induces measurable changes in unit-cell parameters. New kinetic modeling of this crystallographic data supports our previously postulated two-stage reaction pathway for cation exchange, and we can correlate the kinetic steps with changes in crystal structure. In addition, the initial rates of cation exchange, R (ų min⁻¹), were determined from changes in unit-cell volume to follow these rate laws: R = 1.75[]^0.56, R = 41.1[]^1.10, R = 1.15[]^0.50. Thus, the exchange rates for Na in triclinic birnessite decreased in the order: Cs ? K > Ba. These results are likely a function of hydration energy differences of the cations and the preference of the solution phase for the more readily hydrated cation.  相似文献   

A sediment budget for a grazed semi-arid catchment in the Burdekin basin, Australia   总被引：2，自引：2，他引：0  

Rebecca Bartley  Aaron Hawdon  David A. Post  Christian H. Roth 《Geomorphology》2007,87(4):302-321

In catchments adjacent to the Great Barrier Reef World Heritage Area in Queensland, Australia, there is a growing concern that sediments and nutrients being exported from the land are having a detrimental effect on coral reef communities. There is a need to determine the processes and rates of erosion from the major land use types, so that management intervention can be initiated to reduce sediment yields where required. This paper presents a sediment budget for Weany Creek, a 13.5 km² grazed semi-arid sub-catchment of the Burdekin River catchment, Australia. A range of field methods was used to measure erosion from hillslopes, gullies and stream banks, as well as identify the amount of sediment being deposited and remobilised on the bed of gullies and the stream network. The data suggests that at least during drought conditions, the primary erosion source in this catchment is gully erosion. However, the largest source of sediment in the budget is actually associated with the remobilisation of in-channel sediment stores. Overall, the sediment budget is comprised of  81% coarse material and 19% fine sediment and an agreement between the fine sediment yield estimated in the sediment budget and the yield measured at the catchment outlet is within 10%. The total sediment yield estimated for this catchment is  4205 t yr^− 1 and is much lower than expected for a catchment of this size. This may reflect the drought conditions during the measurement period; however, there is also the possibility that the primary erosion sources have been exhausted, and the rates of sediment loss may be much lower now than they may have been in the past. Nonetheless, the results show that stored sediment, which may have been deposited in the channel many decades ago, is an important contributor to end of catchment sediment yields and warrants further investigation.  相似文献   

Fresh and saline groundwater interaction in coastal aquifers: Is our technology ready for the problems ahead?     

V. E. A. Post 《Hydrogeology Journal》2005,13(1):120-123

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Nestling diets of coexisting salt marsh sparrows: Opportunism in a food-rich environment     

William Post  Jon S. Greenlaw 《Estuaries and Coasts》2006,29(5):765-775

The saltmarsh sharp-tailed sparrow (Ammodramus caudacutus) and the morphologically similar seaside sparrow (Ammodramus maritimus) occur together in Atlantic coast salt marshes. Over 2 yr we examined food exploitation patterns to gain an understanding of how these species coexist and to characterize the trophic conditions that allow the maintenance of different mating systems within the same habitat. In the promiscuous saltmarsh sharp-tailed sparrow, only females feed the young, while the young of the socially monogramous seaside sparrow are fed by both parents. To determine dietary patterns, we used a nonlethal method (throat constriction) to obtain food samples from nestlings. Resource states were determined by sweep-netting the vegetation and by taking cores from the marsh surface. Based on volume, the same 4 prey groups (flies, amphipods, grasshoppers, moths) composed > 80% of each species diet. The main food of both sparrows was adult and juvenile (larval and pupal) soldier flies (Stratiomyidae:Odontomyia microstomata). Measures of dietary overlap, based on resource states, indicated that nestling diets did not differ between species on a seasonal basis or over 2-wk intervals. As the season progressed, each species tracked in parallel changes in resource abundance. Diets did not diverge from what was expected if food was exploited randomly; diets frequently overlapped significantly more than expected. Interspecific resource-use patterns were congruent over 2 yr. Based on the results of this study, and on an evaluation of hypotheses based on life history information from previously published work, we conclude that food usually is not limiting for these sparrows and that resource abundance has fostered behavioral and dietary opportunism.  相似文献   

A record of accelerated erosion in the recent sediments of Blelham Tarn in the English Lake district   总被引：1，自引：0，他引：1  

K. D. van der Post  F. Oldfield  E. Y. Haworth  P. R. J. Crooks  P. G. Appleby 《Journal of Paleolimnology》1997,18(2):103-120

Two frozen cores from Blelham Tarn were subsampled and measured using mineral magnetic, loss-on-ignition (LOI), radiometric, granulometric and diatom analyses. A detailed chronology was established using varves, radioisotopes and diatoms. This has enabled an accurately dated reconstruction of sedimentation over the past forty years. Despite a large increase in lake productivity, evidence suggests that the observed exponential increase in sedimentation rates can be attributed to erosion within the catchment. The predominant sediment source has been identified as surface soil. A comparison between the trend of accelerated sedimentation and the record of increased sheep stocking density for the area within which the most of the catchment lies, as well as observations of contemporary surface processes within the catchment, both suggest that much of the recent erosion is a direct response to increased pressure from sheep grazing.  相似文献