摘要:

AbstractDirect observation of surface displacement in two New England salt marshes shows that shrinking and swelling of the sediment is an important mechanism for water storage. This mechanism accounts for 20 per cent of the total change in water content of the sediment in Belle Isle marsh, Massachusetts, and for as much as 36 per cent and 86 per cent of the total at separate sites in Sippewissett Marsh, Massachusetts. Swelling in response to infiltration appears to follow the infiltration model of Hemondet al.(1984). Shrinkage decreases the aeration of the sediment compared to soils that do not shrink, and reduced aeration represents a physiological stress to vegetation. For a given depth of water loss, e.g. one day's evapotranspiration, more shrinkage, less aeration, and higher stresses on vegetation will occur in deeper sediment deposits.

ISSN:0885-6087    

DOI:10.1002/hyp.3360040102

出版商:John Wiley&Sons, Ltd    

年代:1990

数据来源: WILEY

摘要:

AbstractA previous hydrometric study of runoff production in tussock grassland drainage basins in Otago (45°50′S, 169°45′E), New Zealand, revealed a marked change of slope in storm hydrograph recessions. An environmental isotope study was initiated to investigate the runoff mechanisms operating and to test specific hypotheses to explain this break in the hydrograph recession. The results indicated that for quickflow volumes in excess of 10mm, the first part of the storm hydrograph can be attributed to two separate sources, namely, ‘old’ water from a shallow, unconfined groundwater reservoir and ‘new’ water from saturation overland flow on the lower wetlands of concave slopes. Despite the extensive area of wetlands, ‘old’ water runoff from the unconfined groundwater reservoir is delivered more rapidly to the stream than ‘new’ water from saturation overland flow. Substantial surface storage in the wetlands has first to be exceeded before rain becomes a significant part of stream discharge. For quickflow volumes less than 10mm, only ‘old’ water from groundwater contributes to the first part of the hydrograph recession. This means that only the largest 7 per cent of storms (in terms of quickflow volume) generate quickflow containing significant amounts of ‘new water’. The second part of the recession of the storm hydrograph consists of ‘old’ water derived from a remarkably well‐mixed

ISSN:0885-6087    

DOI:10.1002/hyp.3360040103

出版商:John Wiley&Sons, Ltd    

年代:1990

数据来源: WILEY

摘要:

AbstractThe role of the open standpipe Casagrande piezometer for determining soil pore pressures is still important because of its simplicity and reliability in comparison with transducer type instruments. Such factors are especially relevant when instrumentation is used on remote and inaccessible sites. The limitations of Casagrande type systems relate to poor response times, particularly in soils of low permeability, and the complexity of the normal gas bubbling equipment used to monitor and record data from this type of piezometer.The response can be improved, providing the design of the installation is taken into consideration in terms of the piezometer collection area and standpipe sizes. A simple acoustic technique has been developed by Geotechnical Monitoring Ltd, to monitor and record piezometric levels. This is based on measuring the period for the return echo of a high frequency signal; a technique widely used to focus cameras that has been found to be reliable and accurate. However, trials on landslide sites in Indonesia highlighted problems which related more to a lack of development rather than any fundamental problems in the method of monitoring standpipes. This paper describes such problems and how they might be overcome.

ISSN:0885-6087    

DOI:10.1002/hyp.3360040104

出版商:John Wiley&Sons, Ltd    

年代:1990

数据来源: WILEY

摘要:

AbstractAn empirical hyperbolic scale‐dependent dispersion model, which predicts a linear growth of dispersivity close to the origin and the attainment of an asymptotic dispersivity at large distances, is presented for deterministic modelling of field‐scale solute transport and the analysis of solute transport experiments. A simple relationship is derived between local dispersivity, which is used in numerical simulations of solute transport, and effective dispersivity, which is estimated from the analysis of tracer breakthrough curves. The scale‐dependent dispersion model is used to interpret a field tracer experiment by nonlinear least‐squares inversion of a numerical solution for unsaturated transport. Simultaneous inversion of concentration‐time data from several sampling locations indicates a linear growth of the dispersion process over the scale of the experiment. These findings are consistent with the results of an earlier analysis based on the use of a constant dispersion coefficient model at each of the sampli

ISSN:0885-6087    

DOI:10.1002/hyp.3360040105

出版商:John Wiley&Sons, Ltd    

年代:1990

数据来源: WILEY

摘要:

AbstractA large groundwater system in the Amadeus Basin, central Australia, discharges to a chain of playa lakes 500 km long. The playas contain highly concentrated brines; these are sodium‐chloride rich waters with appreciable magnesium and sulphate and very low concentrations of calcium and bicarbonate. Gypsum, glauberite, and other evaporite minerals are precipitating in the playas. The groundwaters evolve to brine by concurrent processes of dissolution, evaporative concentration, mineral precipitation, and mineralogical change. Chemical evolution is considered with reference to a concentration factor based on chloride. Ion transfer calculations demonstrate losses of magnesium and bicarbonate throughout, as a result of precipitation. Sodium, potassium, calcium, and sulphate are gained initially as a result of dissolution but lost subsequently as a result of precipitation.Larger playas in the chain, exemplified by Lake Amadeus, have dual shallow and deep groundwater flow paths whereas the smaller playas, exemplified by Spring Lake, have only shallow flow paths. Brines in the larger playas are diluted by deep groundwaters and this is reflected in the degree of saturation attained with respect to particular minerals. Thus, saturation with respect to gypsum and glauberite is attained earlier in Spring Lake than in Lake Amadeus. Saturation with respect to halite is attained in Spring Lake but not in Lake Amadeus. Both playas are undersaturated with respect to hexahydrite and sylvite although these minerals occur in efflorescent crusts in Spring Lak

ISSN:0885-6087    

DOI:10.1002/hyp.3360040106

出版商:John Wiley&Sons, Ltd    

年代:1990

数据来源: WILEY

摘要:

AbstractThis paper presents case study applications for the hydraulically‐based geomorphologic Instantaneous Unit Hydrograph (IUH), developed by Diaz‐Granadoset al.(1986). This IUH was derived as a function of watershed geomorphology and stream response to lateral inflows. This response was determined by solving one‐dimensional linearized equations of motion including a simple infiltration expression approximated by an infiltration coefficient multiplied by the streamflow discharge. Three gauged watersheds in Saudi Arabia are selected as case studies. A procedure for estimating the stream response parameters (the flow depth, the flow velocity, and the infiltration coefficient) is provided. A comparison is made between the observed and computed hydrographs and an evaluation of the IUH results and limitations is pro

ISSN:0885-6087    

DOI:10.1002/hyp.3360040107

出版商:John Wiley&Sons, Ltd    

年代:1990

数据来源: WILEY

摘要:

AbstractSix stations along the Upper Rhone River above Lake Geneva were sampled by continuous flow centrifuge for recovery of suspended sediment. The samples were taken four times, once in 1982 and three times in 1983. In addition the mouth of the river was sampled in a like manner every two weeks during 1982 until August 1983. Samples were analysed for the major elements SiO2, Al2O3, K2O, MgO, Na2O, CaO, and Fe2O3; for trace elements, Zn, Cu, Ni, Mn, and Cr; for Org. C and Kjeldahl N; and the forms of phosphorus bound as Organic P (OP), Apatite P (AP), and Non Apatite Inorganic P (NAIP). The major elements and trace metals confirmed that there is virtually no change in the major geochemical characteristics of the suspended solids in the Rhone, spatially or temporally, indicating that this river is a well‐mixed sedimentary system. AP also remained consistent in concentration throughout the year. Sediment recovered during the winter low flow, low turbidity period has been designated SED 1 whereas sediment from the high flow, high turbidity summer condition of the river has been designated SED 2. Org C, OP, and NAIP show a dramatic decrease in concentration from SED 1 to SED 2. The decline is ascribed to dilution of a relatively constant supply of organic matter and phosphorus derived mainly from point source sewage treatment plants to the Rhone. This results in variable partitioning of the OP/NAIP and Org C under the different turbidity condition in the river between winter and summer. This interpretation is confirmed by a low and consistent C‐N ratio which except for March remains below 10. Higher values in March may be indicative of soil erosion during spring melt in the agricultural lands of the Rhone Valley. The estimated proportion of particulate bio‐available phosphorus is 14 per cent for SED 1 and 7 per cent for SED 2. These low values would suggest that there would be no observable direct effect on the primary production of the receiving waters of Lake Geneva, which would thus respond only to the cumulative loading of phosphorus from the Rhone

ISSN:0885-6087    

DOI:10.1002/hyp.3360040108

出版商:John Wiley&Sons, Ltd    

年代:1990

数据来源: WILEY

ISSN:0885-6087    

DOI:10.1002/hyp.3360040109

出版商:John Wiley&Sons, Ltd    

年代:1990

数据来源: WILEY

ISSN:0885-6087    

DOI:10.1002/hyp.3360040101

出版商:John Wiley&Sons, Ltd    

年代:1990

数据来源: WILEY