Seasonal connections between meteoric water and streamflow generation along a mountain headwater stream     

Sam J. Leuthold  Stephanie A. Ewing  Robert A. Payn  Florence R. Miller  Stephan G. Custer 《水文研究》2021,35(2):e14029

In snowmelt-driven mountain watersheds, the hydrologic connectivity between meteoric waters and stream flow generation varies strongly with the season, reflecting variable connection to soil and groundwater storage within the watershed. This variable connectivity regulates how streamflow generation mechanisms transform the seasonal and elevational variation in oxygen and hydrogen isotopic composition (δ¹⁸O and δD) of meteoric precipitation. Thus, water isotopes in stream flow can signal immediate connectivity or more prolonged mixing, especially in high-relief mountainous catchments. We characterized δ¹⁸O and δD values in stream water along an elevational gradient in a mountain headwater catchment in southwestern Montana. Stream water isotopic compositions related most strongly to elevation between February and March, exhibiting higher δ¹⁸O and δD values with decreasing elevation. These elevational isotopic lapse rates likely reflect increased connection between stream flow and proximal snow-derived water sources heavily subject to elevational isotopic effects. These patterns disappeared during summer sampling, when consistently lower δ¹⁸O and δD values of stream water reflected contributions from snowmelt or colder rainfall, despite much higher δ¹⁸O and δD values expected in warmer seasonal rainfall. The consistently low isotopic values and absence of a trend with elevation during summer suggest lower connectivity between summer precipitation and stream flow generation as a consequence of drier soils and greater transpiration. As further evidence of intermittent seasonal connectivity between the stream and adjacent groundwaters, we observed a late-winter flush of nitrate into the stream at higher elevations, consistent with increased connection to accumulating mineralized nitrogen in riparian wetlands. This pattern was distinct from mid-summer patterns of nitrate loading at lower elevations that suggested heightened human recreational activity along the stream corridor. These observations provide insights linking stream flow generation and seasonal water storage in high elevation mountainous watersheds. Greater understanding of the connections between surface water, soil water and groundwater in these environments will help predict how the quality and quantity of mountain runoff will respond to changing climate and allow better informed water management decisions.  相似文献   

A high speed near infrared photometer for lunar occultation studies     

Ashok  N. M.  Chandrasekhar  T.  Ragland  Sam  Bhatt  H. C. 《Experimental Astronomy》1994,4(3-4):177-188

A recently developed near infrared high speed photometer intended for lunar oc-cultation studies is described. The primary scientific objective is to reach milli arc second levels of angular resolution so that circumstellar structure of the occulted sources can be resolved. Near infrared sky brightness close to the lunar limb is also studied. Angular diameter derived from the observed occultation of IRC +20169 is presented and system performance discussed.  相似文献   

Evaluation of approaches to calculate debris-flow parameters for hazard assessment   总被引：2，自引：0，他引：2  

Marcel Hürlimann  Dieter Rickenmann  Vicente Medina  Allen Bateman 《Engineering Geology》2008,102(3-4):152

Many different runout prediction methods can be applied to estimate the mobility of future debris flows during hazard assessment. The present article reviews the empirical, analytical, simple flow routing and numerical techniques. All these techniques were applied to back-calculate a debris flow, which occurred in 1982 at La Guingueta catchment, in the Eastern Pyrenees. A sensitivity analysis of input parameters was carried out, while special attention was paid to the influence of rheological parameters. We used the Voellmy fluid rheology for our analytical and numerical modelling, since this flow resistance law coincided best with field observations. The simulation results indicated that the “basal” friction coefficients rather affect the runout distance, while the “turbulence” terms mainly influence flow velocity. A comparison of the velocity computed on the fan showed that the analytical model calculated values similar to the numerical ones. The values of our rheological parameters calibrated at La Guingueta agree with data back-calculated for other debris flows. Empirical relationships represent another method to estimate total runout distance. The results confirmed that they contain an important uncertainty and they are strictly valid only for the conditions, which were the basis for their development. With regards to the simple flow routing algorithm, this methods could satisfactorily simulate the total area affected by the 1982 debris flow, but it was not able to directly calculate total runout distance and velocity. Finally, a suggestion on how different runout prediction methods can be applied to generate debris-flow hazard maps is presented. Taking into account the definition of hazard and intensity, the best choice would be to divide the resulting hazard maps into two types: “final hazard maps” and “preliminary hazard maps”. Only the use of numerical models provided final hazard maps, because they could incorporate different event magnitudes and they supplied output-values for intensity calculation. In contrast, empirical relationships and flow routing algorithms, or a combination of both, could be applied to create preliminary hazard maps. The present study only focussed on runout prediction methods. Other necessary tasks to complete the hazard assessment can be looked up in the “Guidelines for landslide susceptibility, hazard and risk zoning” included in this Special Issue.  相似文献   

Geotechnical properties of evaporite soils of the Dead Sea area     

Sam Frydman  Josef Charrach  Ian Goretsky 《Engineering Geology》2008,101(3-4):236-244

The Dead Sea Basin is the lowest point on earth and is tectonically subsiding. During the Holocene Period the climate became much drier with increasing evaporation whereby initially lacustrine sediments were deposited from the non-marine brines, giving a multi-layered stratigraphy of lime carbonate and halite sediments. The lime carbonate sediments are comprised of laminated, clay to silt sized, clastic sediments (calcite) and authigenic aragonite and gypsum. The halite commonly appears as rock salt. Chemical industries, based on harvesting the salts from the Dead Sea, have developed on both the Israeli and the Jordanian sides of the basin. The lime carbonate soils are used for dike construction, and these soils, together with significant salt layers, are encountered in the foundations of structures, dikes, and tailings dams, requiring definition of their geotechnical properties. Use of standard soil mechanics definitions and testing approaches for the lime carbonates have been found inapplicable, particularly in view of their exceptionally high saline content, and it has been necessary to develop new concepts. The rock salt is encountered at shallow depths, with unit weights considerably lower than those usually discussed in the literature, and with correspondingly different mechanical properties. The geotechnical properties of these soils, and approaches used to define them, are discussed in the paper.  相似文献   

Diffusion of seawater ions. Part II. The role of activity coefficients and ion pairing     

Amitai Katz  Sam Ben-Yaakov 《Marine Chemistry》1980,8(4):263-280

A theoretical evaluation of basic thermodynamic relationships reveals that variation of activity coefficients, ion pairing and electrical interactions must be considered when modelling ionic diffusion in seawater. The contributions of ion-pair formation and change in activity coefficient along the diffusion path were studied experimentally by conducting diffusion experiments in which solutions of KCl, NaCl, MgCl₂, Li₂SO₄, K₂SO₄, Na₂SO₄ and MgSO₄, at an ionic strength of 0.7, were allowed to diffuse into distilled water. The study reveals that the thermodynamic factor, required to correct for changes in the activity coefficient along the diffusion path, is significant for all the salts studied. Agreement between a simple diffusion model, which does not include ion pairing, and observed data was good for completely dissociated salts, but poor for salts which are known to form ion pairs at the concentration levels studied. The diffusion of MgSO₄, 0.425 of which is associated at I = 0.7, was successfully modelled by assuming that the diffusion coefficient of the MgSO₄⁰ ion pair is different from the diffusion coefficient of the dissociated salt. The diffusion coefficient of this ion pair is estimated to be 1.9 × 10⁻⁵ cm² s⁻¹ at 30°C, as compared to 0.49 × 10⁻⁵ cm² s⁻¹ for the dissociated salt. It is suggested that the high mobility of this ion pair could cause magnesium enrichment in pore water of sulfate depleted sediments.  相似文献   

Seasonal growth and mortality of Euphausia superba in Admiralty Bay, South Shetland Islands, Antarctica     

McClatchie  Sam; Rakusa-Suszczewski  Stanislaw; Filcek  Krzysztof 《ICES Journal of Marine Science》1991,48(3):335-342

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Environmental issues with Australian ports     

Sam Bateman 《Ocean & Coastal Management》1996,33(1-3)

Ports and shipping operations are under increased environmental scrutiny in Australia, particularly as so many of Australia's ports and shipping routes are located in or near major environmentally sensitive areas. The environmental risks involved have been highlighted by the publicity given to shipping accidents. Environmental regulations over aspects of port operations, including ballast water management, dredge spoil and waste reception, are also becoming stricter. While port authorities have adopted stringent environmental guidelines, they remain concerned that the full impact of proposed new environmental regulations on maritime industry may not be fully understood. This paper discusses some of the issues involved with achieving a balance between environmental protection and the need to recognise the importance of seaborne trade to Australia and to maintain Australia's competitiveness in international trade.  相似文献   

Determination of palladium and platinum in seaweed     

Jae Sam Yang 《Journal of Oceanography》1989,45(6):369-374

Palladium and platinum concentrations were determined for twenty two species of seaweed from the California coast, U.S.A.. A new sensitive analytical technique using atomic absorption spectrometry was developed for palladium in seaweed. For the first time, palladium contents in seaweed were obtained. The contents of palladium and platinum varied from 0.09 to 0.61 ng g^–1 and 0.25 to 1.75 ng g^–1 in dried material, respectively.The average ratio of Pt/Pd found in seaweed was 3.5, while the ratio of Pt/Pd was 4.5 in seawater. Therefore, it is postulated that there is no discrimination for seaweed to accumulate palladium and platinum from the ambient seawater due to the chemical similarity of the metals.  相似文献   

On the CO₂O₂ system in the Northeastern Pacific     

Sam Ben-Yaakov 《Marine Chemistry》1972

The TCO₂, O₂, TA and δ¹³C data of the 1969 Geosecs Intercalibration Cruise was analyzed and found to be consistent with a vertical mixing model which assumes that each point along a vertical profile is a mixture of the upper and lower boundaries. Calculated regression coefficients are in agreement with the model of Redfield et al. (1963) and with the assumption that TA variation is due to carbonate reaction. Oxygen consumption and TCO₂ production decrease exponentially with depth and approximately 80% of ΔCO₂ can be accounted for, on average, by O₂ consumption. The remaining 20% are probably due to carbonate solution which seems to take place at depths below 2,500 m. The present study suggests that the isotopic composition (δ¹³C) of the carbon source, required to account for most of the oxygen consumed, may be heavier than the value of −23%. assigned to dissolved organic carbon and particulate organic carbon.  相似文献   

Application of FLATModel, a 2D finite volume code, to debris flows in the northeastern part of the Iberian Peninsula   总被引：7，自引：3，他引：4  

Vicente Medina  Marcel Hürlimann  Allen Bateman 《Landslides》2008,5(1):127-142

FLATModel is a two-dimensional shallow-water approximation code with corrections and modifications that create a simulation tool adapted to debris-flows behaviour. FLATModel uses the finite volume method with the numerical implementation of the Godunov scheme and includes correction terms regarding the effect of flow over high slopes and curvature. Additionally, the stop-and-go phenomenon, the basal entrainment and a correction regarding the front inclination of the final deposit are incorporated into FLATModel. In addition, different flow resistance laws were integrated in the numerical code including Bingham, Herschel–Bulkley and Voellmy fluid model. Firstly, our numerical model was validated using analytical solutions of a dam-break scenario and published data on a laboratory experiment. Secondly, three real events, which occurred in the northeastern part of the Iberian Peninsula, were back-calculated. Although field observations of the three events are not very detailed, the back-analyses revealed interesting patterns on the flow dynamics, and the numerical results generally showed good agreement with field data. Comparing the different flow resistance laws, the Voellmy fluid model presents the best behaviour regarding both the flow behaviour and the deposit characteristics. Preliminary simulation runs incorporating the effect of basal entrainment offered satisfactory results, although the final volume is rather sensitive on the selected friction angle of channel-bed material. The outcomes regarding the correction of the calculated front inclination of the final deposit showed that this implementation strongly improves the simulation results and better represents steep fronts of final deposits.  相似文献