bluuebunny/crossref_metadata_2025_split huggingface dataset:
A case study in catchment hydrochemistry: Conflicting interpretations from hydrological and chemical observations
Authors: Jenkins Alan , Ferrier Robert C. , Harriman Ron , Ogunkoya Yinka O. 
Published: February 2007

AbstractSoil water, stream water, groundwater and rain water were sampled through a storm event in a moorland catchment. Samples were analysed for major ions and deuterium. Chloride and deuterium are used as tracers to enable separation of the stream runoff hydrograph into three components: rain, soil and groundwater. The results indicate that rain water arrives in the stream quickly during the event and contributes a significant volume to the runoff peak. The chemical signal in the rain water is, however, significantly damped, apparently due to mixing with soil water held in the catchment before the event. This is further modified before reaching the stream, apparently through mixing with a deeper groundwater component. Interpretation of tracer, chemistry and hydrological data to present an integrated picture of catchment hydrochemical response is difficult due to problems in the chemical and conceptual definition of the flow components.
Isotopic study of alluvial groundwaters, south‐west lockyer valley, queensland, australia
Authors: Dixon William , Chiswell Barry 
Published: February 2007

AbstractThe isotopic chemistry of alluvial groundwaters from two adjacent valleys are described and hydrological processes within related aquifers are identified as evidenced by oxygen‐18, deuterium, tritium and chloride data. A plot of δ18O against δD values reveals isotopic enrichment of the groundwater by the recycling of spray irrigation water. A plot of tritium versus chloride concentrations displays separate linear correlations for alluvial groundwaters within the two valleys. The salinity has a common source, therefore the separate correlations are interpreted as the past transfer of low salinity groundwater from the alluvial aquifers in one valley to the underlying sandstone aquifers.
Numerical versus field studies of delayed yield in response to a moving water‐table
Authors: Gutub S. A. , Awadalla S. A. 
Published: February 2007

AbstractAs pumping proceeds in an unconfined aquifer the water‐table is lowered and slowly drains out of the initially saturated material giving a delayed yield from storage. Although considerable work has been carried out on delayed yield, a definitive solution is still lacking. The unsaturated zone was treated here as a significant factor in delayed yield analysis. The one‐dimensional unsaturated flow equation was solved numerically to simulate the flow in the zone located between successive water levels in the unconfined aquifer for the case with zero flux at the upper boundary. The moisture content distribution curve was integrated numerically to determine the amount of water drained with time. The study shows that the numerical results are in close agreement with the monitored field data, which implies the important role of the unsaturated zone and the reliability of the numerical simulation in describing this physical phenomenon. The results show that the relationship between the flux and time is sensibly in exponential form, which agrees with the general applicability of Boulton's assumption.
Automated system for measuring snow surface energy balance components in mountainous terrain
Authors: Sauter Keith A. , McDonnell Jeffrey J. 
Published: February 2007

AbstractThe ability to continually monitor several meteorological parameters is needed to estimate snow surface energy balance components in mountainous terrain. In remote mountainous locations, limited accessibility and extreme weather conditions limit the use of delicate meteorological instrumentation. Robust instrumentation and radio telemetry are often needed to measure snow surface energy exchanges. This study examined the practicality and effectiveness of robust instrumentation in estimating radiative and turbulent exchanges in the forested Bear River Mountains of northern Utah. Measurement of reflected shortwave radiation was problematic due to possible selective absorption in the infra‐red range. This resulted in overestimates of reflected shortwave radiation and decreased estimates of now surface albedo. During high snowfall, the pyranometer and net radiometer were occasionally covered with snow, resulting in inaccurate radiation measurements. Snow typically melted from instrument surfaces in less than one day under full sun. A relative humidity measurement accuracy of ± 4% may have resulted in a possible error of 20% in the calculation of vapour pressure. Snow depth measurement with an acoustical sensor was affected by new or blowing snow, which resulted in inaccurate snow depth measurement 16.2% of the time. The longest period without a valid snow depth measurement was 19.5 hours. A new snow temperature thermocouple ladder was designed and constructed and provided accurate within‐pack temperature measurements throughout the pre‐melt and melt season.
The link between glacier velocity and the drainage of ice‐dammed lakes: Comment on a paper by knight and tweed
Authors: Lawler D. M. 
Published: February 2007

AbstractThe interesting suggestion by Knight and Tweed (1991) that a link exists between glacier velocity changes and the filling and draining of a marginal ice‐dammed lake at Sólheimajökull, southern Iceland, is examined. The main problem lies not with plausibility, but with a lack of field data to substantiate the argument. Some pertinent hydrological, glaciological and meteorological data from the area are presented here, many of which do not entirely support certain inferences and observations made in their paper. It is shown that this very small lake is likely to have limited quantitative significance in the operation of the glacio‐hydrological or solute and sediment transfer systems in this basin. Further, specific, difficulties include the absence of crucial observations on glacier velocity variations and the precise timing and pattern of lake drainage in relation to such velocity changes, the lack of evidence for a significant relationship between precipitation receipt and ice velocity here [a component of the Knight and Tweed (1991) proposition], and the occurrence of the lake drainage event in a rain‐free period (contrary to the authors' suggestion). The opportunity is also taken to correct some incidental errors.
Impact of post‐mixing chemical reactions on the major ion chemistry of bulk meltwaters draining the haut glacier d'arolla, valais, Switzerland
Authors: Brown G. H. , Sharp M. J. , Tranter M. , Gurnell A. M. , Nienow P. W. 
Published: February 2007

AbstractUntil now, alpine glacial meltwaters have been assumed to consist of two components, dilute quickflow and concentrated delayed flow, the mixing of which has been regarded as chemically conservative for the major dissolved ions and electrical conductivity. Dye tracing results suggest that this two‐component model adequately represents the sub‐glacial hydrology of the Haut Glacier d'Arolla, Switzerland. However, laboratory dissolution experiments in which various concentrations of glacial rock flour are placed in dilute solutions show that this rock flour is highly reactive and suggest that bulk meltwaters may acquire significant amounts of solute through rapid chemical reactions with suspended sediment which occur after mixing of the two components. This view is supported by detailed analysis of variations in the hydrochemistry of meltwaters draining from the Haut Glacier d'Arolla over three diurnal cycles during the 1989 melt season. Variations in the composition of bulk meltwaters are controlled by two main factors: dilution of the delayed flow component by quickflow, and the extent of post‐mixing reactions. The latter depends on the suspended sediment concentration in bulk meltwaters and on the duration of contact between these waters and suspended sediment. Seasonal changes in the magnitude of these factors result in changes in the character and causes of diurnal variations in meltwater chemistry. In June, these variations reflect discharge‐related variations in residence time within a distributed subglacial drainage system; in July, when a channelized drainage system exists beneath the lower glacier, they primarily reflect the dilution of delayed flow by quickflow; in August, when suspended sediment concentrations are particularly high, they reflect varying degrees of solute acquisition by post‐mixing reactions with suspended sediment that take place in arterial channels at the glacier bed.
Modelling sediment transport in stream channels in the arid zone of India
Authors: Sharma K. D. , Murthy J. S. R. 
Published: February 2007

AbstractEphemeral channels in arid regions convey larger amounts of sediment than perennial channels in humid regions. Sediment graphs at the outlet of channels have been derived by the standard sediment rating curve technique and by a lumped model based on the instantaneous unit sediment graph (IUSG) concept. The IUSG gives estimates of sediment transport that are better than those derived with the sediment rating curve as it takes into account the availability of erodible material within the channel bed.
Mapping waterlogging of soils using digital terrain models
Authors: Merot Ph. , Ezzahar B. , Walter C. , Aurousseau P. 
Published: February 2007

AbstractMaps of the potential waterlogging of soils were generated using hypotheses about the effect of topography on the soil water regime inspired by Beven and Kirkby's concept of saturation overland flow. The procedure was validated by comparing the simulated maps with maps derived from a 1: 25 000 soil survey for two contrasting catchments. The value and limitations of the method are discussed in the light of this comparison. The approach proposed here is relevant to modelling the distribution of intensely waterlogged soils, provided the relationship between bedrock and the limit values is established. This approach can be used for several purposes: (1) to distinguish positional waterlogging from other types of waterlogging; (2) to control the quality and consistency of waterlogging maps; and (3) to create soil water regime maps for non‐surveyed catchments. Conversely, soil water regime maps can be compared with contributing areas simulated by hydrological distributed models for validation purposes.
Dynamics of phosphorus compounds in a lowland river system: Importance of retention and non‐point sources
Authors: Svendsen Lars M. , Kronvang Brian , Kristensen Peter , Græsbøl Peter 
Published: February 2007

AbstractIntensive measurements of the fluxes of phosphorus (P) and of P retention were carried out in a Danish lowland watershed (Gjern Å) during two hydrological years (June 1987 to May 1989). Seasonal and short‐term variations of P concentrations were measured by intensive automatic sampling covering P fluxes from the entire Gjern Å watershed and two subcatchments: the Gelbæk and Lake Søbygård. Moreover, infrequent sampling was performed in all major tributaries of the river system. Transport of P compounds (dissolved and particulate P) exposed a seasonal pattern which was highly affected by flow conditions, instream processes, as well as point and non‐point sources. Stormflow P transport during the two study years (1987‐8 and 1988‐9) constituted 56 and 61% in the Gelbæk, respectively, compared with 25 and 23% in the Gjern Å, respectively. Particulate P transport in the Gelbæk constituted 56 and 75% of annual total P transport during the two years compared with 77 and 75% in the Gjern Å. The magnitude of monthly baseflow and stormflow total P loads was significantly correlated with the mean monthly discharge during baseflow and stormflow in the Gelbæk, whereas only stormflow loads were correlated to discharge in the Gjern Å. In situ measurements of retention showed that the maximum amount of P stored in the Gelbæk during summer (June to August) was 22gPm−2 (1988) compared with 27gPm−2 (1987) in the Gjern Å. Lake Søbygård was a P source during summer but a P sink during winter and on an annual basis the net P released was 810 and 1420 kg, which corresponded to 7 and 20% of the annual P export from the watershed, respectively. Retention constituted about 30% of gross P transport in the Gelbæk during summer compared with 20% in the Gjern Å. Resuspension of retained P during stormflows in September 1987 constituted 94% of the stormflow P transport and 54% of the total P transport. Monthly total P and dissolved reactive P (DRP) mass balances for the main channel of the Gjern Å revealed a significant DRP retention over 17 months (p < 0.05) caused by P adsorption on sediments and biological uptake. On an annual basis the main channel was a sink of DRP (1220 and 1660 kg P) but a source of total P (3440 and 1000 kg P). implying that the channel is an important source of particulate P. Bank erosion proved to be a significant P source in the main channel of Gjern Å, whereas P delivery from soil erosion was possibly of minor importance. The annual non‐point P export from two intensively sampled catchments was significantly higher (0.89 and 0.45 kg Pha−1 yr−1) than from the five extensively sampled subbasins (0.43 and 0.17 kg Pha−1 yr−1). No significant relationship could be established between non‐point P export and the proportion of arable land and soil type. Only for the wet year of 1987‐8 was a significant relationship established between non‐point P export and the P load from scattered dwellings outside sewage areas in five subbasins.
Scale: Landscape attributes and geographical information systems
Authors: Band L. E. , Moore I. D. 
Published: February 2007

AbstractThe roles and limitations of geographical information systems (GISs) in scaling hydrological models over heterogeneous land surfaces are outlined. Scaling is defined here as the extension of small‐scale process models, which may be directly parameterized and validated, to larger spatial extents. A process computation can be successfully scaled if this extension can be carried out with minimal bias. Much of our understanding of land surface hydrological processes as currently applied within distributed models has been derived in conjunction with ‘point’ or ‘plot’ experiments, in which spatial variations and patterns of the controlling soil, canopy and meteorological factors are not defined. In these cases, prescription of model input parameters can be accomplished by direct observation. As the spatial extent is expanded beyond these point experiments to catchment or larger watershed regions, the direct extension of the point models requires an estimation of the distribution of the model parameters and process computations over the heterogeneous land surface. If the distribution of the set of spatial variables required for a given hydrological model (e.g. surface slope, soil hydraulic conductivity) can be described by a joint density function, f(x), where x = x1, x2, x3,… are the model variables, then a GIS may be evaluated as a tool for estimating this function. In terms of the scaling procedure, the GIS is used to replace direct measurement or sampling of f(x) as the area of simulation is increased beyond the extent over which direct sampling of the distribution is feasible. The question to be asked is whether current GISs and current available spatial data sets are sufficient to adequately estimate these density functions.
Process controls and similarity in the us continental‐scale hydrological cycle from eof analysis of regional climate model simulations
Authors: Famiglietti J. S. , Braswell B. H. , Giorgi F. 
Published: February 2007

AbstractThe surface hydrological output of a regional climate model is investigated with implications for process controls on the spatial‐temporal variability of the water cycle over the continental USA. Principal component analysis was performed on the seasonal and annual hydrological cycles to determine their dominant modes of spatial variability. At both seasonal and annual time‐scales, the first principal component is dominated by precipitation, which controls seasonal wetness and evaporation and accounts for only 52 to 58% of the variability in the continental‐scale hydrological cycle. The second principal component is related to both snowmelt runoff and the time variability of weather (via its influence on the residence time of soil moisture near the land surface) and explains another 22% to 34% of the variability in the hydrological cycle. Based on these findings, a classification of hydroclimatological similarity is proposed in which two areas are similar in their hydroclimatology if their first and second principal components are similar. The classification scheme differs from classical approaches because it is based on dominant modes of variability rather than specific indices such as vegetation or seasonal wetness.
Stream network morphology and storm response in humid catchments
Authors: Troch Peter A. , De Troch Francois P. , Mancini Marco , Wood Eric F. 
Published: February 2007

AbstractAddressing scaling issues in hydrological modelling involves, among other things, the study of problems related to hydrological similarity between catchments of different scales. Recent research about catchment similarity relationships is based on distributed conceptual models of surface runoff production. In this type of hydrological modelling both infiltration excess and saturation excess runoff production mechanisms are considered. In many humid lowland areas overland flow is a rare phenomenon because of the specific conditions that prevail: moderate rainfall, high infiltration capacity and low relief. The complete drainage system in these regions consists of surface and subsurface components which have organized themselves in a given geological, geomorphological and climatic situation. A surface drainage network has developed through sapping erosion at the zone of groundwater exfiltration. The resulting hierarchical stream network is in equilibrium with large time‐scale conditions and adjusts itself dynamically to the inter‐year and seasonal meteorological fluctuations. Greater understanding of the interrelationships that underlie the storm response of catchments in humid lowland regions can be expected by focusing on stream network morphology as a function of topography, geology and climate. This paper applies the physically based mathematical model of stream network morphology, developed by De Vries (1977), to the Zwalmbeek catchment, Belgium. Based on this model and for different climatic conditions (expressed in terms of rainfall characteristics) the first‐order stream spacing versus average water‐table depth relationship is calculated. From field observations, digital elevation model derived channel network drainage densities and flood event analysis it is concluded that the 1% exceedance probability rainfall can be suggested as representative for the shaping climatic conditions in the catchment under study. The corresponding curves relating channel network characteristics, such as stream spacing, drainage density and channel geometry, to average water‐table depth are basin descriptors and could be used for comparative studies (e.g. regional flood frequency analysis). The model further allows for the prediction of the expansion and shrinkage of the first‐order channel network as a function of catchment wetness expressed in terms of the effective water‐table depth.
Global atmospheric water balance and runoff from large river basins
Authors: Oki Taikan , Musiake Katumi , Matsuyama Hiroshi , Masuda Kooiti 
Published: February 2007

AbstractAtmospheric vapour flux convergence is introduced for the estimation of the water balance in a river basin. The global distribution of vapour flux convergence, ‐ ΔH · Q is estimated using the European Centre for Medium‐Range Weather Forecasts global analysis data for the period 1980‐1988. From the atmospheric water balance, the annual mean ‐ ΔH · Q can be interpreted as the precipitation minus evaporation. The estimated ‐ ΔH · Q is compared with the observed discharge data in the Chao Phraya river basin, Thailand. The mean annual values are not identical, but their seasonal change corresponds very well. The four year mean ‐ ΔH · Q is also compared with the climatological runoff of nearly 70 large rivers. The multi‐annual mean runoff is calculated from the Global Runoff Data Centre data set and used for the comparison. There is generally a good correspondence between the atmospheric water balance estimates and the runoff observations on the ground, especially in the mid‐ and high latitudes of the northern hemisphere. However, there are significant differences in many instances. The results emphasize the importance of accurate routine observations in both the atmosphere and river runoff. The global water balance of the zonal mean is compared with prior estimates, and the estimated value from this study is found to be smaller than previous estimates. The annual water balance in each ocean and each continent are also compared with previous estimates. Generally, the global runoff estimation using the conventional hydrological water balance is larger than the result by the atmospheric water balance method. Annual freshwater transport is estimated by atmospheric water balance combined with geographical information. The results show that the same order of freshwater is supplied to the ocean from both the atmosphere and the surrounding continents through rivers. The rivers also carry approximately 10% of the global annual freshwater transport in meridional directions as zonal means.
Scaling snowdrift development rate
Authors: Lever J. H. , Haehnel R. 
Published: February 2007

AbstractFor successful snowdrift modelling, measured drift shapes should be geometrically similar to full‐scale shapes and develop at rates that scale in a known manner. Consensus exists on most modelling methods and the similitude requirements needed to meet these objectives. A notable exception is the manner to scale drift development rates. A rationale is presented for rate scaling based on an independent model and prototype mass transport measurements. This approach is validated by comparing the rate of drift development for a model Wyoming snow fence with corresponding field data. This method yields excellent agreement, whereas the alternatives differ substantially.