bluuebunny/crossref_metadata_2025_split huggingface dataset:
The physical framework of the dependence between channel flow hydrographs and drainage network morphometry
Authors: Garbrecht J. , Shen H. W. 
Published: February 2007

AbstractThe physical basis of the linkage between magnitude and timing of channel flow hydrographs and drainage network morphometry is reviewed. Small Hortonian and structurally Hortonian networks are analysed using numerical runoff simulation. For Hortonian networks the variability of the geometry of individual channels and subcatchments within each Strahler order has generally little effect upon the overall character of the hydrograph in channels of higher order. If the network is also structurally Hortonian, the analysis of the simultaneous formation, travel, and concentration of the hydrographs in all channels of the network can be simplified to a sequence of one representative hydrograph per channel order. This approach is used in this study. Three major runoff processes control the flow hydrograph characteristics: the overland flow process which determines the water supply to the drainage network; the channel flow process which translates the hydrograph in space and time; and the drainage network process which concentrates and magnifies the flow at the junctions of the drainage network. Functional relations for the hydrograph peak, timing, and flow velocity are presented. For a given uniform rainfall and infiltration rate, the peak of the channel flow hydrograph is shown to increase geometrically with channel order, and its magnitude is directly related to the bifurcation ratio. The travel time of the peak also increases geometrically with channel order, and it is directly related to the channel length ratio over velocity ratio. The flow velocity of the peak changes in a downstream direction as a function of the bifurcation and slope ratio. It was also found that for negligible channel storage the channel flow and drainage network processes do not contribute significantly to the observed nonlinear response of a watershed to precipitation.
Water use by intensively cultivated willow using estimated stomatal parameter values
Authors: Grip Harald , Halldin Sven , Lindroth Anders 
Published: February 2007

AbstractLarge land areas in Sweden are planned to be planted with high producing, short rotation forest stands of willow in the beginning of the 1990s. Since willow is a highly hydrophilic species, this new land use may have strong implications on water resources. To assess these implications, evaporation of Salix viminalis and Salix viminalis x caprea stands in lysimeters was analysed with the simple, yet physically realistic KAUSHA model. Parameter values for the Lohammar equation were deduced (b = 100 m3 kg−1, kmax = 0.01 m s−1), believed to be applicable to other sites. Simulated evaporation during the 1980 growth season for a normal stand with a production of 12 tonnes of dry matter per hectare per season was 526 mm, of which 375 mm was transpiration, 56 mm interception evaporation, and 95 mm soil evaporation. For an optimally irrigated 20‐tonnes stand, the total evaporation was 584 mm, of which 430 mm was transpiration. As a comparison, Penman open water evaporation was 430 mm. To avoid soil water stress in the 20‐tonnes stand, 140 mm was needed as irrigation, equivalent to 25 per cent of the mean annual precipitation. Since intensively cultivated willow plantations seemed to be using much water, it was concluded that introduction of this agri‐forestry practice must be carefully planned to make use of this property, e.g. in biological filters or in reclaiming water‐logged land.
Recovery and concentration of suspended solids in the upper rhone river by continuous flow centrifugation
Authors: Burrus D. , Thomas R. L. , Dominik J. , Vernet J.‐P. 
Published: February 2007

AbstractSix stations along the Rhône River from the Rhône Glacier to Lake Geneva were sampled by continuous flow centrifuge for recovery of suspended sediment. The samples were taken four times in the year in both 1982 and 1983. In addition, the mouth of the river was sampled in a like manner every two weeks during 1982 until August 1983. Concentration of sediment and composition did not vary as a function of depth or location across the river. Concentrations varied in time and as a function of flow and samples showed both increasing concentration in suspension and an increase in the proportion of finer particles moving downstream from source to mouth. Only slight variations in texture could be observed down the river as a function of time and appeared to relate to freezing and melting of the Rhône and other headwater glaciers as the primary sediment source. Little variation was observed annually in the texture and composition of the sediment at the river mouth despite large changes in concentration between the high flow summer and low flow winter discharges. These findings are consistent with a well‐mixed system in which the suspended sediments are directly related to the primary supply of material from the glaciers.
Hydrogeochemical processes involved in salt‐dissolution zones, texas panhandle, U.S.A.
Authors: Dutton Alan R. 
Published: February 2007

AbstractPermian evaporite deposits have been extensively dissolved beneath the perimeter of the Southern High Plains in the Texas Panhandle. Hydrologic and geochemical data were collected from six test wells to determine hydrogeochemical processes involved and the source and flow paths of ground water moving in salt‐dissolution zones. Geochemical similarities and hydraulic‐head relationships indicate that ground water dissolving halite and anhydrite moves downward from aquifers in post‐Permian formations and follows flow paths influenced by topography. Holocene salt‐dissolution rates probably are lower than Tertiary and Pleistocene rates owing to regional changes in physiography and climate that probably decreased the amount of recharge to salt‐dissolution zones. Present as well as palaeohydrologic ground‐water velocities and salt‐dissolution rates are probably less beneath the Southern High Plains than in adjacent, peripheral salt‐dissolution zones because of lower hydraulic conductivities and lower hydraulic‐head gradients. Salinities in peripheral salt‐dissolution zones are low (67 000 to 95 000 mg L−1) despite high solubility of halite, reflecting relatively open circulation of ground water. In interior salt‐dissolution zones beneath the Southern High Plains, ground‐water circulation is low and water composition tends to reach halite saturation.
The nature of iron and manganese species in dam waters
Authors: Chiswell Barry , Zaw Myint 
Published: February 2007

AbstractThe molecular weight (M. W.) distributions of iron and manganese species in dam water samples were investigated by use of gel filtration, while the ion‐exchangeable and non‐ion‐exchangeable fractions of these metals were also analysed by ion‐exchange chromatography. For the samples studied, more than 96 per cent of the manganese species present were found to be ion‐exchangeable, whilst less than 35 per cent of iron species were ion‐exchangeable. These results correlated with the finding that all the manganese species had molecular weights less than 700, but that the molecular weights of the iron species were mostly in excess of 5000. Electron paramagnetic resonance (EPR) spectroscopy has been used to support the finding that manganese is almost totally present in the form of simple aquated Mn(II) ions.
The prediction of aquatic sediment‐associated trace element concentrations using selected geochemical factors
Authors: Horowitz Arthur J. , Elrick Kent A. , Hooper Richard P. 
Published: February 2007

AbstractMultiple linear regression models calculated from readily obtainable chemical and physical parameters can explain a high percentage (70 per cent or greater) of observed sediment‐trace element variance for Cu, Zn, Pb, Cr, Ni, Co, As, Sb, Se, and Hg in a widely divergent suite of 61 sediment samples. The independent variables used in the models may be single parameters, principal component scores, or principal component scores combined with their cross‐products. The most useful type of variable must be determined on a case‐by‐case basis.The independent variables (geochemical parameters) incorporated in the models calculated during this study probably are applicable to many aquatic sediments; albeit, use of a larger data set (>61) could alter the magnitude of the calculated coefficients. The geochemical parameters included in the models were of a physical (e.g. grain size, surface area) and a chemical (e.g. organic matter, amorphous iron oxides) nature. Comparison between actual and predicted trace element concentrations obtained from the models may provide a means of defining ‘average’ sediment‐trace element concentrations. In this context, the models may also help identify either naturally or anthropogenically impacted sites for additional study.
The transformation and export of phosphorus from Wetlands
Authors: Gehrels Jim , Mulamoottil George 
Published: February 2007

AbstractThere is widespread acceptance of the phosphorus retention capability of wetlands even though research findings are often inconclusive and contradictory. The results of a one year phosphorus budget study indicate that internal wetland processes may transform sediment bound phosphorus to plant available orthophosphorus. While total phosphorus imports were nearly double the total phosphorus exports for the study wetland, orthophosphorus exports were 22 per cent greater than imports. This study supports the recent finding that wetlands have limited capability to retain orthophosphorus and indicates that wetlands may even increase the export of orthophosphorus. The generally accepted nutrient retention function of wetlands and their possible role in eutrophication is thus questionable.
Characteristics of suspended sediment in the upper rhone river, switzerland, including the particulate forms of phosphorus
Authors: Burrus D. , Thomas R. L. , Dominik B. , Vernet J.‐P , Dominik J. 
Published: February 2007

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 River.
One‐dimensional dispersion in unsteady flow in an adsorbing porous medium: An analytical solution
Authors: Yadava Raja Ram , Vinda Ram Raj , Kumar Naveen 
Published: February 2007

AbstractAnalytical solutions describing the concentration distribution along one‐dimensional unsteady seepage flow through adsorbing saturated finite porous medium have been obtained. An exponential function concentration is enforced at the source of the dispersion, while the change in the concentration is zero at the other boundary. A new time variable has been introduced to solve the unsteady flow problem and the solution is illustrated.
Rainfall interception in two tropical montane rain forests, Colombia
Authors: Veneklaas E. J. , Van Ek R. 
Published: February 2007

AbstractRainfall interception was studied during one complete year in two montane rain forests in the Colombian Andes at altitudes of 2550 and 3370 m. Additional measurements were made in a subsequent period at 3370 m, comparing two plots with different tree genera. Special attention was paid to the possible consequences of the abundant epiphytic vegetation, representing a high but spatially variable storage capacity. On an annual basis, interception amounted to 262 mm (12.4 per cent) of 2115 mm incident precipitation at 2550 m, and to 265 mm (18.3 per cent) of 1453 mm incident precipitation at 3370 m. There was no evidence for fog precipitation. The fact that, in spite of lower annual rainfall and lower evaporation rate, absolute quantity of interception at 3370 m was not lower than at 2550 m is probably related to differences in rainfall distribution and canopy storage capacities. The different responses of the two tree genera (characterized by distinct epiphyte cover) and the lower interception after prolonged wet periods support the idea that epiphytes play a significant role in the interception process. A realistic description of the water balance of such ecosystems will require the adaptation of existing interception models.
Processes of water movement through a chalk coombe deposit in Southeast England
Authors: Hodnet M. G. , Bell J. P. 
Published: February 2007

AbstractThe processes of water movement through the Coombe Deposit in a chalk dry valley near Eastbourne in Southeast England were investigated using simple methods based on regular weekly measurements of rainfall, soil water content, and soil water potential. The drainage flux (recharge) through the soil was determined using the water balance method during the winter and the zero flux plane (ZFP) method after the appearance of the ZFP in the spring. The unsaturated hydraulic conductivity was derived applying Darcy's Law in a novel way using the measured potential gradients and weekly drainage fluxes. The derived conductivity characteristics were adequate to identify the flow mechanisms, to illustrate the difference in behaviour between the horizons of the soil profile, and to give some indication of pore water velocities.The mean daily drainage flux at 2.85 m depth during the recharge period from 10 October 1980 to 29 May 1981 was 1.6 mm d−1. Weekly mean rates of up to 3.7 mm d−1 were observed, but peak short term rates must have considerably exceeded this figure. It was shown that, in the lower part of the Coombe Deposit, when drainage fluxes are large, much of the flux passes through a very small proportion of the wetted cross‐sectional area of the soil. This gives rise to pore water velocities of at least 3 m d−1 at a depth of 2.85 m and 0.5 m d−1 between 0.5 m and 2.5 m depth. These results show that pollutants may be moved very rapidly through the profile in this, and similar, material. The core sampling techniques normally used to monitor pollutant movement in the chalk are unlikely to succeed in detecting this movement, not only because it is transient but also because it occupies only a very small proportion of the water filled pores.
Digital terrain modelling: A review of hydrological, geomorphological, and biological applications
Authors: Moore I. D. , Grayson R. B. , Ladson A. R. 
Published: February 2007

AbstractThe topography of a catchment has a major impact on the hydrological, geomorphological, and biological processes active in the landscape. The spatial distribution of topographic attributes can often be used as an indirect measure of the spatial variability of these processes and allows them to be mapped using relatively simple techniques. Many geographic information systems are being developed that store topographic information as the primary data for analysing water resource and biological problems. Furthermore, topography can be used to develop more physically realistic structures for hydrologic and water quality models that directly account for the impact of topography on the hydrology. Digital elevation models are the primary data used in the analysis of catchment topography. We describe elevation data sources, digital elevation model structures, and the analysis of digital elevation data for hydrological, geomorphological, and biological applications. Some hydrologic models that make use of digital representations of topography are also considered.
The prediction of hillslope flow paths for distributed hydrological modelling using digital terrain models
Authors: Quinn P. , Beven K. , Chevallier P. , Planchon O. 
Published: February 2007

AbstractThe accuracy of the predictions of distributed hydrological models must depend in part on the proper specification of flow pathways. This paper examines some of the problems of deriving flow pathways from raster digital terrain data in the context of hydrological predictions using TOPMODEL. Distributed moisture status is predicted in TOPMODEL on the basis of spatial indices that depend on flow path definition. The sensitivity of this index to flow path algorithm and grid size is examined for the case where the surface topography is a good indicator of local hydraulic gradients. A strategy for the case where downslope subsurface flow pathways may deviate from those indicated by the surface topography is described with an example application.
Periodic drainage of ice‐dammed lakes as a result of variations in glacier velocity
Authors: Knight Peter G. , Tweed Fiona S. 
Published: February 2007

AbstractPrevious discussions of the catastrophic drainage of ice‐dammed lakes have centred on mechanisms where characteristics of the lake are crucial to drainage initiation, for example dam flotation or tunnel formation at a critical lake depth. This paper describes a mechanism for lake drainage where drainage initiation depends on the characteristics of the glacier and is independent of the characteristics of the lake. Prediction of this mechanism must be based on glacier dynamics, whereas the mechanisms most commonly discussed previously are best predicted primarily on the basis of lake evolution.An ice‐dammed lake at the margin of the glacier Solheimajokull, in southern Iceland, was observed to drain rapidly into the sub‐ or englacial drainage system, supplying water and debris to the bed or interior of the glacier. Geomorphological evidence suggests that the lake drains and refills periodically, discharging up to 13300 m3 of water into the glacier‐hydrological system. The depth of the maximum lake is insufficient to cause either flotation of the ice margin or tunnel opening by plastic deformation of the ice, and we suggest that sudden drainage is related to ice‐bed separations associated with specific glacier flow states rather than to a critical lake depth threshold. This mechanism of lake drainage has implications for conditions at the glacier bed, for the development of basal ice and for the entrainment of debris into the glacier, as well as for the prediction of potentially hazardous catastrophic drainage events and jokulhlaups from ice‐dammed lakes.
The use of 137Cs as a tracer in an erosion study in south limburg (the Netherlands) and the influence of chernobyl fallout
Authors: De Roo A. P. J. 
Published: February 2007

AbstractThe 137Cs radioactivity of soils was used as a tracer of soil erosion in a catchment in the Netherlands: 143 samples were analysed to map the 137Cs redistribution using geostatistical interpolation methods. Caesium‐137 activities on grassland are significantly higher than on arable land. Also, 137Cs activities on waning slopes are higher and activities on steep slopes are lower. The soil erosion estimates, derived from the 137Cs data, are used to validate the USLE erosion model. The recent Chernobyl nuclear accident also contributed to the 137Cs activity. However, the Chernobyl input of 137Cs, with a constant ratio of 1.765:1 to 134Cs, cannot be used as a tracer of soil erosion. Because of the rapid decay of 134Cs, we will not be possible to separate the sources of 137Cs in the near future in areas significantly influenced by Chernobyl fallout and in these areas 137Cs can no longer be used as a soil erosion tracer.
II: Wind related errors in different methods of solid precipitation measurement
Authors: Günther Th. , Graf B. 
Published: February 2007

AbstractUsing data sets assembled within the WMO Solid Precipitation Measurement Intercomparison, the paper deals with the wind related losses in national methods of solid precipitation measurement. Fourteen different types of precipitation gauges are included in the Harzgerode/GDR intercomparison field. Initial results of the comparisons between the Valdai double fence reference method and the other gauges in terms of dependence on wind speed and type of precipitation are presented. These results reveal that the national unsheltered HELLMANN gauge catches only 24 per cent to 70 per cent of the daily totals of solid precipitation as compared with the reference gauge. Results of the analysis of monthly totals and individual events reveal a similar dependence of gauge deficiencies on wind speed and type of precipitation. Case studies of single snow falls and the wind field conditions around and within the double fence reference are also described.
III: Methods of correcting for systematic errors in atmospheric precipitation measurements in Czechoslovakia
Authors: Lapin M. , Šamaj F. 
Published: February 2007

AbstractThe methods of correcting for systematic errors in precipitation measurements using the Czechoslovak gauge METRA 886 are presented. This gauge has an orifice area of 500 cm2 and is elevated 1 m above the ground. The wetting correction amounts to 0.1–0.2 mm per measurement. The evaporation correction ranges from 3 per cent in frost‐free periods to 10 per cent in frost periods. The wind‐induced correction amounts to 5 per cent for rain and 45 per cent for snow. The total sum of corrections on average 10–15 per cent per year in lower localities.
Variation in suspended sediment concentration during storm discharges in three small streams in upper osun basin, Central Western Nigeria
Authors: Jeje L. K. , Ogunkoya O. O. , Oluwatimilehin J. M. 
Published: February 2007

AbstractThe suspended sediment concentration response of three small streams draining quartzites and quartz‐schists in southwestern Nigeria to storms of varying magnitude are presented. A total of 1468 water samples from 62 storm responses with peak stream discharge values ranging from 80 to 120 l s−2 were analysed and storm and suspended sediment concentration hydrographs and hysteresis loops were used to depict the response patterns. The six different types of responses identified include the single and multiple discharge peak rises with sediment lead and lag and also the mixed response patterns. Both valley slope and channel erosion constituted important sources of suspended sediment. However, sediment availability, exhaustion, and flushing effects determined the variation in the different response types.