bluuebunny/crossref_metadata_2025_split huggingface dataset:
Mathematical model for evaluation of the effect of soil erosion on soil productivity
Authors: Todorovic P. , Woolhiser D. A. , Renard K. G. 
Published: February 2007

AbstractThis paper is concerned with the development of a stochastic model for evaluating the long‐term effect of soil erosion on soil productivity. Due to random variations in annual crop yield, the effect of erosion on crop production is not easily detectable in the short run, but becomes gradually evident over a sufficiently long time period. Under these circumstances, it seems that an experimental approach to this problem may be very difficult. The long period of time over which such an experiment has to be conducted may result in prohibitively high costs. In addition, it also means that eventual resolution of this problem must be postponed until a distant future time. The stochastic model formulated here provides us with a useful tool to assess the trend in quantitative changes in crop production due to erosion and to project future crop losses. The model is a discrete parameter stochastic process. Its derivation is based on a single assumption that the annual loss rates form a sequence of independent random variables {Zi}1∞ (in this paper, we consider only two particular cases: (a) {Zi}1∞ is a sequence of constants; (b) {Zi}1∞ is a sequence of independent identically distributed random variables). For these particular cases, we obtained its marginal n‐dimensional distribution function and correlation function. One of the principal model features is its simple structure and remarkable lack of restrictive and unrealistic assumptions.
An evaluation of the universal soil loss equation and field techniques for assessing soil erosion on a tropical alfisol in western Nigeria
Authors: Mtakwa P. W. , Lal R. , Sharma R. B. 
Published: February 2007

AbstractFour techniques for soil erosion assessment were compared over two consecutive seasons for bare‐fallow plots and a maize‐cowpea sequence in 1985 at IITA, Ibadan, Nigeria. The techniques used were: tracer (aluminium paint), nails (16 and 25), the rill method, and the Universal Soil Loss Equation (USLE). Soil loss estimated by these techniques was compared with that determined using the runoff plot technique.There was significantly more soil loss (P < 0·01) in bare‐fallow than in plots under maize (Zea mays) or cowpea (Vigna unguiculata). In the first season, soil loss from plots sown to maize was 40·2 Mg ha−1 compared with 153·3 Mg ha−1 from bare‐fallow plots. In the second season, bare‐fallow plots lost 87·5 Mg ha−1 against 39·4 Mg ha−1 lost from plots growing cowpea. The techniques used for assessing erosion had no influence on the magnitude of soil erosion and did not interfere with the processes of erosion. There was no significant difference (P < 0·05) between soil erosion determined by the nails and the runoff plot technique. Soil loss determined on six plots (three under maize, three bare‐fallow) by the rill technique, at the end of the season, was significantly lower (P < 0·05) than that determined by the runoff plot technique. The soil loss estimated by the rill method was 143·2, 108·8 and 121·9 Mg ha−1 for 11, 11, and 8 per cent slopes respectively, in comparison with 201·5, 162·0, and 166·4 Mg ha−1 measured by the runoff plot method. Soil loss measured on three bare‐fallow plots on 10 different dates by the rill technique was also significantly lower (P < 0·01) than that measured by the runoff plot. In the first season the USLE significantly underestimated soil loss. On 11, 11, and 8 per cent slopes, respectively, soil loss determined by the USLE was 77, 92, and 63 per cent of that measured by the runoff plot. However, in the second season there was no significant difference between soil loss determined by the USLE and that determined by the conventional runoff plot technique.
Hydrologic parameters of salt marsh peat
Authors: Knott Jayne Fifield , Nuttle William Kensett , Hemond Harold Field 
Published: February 2007

AbstractBecause of their profound influence on water movement and nutrient cycling in salt marshes, the two key physical properties of hydraulic conductivity and compressibility were studied in the Great Sippewissett Marsh and in the Ebben Creek Marsh in Massachusetts. Hydraulic conductivity was the most variable property: most frequently observed conductivities were of the order of 10−3 cm s−1 in both marshes, but extremes ranged from about 10−1 to 10−5 cm s−1. Compressibility was much less variable, and contributed of the order of 10−3 cm−1 to the specific storativity of marsh sediment, making compression a major mechanism for changes in water storage in the sediment. Surface sediments frequently exhibited below‐average conductivity, in contrast to freshwater bog peats which are usually most conductive at the surface. These measured properties may be applied to estimate the importance of many critical processes, such as the extent of infiltration occurring on the marsh surface, the hydrologic influence of the tidally varying creeks, and the hydrologic response to spring‐neap tidal cycles.
The erodibility of some Nigerian soils: A comparison of rainfall simulator results with estimates obtained from the Wischmeier nomogram
Authors: Vanelslande A. , Lal R. , Gabriels D. 
Published: February 2007

AbstractThe erodibility (K) of 55 surface soils, sampled from different regions of Nigeria, was assessed using a rainfall simulator, and compared with estimates (Kc) obtained using the Wischmeier nomogram method (Wischmeier et al., 1971). Soil erodibility values ranged from 0.000 to 0.535. The actual measured erodibility was greater than that estimated, often by several orders of magnitude. In soils with high silt content, however, the estimated Kc was slightly higher than the measured K. The K factor was significantly and negatively correlated with the infiltration rate, organic carbon content, sand fraction, wet density, and percentage stable aggregates. In contrast, the K factor was positively correlated with per cent reduction in infiltration rate, clay, and silt content, and the instability indices proposed by Henin and De Leenheer‐De Boodt. Slaking of aggregates and surface sealing were important factors governing runoff rate and sediment transport. Possible modifications to the nomogram for adaptation to tropical soils are also discussed.
A computer‐based datalogging system used to investigate the infiltration process under natural rainfall conditions
Authors: Essery C. I. , Wilcock D. N. , McClean W. 
Published: February 2007

AbstractThe system described in this paper uses a commercial, portable computer to monitor rainfall, surface runoff, soil moisture potential, soil temperature, and water table levels. The system is designed as a permanent field instrument which reads 16 analogue and two digital channels. It offers 10‐bit accuracy and records data on both magnetic tape and paper for greater security. The computer program is in Microsoft BASIC and can therefore be readily altered to change the measurement regime. Although designed to investigate the infiltration process the system is easily adapted to monitor other environmental processes.
Exceedance probability distributions of steady conduit flow in karst aquifers
Authors: Smart C. C. 
Published: February 2007

AbstractDischarge exceedance probabilities are calculated for a simple model karst aquifer composed of a few multilevel conduits with recharge from a single sinking stream with an exponential flow exceedance distribution. It is assumed that outflow instantaneously matches inflow, so that the conduit volume is constant but discharge is governed by the head in a volumeless shaft at the top end of the system. It is shown that small single conduit aquifers will frequently overflow at the surface during floods and the exceedance probability of flow through the aquifer and over the surface can be defined as a function of the inflow distribution and the form of the aquifer. Systems with multiple conduits will overflow less frequently, but each conduit will exhibit a flow distribution characteristic of its form and position in the vertical hierarchy. Comparison of these findings with actual flow data from a conduit aquifer shows that the approach is valid, although imprecise. The model is unlikely to be applied directly, as it requires unusually detailed data. However, it provides for the first time an indication of typical flow durations for surface overflows and individual conduits in a karst aquifer. Contrasts in flow duration will have a profound influence on solutional and sedimentary processes in the karst system.
Some aspects of the hydrology of one‐day annual minimum low flows of malawian rivers
Authors: Sefe F. T. K. 
Published: February 2007

AbstractFive aspects of the hydrology of one‐day annual minimum flows QIM, have been studied using data from twelve catchments in Malawi. Results indicate that the log‐normal distribution can be fitted to all twelve catchments. Four of the rivers studied are intermittent. Application of statistical methods developed in meterology to the dichotomous‐transformed data of these catchments revealed that two are ‘flow‐dominant’ and the other two are ‘dry‐dominant’. Another catchment is entirely dominated by a hydraulic gradient towards the Shire River and Elphant Marsh and so dries up every dry season for considerable periods of time despite the relatively high rainfall in the catchment. QIM, t‐days after the date of occurrence of QIM(May), can be better estimated from simple regression than from an empirically determined recession constant.
Soil saturation patterns in steep, convergent hill‐slopes under forest and pasture vegetation
Authors: Petch R. A. 
Published: February 2007

AbstractThe relationships between hillslope form and the development of zones of hillslope saturation are central to studies of process hydrology. These relationships are examined in two small, steep (30°) first‐order basins under forest and pasture vegetation. Hillslope saturation patterns are described using a probability analysis of observations of peak water table elevations made at individual sites in each basin. In both first‐order basins, the effects of topographic convergence on the spatial variability of hillslope saturation zones are most pronounced on shallow slopes and in steeper areas where hillslope form is strongly concave.The implications of vegetation type on the formation and variation of hillslope saturation are also examined. The differences in hillslope saturation patterns in each vegetation type are attributed primarily to differences in net rainfall and not soil physical properties or other features of topography.
A model of river flow forecasting for a small forested mountain catchment
Authors: Fukushima Yoshihiro 
Published: February 2007

AbstractA model for quantitatively expressing the hydrological cycle in a forested mountain catchment is proposed as a HYCYMODEL. HYCYMODEL is able to predict both short‐ and long‐term hydrographs because the model parameters remain independent of time. It shows a good applicability for ten years of continuous data at both hourly and daily intervals for the Kiryu catchment—a forested mountain basin. Since HYCYMODEL does not need hydrograph separation between storm flow and base flow, it is a particularly attractive model.
Drainage basin peak discharge rating curve
Authors: Rogers Wilbur F. , Singh Vijay P. 
Published: February 2007

AbstractThe stream gauge rating curve for a drainage basin can be transformed into a drainage basin peak discharge rating curve that is more stable than the rating curve from which it is derived. The resulting drainage basin peak discharge rating curve can be used to predict peak discharge, identify anomalous discharges caused by channel obstructions or other causes, evaluate the effect of flood retarding structures, and evaluate historical records. The drainage basin peak discharge rating curve is valid for drainage basins of any size, for any discharge up to the time of concentration, and for snowmelt.
Stream nitrate levels in a small catchment in south west England over a period of 15 years (1970‐1985)
Authors: Burt T. P. , Arkell B. P. , Trudgill S. T. , Walling D. E. 
Published: February 2007

AbstractStream nitrate levels in a small catchment of mixed land use (the Slapton Wood catchment) have been studied since September 1970; a record of this length is possibly unique in the United Kingdom for such a small basin (94 ha). A sustained increase in nitrate concentration has been observed during the study period. In addition to this long‐term trend, short‐term changes in nitrate concentrations relate to stream discharge levels and to seasonal variations. Multivariate statistical analysis has been used to quantify these trends and to identify those factors controlling the production and loss of nitrate from the catchment system. The main period of nitrate removal occurs in winter when high concentrations coincide with the main period of throughflow generation. The influence of climatic variability is illustrated by reference to the 1975/76 drought and post‐drought period.
Field application of a numerical method for the derivation of baseflow recession constant
Authors: Bako M. D. , Owoade Ayodele 
Published: February 2007

AbstractIn an earlier paper (Bako and Hunt, 1988), a method for the derivation of the baseflow recession constant (K) using one‐way analysis of variance was presented. This paper presents the results of the field application of this method. The K values obtained by using the numerical equation of Bako and Hunt (1988) were inserted in the exponential recession equation (Barnes, 1939) to generate a series of baseflows. The fit between the model and the historical flows was found to be greater than 99 per cent thus confirming the applicability of the numerical method under field situation. The main advantage of this technique is its amenability for computerized application thus making it relatively faster than any of the existing techniques of fitting the recession equation. For this reason, the subjectivity inherent in most of the existing techniques is eliminated and a measure of procedural consistency can be guaranteed. Consistency is necessary if intercatchment comparison or interpolation of K values is to be meaningful.
Effect of groundwater interception and irrigation on salinity and piezometric levels of an aquifer
Authors: Ghassemi F. , Thomas G. A. , Jakeman A. J. 
Published: February 2007

AbstractThe major strategy used to prevent the discharge of highly saline groundwater to the River Murray in southeastern Australia is groundwater interception and disposal. The basic design principle assumes that the extraction of groundwater from an aquifer hydraulically connected to the river, using a line of pumps positioned close and roughly parallel to the river, will decrease piezometric heads thereby reducing the discharge of saline groundwater to the river. The paper considers one of these schemes which was designed for the Mildura area on the basis of a hydrogeological investigation. It analyses the effects on piezometric head and groundwater salinity due to the groundwater interception scheme and adjacent irrigation activity over a period of several years from January 1980. It is shown that piezometric heads have decreased significantly in the stretch close to the river. A slight reduction in groundwater salinity is also apparent in this stretch except for an area between the river and a holding basin used for disposal of the saline effluents emanating from the groundwater interception scheme. This general reduction in groundwater salinity is mainly caused by pumping from the groundwater interception scheme and recharge from irrigation. The exception in the trend in groundwater salinity is due to the movement of a highly saline body of groundwater from the holding basin towards the River Murray. Results of this Australian experience should be helpful to the designers of similar salinity mitigation schemes elsewhere.
Measurement and analysis of depression storage on a hillslope
Authors: Sneddon J. , Chapman T. G. 
Published: February 2007

AbstractA precise photogrammetric technique was used to determine the microtopography of seven 2.6 m × 1.2 m experimental units located on a hillslope. Surface elevations were determined with an accuracy of better than 1 mm, from which contours at 2mm intervals were interpolated. These contour plots were then manually interpreted to define depressions and associated storage volumes. Analysis of the results highlighted the complex variability of depression storage over the hillslope, for example there being little relation between depression storage volumes and unit slope. This study also highlights the sampling problem for the measurement of depression storage on natural surfaces, which appears not to have been formally recognized previously, and also emphasizes the practical difficulty of achieving depression storage estimates with coefficients of variation less than ten per cent to 50 per cent, much of this variability being due to problems of interpretation rather than measurement of the surface.
Calibration and use of pressure transducers in soil hydrology
Authors: Dowd J. F. , Williams A. G. 
Published: February 2007

AbstractLaboratory and field experiments demonstrated that solid state pressure transducers are accurate and reliable devices for frequent measurements of soil suction. However, each transducer had to be individually calibrated before use and a hanging column procedure designed for this purpose is described. Analysis showed that each transducer had a linear response and that environmental conditions such as temperature had minimal influence. Twenty four tensiometers with pressure transducers were intalled in a forest soil to test their operation and their output was monitored by a data logger. An example of soil suction results measured during four storms is given to demonstrate their stability and their rapid response. The transducers were found to perform accurately and were only affected by temperatures below 0°C.
Water balance approach under extreme arid conditions — A case study of Tabalah Basin, Saudi Arabia
Authors: Abdulrazzak M. J. , Sorman A. U. , Alhames A. S. 
Published: February 2007

AbstractQuantification of water balance components, under arid conditions, is essential to the development of water management policies. This study demonstrates the application of the mass water balance approach for the assessment of water resources in a typical watershed located in the southwestern region of Saudi Arabia.The water balance approach was used, on an event basis, to express the amount of precipitation for 13 storms over a three year period, as a percentage of other hydrological components such as runoff, evaporation, and recharge. The study indicated that 63 per cent of precipitation is lost through evaporation from the water surface during flooding, and from the upper layers of the soil surface immediately after storms. Another 32 per cent is stored in the form of soil moisture in the unsaturated layers below the effective evaporation depth. Only 3 per cent of the precipitation was transformed into surface runoff; however, 75 per cent of this contributes towards groundwater recharge.This study has illustrated that the mass water balance approach can be used, with reasonable accuracy, to quantify the components of the hydrological processes under arid conditions, where a reliable data base is available. This, in turn, will help in the development of appropriate water management policies for arid regions.
Particle size analysis of the sediment suspended in a proglacial stream: Glacier De tsidjiore Nouve, Switzerland
Authors: Fenn C. R. , Gomez B. 
Published: February 2007

AbstractHourly, at‐a‐point samples of suspended sediment taken from the outflow stream of Glacier de Tsidjiore Nouve, Switzerland, over a 60 day sampling period (n = 1440) are shown to be dominantly composed of silt‐sized particles. Particle size, SEM, and XRD analyses indicate a subglacial provenance for the suspended sediment. Temporal variations in particle size and sorting correspond poorly to fluctuations in water discharge, being dominated by erratic hour‐to‐hour fluctuations and clockwise hysteresis over diurnal flow events. Examination of grain size and sorting dynamics over snowmelt‐ and icemelt‐related ablation events, during precipitation events, and during glacier drainage events enables some inferences to be drawn regarding sediment source areas and supply regimes. We conclude that although the bulk of the suspended sediment in the proglacial stream of Glacier de Tsidjiore Nouve is derived directly from subglacial sources (with occasional contributions from the valley train during rapid snowmelt and heavy rainfall periods), a portion of the suspended load undergoes intermittent ‘flush‐fall’ transfer through the proglacial zone, which acts as a sediment source during rising flows and as a sink during periods of waning flow.
Hydrology of a small wet catchment
Authors: Stagnitti F. , Parlange J.‐Y. , Rose C. W. 
Published: February 2007

AbstractThe hydrology of a small wet forested region is studied. Catchment discharge, solar radiation, air temperature, humidity, precipitation, soil moisture, and the water elevation in a swamp were monitored for several months in 1973 and 1975. These data are used to investigate various aspects of the catchment's hydrology and in particular to study the catchment's evapotranspirational requirements. The actual evapotranspiration loss is calculated from a water budget approach. The Priestley‐Taylor model is used to predict the medium to long‐term evapotranspiration from the basin. The predictions based on the model are in very good agreement with the actual evapotranspirational demand. Evapotranspiration is found to play a significant role in the catchment's water balance.
Influence of mineral weathering reactions on the chemical composition of soil water, Springs, and ground water, Catoctin Mountains, Maryland
Authors: Katz B. G. 
Published: February 2007

AbstractDuring 1983 and 1984, wet precipitation was primarily a solution of dilute sulphuric acid, whereas calcium and bicarbonate were the major ions in springs and ground water in two small watersheds with a deciduous forest cover in central Maryland. Dominant ions in soil water were calcium, magnesium, and sulphate. The relative importance of mineral weathering reactions on the chemical composition of these subsurface waters was compared to the contribution from wet precipitation, biological processes, and road deicing salts. Mineral reaction models, developed from geochemical mass‐balance relationships, involved reactions of primary and secondary minerals in metabasalt and metarhyolite with hydrogen ion. Geochemical weathering reactions account for the majority of total ion equivalents in soil water (46 per cent), springs (51 per cent), and ground water (68 to 77 per cent). The net contribution of total ion equivalents from biological processes was 20 and 16 per cent for soil water and springs, respectively, but less than 10 per cent for ground water. The contribution of total ion equivalents from deicing salts (10 to 20 per cent) was related to proximity to roads. Strong acids in precipitation contributed 44 per cent of the total amount of hydrogen ions involved in mineral‐weathering reactions for ground water in contact with metarhyolite compared to 25 per cent for ground water in contact with metabasalt, a less resistant rock type to weathering.
Dewatering suspended solids by continuous‐flow centrifugation: Practical considerations
Authors: Ongley Edwin D. , Thomas Richard L. 
Published: February 2007

AbstractHorowitz et al. (in press) have reported a quality assurance study for metals for two continuous‐flow centrifuges commonly used for environmental applications in field situations. Their work is at an experimental level and avoids discussion of practical considerations involving portability, flow rates, maintenance, etc. In this paper we examine these practical considerations which should be included in application decisions.