摘要:

AbstractMost sulphur diagenesis models predict that SO42‐concentrations decrease exponentially with increasing sediment depth and are lower than that of the overlying water throughout the sediments. Low SO42‐concentrations (less than 0.2 mM) are common in the sediments of Lake Anna that receive acid mine drainage; however, sediment with as much as 20 mM SO42‐at about 20cm below the sediment surface is also seen in this section of the lake. A decision tree was proposed to investigate the cause of the high SO42‐concentrations at depth (HSD) in the sediment. The first possibility proposed was that an increase in the quantity of groundwater flowing through Lake Anna sediments may increase groundwater advection of SO42‐or oxygen which would induce sulphide oxidation. This hypothesis was tested by measuring groundwater flow. HSD profiles were found in a discrete region of the lake; however, stations having these profiles did not have higher groundwater flow than other sites sampled. Alternate explanations for the HSD profiles were that the region in which they occurred had: (1) unusual sediment chemical compositions; (2) a different source of regional groundwater, or (3) a lateral intrusion of high SO42‐groundwater. There were no differences in sulphide and organic matter concentrations between the two regions. The area which has HSD in the sediment covers a large area in the middle of the lake, so it is unlikely that it has a unique source of regional groundwater. The third alternative was supported by the fact that in all three sample years, HSD stations were located in the preimpoundment stream channel, which is a likely lateral flow path for groundwater containing high SO42‐c

ISSN:0885-6087    

DOI:10.1002/hyp.3360020302

出版商:John Wiley&Sons, Ltd    

年代:1988

数据来源: WILEY

摘要:

AbstractThe Kirkham piezometer tube method of measuring hydraulic conductivity of saturated soil uses a numerical constant (shape factor) to account for the relative geometrical parameters of the cavity and the soil domain. Published shape factors have mostly been determined using an electrical analogue. In this paper the application of the finite element method to shape factor determination is considered. Convergence is studied and methods of extrapolation evaluated. A determination is made of the size of finite region required to represent adequately the radially unbounded domain assumed for the piezometer method. Computed shape factors were found to be in good agreement with analogue data.

ISSN:0885-6087    

DOI:10.1002/hyp.3360020303

出版商:John Wiley&Sons, Ltd    

年代:1988

数据来源: WILEY

摘要:

AbstractRainfall and runoff were monitored simultaneously for one year from a residential road, a car park, nine sections of road draining to individual gullies, two house roofs, two garage roofs, and three types of factory roof. The sites, which included an automatic weather station, were in Redbourn, Hertfordshire on Flood Studies Report Soil Type 1. The 2906 quality controlled ‘station‐storms’ represented 193 rain storms and involved 57.2 per cent of the annual rainfall. 1732 storms were of less than 1.4mm of rain, whilst 77 had over 10mm.The percentage runoff averaged 11.4 per cent for roads and 56.9 per cent for roofs (28.3 per cent and 90.4 per cent respectively for rainfalls>5mm). Percentage runoff from the roads was cyclic with a peak during the summer months but there was a marked variation in monthly percentage runoff within and between sites. Regression analysis to explain percentage runoff was undertaken with various subsets of data for: each site; roads; and roofs. The regression analysis considered all storms;>1 percent runoff events;>5mm rainfalls; and events with>= 4 mm rain and>= 5 per cent runoff. The variable values in percentage runoff could not be explained satisfactorily with statistical methods. Only eight of the 72 equations explained more than 57 per cent of the variance. The most important explanatory variables for roads were short term rainfall intensity and rainfall amount, the former was the most important for roofs. ‘Seasonal’ variables had a positive relation ship for roads which shows that the percentage runoff from roads is higher in summer than winter. The antecedent variables showed that percentage runoff from roads and roofs is increased by antecedent rainfall. Seasonal factors and evaporation were unimportant for the percentage runoff from roofs.Depression storage, assessed by examining rainfalls that did and did not produce runoff, showed a diversity of monthly values. The depression storages derived by the regression intercept method were usually smaller. There were no relationships between depression storage and catchment or roof slope. The mean values for roofs and roads respectively were 0.52 mm and 1.23 mm for the classification method and 0.42 mm and 0.6mm with the regression approach.Peak runoff from the roads showed an attenuation to 12.8 per cent for 1 minute rainfall intensities and 24.2 per cent for 5 minute intensities. For roofs the attenuation averaged 36.8 per cent for 1 minute intensities and 92.6 for 5 minute intensities. Regression for peak runoff coefficients from roofs and roads explained negligible amounts of the variance except when events with 1 minute rainfall intensities of over 30 mm hr−1over the roads were analysed. Total rainfall was an important explanatory variable as was the slope of the road. There was evidence that peak coefficients for roads are greater during

ISSN:0885-6087    

DOI:10.1002/hyp.3360020304

出版商:John Wiley&Sons, Ltd    

年代:1988

数据来源: WILEY

摘要:

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.

ISSN:0885-6087    

DOI:10.1002/hyp.3360020305

出版商:John Wiley&Sons, Ltd    

年代:1988

数据来源: WILEY

摘要:

AbstractArid‐site recharge, while generally low, can be highly variable. Recharge under similar climate and soil conditions but with different plant cover and topography can vary from zero to more than the annual precipitation. Simple estimates of recharge based on fixed fractions of annual precipitation are misleading because they do not reflect the plant and soil factors controlling recharge. Detailed water balance models, successful for irrigated agriculture, fail to predict evapotranspiration accurately under conditions where plants suffer seasonal water stress and cover is sparse. Recharge, when estimated as a residual in water balance models, may be in error by as much as an order of magnitude. Similar errors can occur when soil water flow models are used with measured or estimated soil hydraulic conductivities and tension gradients. Lysimetry and tracer tests offer the best hope for evaluating recharge at arid sites, particularly in siting waste disposal facilities, where reliable recharge estimates are needed. Quantification of drainage using lysimetry over several years under a given set of soil, plant, and climate conditions for a specific site can provide a basis for calibrating models for recharge prediction. Tracer tests using such long‐lived tracers as36Cl or perhaps stable isotopes (180, deuterium) can provide qualitative estimates of recent recharge at a given s

ISSN:0885-6087    

DOI:10.1002/hyp.3360020306

出版商:John Wiley&Sons, Ltd    

年代:1988

数据来源: WILEY

摘要:

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 p

ISSN:0885-6087    

DOI:10.1002/hyp.3360020307

出版商:John Wiley&Sons, Ltd    

年代:1988

数据来源: WILEY

摘要:

AbstractHuman activity is exerting an increasing influence on the hydrological cycle. In order to avoid adverse impacts and to establish optimum conditions for the water balance, it is necessary to understand the role of environmental parameters in influencing the hydrological cycle. Work is currently in progress in China to study the relationships between environmental parameters and the hydrological cycle to provide a basis for planning future development.

ISSN:0885-6087    

DOI:10.1002/hyp.3360020308

出版商:John Wiley&Sons, Ltd    

年代:1988

数据来源: WILEY

ISSN:0885-6087    

DOI:10.1002/hyp.3360020309

出版商:John Wiley&Sons, Ltd    

年代:1988

数据来源: WILEY

ISSN:0885-6087    

DOI:10.1002/hyp.3360020310

出版商:John Wiley&Sons, Ltd    

年代:1988

数据来源: WILEY

ISSN:0885-6087    

DOI:10.1002/hyp.3360020301

出版商:John Wiley&Sons, Ltd    

年代:1988

数据来源: WILEY