ISSN:0262-6667    

DOI:10.1080/02626669709492015

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

Pressure measurements and records of drill-stem tests (DST) from deep petroleum exploration wells in the Anambra basin have been analysed together with fluid potential data obtained from over 500 water wells drilled in the basin. The analyses indicate the existence of three distinct hydraulic systems in the basin, viz.: an upper system with hydrostatic formation pressures; a middle system in which pressures are just moderately higher than hydrostatic; and a relatively deep system of abnormally high formation pressures. The three hydraulic systems correspond approximately to three hydrostratigraphic units that are clearly discernible from the lithologie logs of boreholes and oil wells drilled in the basin. The main fluid in the uppermost hydraulic system is circulating meteoric water, and the fluid potential distribution is largely governed by the local topography at the surface. Within the middle hydrostratigraphic unit, hydraulic heads and fluid energies are highest at me basin edge to the east where the major aquifer of the unit is exposed, and much lower in the basin centre to the southwest where the aquifer is confined. The magnitude and distribution of fluid potentials in the two top hydraulic systems suggest that the general hydrodynamics of the basin are, to a large extent, responsible for the generation of the fluid pressures. In the third and deepest hydraulic system, however, the situation is different. The hydraulic heads and formation pressures are very high indeed, and cannot be explained purely in terms of circulating meteoric waters. Some other fluid energy sources must also be active in this part of the basin. The fluid potentials and pressures fluctuate very rapidly both laterally and vertically, suggesting the existence of distinct flow units within the entire system. Each flow unit appears to be hydraulically closed, sealed both vertically and horizontally, and characterized by a unique fluid energy distribution. The existence of both vertical and horizontal potential gradients at depth, especially at the basin centre, indicates that the fluids are not static, but mobile, and that the complex movement of fluids could be through deep-seated drains. Such fluid movements obviously affect the temperatures of the sedimentary layers and could also be significant in the migration and accumulation of hydrocarbons in the basin.

ISSN:0262-6667    

DOI:10.1080/02626669709492016

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

Due to the difficulty of field characterization, one is often forced to employ hydrological models in order to determine estimates of aquifer recharge. A Geographical Information System (GIS) and Digital Elevation Model (DEM) may provide the basic support for such hydrological models. Unfortunately, despite the availability of these tools, the values of many parameters within distributed models remain uncertain for application to real world problems. Using the Bisagno basin (100 km2) in the Liguria region of Italy, the role of model parameter uncertainty on estimates of recharge to the Bisagno Aquifer is demonstrated. Uncertainty estimation is achieved through Monte Carlo simulations with the aid of the Generalised Likelihood Uncertainty Estimation procedure of Beven & Binley (1992).

ISSN:0262-6667    

DOI:10.1080/02626669709492017

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

In hydrological practice, flood routing is rarely achieved using the complete Saint-Venant equations. Instead, hydrological methods have been developed to provide users with simple methods that are robust yet efficient. The lag-and-route method has been widely used but its parameters have never been related to the physical parameters of channels. Moreover, the linear reservoir in this method is not well suited to reproduce effectively actual channel routing. A quadratic reservoir coupled with a lag component results in a far more accurate method while remaining numerically workable. This latter method depends on only two parameters which have been successfully related to physical channel features. This simple and efficient method enables one to gain insight into the main features of flood propagation in river channels.

ISSN:0262-6667    

DOI:10.1080/02626669709492018

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

La gestion de l'eau en Algérie pose un problème épineux aux autorités. Les ressources disponibles sont en deçà des besoins. La vétusté des réseaux d'adduction et la capacité de stockage déficiente entravent la bonne distribution de l'eau aux consommateurs. La dotation journalière par habitant reste faible par rapport aux normes internationales. Les instruments de gestion de l'eau ne sont pas efficaces.

ISSN:0262-6667    

DOI:10.1080/02626669709492019

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

This paper outlines the results of a pilot study using data at 12 min intervals from 20 miniature temperature dataloggers to establish vertical and longitudinal temperature patterns within a river bed. Data are presented from two adjacent riffles immediately below the Blithfield Reservoir on the River Blithe, Staffordshire, UK, for a five day period in July 1994. Hyporheic temperatures were warmer than those of groundwater, colder than those of surface water and decreased with depth into the river bed. At the heads of the riffles shallow sites (20 cm depth) mirrored surface temperature patterns but were on average 1.53°C cooler while deeper sites (40 cm depth) were 2.60°C cooler on average. Hyporheic temperatures lagged behind the surface water pattern and lag times increased with depth. Sites at the riffle tails generally displayed temperature patterns similar to those of the groundwater system: on average, temperatures were 4.32°C cooler than surface water temperatures and showed no significant variation. Hyporheic temperature patterns at the heads of the riffles suggested downwelling surface water, while the tails appeared to be influenced by upwelling groundwater. Both riffles displayed similar hyporheic temperature patterns but riffle 1 was on average 1.22°C warmer per site than riffle 2. Temperature differences between the riffles are attributed to bed form and substratum composition. These factors may have significant ecological implications including rates of organic matter decomposition, invertebrate life cycles and salmonid egg hatching times.

ISSN:0262-6667    

DOI:10.1080/02626669709492020

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

Most research on hydrology in developed countries does not emphasize problems that are often encountered by hydrologists in developing countries, problems such as the scarcity and poor quality of data. In developing countries the available data base is often a major constraint and a limiting factor in any hydrological study. This paper analyses the consistency of a network of nonrecording raingauges based on the annual rainfall recorded by six representative stations in the Tacuarembô River basin in Uruguay. The identification of possible errors not revealed in the printed records was accomplished by application of the factor correspondence analysis method and verified with success by the classical double-mass analysis. This ability to identify suspicious data with very modest requirements for data management implies that the methodology based on factor correspondence analysis could find wide application.

ISSN:0262-6667    

DOI:10.1080/02626669709492021

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

A summary of the results of regional flood frequency analyses that have been carried out in many tropical and sub-tropical countries is presented. The results provide a set of flood estimation methods which should be of immediate usefulness in practical applications, bearing in mind the errors of generalization. By defining the representative values of the mean annual flood and of the flood frequency curves for each region, an attempt has been made to develop relationships between the methods and climatic characteristics. These show that adequate relationships can be obtained based solely on the median annual average rainfall and the median catchment area for the regions. In particular, the steepness of the regional flood frequency curve can be estimated reasonably well from these two parameters. The relationships confirm that, broadly speaking, for humid regions the “average” flood—the flood that occurs regularly every one or two years—is relatively large, but the flood frequency curve is not very steep; rare floods (occurring once in every 100 to 1000 years) are not very much larger than the average flood. Conversely, in arid regions, the average flood is small, but rare floods can be extremely large multiples of the average. These relationships provide a useful initial indication of the type of regional flood frequency estimation method likely to be found in tropical and sub-tropical regions throughout the world.

ISSN:0262-6667    

DOI:10.1080/02626669709492022

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

Aquifer remediation operations are often behind schedule. Usually, a rather sharp concentration decrease shortly after the start of an operation is followed by a situation in which hardly any concentration decrease is observed. Furthermore, the concentration increases after stopping the groundwater recovery. These phenomena are caused by so-called tailing. An important cause of tailing is the phenomenon that equilibrium is not reached for some of the transport and sorption processes involved. To predict these effects of tailing, IWACO has developed a program SORWACO, which describes the behaviour of solutes along a path line. Processes for which equilibrium is reached quickly as well as processes for which equilibrium is reached only slowly are taken into account. The program has been verified against break-through curves observed in column experiments reported in the literature. The program parameters were calibrated using the data of several experiments. The resulting set of parameter values accurately described the transport for different flow velocities. The fact that quite good results can be obtained without a lot of data from a specific site makes the program a valuable tool for the design of remediation operations. The program is especially useful when extensive input data are not available so that detailed three-dimensional or stochastic models cannot be applied. The use of the program is illustrated by means of a case study. The progress was monitored and the data show good correspondence with the predictions of the program.

ISSN:0262-6667    

DOI:10.1080/02626669709492023

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

This paper describes the development and validation of a water balance model of the Upper Blue Nile in Ethiopia. A major requirement of any modelling attempt is the availability of climatic and hydrological data. However, for the Upper Blue Nile, only a limited number of observation sites are available over a very large area. As a result, the model described here is a grid-based water balance model which requires limited data inputs, few parameters and runs on a monthly time-step. Climate is dominated by the influence of elevation in the river basin. Estimates of potential evapotranspiration (PE) and rainfall are predicted for 10-minute resolution grid cells for input to the model. These estimates are based on multiple regression models using latitude, longitude and elevation. In the basin, annual meanPEand rainfall range, with increasing elevation, from 1800 mm to 1200 mm and 924 mm to 1845 mm, respectively. In the model, vegetation cover is not explicitly treated and soil characteristics are spatially invariant. The model is calibrated to reproduce mean monthly runoff over a 37-year period (1953–1987), and validated by its ability to simulate sub-catchment runoff and historical variations in Blue Nile runoff. The key factor that determines model performance is the quality of the rainfall inputs, with the best results obtained with a time series comprised of long, good quality station data. Over a 76-year period the correlation between observed and simulated annual flows was 0.74 and the mean error was 14%, although fairly large errors occurred in individual years. Considering the paucity of data for the basin, these results are encouraging. The model is used to investigate spatial variability in the sensitivity of runoff to changes in rainfall andPE. The sensitivity is greatly affected by the runoff ratio of the model grid cells and it increases as grid cell runoff ratio decreases. The sensitivity is also affected by the seasonal distribution of rainfall. The paper ends with a discussion of the model's performance and its potential for future development.

ISSN:0262-6667    

DOI:10.1080/02626669709492024

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor