PUBLICATIONS DE L'ASSOCIATION INTERNATIONALE DES SCIENCES HYDROLOGIQUES

ABSTRACT

The evaporation losses from the container of an old galvanized Hellmann gauge, 7·1 cm² aperture area, were five times greater than the losses from the container of a new gauge, 1·8 cm² aperture area, of almost the same grey colour. The maximum evaporation from the old gauge amounted to 0·75 mm per day. The same evaporation losses in the Baye of Montreux basin over a period of 10 years from April to September amounted to 0·09 mm per measurement or to 0·7 per cent of the precipitation catch. There is a relationship between the monthly percentage evaporation losses and the ratio of evaporation time and rainfall duration (r = 0·803).     

DETERMINATION DIRECTE DE L'EVAPOTRANSPIRATION ET DE L'INFILTRATION PAR MESURE DES TENEURS EN EAU ET DES SUCCIONS

ABSTRACT

A local water balance is determined with the aid of measurements of changes in water content and water potential in the unsaturated zone of soil. For purposes of clarification first the basic laws which state the flow physics in the unsaturated zone are briefiy discussed; thereafter some technical aspects of the field measurement of water content and water potential are presented.

Finally these techniques are illustrated by an example of the local water balance determined for a basin with data taken over ten months.     

PUBLICATIONS OF THE INTERNATIONAL ASSOCIATION OF HYDROLOGICAL SCIENCES

Abstract

Most commonly used biochemical oxygen demand (BOD) and dissolved oxygen (DO) models have been tested for their applicability in the River Kali, which is one of the most polluted rivers in India. A total of 732 field data sets were generated during field survey from March 1999 to February 2000. The modelling of BOD and DO in the River Kali involves derivation and solution of the governing equations that describe concentration change with time and space brought on by advective, decay, settling and loading functions. However, due to continuous discharges (e.g. from wastewater treatment plants) and steady-state flow conditions in the River Kali, the dispersion effects are found to be insignificant. In the analysis, the model parameters used in BOD-DO models were optimized using the Newton-Raphson technique and the performance of different models was evaluated using correlation statistics (r ²) and error estimation, viz. standard error (SE) and mean multiplicative error (MME). The results indicate that the BOD-DO models developed after Camp (1963) yielded the best agreement with the observed values as compared with several other approaches.     

PUBLICATIONS OF THE INTERNATIONAL ASSOCIATION OF HYDROLOGICAL SCIENCES

Abstract

Explicit algebraic expressions of influence coefficients of an aquifer system are addressed. The methodology is straightforwardly exemplified using a one-dimensional (1D) semi-confined homogeneous aquifer model. It consists of the integration of the governing equation from two different viewpoints. On the one hand, the analytical solution to the governing equation is presented under an integral form involving the appropriate Green function. On the other hand, equations resulting from a finite difference discretization are processed to deduce a fully explicit algebraic expression of the nodal hydraulic head. This latter, arranged after the previously developed continuum solution, helps with deriving an explicit algebraic expression of influence coefficients corresponding to the studied aquifer model. Finally, the study is extended to an inhomogeneous aquifer model.     

PROCEDES DE FILTRAGE ET DE FOCALISATION DE CHAMP POUR LA DETECTION ELECTROMAGNETIQUE DES CARRIERES SOUTERRAINES *

The electromagnetic surface detection of underground quarries by classical methods becomes difficult when they are situated at depths greater than ten meters and when the thickness and conductivity of the superficial layers are irregular. The problem is tackled in two stages: at first using successive approximations, characteristics of the miscellaneous layers of a stratified medium are identified, and the quarries are then detected by observation of the conductivity changes of one of the lower layers. Computer interpretation, however, is necessary. The chances of detection of the quarries are considerably improved by a field localization method developed by us: computer interpretation is eliminated. The new aspect is an auxiliary transmitter which annuls the currents induced by the principal transmitter in the uppermost—generally more conductive—layers. The theoretical and experimental results show that the probability of detection of the quarries by this method are four times as high as by the classical one.