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A method is proposed for the simulation of groundwater flow in regional aquifers dissected by dykes of low permeability or by geological faults, which act as barriers to flow and which can have a considerable influence on the available groundwater resources. The method has been verified by a comparison of numerical results with the analytical solution to a test problem. The method has been applied to an area of the Cave Sandstone aquifer in Botswana which has been affected by dyke intrusions which significantly affect its potential for large-scale groundwater development. Etablissement de modèles numériques pour l'écoulement souterrain dans des aquifères régionaux cloisonnes par des dykes RESUMEOn propose une méthode pour la simulation de l'écoulement souterrain dans des aquifères régionaux cloisonnés par des dykes de faible perméabilité ou par des failles géologiques qui se comportent comme des barrières, vis à vis de l'écoulement et qui peuvent avoir une influence considérable sur le volume des ressources en eaux souterraines disponsibles. La méthode a été verifée par la comparaison des résultats numériques avec ceux de la solution analytique à un problème de test. La méthode a été appliquée à une zone d'aquifères situés dans des grès caverneux dans le Botswana. Cette zone a été affectée par des intrusions de dykes qui ont eu une influence significative sur les possibilités d'y réaliser un aménagement à grande échelle des eaux souterraines.

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This paper considers an approach to generating uniformly distributed pseudo-random numbers which works well in serial applications but which also appears particularly well-suited for application on parallel processing systems. Additive Congruential Random Number (ACORN) generators are straightforward to implement for arbitrarily large order and modulus; if implemented using integer arithmetic, it becomes possible to generate identical sequences on any machine.Previously published theoretical analysis has demonstrated that a kth order ACORN sequence approximates to being uniformly distributed in up to k dimensions, for any given k. ACORN generators can be constructed to give period lengths exceeding any given number (for example, with period length in excess of 2 30p , for any given p). Results of empirical tests have demonstrated that, if p is greater than or equal to 2, then the ACORN generator can be used successfully for generating double precision uniform random variates.This paper demonstrates that an ACORN generator is a particular case of a multiple recursive generator (and, therefore, also a special case of a matrix generator). Both these latter approaches have been widely studied, and it is to be hoped that the results given in the present paper will lead to greater confidence in using the ACORN generators. The ACORN generatorThe kth order additive congruential random number (ACORN) generator is defined by Wikramaratna [11,12] from an integer modulus M, an integer seed Y 0 0 satisfying 0 < Y 0 0 < M and an arbitrary set of k integer initial *