Flow and Transport at the Regional Scale

As we have mentioned already in the preceding parts, natural formations are generally of a much larger horizontal extent than their vertical dimensions. Whereas the thickness of the aquifers is usually in the range 100–102 meters, the planar dimension is of the order 103–105 meters. In many applications we are interested in investigating the behaviour of the formation as a whole unit, e.g. to compute the change of water head caused by natural or artificial recharge applied to the entire aquifer, to predict the yield of wells to be operated in the aquifer or to predict the fate of a solute plume which traverses the aquifer over an extended period of time. The problems we are addressing now are at a much larger scale than those of the local one, of the order of the depth, considered in Parts 3 and 4. This new scale, of the order of hundreds to thousands formation thicknesses, is termed here the regional scale, by following the terminology adopted in Dagan (1986).