The main variables affecting the fluid potential distribution are topography and geology, and the effect of topography is treated by consideration of the three‐dimensional flow net by means of fluid potential slice maps and cross‐sections and is shown to be adequate to explain the major flow net. The dominant fluid potential in any part of the basin corresponds closely to the fluid potential at the topographic surface in that part of the basin. Major recharge areas correspond to major upland areas, and major lowland regions are major discharge regions. Large river valleys commonly exert a drawdown effect on the fluid potential distribution, which may be observed to depths of up to 5000 feet. The presence of a thick sequence of highly permeable Upper Devonian and Carboniferous carbonate rocks in the medium‐depth portion of the Alberta basin has resulted in the development of a low fluid potential drain, which essentially channels flow from most of the Alberta basin towards the Athabasca oil sands and has modified the theoretical relation between local and regional flow sy
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