The buried condition for the formation of confined water is that there is a water-resisting layer above and below, and a permeable layer in the middle. Secondly, water must fill the whole permeable layer. The following strata can form confined water: clay covered sand layer; Shale covered sandstone; Shale is covered with dissolved limestone; Dense and impure limestone covers limestone with developed cracks and crevices; Dense karst rocks are covered by porous karst rocks. The formation of confined water is closely related to geological structure. Confined water can be formed as long as there is suitable geological structure, whether it is loose sediment or bedrock. The most suitable geological structures for the formation of confined water are syncline structure and monocline structure.
Great artesian basin, Australia, is a large shallow dished depression basin. Also known as great basin, Australia has a confined aquifer. The eastern edge is roughly bounded by the western foot of the great watershed, with higher terrain and lower in the west, north and south. Paleocontinental strata in Australia are covered with bedrock aquifuge, Jurassic sandstone confined aquifer and Cretaceous shale aquifuge, which are exposed in rainy areas in the east and form water receiving areas. Groundwater flows along the aquifer to the western rainless area at the rate of11~16m per year. Confined water gushes out of the surface through drilling or natural springs, hence the name artesian basin. The water quality of confined water ranges from fresh water to high salinity brine, and the water quality of groundwater is diverse, with vertical or horizontal zoning law. The vast majority of confined water comes from seepage water, which is fresh water suitable for drinking. The water in great artesian basin is salty, because under the condition of closed aquifer structure, there may be ancient buried water formed at the same time as sediments.
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