Regional groundwater flow in sedimentary basins in the U.K.

flow systems occur in these provinces above an essentially impermeable basement of varying age. The pattern of flow in the U.K. is strongly influenced by the distribution of the Permo-Triassic sandstones. Intermediate flow systems are encouraged by the scarp and vale topography that has developed as a consequence of the alternating sequence of aquifers and aquicludes in the M sozoic. Regional changes in groundwater chemistry reveal the direction of flow paths, and isotopic ratios and inert gas contents give an indication of the residence time of water in the flow systems. The composition of the groundwater in deep systems has been modified by shale-membrane filtration. Density settling may be a feature in thick relatively homogeneous aquifers. Groundwater flows from areas of high fluid potential (i.e. high mechanical energy per unit of mass) to areas of low fluid potential (Hubbert 1940, p. 797). The general direction of flow is reflected by the form of the water table and th