Geography essays

Groundwater is water which occurs in the pore spaces of rocks and soils - there is a saturated (or phreatic) zone below and an unsaturated (or vadose) zone above, in which the pore spaces are filled with air. The water table is the surface separating the two zones. The water table approximately mirrors the topography of the landscape, except for example, where you've got boreholes, in which case the water will be drawn down towards the borehole to form a somewhat triangular 'cone of depression'. A perched water table occurs when you've got an impermeable lense/layer of rock or sediment (such as clay) which is located higher than the regional water table, i.e. in the unsaturated zone. The water cannot percolate through the impermeable layer, so remains above the regional water table as a perched water table or perched aquifer.

Diagrams should be easy to find online