Theory question 308
Underground Water and Karst(a) With the aid of a diagram, describe water table. (b) Outline three factors that influence the depth of water table.
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(a) The water table is the upper surface of the zone of saturation in permeable rock, below which all pore spaces are filled with water; above it is the zone of aeration (unsaturated); it roughly follows the shape of the land surface, being higher under hills and nearer the surface in valleys; it rises in the wet season and falls in the dry season (permanent and intermittent saturation zones); where it meets the surface springs, swamps, lakes or rivers form. Diagram showing land surface, zone of aeration, water table, zone of saturation, impermeable rock, well and spring.
(b) Amount and season of rainfall; permeability and porosity of rocks; relief/slope of the land; vegetation cover; rate of evaporation and temperature; human use (wells, boreholes, irrigation); nearness to rivers, lakes or the sea; tides near coasts.
Label both saturation zones on the diagram.