relationship between variation of water table & surface runoff

Water table is the upper level of the zone of saturation (ground water) in permeable rocks.It represents the surface at which the pressure in the ground water is equal to the atmosphereis pressure.It is situated below the zone of intermittent saturation.Level of sturation instead of water table is an appropiate term because the term water table indicates a horizontal surface which in fact rarely exists.

Runoff is used to indicate pecipitation excess & is determined by deducting the loss from rainfall.

The water table tends to sink as irt approaches a valley as runoff water readily escapes at the surface on the hillsides above the valley & drains off more rapidly.Interflow through beds of saturated permeable rocks occurs where ground water table is lower.

 

In Britain water table is lower in summer & higher in winter.This is because the rainfall in summer only moistens the dry upper layers which soon gets dried up due to evaporation or is used by plant's growth.

The autumn rain moistens the unsaturated zone & when the winter rain occurs the water is supplied underground which causes high water table.this implies when the rain occurs a portion of the interflow enters ground water as recharge since,the zone of aeration is already saturated.

 

If the surface runoff is high because the section of the drainage basin over which it is occurring has soil which has low permeability will encourage deep location of ground water table due to absence or negligible ground water.

 

Thus,in conclusion it can be said that there is inverse relation between surface runoff & water table variation,although surface runoff itself is dependent upon several other factors.