Common wells Where water is artificially withdrawn from the earth. Result in drawdown of the water table - a conical depression in the water table known as a cone of depression. Cone of depression increases the hydraulic gradient in the vicinity of the well. Where the hydraulic gradient causes the water in a well to move to a level above the aquifer. Aquitards must be present both above and below the aquifer to keep the water from escaping.
Friction reduces the artesian effect the further the well is from the recharge area.
Problems Associated with Groundwater Withdrawal Natural systems establish a condition of equilibrium. This is especially true in farming areas. The water table can drop at rates up to 1 meter per year. As water is withdrawn from unconsolidated sediment, the water pressure drops, and the weight of the overburden is transferred to the sediment. Several meters of subsidence is not uncommon - e.g., San Joaquin Valley and Mexico City.