Rate of water movement in the strata:

The rate of water movement in the strata depends upon two factors; i.e.

(i) permeability of the soil strata, and (ii) driving force for the hydraulic gradient, usually expressed as the ratio between the difference in elevation of the two points on the water table in the direction of flow, and the distance between them.

The quality of ground water mainly depends on the contact of meteoric water with geologic strata in their downward percolation. It provides opportunity for the top soil which is continuously undergoing oxidation with the corresponding production of carbon dioxide. It is natural that percolating water contains gas in solution. Contact of this carbonic acid (H₂O + CO₂ → H₂CO₃) laden water with lime, magnesia and ferrous iron leads to the solution of these substances. Iron containing sand yields iron-bearing water. Water traversing limestone strata usually contains good concentration of these minerals. Water flowing over and through igneous formations frequently contains little mineral matter. The greater the distance through a given formations water has traveled, the greater will be its mineral content.