6. Soil Water Inter-relationship

The quality as well as the exploitable quantity of ground water in a particular property is dependent on the nature of the soil that exists under the surface therein. A sandy soil is said to have high permeability i.e. it allows water to pass through it easily, and therefore, its ability to retain water is low. It also does not alter the quality of water significantly. On the other hand, a clay soil has poor permeability, i.e. it does not easily allow water to pass through it. It, however, has high porosity, i.e. it can, like a sponge, retain substantial quantity of water in its pores. ( However unlike a sponge it does not yield water readily). And because of such retention, it tends to pass on to the water, mineral salts and thereby affect the quality of the retained water. If the vertical profile of the soil is one that is sandy at the top and rocky or clay below, then a shallow well in such a place is likely to yield good quality water in abundance, as the clayey or the rocky soil will tend to force the sandy layer above to retain water which thereby becomes readily exploitable. On the other hand, if the profile is essentially clayey, then the quantity as well as yield are likely to be unsatisfactory. Soils with a mixed sandy-clayey profile are likely to yield satisfactory quantity of water, but of quality that may vary from potable to brackish.