Compound Wells for Skimming Freshwater from Fresh Saline Aquifers
Several aquifers worldwide contain fresh usable groundwater only in a not-so-thick layer toward the top. This freshwater layer is underlain by a relatively thick layer of unusable saline water. In India, Fresh Saline (F-S) aquifers are frequently encountered in the fertile alluvial Indo-Gangetic Plains of North India, and deltaic formations on the east coast of India and Saurashtra coast of Gujarat. The design challenge posed by the F–S aquifers is to arrive at such a well configuration that permits skimming of freshwater without drawing the saltwater into the pumped discharge. Such wells termed skimming wells have traditionally been partially penetrating wells tapping only the upper portion of the freshwater layer. The production well taps the freshwater zone while the scavenger well taps the saline water zone. Groundwater is developed in F–S aquifers through partially penetrating wells tapping only the freshwater layer and leaving out adequate cushion between the screen-bottom and the static interface between the freshwater and saltwater.