Many scientists are concerned that the ogallala aquifer in the united states is being depleted at an alarming rate ? what would most likely be a major effect on this aquifer running dry ?

This can cause other organisms that relay on this specific aquifer to find other sources of water or die. 

An aquifer is actually an underground layer of water that contains permeable rocks, gravel, sand etc. the water can be brought to the surface by making a water well. Hydrogeology is the study of aquifers and the way of water flow in the aquifers. The depth of the aquifers differs from area to area and the aquifers that are closest to the surface are used for drinking and irrigation purposes.