The most easily polluted groundwater reservoirs are in? Why is that?

The most easily polluted groundwater reservoirs are in water-table aquifers. Water table aquifers are the saturated part of the upper soil profile that is found above a confining layer. The saturated soil is made up of sand or gravel making the water very easy to withdraw. The said confining layers can be represented by bedrock layers or clay-rich soil layers. These impede downwards up to the infiltrated water resulting to a saturated soil condition caused by the rainfall entering the soil above the confining layer.