Water zones can be a hundred feet or less from the land surface to over 1,000 feet deep. The basalt is thought to be over thousands of feet thick in many places. The aquifer is connected hydrologically from one end to the other. Because of the hydrologic connections and the high water yield, the ESRP Aquifer is one of the largest and most prolific aquifers in the country. Most of the water that we extract from it is less than 1,000 feet from the land surface.
Some places have water as shallow as a couple hundred feet from the land surface.
Sedimentary and Volcanic Rocks Aquifers that occur in sedimentary rocks are commonly found in southwestern Idaho. Sedimentary rocks were originally deposited as alluvial sediments and then later compacted and cemented into rocks. They are often buried deeper in the earth than unconsolidated alluvium. However, sometimes they are not very good aquifers because their porosity and permeability are so low that they do not transmit water very well. Still, people have to use them sometimes as their main water source because other sources are not available or they have even lower yields.