A new study finds that U.S. groundwater supply is smaller than originally thought and drilling deeper wells may not be a good long-term solution because water may become contaminated in areas where the oil and gas industry injects wastewaters into or in close proximity to aquifers.

According to researchers, groundwater is the primary source of domestic water supply for about half of the people living in the U.S. About 40% of all of the water used in the U.S. for irrigated agriculture comes from groundwater.