A Guide for the Pesticide User Groundwater Categories Groundwater Categories Groundwater is a vital economic resource. Approximately one-half of the population in the United States relies on groundwater for drinking water. Even so, this use accounts for only 18 percent of the total groundwater use as shown by the slide. Withdrawal of groundwater is increasing at twice the rate of surface water, and this trend is expected to continue.
Agriculture relies heavily on groundwater, especially where water is the most scarce.