Each day, groundwater provides drinking water for half of U.S. consumers and another 50 billion gallons for agriculture. Other U.S. industries also rely on groundwater. Unfortunately we take more of this clean low cost water than we put back. The supply is dwindling and since we cannot do without massive quantities of clean water, we must find a way to reverse the depletion of our water supplies. In Part One, we outline the facts about groundwater use.
Surface water in streams, rivers, and lakes supplies the other half of water we use. Surface water and ground water interact in several ways. Groundwater usually seeps into streams to supplement flowing surface water, and surface water often trickles down to the water table top of groundwater. When water is pumped from groundwater, three things happen: the water table lowers, stream flows are reduced or eliminated, and in coastal areas, saline groundwater can move inland.
Aquifers are massive groundwater storage formations composed of permeable rock and materials such as sand or gravel. The Ogallala aquifer serves eight western states (CO, KS, NE, NM, OK, SD and WY). Other aquifers include the Edwards (in TX), the Floridian (in parts of AL, FL, GA and SC) and the Great Artesian Basin (in Australia). The crops that aquifers support supply food for many across the world. Drawing from the aquifer makes possible the gigantic circular sprinkler patterns visible from airline flights.
The Ogallala contains mostly ancient water and today’s replenishment into the Ogallala is at half the rate of withdrawal. Rain and snow are the main replenishment sources and they can take years to settle into the aquifer. Today’s water “mining” (extraction minus replenishment) is 5.5 centimeters per year of which 94% is used for irrigation. The Ogallala will be exhausted in less than 100 years.
Aquifer water comes in varying grades of purity. Saltwater can infiltrate making it brackish (as is the Floridian aquifer). Some aquifers contain contaminants that are even more noxious. The main man-made contamination sources are: bacteria from septic tanks, oils from underground storage tanks, and chemicals from residential and commercial landfills. Other industries can contaminate surface and underground water, most notably the pesticides and fertilizers used in agriculture. Careless handling of wastewater can contaminate groundwater. Discarded consumer and animal drugs also end up in groundwater. Some contaminants in groundwater can be difficult or prohibitively expensive to remove making that ground water unusable.
Gas and crude oil “fracking” injects a water and chemical cocktail underground. When fracking concludes, the cocktail is pumped up into holding ponds or tanks. No doubt traces of the cocktail remain underground and might trickle toward the aquifer, but the EPA seems to monitor this closely.
In Aquifer Depletion: Part 2, Pragmatic Approaches, suggestions are offered on how to address depletion and contamination.
Alan Daley is a retired businessman living in Florida who follows public policy from a consumer’s perspective