Groundwater starts as precipitation, and the portion of the rain water that infiltrates beneath the ground’s surface, either naturally or artificially, becomes groundwater. The remaining precipitation is used by plants, evaporates, or becomes surface water runoff which can either add to groundwater levels in other areas or be increased by groundwater outflows depending on the geology the surface water travels through.
Groundwater is critical to the communities that are built on or near an aquifer, or the underground layer of water that fills cracks in the rock or sand that makes up the soil. This groundwater layer which makes up about 30% of the world’s freshwater supply is used for many purposes including irrigation, private drinking water, and municipal water supplies.
Groundwater is a key part of a country’s ability to irrigate its farmland. Irrigation systems account for the use of about 201.8 billion liters of groundwater per day. This usage can be compared to the 1900s when the US only used 8.3 billion liters per day for irrigation.
Information regarding groundwater use for drinking water worldwide is limited, however it is estimated that one-third of the world’s population depend on groundwater as the main source of their drinking water. Over 13 million US households regularly depend on private groundwater wells.
Groundwater sources are used by about 33% of the public water systems in the United States. Between public and private water wells about 44% of the US population depends on groundwater for their drinking water. Including drinking water and farming, along with other uses of groundwater such as manufacturing, mining, and thermoelectric power to name a few…301.3 billion liters a day of fresh groundwater are used.
Knowing the groundwater level is important for several reasons, including understanding aquifer levels under static and pumping conditions, determining how the levels interact with local surface water sources, and understanding how surface development has impacted the aquifer.
A groundwater well may have high water levels; however it may still be unsuitable for drinking water. Water can easily become contaminated because it is a very good solvent and can contain many dissolved chemicals. Rainwater or surface water can come into contact with contaminated soil while seeping into the ground, from that point it can become polluted and carry the pollution from the soil to the groundwater aquifers. Groundwater can also become contaminated when liquid hazardous substances soak down through the soil or rock.
One source of groundwater contamination often overlooked by the general media is contamination from naturally occurring chemicals found in the surrounding rock and soil. Groundwater is not static and as it moves through the ground it dissolves the rock and soil along with any chemicals they may contain. For example, toxic chemicals such as arsenic and selenium are common in some types of rock formations and groundwater near those sites should not be used as drinking water sources until it is treated.