Celebrate National Groundwater Awareness Week
March 5 through March 11, 2017, is National Groundwater Week. Celebrate this important resource by learning more about it and adopting actions to help protect it.
When you turn on the tap, clear, cold water comes out. But do you know where that water is coming from for your use? Approximately 44 percent of the population in the U.S. and 43 percent of the population in Michigan depends on groundwater as their main drinking water supply, either from municipal wells or private wells. That equals about 79.6 billion gallons of groundwater per day, for everything from cooking and washing to thermoelectric power generation. According the National Groundwater Association, “Of all the fresh water in the world (excluding polar ice caps), 95% is groundwater. Surface water (lakes and rivers) only make up about 3% of our freshwater.”
What is groundwater and why is it important?
Groundwater is the water that soaks into the ground from any precipitation event, such as rain, snow or sleet. As it moves down through the ground, it fills up all the spaces, pores and cracks between the rock and soil particles. Think of it as a giant underground sponge. The water found just below the earth’s surface, filled with both water and air, is called soil water. The layer beneath that, in the deeper spaces that are completely filled or saturated with water with no room for air, is called groundwater. Water for drinking and other uses comes from this saturated zone known as an aquifer.
About one quarter of all rainfall becomes groundwater. Some precipitation is also absorbed by plants and trees, becomes runoff ending up in local rivers and lakes, or is diverted for other uses.
Groundwater and surface water are connected. The USGS estimates that about 30 percent of all stream flows in the U.S. are from groundwater. If the water table is high in an area or region, such as Southeast Michigan, groundwater exits the ground into the stream channel or lake.
Groundwater supplies are not distributed evenly. It is found at different depths, from shallow to very deep within the ground. The composition of the soil, rock, clay or sand, impacts the amount, depth and quality of groundwater. Areas where water enters the ground is called the “recharge area” because it is recharging the water supply. Locations where water exits the ground either through well pumps, river or stream channels or into lakes is called the “discharge area”.
Groundwater moves at different rates from a few inches to a few feet per day. Movement is impacted by the number and size of pore spaces in the soil. The flow is also irregular. It moves from less porous to more porous areas, following the path of least resistance, and from shallow to deep areas in most instances. But it can also move from deeper to shallower areas depending on pressure.
How can groundwater become contaminated?
A lot of our daily activities can lead to groundwater contamination if we are not aware of proper use, storage and disposal of the products we use. Improper disposal of household chemicals and cleaners can result in contamination. A malfunctioning septic system can pollute local groundwater. Excessive use of lawn chemicals, including fertilizer and pesticides, can end up in groundwater supplies.
Other potential sources of contamination include leaking underground storage tanks, old garbage dumps or landfills, community transportation garages, industrial or gas station leaks or spills and improperly handled agricultural animal waste.
Because groundwater moves very slowly and air, sunlight and microorganisms that help clean surface water are not available to groundwater supplies, contaminants in groundwater can accumulate to cause pollution. Determining where the polluted groundwater has moved to is difficult because it moves in a three dimensional plume. So, one area can be heavily polluted while an adjacent area is clean.
The best option is to prevent groundwater contamination in the first place by practicing good habits and being aware of potential contamination and reporting it to local health department authorities.
For more information on groundwater:
- See the Michigan State University Extension bulletin, What is Groundwater? (WQ 35).
- Visit the National Groundwater Association site
- Check out the U.S Environmental Protection Agency website