Effects of Climate Change on our Groundwater Supplies
Groundwater is water that is stored in the void spaces of the soil underneath our feet. In general, water arrives to the depths of the saturated zone by slowly infiltrating through the top layers of soil. Eventually it collects in vast underground reservoirs called aquifers. Humans can use this precious resource by pumping it out of the ground and distributing it to storage tanks and treatment plants. Most groundwater is safe to drink immediately after its removal because the sands, silts, and clays act as a natural sieve that filter the water into a clean and usable product. Groundwater is very important because it supplies approximately 39.1% of the nation’s drinking water. Many rural homes, for example, rely solely on groundwater for drinking, showering, and cooking. In addition to this, groundwater is also in integral resource for the nation’s agricultural lands. However, our supply of groundwater is slowly disappearing. Simply put, the causes for this are twofold: We are overusing our water and the climate is changing.
Climate change is an issue that has gained major importance in today’s society. Many scientific studies have been completed to try to understand how and why the climate is changing. What ever the reasons, climate change is severely impacting our nation's groundwater supplies. For example, some areas of the west and southwest United States are currently experiencing unprecedented droughts. The Lower Colorado River Authority (LCRA) has stated that the recent droughts in Texas were the "driest nine months on the books since the state began keeping records in 1895." Droughts negatively impact groundwater levels because there isn't any precipitation to replenish the underground reservoirs. On the other hand, many areas of the country have seen increases in precipitation, however the net effect across the nation is still in the negative direction.
Another impact to our groundwater supplies is the rising sea levels. Depending on topography and surface geology, saltwater can penetrate at least 50% further underground than it does on the surface. As saltwater slowly moves upward and inland, more and more of it reaches and contaminates the groundwater. The salty sea water mixes with the freshwater making it completely unusable for normal human consumption. According to scientists at Ohio State University, in the next 100 years all wells within 37 miles of the current coastline could be rendered useless. With as much as 40% of the world's population living within this distant from a shoreline, it's quite easy to see the severity of this problem. This is just another blow to our coastal cities and towns.
A third issue that we will have to deal with is an increase in land subsidence. Land subsidence is the lowering of the ground surface elevation that occurs to due changes underground. Most of the time subsidence is caused by well pumping, but un-replenished dry aquifers can also lead to the same result. When the water is removed from the ground, the void spaces open up and can no longer support the weight of the soil above it. This collapse of the soil structure can damage roads, buildings, and other infrastructure on the surface. As the groundwater gets increasingly used up, the soil layers will continue to compress. After a certain point, some of the deformation of the soil becomes a permanent change. Even if the soil were to be recharged in the future, it would almost certainly never hold the same amount of water that it historically did.
Whether or not humans have caused major changes to the climate isn’t as important as the fact that changes are occurring. Research shows that the average temperature of the earth as risen about half a degree Celsius in the past 140 years. This will also have the effect of promoting sea level rise which will in turn contaminate a significant amount of groundwater. Overall, climate change can and will have a detrimental effect on our water resources (actually, it already has). Unless something changes, it is expected that a large percentage of our groundwater resources will either dry up or become unusable sometime within the next 100 years.
References & Resources
Bigg, Mathew. Town Learns to Live with Water 3 Hours a Day. November 22, 2007. <http://www.msnbc.msn.com/id/21582319/ns/weather/t/town-learns-live-water-hours-day/#.TolJv9SyDV4>.
Earman, Sam. Possible Impacts Of Climate Change On Groundwater And Surface Water Resources In The Western U.S.A. October 31, 2007. <http://gsa.confex.com/gsa/2007AM/finalprogram/abstract_129272.htm>
Hylton, Hilary. The Great State of Texas: The Drought That Wouldn't Leave Has Lone Star Farmers Scared. August 10, 2011. <http://www.time.com/time/nation/article/0,8599,2087489,00.html>
Intergovernmental Panel on Climate Change. The Regional Impacts of Climate Change: An Assessment of Vulnerability. November 1997. <http://www.ipcc.ch/pdf/special-reports/spm/region-en.pdf>
Leake, S A. Land Subsidence From Ground-Water Pumping. January 6, 2004 <http://www.usgs.gov/science/cite-view.php?cite=687>.
National Academy of Sciences. Global Warming Facts and Our Future. October 2, 2011. <http://www.koshland-science-museum.org/exhibitgcc/causes01.jsp>
Ohio State University. Climate Change Threatens Drinking Water, As Rising Sea Penetrates Coastal Aquifers. November 7, 2007. <http://www.sciencedaily.com/releases/2007/11/071106164744.htm>
RealClimate. How much future sea rise? More evidence from models and ice sheet observations. March 26, 2006. <http://www.realclimate.org/index.php/archives/2006/03/catastrophic-sea-level-rise-more-evidence-from-the-ice-sheets/>.