How Florida's Aquifer Models Are Inaccurate, And Why That Might Be A Problem For Our Water Supply

Jan 30, 2013

Florida's current computer models for tracking underground water flow are coming up short.
Credit eutrophication&hypoxia / Flickr Creative Commons

Understanding how water flows through Florida's aquifer is integral to maintaining  safe and sufficient supply of fresh water, but current computer models used to monitor the state's aquifers and springs are "full of holes" according to some critics. 

The Tampa Bay Times reported on Monday that there is a disconnect between "how water pumping permits are routinely issued throughout much of Florida" and the impact those permits have on the state's rapidly dwindling resources. Currently, state officials employ computer models "that use a false assumption" about how water flows under the ground's surface when issuing permits.

Though the current models predict a steady rate of movement through sand and gravel, field tests have demonstrated the unpredictability of the water flow, owing in large part to the existence of karst (limestone filled with holes) below the surface. Scientists using a "dye test" were able to more accurately track the speed at which water moves underground.

The dye test gave a vivid illustration of the difference. The scientists running the test picked their drop sites with help from one of the state's models. The model predicted how fast a liquid would trickle along underground toward the spring. Different zones would give the dye a 2-year trip, a 10-year trip and even a 100-year trip. But when they dropped the dye in, the stuff rocketed through the aquifer. It zoomed across half the predicted 100-year distance in just six months. 

Pete Butt, the scientist who supervised the test, said the dye would have traveled even faster if the test had taken place during Florida's rainy season. The findings reveal potential vulnerabilities in the state's water management system. Not only are the computer models used to monitor water use and levels, but to track the rate of contamination from chemicals, sewage, and other pollutants. 

Though another "more accurate" computer model based on water flow through karst exists, the state reportedly will not "touch it" because it was created by Coca-Cola, which at one time owned a bottling plant near High Springs.