The other day, as I was sitting in my office working on the draft agenda for our upcoming 2010 FRWA Annual Conference, my boss, Gary Williams, came into my office and asked a favor of me.  “Can you write an article to help us explain to folks what effects, if any, the oil release in the Gulf of Mexico will have on our ground water resources”?  Sure, I replied, no problem.  So with that task at hand, I began to think about the basics of ground water hydrogeology and the cycle of water (hydrologic cycle).

As most folks know, ground water in the State of Florida supplies the majority of drinking water to the overall population.  This drinking water comes from aquifers, which are permeable beds of sediment with water in the pore spaces that can be extracted or pumped out with wells.  These aquifers are either layers of limestone or layers of sand and gravel located below land surface and is recharged by rainfall.  When it rains, the rain water percolates through the pore spaces, moving downward until it reaches the water table, at which depth the sediment’s pore spaces are completely full of water (now called ground water).  Once reaching the water table, the ground water moves through the pore spaces of the sediments basically by gravity feed toward places of lower elevation.  The lowest elevations are usually water bodies such as creeks, rivers, bays, and the Gulf.  The proper terminology is that aquifer discharges its ground water to these surface water bodies.  If you pressed me to give you an estimate of how fast this general vertical movement of ground water occurs, I would have to say on the order of approximately a foot per day.  

Now, this is a “round-the-clock 24/7 cycle”.  Rainfall coming in, percolating down, hitting the water table, moving from high ground toward the low ground, and eventually discharging to creeks, rivers, bays, and the Gulf.  In one form or fashion, most all ground water that is found below the land surface inland, will eventually make its way to the Gulf. 

Now, with this very basic cycle mode of water as described above, the ground water movement is continuously moving toward the coastal area, away from the inland areas.  Let’s now consider the oil release that is currently in process in the Gulf of Mexico.  The oil sheen and/or oil product may reach the coastal areas, and if so, can only be transported to the coastal areas or inland as far as the tide can carry it.  It will be meeting “head-on” the fresh ground water discharges that are coming from the other way.  The force of the discharging freshwater (ground water) will be greater than the passive “floating” oil product occurring along the coastline, thus, creating, in essence, a natural protective barrier to inland transport of the oil.  We all know the old saying that “oil and water won’t mix”.  In this case, the oil shouldn’t mix with our drinking water resources or supplies and it’s my opinion that the risk to Florida’s drinking water supplies is minimal.

 However, but again, low likelihood, the oil release in the Gulf could affect saltwater intakes for a total desalination removal process or if a very strong storm surge pushed the oil laden saltwater inland.  But, should we be spending a significant amount of valuable utility resources and manpower on addressing this possibility?    I’ll let you answer that question for your utility.