FL Lake Country - Springs, Water Management, and the BIG OAK

This is going to be a very watery post.  All numbers etc. come from State park brochures and signs.

The Floridian aquifer is actually the largest freshwater aquifer in the world, covering 82,000 square miles and in places  10,000 feet deep. Water seeps through the top layer of sand and is then trapped in the limestone below. The Lake county where we're wandering is just riddled with lakes, springs, seeps, rivers creeks, etc.

Our first stop was Wakiwa springs state park. The Wakiwa river is one of only two wild and scenic rivers in Florida, but Wakiwa springs is actually developed as a swimming hole:

 

This spring, one of 27 or so on the river, discharged on average 45 million gallons of water per day (Extra credit for students: what is that in cfs?) We went swimming here, and it was re-freshing.

Next, we visited Blue Springs State Park.  This is the last free-flowing, undeveloped class 1 spring in the John's River watershed (class 1 means it discharges a lot of water, on average 102 million gallons of water per day).  The water is 74 degrees F year round, so in the winter when other streams are too cool, manatees congregate here to be warm.  Apparently, the manatees prefer water warmer than 66 degrees.  The water was a beautiful clear green color, FULL of fish of all sorts.

Here, you can see some of those fish. We saw a lot of big catfish.

These are Gar, but I'm not sure what kind.  About 4 feet long!

Live oaks shaded the spring.

Though closed now to allow manatees to use the area, in the summer the spring is a haven for divers and inner-tubers.  This is the upstream most launch point.

This picture doesn't show it too well,  but there's a boil where the groundwater feeds the spring. You can however see the darker slot in the rock where it comes from. People actually dive the spring to explore it (you need a permit, of course).

Here is a cross section of the springs, as surveyed by divers. 

I believe this is a video setup to monitor the manatees.

Here's stormwater retention basin we saw at Lake Griffin State Park.  Students in my Environmental Impact Analysis and Water Resources classes will recognize some features.  When we pave, have roof tops, and other impervious surfaces, rainwater that would have recharged the groundwater typically gets quickly funneled away into lakes, rivers, and streams.  This causes several problems.  First, the water that would have gone into the ground doesn't, so there is less groundwater.  Second, water that would have slowly passed through the ground and into the waterways is instead quickly diverted to it, causing downstream flooding.  Third, the water is often polluted with surface pollutants.  

The goal of a stormwater retention basin is to put that water in the ground, where it belongs.  This fixes all three of the the above problems.  In most states, developers are required to create stormwater management plans.  Here, there's a decent sized parking lot that runs into this stormwater retention basin.


This ramp from the parking lot has concrete blocks cemented to it.  These blocks break up the energy of the water as it flows down the ramp, preventing erosion of the soft sandy soil.

Beside me is the standpipe.  For small rains, the water just goes into the basin and slowly infiltrates into the ground.  For larger rains - when the water fills the basin to the height of my hip, excess water runs off into the standpipe and on into the river.  That flat bit is a barrier to prevent debris like Styrofoam cups from leaving the basin.

This is the second largest live oak tree in FL (at Lake Griffin State Park).  It's a beautiful tree, and was estimated to be 350-500 years old.  Really cool.