Here’s a Caloosahatchee River “Rosetta stone” for the WP Franklin S-79.
I call it that because it decodes, or rather recodes, the historic set of flow data measured at the structure – similar to the Rosetta stone – into a format that is useful for interpreting what is going on in the downstream estuary.
Below that range saltwater intrusion creeps in,
Above it the estuary becomes over-diluted with freshwater.
(Over 6,000 cfs the estuary turns completely fresh.)
The dots on the graph to the left show those instances — cool colors indicate too much fresh water and warm colors not enough.
While the lake is not naturally connected to the river, tying the two together was one of the earliest and most pivotal moments in Everglades drainage history.
In modern times the river is used as both (1) a high-water release valve for the Lake – which runs the risk of overflowing the estuary with freshwater during the wet season – and (2) a hedge against inland-encroaching saltwater during the dry season.
It’s a complicated tale to be sure.
Earlier in the decade too much fresh water was the issue (2003-2005), but in recent years – especially with the lake’s record low-water streak (2007-2008) – saltwater intrusion has come to fore.
Now with a new wet season starting it’s anyone’s guess.
To be sure, the Caloosahatchee River “Rosetta stone” can’t answer every question, but it’s a useful translational guide to have around,
Especially if you happen to be on a boat in the estuary looking upstream.