Monitoring Flow and Salinity in Florida's Caloosahatchee River Estuary

Control structure S-79 at the W.P. Franklin Lock. USGS.

Why monitor

The tidal Caloosahatchee River and the estuaries below it have great environmental, recreational and economic value for southwest Florida. Changes to the watershed have altered its natural flow, threatening the estuaries' health. Measuring how much fresh water — and what it carries — reaches this delicate system from its tributaries is essential.

The networks

From 2007 to 2013, the USGS, with the Florida Department of Environmental Protection and the South Florida Water Management District, ran a flow and salinity network on tributaries and key points of the tidal river. It supplemented long-term stations such as the W.P. Franklin Lock (S-79), run with the U.S. Army Corps of Engineers, Lee County and the City of Cape Coral. A station on Sanibel Island (2010–2013) was part of the USGS Greater Everglades Priority Ecosystem Science initiative, with the J.N. "Ding" Darling National Wildlife Refuge.

The data helped the state set total maximum daily loads for pollutants and calibrate a hydrodynamic model, and support the Caloosahatchee River Watershed Protection Plan.

How flow was measured

• At control structures — S-79, Whiskey Creek, and Aries, Meade, San Carlos and Courtney Canals — flow and water level were measured continuously at gates and weirs using standard USGS methods.
• Where the tide reverses the flow — Telegraph Creek, Orange River, Popash Creek, Billy's Creek, the river at Channel Marker 52, Hancock Creek, the river at Shell Point, Shell Point Canal and McIntyre Creek — index-velocity meters were installed.
• Salinity and temperature were recorded continuously at water-quality stations.

The Caloosahatchee River at the Channel Marker 52 monitoring station. USGS.

What it showed

Tributary flows rise and fall with local rain, while discharge at S-79 follows the lock's operating schedule and the management of Lake Okeechobee's water level. From 2007 to 2013, fresh water released at S-79 was far greater than the flow from all monitored tributaries combined.

Total monitored discharge into the tidal river, split between the Franklin Lock (S-79) and the monitored tributaries. USGS.

Boat surveys

At least six times a year since 2011, a boat has mapped near-surface water quality from the Punta Rassa boat ramp through San Carlos Bay, around Pine Island and up the river to the Franklin Lock, pumping water past sensors that log salinity, temperature, dissolved oxygen, pH and turbidity every 5 seconds. One survey on August 1, 2013, during large freshwater releases at S-79, showed fresh water reaching far down the river toward the bay.

Getting the data

Fifteen-minute and daily data are available from the USGS National Water Information System and the South Florida Information Access (SOFIA) site, searchable by station name or number; survey maps and data are on SOFIA.

Sources

Based on Eduardo Patino, "The Caloosahatchee River Estuary: a monitoring partnership between Federal, State, and local governments, 2007–13," U.S. Geological Survey Fact Sheet 2014–3121 (2014), prepared with the Florida Department of Environmental Protection and the South Florida Water Management District; a work of the United States government in the public domain. The photographs and chart are taken from the fact sheet's PDF; its station map and salinity-survey map, drawn on Esri basemaps, are not reproduced.