Characteristics of flow through the Franklin lock and their effects on downstream water-quality

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The USGS completed a study to investigate correlations between flow rates and volumes through the W.P. Franklin Lock and Dam and water-quality constituents inside the J.N. "Ding" Darling National Wildlife Refuge from March 2010 to December 2013. Scientific Investigations Report 2016-5033, authored by Amanda Booth, Lars Soderqvist, and Travis Knight, summarizes the results of the study. A companion Data Release provides public access to data associated with the study.

Lake Okeechobee and Moore Haven, Ortona, and W.P. Franklin Lock and Dam.

Lake Okeechobee, Moore Haven Lock and Dam, Ortona Lock and Dam, and W.P. Franklin Lock and Dam.

Boat leaving the dock at the beginning of a water-quality survey.

Boat leaving the dock at the beginning of a water-quality survey.

The USGS completed a study to investigate correlations between flow rates and volumes through the W.P. Franklin Lock and Dam and water-quality constituents inside the J.N. "Ding" Darling National Wildlife Refuge from March 2010 to December 2013. Scientific Investigations Report 2016-5033, authored by Amanda Booth, Lars Soderqvist, and Travis Knight, summarizes the results of the study. A companion Data Release provides public access to data associated with the study.

Water-quality sensors and pump system used for moving-boat surveys.

Water-quality sensors and pump system used for moving-boat surveys.

Outflow from Lake Okeechobee, and flows from Franklin Lock, tributaries to the Caloosahatchee River Estuary, and the Cape Coral canal system were examined to determine the sources and quantity of water entering the study area. Salinity, temperature, dissolved-oxygen concentration, pH, turbidity, and fluorescence of chromophoric dissolved organic matter (FDOM) were measured during moving-boat surveys and at a fixed location in McIntyre Creek. Chlorophyll fluorescence was also recorded in McIntyre Creek. Water-quality surveys were completed on 20 days between 2011 and 2014 using moving-boat surveys.

Franklin Lock contributed the majority of flow to the Caloosahatchee River. Between 2010 and 2013, the monthly mean flow rate at Franklin Lock ranged from 29 cubic feet per second in May 2011 to 10,650 cubic feet per second in August 2013. Instantaneous near-surface salinity in McIntyre Creek ranged from 12.9 parts per thousand on September 26, 2013, to 37.9 parts per thousand on June 27, 2011. Salinity in McIntyre Creek decreased with increasing flow rate through Franklin Lock. Flow rates through Franklin Lock explained 61 percent of the variation in salinity in McIntyre Creek.

Salinity data from moving-boat surveys also indicate that an increase in flow rate at Franklin Lock decreases salinity in the Caloosahatchee River Estuary, and a reduction or elimination in flow increases salinity. The FDOM in McIntyre Creek was positively correlated with flow at Franklin Lock, and 54 percent of the variation in FDOM can be attributed to the flow rate through Franklin Lock. Data from moving-boat surveys indicate that FDOM increases when flow volume from Franklin Lock increases.

Chlorophyll fluorescence was positively correlated with flow at Franklin Lock, with 23 percent of the variation explained by the flow rate at Franklin Lock. An increase in flow rate at Franklin Lock resulted in a decrease in pH (21 percent of variation explained by flow rates). Data from the pH surveys indicate an increase in pH with distance from Franklin Lock. Turbidity and dissolved oxygen near the surface in McIntyre Creek were not correlated with flow rate at Franklin Lock. Moving-boat surveys did not document a change in turbidity or dissolved oxygen with a change in distance from the Franklin Lock. Correlations between Franklin Lock flow rate and water quality in McIntyre Creek indicate that releases at Franklin Lock affect water quality in the Caloosahatchee River estuary and Ding Darling Refuge.