Corps reduces lake releases to Caloosahatchee River

The U.S. Army Corps of Engineers reduced pulse releases to the Caloosahatchee River to a seven-day average rate of 600 cubic feet per second (cfs) on Saturday, May 4.

For most of the dry season, releases to the Caloosahatchee River averaged around 1,000 cfs, measured at the Franklin Lock, which is 43.4 miles from Moore Haven, where lake water enters the river. The flow at the Franklin Lock is a mixture of lake water and local basin runoff. On April 17, flow to the Caloosahatchee was reduced to 800 cfs.

The dry season schedule guarantees the Caloosahatchee River a flow of 400 cfs. Lee County officials have long argued the river needs more dry season freshwater flow, and have even filed lawsuits in attempts to increase the flow from the lake. The lake releases are needed to prevent saltwater intrusion. The optimum dry season flow for the Caloosahatchee estuaries is 1,000 cfs, according to the most recent lawsuit.

No water has been released to the St. Lucie canal east of Lake Okeechobee since March 30. From Feb. 23 to March 6, flow at the St. Lucie lock was 500 cfs. This included releases from the lake at Port Mayaca and local basin runoff. Port Mayaca is 23.9 miles from the St. Lucie Lock. From March 6 to March 30, flow at the St. Lucie lock was 250 cfs. The releases to the St. Lucie canal were part of an attempt by the Army Corps of Engineers to lower Lake Okeechobee before the wet season in order to avoid harmful freshwater releases to the St. Lucie during the wet season. At the time, Col. Andrew Kelly of the U.S. Army Corps of Engineers said, “We will consider this effort to be a success if we can get through the summer without having to make high-volume releases while harmful algal blooms are on the lake.”

At the March 22 meeting of the County Coalition for Responsible Management of Lake Okeechobee, St. Lucie and Caloosahatchee Estuaries and the Lake Worth Lagoon, Lt. Col. Jennifer Reynold explained that the corps’ decision to attempt to lower the lake level was also to benefit the ecology of the lake itself, as the lake needs lower levels to stimulate the growth of submerged aquatic vegetation. She said the corps is using the flexibility available under the Lake Okeechobee Regulation Schedule to try to lower the lake this year only. The science does not support lowering the lake to 10.5 feet every year, she added.

Over the past three years, the Lake Okeechobee watershed has experienced weather extremes that have resulted in ecological damage to the lake, she explained. As a result, the lake has lost most of the submerged aquatic vegetation, which helps clean the water, and also provides habitat for fish and wildlife.

Since the lake dropped below 12 feet, water cannot flow east at Port Mayaca. Flow at Port Mayaca is gravity driven. When the level of the lake is lower than the level of the canal, water from the St. Lucie canal backflows into the lake. As of Thursday, water was backflowing at Port Mayaca into the lake at 36 cfs.
Monday’s lake stage was 11.21 feet NGVD. Lake levels have seen a 0.69 foot recession in the past 30 days. The corps will continue to monitor conditions and adjust flows as necessary. Any changes in flows to the estuaries will be announced to the public.

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