Understanding the Caloosahatchee and the Lake
Lake Okeechobee and Caloosahatchee Salinity
As lake levels dropped in Fall 2010, concerns about a predicted drought prompted the South Florida Water Management District (SFWMD) to recommend on December 15, 2010 that all flow from the lake to the Caloosahatchee be stopped. Lack of freshwater flow to the Caloosahatchee in the dry season causes high salinities and algal blooms. Click here for background on the Caloosahatchee and salinity requirements prepared for the Army Corps in December 2010.
Salinity and Habitat -- Without freshwater inflow during the dry season, high salinities extend all the way upriver to the W.P. Franklin Lock structure (S-79), eliminating all the low salinity, freshwater habitat in the estuary. This low salinity zone in the Caloosahatchee is critical habitat for the reproduction and survival of economically important fishery species including bay anchovy, drum, silver perch, redfish, snook, crabs, shrimp and tapegrass.
Algal Blooms -- The water upstream of the Franklin Lock stagnates, which spawns algal blooms. Learn more about 2011 algal blooms in the Caloosahatchee.
Pulse Releases -- On February 4, 2011, the U.S. Army Corps of Engineers began authorizing pulse releases from the lake in order to bring salinity levels in the Caloosahatchee and estuary to more natural levels. Those welcome pulse releases broke the pattern of increasing salinities until the lake level fell below the Water Shortage Management Band in mid-March and releases to the Caloosahatchee were cut off.
Water Shortage Management -- When Lake O levels fall below the Water Shortage Management Band (see illustration below), the control of lake releases shifts from the Army Corps to the SFWMD. On Friday, May 27, lake levels dropped below 10.5 feet, which is too low for gravity to keep sending water to the canals south of the lake. Read more from the Sun Sentinel.
At the March 2011 SFWMD Governing Board meeting, Chairman-elect Joe Collins berated the Corps of Engineers for providing minimal base flows to the Caloosahatchee against the District’s recommendation of no flow, in spite of the objections of our representative at the time, Vice Chair-elect Charles Dauray.
In mid-March, lake levels fell below the Water Shortage Management Band. Aside from some rain in March, there have been no releases for the Caloosahatchee and salinity levels are again soaring.
In the drought years of 2007-2009 lack of flow caused a quantifiable loss of habitat for commercially important food and recreational species and placed endangered species at risk. Optimum
flow at S-79 (W.P. Franklin Lock, which includes Lake Okeechobee
releases from S-77 as well as water from the Caloosahatchee watershed)
is between 650-800 cfs
. Flows over 2800 cfs are damaging (during periods of heavy rain, flows have exceeded 11,000 cfs).
In contrast, the SFWMD issued no water restrictions at all until March 26, 2011, when a Regional Water Shortage was announced limiting residential irrigation, agriculture and other uses. Click here for the Order.
The SFWMD has consistently recommended cutting off flow to the Caloosahatchee while making no cuts to other permitted users. During the 2007-2009 drought, when the Caloosahatchee suffered loss of habitat, record agricultural harvests were recorded. Harvest data is available at: http://www.nass.usda.gov/Statistics_by_Subject/index.php?sector=CROPS.
Posted May 2011