Too little, too much: The Caloosahatchee paradox

Since June 2, the focus of the regulatory agencies, the public, and the environmental community has been on the damaging high volume discharges to the Caloosahatchee and St. Lucie from Lake Okeechobee, and the resulting toxic cyanobacteria algae blooms fouling the rivers and estuaries. We are all grappling with the ripple effect of the releases — truly awful harmful algae bloom impacts on the ecosystem, human and wildlife health, and our tourism-based economy.

The Caloosahatchee paradox is that earlier in 2018 the estuary was not receiving enough freshwater releases from Lake Okeechobee to maintain the delicate salinity balance for estuarine organisms to survive. For over 75 days the Caloosahatchee was experiencing an exceedance of the river’s “minimum flow and level” or MFL, which is supposed to keep salinities in an optimal range for estuarine resources like tapegrass (an important food source and habitat) and oysters. In May, that swiftly changed with high rainfall events that caused significant stormwater runoff from the Caloosahatchee’s watershed compounded by the releases from Lake Okeechobee starting on June 2. Ironically, there was plenty of capacity in the Lake to release more water in the preceding months due to how high the lake levels were thanks to Hurricane Irma in 2017.

If more water had been released between January and April, it’s likely the releases in June would not have been as severe. These extreme swings — from too little water to too much — are ecologically devastating to the Caloosahatchee, and they occur nearly every year.

To add even more complexity to the Caloosahatchee flow issue, we also know that the MFL rule currently in place, which dictates minimum flows, is not sufficient to provide enough freshwater to protect the estuary. Unfortunately, the low flow times are often overlooked because the harmful impacts are not as readily apparent as the high flow periods which bring dark freshwater plumes into San Carlos Bay and are periodically accompanied by blue-green algae. [1]

The Conservancy petitioned over eight years ago for the rule to be updated. Subsequently, the South Florida Water Management District (SFWMD) has been engaged in an updating effort over the past several years. The Conservancy and our partners have been deeply involved in commenting on the proposed rule and we have some good news and some bad news to report. The SFWMD held a number of workshops and technical meetings with the stakeholders concerned about the MFL and provided a number of opportunities for public comment.

The Conservancy and partners raised many red flags about the proposed update — first, the SFWMD is only increasing the MFL flow from 300 cubic feet per second (cfs) to 400 cfs. Real-time monitoring data shows that over 700 cfs is needed to provide enough flow to the Caloosahatchee. Secondly, the SFWMD proposed to allow the flow to fall below the MFL for 55-consecutive days, which could result in losing over 80% of the remaining tapegrass resources.

The good news is: the SFWMD listened to our concerns on the 55-days and has improved the rule by revising to a shorter timeframe — this is a change for the better because the resource will be under stress for a shorter period of time, making recovery more achievable. The bad news is: they are still proposing 400 cfs, which we know will not protect the estuary in the dry season.

The Conservancy is remaining engaged in this rulemaking to help ensure that those managing our water resources consider both ends of the spectrum — the high flow times, and the low flow — because both cause significant harm to the Caloosahatchee.

Learn more about the work inside the Conservancy policy department visit

[1] Note: low flow periods also periodically result in blue-green algae blooms.