Liberty flows

Here’s an update on the Apalachicola River, from Lanier to Sea.

As a hydrologist working within the great state of Florida, I try to stay conversant in the major issues at play in its water ways. The so-called tri-state water war is one of them.

The Corps of Engineers is in the process of updating its operating manual for Lake Lanier and a few other reservoirs on the Chattahoochee River.

A recent article in the Atlanta Journal Constitution gives a really nice thumbnail of the issues, history, and status of the process. ┬áHere’s another one hot off the press.

The primary problem lies at its headwaters: Lake Lanier is low, and its been low for the better part of 2 years. Currently its down 10 ft from its long-term October average.

That’s in part a result of the drought that plagued the southeast, but droughts always become more accute when water demands increase, and that’s the case here with a growing nearby Atlanta, not to mention other downstream water uses.

Lanier’s low stage made national news during last year’s drought: water rules dictated releases from Lanier to maintain freshwater flows all the way downstream into Florida’s Apalachicola Bay. Those rules were tweaked to maintain adequate supplies in Lanier.
But the fresh/salt water balance in the bay becomes almost 100 percent dependent on flows from the mainstem Apalachicola during drought, because flows diminish from its tributaries.
When that happens, releases from Lanier, which eventually pass through downstream Woodruff Dam, is the only flow in town. Outflows through Woodruff Dam dropped at or slightly below 5,000 cfs for 6 consecutive months in 2007.

The true yardstick for measuring freshwater flows into the Bay is at the US Geological Survey’s flow monitoring station near Sumatra, in Liberty County. The graph below shows current year discharge measured there relative to its 25 year history.
It peaked at around 40,000 cfs this spring before dropping down to 6,000-8,000 cfs during the early summer. Fay briefly shot it back up to spring-time levels, and currently it is tracking along the 25th percentile … at around 10,000 cfs.

When it rains, the tributaries kick back on, and flows from Lanier aren’t as critical. But when the drought descends, Lanier becomes the sole source for maintaining flows to Apalachicola Bay.

Photo at top courtesy of Northwest Florida Water Management District’s web page.
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