Atlanta Water Shortage

The various rivers and streams that flow into Lake Lanier are at (or near) their all-time lows, which isn’t a good sign for the lake.

According to 11Alive, the Chattahoochee River north of the lake is at 28% of its normal flow.  Other than the 28% figure, the article didn’t give any other numbers, just quotes from local residents talking about how low it looks.

So far this year, the lake has done pretty well.  It even surprised some folks (like myself) when it rose a few inchdes last month.  This month has been a slow but steady drop, down about 4 inches so far.  Last June, the lake dropped by about 21 inches, so at least we’re still dropping at a slower rate.  Of course, we’re already about 10 feet lower than this time last year…

If the inflow continues to dwindle, this could create some big problems, even with the revised operating plan in place.

(Note: This is a guest post by Rich S.)

On June 2nd, the U.S. fish and wildlife service gave their blessing to the Corps of Engineers Revised Interim Operating Plan (PDF).

So for the foreseeable future, this plan defines how decisions will be made concerning water retention in the ACF system including Lake Lanier.  This plan is a modification of the operating plan the corps has been using for the last several years.  The modifications are intended to favor retention or storage in the reservoirs of the ACF above the old plan which clearly released too much water during the recent drought.

I was surprised to see that the plan doesn’t really address Lanier or any of the other lakes individually, but mainly addresses the release from Jim Woodruff dam because of course everything that isn’t released from that Dam is held in the five reservoirs of the ACF.

Decisions about how much water is to be released vs. stored are based on three factors: Composite action zone, season, and inflow.

The composite action zone is similar to the one you are likely familiar with from this lake Lanier forecast chart - http://water.sam.usace.army.mil/lanfc.htm

The composite chart adds the storage from all five reservoirs and treats it as a sum of the entire system.  The action zones are similar with zone one being relatively good and zone four being very low water levels.  They also added a fifth zone that they call the “drought zone”.

Release levels vary by three seasons: spawning season (March-May); non-spawning season (June-November); and winter (December-February).  Regardless of the season, when the composite level reaches zone four, releases from Woodruff dam are reduced to 5000 cf/s.  Any inflow above that level can be retained as storage.  Likewise, when the composite level reaches the drought zone, releases are reduced to 4500 cf/s.

During the winter period, releases are reduced to 5000 cf/s regardless of the composite zone (except 4500 cf/s in the drought zone).  All additional inflow is stored.

Aside from the above situations, releases from Woodruff dam are based on season, zone, and inflow with some portion of any inflow above 8000 cf/s  retained for storage.

Compared to the old plan, this one lets us release a little less water when times are bad, and store a little more of the excess when times are good.  It’s not going to solve all of our problems, but it may actually be sustainable over time, which the old plan clearly proved not to be.

Rich