The dirty water in Lake DeCade is NOT, repeat NOT from the dredging. The dredge operates EVERY year in DeCade to re-build the levees. You may have noticed that they have put 'rick rack' along a long portion of the South shore. Whenever the Mississippi River gets to 12.5 feet on the Carrollton gauge, river water starts coming into Lake DeCade.
I discussed this with the Corps of Engineers in New Orleans about 5-6 years ago when we would start to see River water in DeCade. They told me that the reason was DEFINITELY caused by the high River gauge. They put me in touch with the Manager of the Old River locks in New Roads. He gave me the computer link to see the flow through the Old River Structure. He told me that they measure the flow and water velocity for both the Red River and the Mississippi River. When the flows and velocity reach a pre-determined level, he told me they begin to increase the pumping rate through the Old River Structure into the Atchafalaya river. Further south, where the Atchafalaya meets the Houma navigation canal (there is a lock there but he told me it is ALWAYS open), the water enters the Houma navigational canal and enters Lake DeCade through Minors canal and other sources. It happens EVERY year, but usually not until mid to late February. The high River levels this year were VERY EARLY.
I fish Lake DeCade every fall. From my experience, the speckled trout fishing in Lake DeCade is GONE for this Jan/Feb.
Anyone who would like the links to monitor this, see the links below:
NOAA LOWER MISSISSIPPI RIVER STAGE FORECAST
Look at the bottom of this forecast table for New Orleans (Carrollton gauge). Look under the ?River State Forecast? header to see the dates. When this New Orleans Carrollton gauge goes above 12 feet, we've found that, combined with the over 200,000 cfs Old River Structure flow rate into the Atchafalaya River is when we start to see River water in Lake DeCade. It is running over 500,000 currently.
OLD RIVER STRUCTURE PUMPING FLOW RATE
On this page, under the table titled Available Parameters, select the 00060 Discharge by checking that button to give you the flow rate. Then on the Output Format table, select Graph w/stats button.
Next, under Days, click Begin Date and select the start date where you want to start the graph (click the right arrow button to advance to the date you want to start the graph)..I usually select the last 6 months. On the End Date, select the current date. Then click the GO button and it will plot the graph. Any flow BELOW 200,000 CFPS (cubic foot per second) usually means there is not enough flow to put river water in Lake DeCade.
The Old River Structure measures the flows through both the Red River and the Mississippi. When the flow rates reach a prescribed rate as determined by the Corps of Engineers, they start increasing their pumping rate. This discharges through the Atchafalaya River. There is a lock where the Houma Navigational Canal links with the Atchafalaya river, but the lock is ALWAYS OPEN. That?s how river water gets into Lake DeCade. I got this info from the Corps of Engineers office in New Orleans years ago.
Hope that helps answer your question.