Thursday, June 30, 2016

Hitting Manawa Hard

The early spring when the temperatures were chilly, it was rainy or windy and on many days or a little of both.  Dredging operations were scheduled on Lake Manawa to start and we did not know what the effect would be on water quality or the different method of dredging that would be used.  So, I missed a month and did not get on the water.

The dredge is to the top of the picture.  Notice the pipe coming off the back end of the unit.  This is one of the signs that is posted in the lake for the boaters.  The buoys are not visible supporting the pipeline, but you motor right over the top at a low spot between the boys.  I lifted the motor to the max and still keep the prop in the water.
Putting in at the Fish & Game Club on a beautiful June morning we made our way slowly close to the dredging operation to put the boat on the southwest side of the lake.  This is hydraulic dredging. 
The dredge floats on the water and pumps the material through a temporary pipeline to an off site location, several thousand feet away. The dredge acts like a floating vacuum removing sediment very precisely.

Hydraulic dredges use a discharge line, and a return line, which are the only disturbances to the surrounding environment. These lines can easily be run under roads or sidewalks. Other than this, the dredge, which is not much larger than a small boat, is the only machine to be seen. It is an unobtrusive method that does not require disturbing the shoreline and requires one trip in to put the dredge in the water and one trip out when the project is complete.

The pipeline comes over to this unit, and I assume this must be some form of pumping station because the next stop is the area where the sediment is collected and piled higher than the trees.  I understand this material will be used by the highway department.
 Hydraulic dredging uses the energy of pumping water at a high velocity through a pipeline to carry sediment away from the lake bottom to a distant location. Because moving water is utilized as the mode of transportation for the sediment, the water and sediment must be separated once the sediment has reached its final destination.
This is an aerial map of Lake Manawa. At the top of the map where the finger sticks out is where the dredge was located.  The finger sticking out of the water at the lower left is Boy Scout Island, and where we worked around and off the tip of the peninsula.  A lot of fisherman fish this area from the bank.

The sediment is separated from the water in a temporary settling basin. Since the slurry velocity greatly decreases once it is discharged into a settling basin, there is no longer energy to carry the solids. Therefore, the solids fall to the bottom and clear water flows over a weir to return to the lake. When the dredging is complete and ample time is given for this material to dry. The material can also be loaded out and beneficially deposited at other various sites to fill in low areas, utilized for topsoil, etc.

Driving to the south side of Lake Manawa, there are two pipelines coming out of the lake, around a picnic area and under the roadway.  Beyond the levee that surrounds the area, was a huge pile of sediment that had been taken from the lake.  We tried to find a way into the area to get a picture, but were not able to do so.  
Another warning sign.
The dredging company had put colored marker buoys over the top of the floating pipeline and warning signs were posted on where not to go.  It was slow going for about 50 yards in the general area of the barge, and the prop was just barely in the water as we crossed over the pipeline.  
Now to the fishing.  It stunk.  The water temperature was 72 degrees at the surface and I would have preferred to have it much cooler, but it was our fault we did not get over sooner.  We steered the boat to the west bank and moved out to about 5 feet of water.  The breeze was perfect for using a jig and floating it above the bottom of the lake and working it up and down.  A crawler was the bait of choice per the recommendation of the bait shop.  Also with the greenish water color, we selected chartreuse as our color.
The chute to the center of the picture leads to the south end of a housing area on the west shore of the lake.  Fish about 20 yards out and south to the next picture.  I have had luck there in really cool weather.

For the first hour, nothing happened.  As we approached the south shore, we started getting some hits.  These were small fish and probably could not get the bait in their mouths.  Covering the bait with Berkley's Powerbait increased the hits, but nothing was taking a hold.  A couple of times I felt resistance, eased up on the pressure then set the hook on nothing.  The assumption was if it was a walleye, they were mouthing it.  One needs to be patient, and then give the rod a strong hook setting action.  That strategy was a failure.  
Start at the chute from the above picture and fish south to the dead tree.  I have had luck doing that, but today was not the day. It beats working.
 We worked around the peninsula on the south end of the lake, but had no luck.  With the sun high and pounding on us, it was lunch time and my wife and I were both hungry.  Tomorrow is another day. 


Good hunting, good fishing, and good luck.   Hank


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