Hamlin Lake Preservation Society

 

Protecting Hamlin Lake for Future Generations 

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Diary of the Lake Level
There is quite a bit of interest in the timing of the raising and lowering of Hamlin Lake. The nature of the inquiries suggest that the inquirer assumes that the lake level very closely follows the weir height at the dam. While the weirs do ultimately control the lake level, a rain event will cause a dramatic level change and demand a prompt response by the State Park personnel.

Figure 1 illustrates the highly variable nature of the water flow going over the dam. Viewed from above, the apparent depth of water going over the weir is deceptively shallow. Data shown in Figure 1 shows the depth of water above the top of the weirs ranging from 3 to 29 with a mean value of 18 inches. That is a lot of water going down each spillway.

The height of the weirs is adjusted as much as a foot in short order to maintain the lake level during the summer. Figure 2 shows a rainfall event just before August 2, 2012. The weirs were lowered 10 inches and the lake still rose 2 inches. During those 13 days in August of 2012, the flow changed from 16 inches of water over the weirs to only 3 inches.

Variations between years can be seen between the Fall of 2015 and2014 in figure 3. The weirs were lowered 16 days later in 2015, but the lake level fell at essentially the same rate for both years.
   

The two south spillways have weirs that are affixed at 20 inches. Above the weirs there are sluice gates that can be lowered to further restrict the flow. This presents a bit of a challenge. During the winter, only four of the spillways are able to operating, because the fixed weirs on the two south spillways are higher than the lake, so the winter lake level is a bit higher as a result. During the summer, the 20-inch weir height is a bit low allowing if open, too much flow relative to the other four spillways. When one thunderstorm dumps a lot of rain, the two sluice gates must be raised manually in a timely manner.
   
   

One useful item that is missing is a river level gage located below the dam.  This gage would give provide an estimate of the flow rate in the river and provide additional information to the folks who control the weirs.
   
     
JClark4626@aol.com Hamlin Lake Preservation Society PO Box 178, Ludington, MI 49431