Dam Lowering  effects on the fishery and wildlife

With the draining of the lake, the lake temperature rises in the water.  This will only get worse with the global warming changes to weather patterns.   This effects the fish reproduction cycles and the fish life span.  It also eliminates several spawning sites in the shallow parts of the lake.  The have been no environmental impact studies to determine the extent of this damage from lowering the lake.

It is also changing the ecosystem for the birds and other wildlife

 

This is a reference from the following article from the New Jersey Fish and Game Department on the effect of lake lowering.

ref https://www.njfishandwildlife.com/pdf/fwfisheries/wtrlower-info.pdf

Extent of Lowering:  A stream, lake or pond should be lowered only as much as is necessary to accomplish the objective of the lowering.  A pool of water which is capable of supporting the fish population should be maintained at all times.  Substantial lowerings (remaining water level not sufficient to support the existing fish population) or complete draining of a waterway should only be done when absolutely necessary.  These types of lowerings require that the fish be salvaged (collected and relocated), which can be costly. It also often results in the undesirable release of silt, detritus, and debris downstream, which can seriously affect water quality and damage critical habitat in the receiving water.  These lowerings also result in loss of recreational use of the waterway for fishing for several years.  Substantial and complete drawdowns for aquatic vegetation control are not permitted.

Time of Year: Timing is one of the most critical components to minimizing impacts to aquatic biota.   At certain times of the year aquatic biota (especially fish) are less likely to be adversely affected by a drawdown during others the results can be catastrophic.

Winter 
Except under special circumstances (dam safety concerns, catastrophic events etc.) water lowerings will not be approved to begin after November 1 for northern lakes, and November 15 for southern lakes.  Lowerings for aquatic vegetation control must be lowered prior to these dates.  These timeframes prevent hibernating turtles and frogs, buried in the substrate, from being exposed to the elements.  

 

Spring 


A waterbody should be full of water during the spring spawning and summer growing seasons.  Pickerel and perch spawn in late winter after ice-out, bass spawn in May and June, and sunfish spawn in May, June, and July.  Lowering during these periods can harm fish populations by eliminating suitable spawning areas.  Fluctuating water levels can also contribute to egg mortality (by exposure to air) and death of newly hatched and small fish as they become stranded in weed beds and shallow pools.  Lowerings for projects that must be conducted in the spring will be limited in duration (several days or weeks) and extent in order to avoid fish mortality.

Summer 


Except in extreme circumstances (imminent dam failure, mandated lowering, etc.) water lowerings will not be approved to begin, or to extend over the summer months.  Elevated water temperatures resulting in depleted dissolved oxygen levels can lead to stressed conditions for the entire fish population.  These conditions are further exacerbated when fish are crowded in a reduced volume of water.  These conditions almost always result in extensive mortality.   Duration:  A body of water should not remain lowered any longer than is necessary to accomplish the objective of the lowering.  Water levels should never be raised and lowered repeatedly.  Waterbody owners should proactively develop water lowering plans to coordinate upcoming activities and projects.  

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