Napanee residents are used to seeing driftwood floating down the Napanee River, then having it return upstream a couple of hours later. You can note that the rocks and stones uncovered by water along the Boardwalk would be wet. Upon return hours later, you would find them submerged. The river will actually rise and lower regularly between six to sixteen inches.
In 2003/2004 local Napanee resident Mac Smith conducted his own study after hearing stories of the water in the river rising and falling quickly, similar to a tide effect, and over a period of two years confirmed a regular 12-14” change in water level every 2 hours. Lake Ontario’s normal seiche rhythm is just 1-2”.
What causes this tide effect?
As the winds cross Lake Ontario, they push the lake water to the north shore. As the water enters the Adolphus Reach – Long Reach – Napanee River system which is connected to Lake Ontario, the prevailing winds push the water upriver. When the wind eases, the water surges back to where it came from. The surge repeats itself again and again, and the sloshing of the water back and forth is called the “seiche” effect. This seiche effect can go on for several days.
For the residents of Napanee this creates the illusion of a regular tidal effect. A seiche is a standing wave in an enclosed or partially enclosed body of water. Seiches and seiche-related phenomena have been observed on lakes, reservoirs, swimming pools, bays, harbors and seas. The key requirement for formation of a seiche is that the body of water be partially enclosed or bounded, allowing for the formation of a standing wave.
The reason for this strange phenomenon on the Napanee River is a combination of a couple of factors. One factor is the length of the Napanee River. If the river was longer or shorter, this phenomenon would not occur. Another factor is the direction of the river in relation to Lake Ontario. The river moves inland in a northwest direction, the same as the prevailing winds. The river is narrow and shallow, all factors that amplify the illusion.
To log this Earth Cache you must send me the answers to the following questions via my geocaching profile. Photo’s are not required but always welcome.
The posted coordinates will bring you to a plaque along the boardwalk that talks about the Seiche effect and Mac Smith’s discovery. From this spot conduct your observations.
1. At the time of your visit, what direction was the water flowing? Upriver or downriver? (Note: if unsure toss a small stick or leaf in the river to see what direction it goes.)
2. There is a small island in the river approximatly 50m from where you are standing. Based on the information on the plaque, if the water was at the highest level during the seiche would this island be totally uncovered, awash (water to the top) or totally covered?
3. Note any unusual observations including if the rocks close to shore are wet as if they were recently covered by the river, or you observe driftwood or ice travelling backwards or upriver.
You can put your answer to question # 1 and # 3 in your log so others can compare the results from their visit.
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