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Steve M.
Frequent Contributor
USA
107 Posts |
 Posted - 05/05/2006 : 11:05:37 AM
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| I am confused. Could someone explain how the flow rate (at Shawmut for example) can be independant of water level. I see posts and the Friday updates refering to the water level being good, but the flows being fast. How can the river flow faster or slower with the water level remaining the same. Or am I misunderstanding these references. |
"So much water, so little time"
Steve |
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titleguy
Big Fish in a Small Pond
1128 Posts |
Posted - 05/05/2006 : 11:11:37 AM
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| I think Steve that it depends on how that level of water is coming over or through the dam. You can have the same water level, 5000cfs say, but instead of coming through the penstock and a little bit of the middle gate, it's all middle gate or over the flashboard area of the dam and that generates if not necessarily more flow, but different flow. ( Remember- if it can't be checked, go for it. If it gets checked, complicate, lie through your teeth or blame it on a friend). |
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Rory
Frequent Contributor
USA
672 Posts |
Posted - 05/05/2006 : 11:33:16 AM
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| Steve, you beat me to it. I've seen this phenomenon mentioned twice lately, and I was thinking of making the same inquiry. Perhaps titleguy is right. |
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Mike Holt
Member
USA
2822 Posts |
Posted - 05/05/2006 : 12:56:45 PM
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Steve,
Titleguy is on the right track with his comment. There are basically three sources of water at Shawmut. The turbine flows from the “new” turbines, which is the flow right next to the Shawmut side parking area. The flow from the “old” turbines, which is the flow from the brick building at the base of the dam. And finally from the dam itself in the form of leakage or the opening of the center gate.
If they are only running the “new” turbines the only strong flow is the flow on the West Shore. The middle or East Side of the river flow is fairly mild in comparison. However, if they spread the generation load between the “old” and “new” turbines the “old” turbine flow directs water towards the middle of the river – same flow – but now half of it is directed to the middle making the flow feel much stronger in the middle and on the East Shore.
Then if you open the gate and add more flow to the center (and today the gate is about ½ open) you really increase the force of the flow out in the middle. Now I understand that it seems like opening the center gate should raise the level but actually it makes little difference.
I’ve been wading when they open the gate and left the water anticipating a substantial rise in the level. What I’ve found is that the opening of the center gate only brings the level up about two or three inches but it makes a BIG difference in the speed and force of the flow.
The same thing happens with spillage over the top of the flashboards – little level change but a noticeable increase in the speed of the flow. Remember the river in Shawmut is 200 – 300 yards wide. It takes a lot of water to raise it two inches and when you’re wading you feel it.
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Coachman
Frequent Contributor
169 Posts |
Posted - 05/05/2006 : 1:22:40 PM
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| Great answer Mike. I knew there was a difference between the level and flow at Shawmut, but never really could explain why logically. Thanks. |
Chris
http://chrisbolducphotography.com
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Steve M.
Frequent Contributor
USA
107 Posts |
Posted - 05/05/2006 : 4:51:57 PM
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| Well thank you for clearing up that mystery. I'll keep this information in mind when deciding which side of the river to fish. |
"So much water, so little time"
Steve |
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