lake level

[ishoot308]

This past weekend and according to my dock, the lake was at full pool. With the rain we got today and the rest of this week things are shaping up nicely!

Dan

[Descant]

Your dock is probably a better indicator than the scale on the Weirs bridge. The channel compresses the water flow and the level is likely artificially high in the spring. Hence my desire for full pool to be in July, not May.

[8gv]

The post above makes me wonder...

Paugus Bay passes the lake's water on into Opechee where it ultimately travels to the sea.

Are there any other "outlets" on the big lake?

[jeffk]

Originally Posted by ishoot308

This past weekend and according to my dock, the lake was at full pool. With the rain we got today and the rest of this week things are shaping up nicely!

Dan

The DES gauge at the Weirs boardwalk shows ~1/2 inch below Full Pool. There is 1" of rain forecast this week by the end of this Sunday that should cause the lake level to go over the "Full" mark. That would be about 6 weeks earlier than the DES 40+ year mean reaches it around June 1st.

The Lakeport dam output is still at minimum, 250 CFS. Both Silver Lake and Winnisquam are at "normal" low levels so if we got a deluge of rain in the future, it could be dumped downstream without a significant problem. It seems we can let the level continue to go up for another few inches over Full without any major problems.

[John Mercier]

What is the maximum rate at the Avery Dam?

[jeffk]

Originally Posted by John Mercier

What is the maximum rate at the Avery Dam?

Max Discharge (Cubic Ft/Second) 5960 (online lookup)

Which is a lot more than Lakeport, which is ~2000 CFS. At that rate, it drops the lake about an inch a day.

[LIforrelaxin]

Originally Posted by John Mercier

What is the maximum rate at the Avery Dam?

Doing a little research I found the following on the Avery Dam from a Study/Inspection done by the Army Corp of Engineers in 1978....

The dam itself if capable of 5K+ cfs (true Max in the report is ~8K under specific conditions)..... however the actual max recommended flow back at that time was around 2.6K do to the capacity of the River in that area....

The output of Avery Dam is really dependent on the level at which the lake is being maintained.

in short my take here is that what ever goes in from Winni, goes out through Avery Dam......

[LIforrelaxin]

Originally Posted by jeffk

It seems we can let the level continue to go up for another few inches over Full without any major problems.

That really depends on who you ask... I know that both Fay's and Sheps start to see problems at full lake.... Nothing Horrific mind you, but issues.....

Unfortunately many of the older permanent docking structures are built at the high water mark... over the years I have seen some boat houses get raised, when they have gone major renovations. I supposed some docks get the same treatment, the boat houses are just more noticable.

[jeffk]

Originally Posted by LIforrelaxin

That really depends on who you ask... I know that both Fay's and Sheps start to see problems at full lake.... Nothing Horrific mind you, but issues.....

Unfortunately many of the older permanent docking structures are built at the high water mark... over the years I have seen some boat houses get raised, when they have gone major renovations. I supposed some docks get the same treatment, the boat houses are just more noticable.

While true, if you asked the marinas (and lakefront owners with docks, and boaters in general) if they could trade the low water problems from last Fall for the high water ones they would have done it in a heartbeat. Also, if the water is a little high, it can be adjusted down, usually within a week or so. If it is low, you are out of luck. People started noting the low water last year in August and we had to deal with it for over 2 months as it got significantly worse.

[jeffk]

The DES tracking is now reporting that the lake is over Full Pool. 1/2" more rain on Sunday. Then on and off April showers, no major storms, predicted until the end of the month.

My guess is that the Lakeport dam management, given the last two years bad experiences, will leave it full or a little more into the summer. Usually, a slow drawdown is allowed to happen starting mid-June. It might be smart to delay that or proceed at a slower drawdown pace through the summer.

[LIforrelaxin]

Originally Posted by jeffk

While true, if you asked the marinas (and lakefront owners with docks, and boaters in general) if they could trade the low water problems from last Fall for the high water ones they would have done it in a heartbeat. Also, if the water is a little high, it can be adjusted down, usually within a week or so. If it is low, you are out of luck. People started noting the low water last year in August and we had to deal with it for over 2 months as it got significantly worse.

High water problems are always easier to deal with.....and preferable....
I have always been on the side of keeping the water as high as possible, for as long as possible. But what I have witnessed over the years tells me that maintaining the lake too high at the beginning of the year, can lead to problems in mid summer. There are always going to be years that we see flukes in the weather... last summer's drought for instance..... but than again I have also seen years where their are huge rain storms, that cause the lake to rise suddenly as they work to minimize flooding down stream....

Operating the Dams is challenging.... and mother nature is ultimately in control.....

The good news is the lake is currently nice and full..... I do anticipate that they will soon open the dam a bit more.... to match the pace of water coming into the lake..... Right now I think people are going to get what they are wishing for which is that the lake will be maintained close to full, as long as possible...... but once the lake starts droping their is only so much that can be done, and if mother natures feels like a drought is what she wants.... it could be another rough year.....

[jeffk]

I wonder if a better strategy to lake level management could be applied? For example, if the lake is at a "good" level right now and a big storm is very likely to drop 4" in a week from now, adjust the dam to drop the lake 2" before the storm arrives. After the storm, evaluate how much rain actually fell and continue adjust as needed. If 2" fell, you're done. If 4" fell, you continue for another week. If the storm fizzled out, cut the dam output to minimum to recover the 2", if possible.

There are obviously other factors, like if the lake is already too low, just wait. It the lake is already too high, maybe dump more than half the expected amount. Also, maybe the target "good" levels need to be reexamined; a slower drawdown at first, and then faster at the end.

You can still get burned by extremes, like the last two years, but maybe the impact could be reduced.

[Descant]

JeffK makes some good points. Somehow, DES seems afraid to let the lake go a little bit above full. Understood, as when we're way above full there can be shore damage, and everything downstream is likely high too. The difficulty in part of this is the saturation factor of the watershed. Half a dozen sensors located 0.5 -1.0 miles upgradient from the lake might give some indication. When the watershed is saturated; 0.5" of rain can translate to 2" increase in lake level, but it is some days later, not instant. We need high water right after ice out so debris can blow to shore and be stranded as the lake drops to full. To me, that is key: "Drops to full" not full and goes lower.
Some Forum members watrch the DES lake level apge and report it. Thank you. A weekly report from DES saying "The outflow for the coming week willl be "x" and here's the plan:...would help understand as opposed to just watching and wondering "Why did they do that?"

[jeffk]

One of the issues in determining what to do about the lake level is the general impact of rain/no rain and subsequent drought conditions.

Right now the US drought map shows the lakes region in Severe drought.
Historic impacts of this level of drought have been:
Fish kills occur; wildlife move to farms for food
Golf courses conserve water
Producers begin feeding cattle; hay prices are high
Specialty crops are impacted in both yield and fruit size
Trees are brittle and susceptible to insects
Warnings are issued on outdoor burns; air quality is poor
Water quality is poor; groundwater is declining; irrigation ponds are dry; outdoor water restrictions are implemented
This seems NOT to fit current conditions.

In fact, even the historic results of Moderate drought and even Abnormally Dry seem not to significantly apply, except perhaps that groundwater levels are on the low side in some areas.

If we can't accurately determine the conditions, our expectations and choices will not line up with reality.

As to adjusting the dam output, we are currently about 1 1/2" above Full. We are expecting about .6" in rain tomorrow. Just a rough estimate, but, with the ground still fairly damp from the spring melt, that will probably raise the lake another 1 1/2" to a total of 3" over Full. That is usually when people start mentioning problems. The dam is still running at minimum. Maybe it is past time to open it up a bit (700 cfs?) in anticipation of the rain coming tomorrow and drop it back in a few days to maintain the level at just slightly over full for the time being, maybe until the end of June.

I respect that dam management is not as straightforward as 1 + 1 = 2 but it seems we are too reactionary instead of anticipatory.

[kjbathe]

There are so many factors in play that it's actually pretty impressive that the level can be managed as effectively as it is.

One example is last Tuesday night's rain. I don't recall it being heavy or long and on Wednesday morning the docks at Goodhue were dry. Mid day, they had maybe a half inch over them. At end of day, maybe a half an inch more again.

My numbers are estimates. It was just neat to observe how a rain I didn't see the night before had the docks properly under water an afternoon later.

[jeffk]

So, here we go.

As of Wednesday afternoon, rain is starting and is forecast to continue for the next 10 days, dropping about 3" total by May 9. We are 2.5" over Full Pool. The dam, at it's current 250 cfs will dump about 1" by may 9. That gives us 2.5 +3 -1 = 4.5" over Full Pool by May 9th and that doesn't account for the fact that the runoff is likely to dump MORE than the measured rainfall. 4.5" over Full Pool WILL be a problem. And dumping water downstream at the end of the rain will be a problem because they will all be full by then as well.

NOW is the time to open the dam to 500 cfs (or a bit more) and leave it that way until the rain stops and reassess. That would drop an additional 2+" by May 9 and lessen the impact. Then leaving it open at that level to deal with runoff. The goal would be to maintain Full Pool and perhaps an inch or two more as reserve for possible summer dryness.

This is proactive planning. If the rain doesn't happen as forecast, once the level drops to Full Pool, back off the dam flow.

[Biggd]

A lot of rain fell yesterday, that should alleviate some of the drought situation!

[jeffk]

Yup.

And the lake is now about 6 1/2 inches over full pool and still rising.
The Lakeport dam is still at minimum, 250 CFS.

[John Mercier]

Is that because of downstream levels?

[jeffk]

Originally Posted by John Mercier

Is that because of downstream levels?

It may be NOW, but they could have proactively started dumping water a week ago when this big storm system became apparent. They could have gone into the storm down a couple of inches and then kept, slowly, dumping water to keep the levels a inch or two above full pool and less problematic.

Now, it will be harder to do that and I suspect the lake will continue to rise from the runoff of this 3+" rainstorm.

[NHskier]

Looks like the outflow was bumped up to 600cfs today.

[jeffk]

It's good that they are doing something. At that rate, it will take about 10 days to dump the 3" of water that just fell. Hopefully we won't get any more heavy rain during that time.

After Memorial Day, boat traffic will pick up and the consequences of having a significantly too full lake will rise.

[phoenix]

I was sent a couple pictures of a Meredith marina and their dock are underwater