Truesdale Lake  

South Salem, New York

March 1, 2020
by rob
Comments Off on Drawdown Report 13

Drawdown Report 13

All Posts tagged drawdownreport – see all blow-by-blow updates (inclucing this post) as they were posted and communicated in late 2019 through early 2020.

Summary: January 25, 2020 marked the last day of drawdown target depth – where the lake’s level, in its fifth cycle, was three feet below the spillway ramp. The water began to rise after both 12” siphons had shut themselves down. The west siphon shut down early due to an enormous mass of fishing line and a fishing rod around tree limbs wedged against and inside the intake. See photos at the end of this report. 

When both 12″ siphons shut themselves down at the fifth target depth, reached on JAN 22nd, the lake refilled quickly in the next two weeks with only two inches of rainfall plus frozen ground and snow melt which greatly increased inflow from our vast watershed area. 

Our ‘Galapagos’ (the northwest normally submerged boat-pranging archipelago) is once again underwater (aerial view).
Map showing actual Galapagos Islands for comparison.
Our ‘Galapagos’ (the northwest normally submerged boat-pranging archipelago) is once again underwater (terrestrial view).
Aerial view of Indian Lane dam, spillway, and siphon tubes with drawdown level around 3 feet below spillway height in October 2019.

February 8th, 2020 marked the day the lake reached winter level when the water rose three feet back to the spillway ramp with the 6″ siphon still flowing. This represents a ratio of 18 inches of lake level rise for each inch of rainfall.

DD Month       Rain and       30-year       3-foot below Spillway

2019-2020     SWE total      average       Target Depth achieved 

SEP (dry)           0.6”            4.5”           1st – SUN 09/22/19

OCT (wet)          7.4”            4.6”           2nd – MON 10/07/19

NOV (avg)          3.1”            4.4”           3rd – TUE 11/07/19

DEC (wet)          6.3”            4.1”           4th – SUN 12/01/19

JAN (dry)           2.3”             3.7”           5th – WED 01/22/20

FEB (dry)           3.1”             3.0”           Weir Boards – FRI 02/14/20 

Note that December 2019 was quite wet and matched last year’s December 2018 total of 6.3 inches of rain. This graph was prepared by Janet Andersen, who operates the sister-gauge (NY-WC-6) to our Truesdale Lake precipitation gauge (NY-WC-22).

2018-2019 precipitation comparison chart showing 30 year average overlaid.
Ice-Out (lake thaw after a solid lake freeze) this year occurred Saturday 2/8/2020, which is the earliest of the past recorded six years, so no further beneficial effect from extended freezing would be gained by continuing the drawdown. 

For comparison, the recorded final Ice-Out dates for Truesdale Lake are:

2014 ~ APR 04

2015 ~ MAR 10

2016 ~ FEB 26

2017 ~ MAR 27

2018 ~ FEB 22

2019 ~ MAR 20

2020 ~ FEB 08  

I dove down after both siphons had shut down and the surface iced had melted. I found an enormous mass of vegetation and tree limbs wrapped in tangled fishing line and an entire broken fishing rod and reel against and inside the intake of the west siphon. Remember please, that all fishing from the bridge and the entire dam, all boatyards and all beaches and the entire exposed lakebed during drawdowns is prohibited.   

No fishing from the dam!
Climate change factors into our little local action to affect weed growth in Truesdale Lake. 2020 marked the warmest January in 141 years of NOAA recorded temperatures.
February 14, 2020 marked the day the lake reached its normal summer level, since the weir boards remained in place as the foundation for the anchored siphons. Only the smaller, 6″ back-up siphon is still flowing, and even if it continues to do so all year, it will have little effect on the overall lake level.  

Daily Observations:

1/10 FRI  LG -2.2’       Outflow exceeds inflow. Dry hydrant intake head exposed.

1/12 SUN  LG -2.5’     West 12” siphon shuts down. The 6’’ & east 12” siphons continue flowing.

1/13 MON  LG -2.4’    Winter Storm ISAIAH brings 0.27” rain. 

1/18 SAT  LG -2.7’      Winter Storm JACOB brings 3.2” snow with 0.4” SWE.

                                    Fire Dept works to extend the #8 dry hydrant intake head.

1/22 WED  LG -3.0’     Target Depth reached for the fifth time during this drawdown.

                                    East 12″ siphon shuts down.

1/25 SAT  LG -3.0’      4th day at target depth #5. Exposed beaches are compacted and frozen.

1/26 SUN  LG -2.0’     Lake level rises 12” after 1.15” rainfall & 0.4” snow melt.

1/31 FRI  LG -1.0’       Lake level rises another 12” with only 6” siphon outflow.

2/2 WED  LG -0.8’       Dry day #7 with inflow exceeding outflow. Ice melting.

2/5 WED  LG -0.5’       Lake rising and approaching spillway winter level. 0.12” rain.

2/6 THU  LG -0.3’        Lara’s Galapagos re-submerge until next drawdown.

2/7 FRI  LG -0.0’          Winter Storm KADE with 0.7” rain & 6″ siphon flowing.

2/8 SAT  LG +0.1’         ICE-OUT occurs. The lake level rises to the spillway ramp (normal winter level). Tree limbs tangled in fishing line and a fishing rod were found inside and against the west siphon intake, which was pulled free. 

2/10 MON  LG +0.3’     Winter Storm LAMONT, light lake freezing and brief flurries under “Full Snow Moon.”

2/12 WED  LG +0.5’     Winter Storm MABEL approaches.

2/14 FRI  LG +1.0’        Lake at Summer level after additional 1.7″ rain. Members who are not in the Polar Bear Club may want to wait before swimming. Lake is again available for resident-only fishing and sailing in boats with blue Truesdale Lake registration stickers. Fishing from beaches, boat yards and the bridge is prohibited.

Janet Andersen is the President of the Three Lakes Council ( which was organized in 1970 to coordinate the environmental efforts for the Lake Waccabuc – Oscaleta – Rippowan watershed. Janet also operates the precipitation gauge in Twin Lakes Village and it is her data that I provided to Harold Ossher for 2018. (All the data for 2019 came from our Truesdale Lake precipitation gauge which began operation January 2019.) 

From: Janet Andersen

Date: Sat, Feb 29, 2020 at 4:31 PM
Subject: Re: Drawdown Report #13
To: Scot Evans

Scot – 

Thanks so much for continuing to keep me on copy and for the shout out on the precip graph.  

I’ve also been keeping daily lake levels (with an arbitrary zero) for a few years, but I haven’t been able to tie the lake level to the precip very accurately. Your number of 18″ for every inch of rain is amazing.   I’ve never been able to do this for our lakes with the snow / rain / evapotranspiration / dam leakage all involved.  Have you gotten an evapotranspirator gauge yet?  It’s only out during non-freezing weather.   And then we have beavers that sometimes dam up one, two, or three lakes – lots of factors make this too tough for me to feel confident about.   Do you have any idea of the acres of watershed : acres of lake ratio? I suspect the lake gain per inch of rain is seasonal, but it’s still a fascinating number.  

I’ve pasted a chart for this year’s precip. I’ll add the one for last winter, which was also benign. 

With great appreciation for the info you’re providing! 


Jan – Thanks for your note and your data!

Our watershed : lake ratio is 2380 acres watershed : 83 acre lake surface — or 28.7 : 1.  Here’s the relevant paragraph from our 2001 lake study:

“The portion of this watershed contributing surface runoff to the lake is large (2,380± acres, 963 ha), relative to the size of the lake (83 acres, 33.6 ha) (Figure 1). The majority of this watershed is located to the east of the lake and contains the Pumping Station Swamp. The size of the watershed creates a watershed to lake ratio of 28.7:1. The amount of rainfall draining to the lake was calculated using a runoff value of approximately 55 percent of precipitation (CT DEP 1982), an annual precipitation value of 47.5 inches per year (Soil Survey of Putnam and Westchester Counties, New York, 1994), and 68.6 cm (27 inches) per year of surface lake evaporation. Therefore, the net amount of rainfall that drains to the lake is large, (1.6 billion gallons) annually or an average daily flow of 4 million gallons per day. Thus, on an annual basis, the lake, with a volume of approximately 99,150,000 gallons, shows a moderate turnover rate (hydraulic residence time) of 16.2 times per year or every 22 days.”

Source: (8th paragraph of report)

The flow rates are average over the year. For example at the end of our summer 2019 drought with our October rains, I suspect we had more absorption into our parched watershed soils for a few weeks until they became saturated again. Then when the additional rains came after then in Nov and Dec we likely got a higher % run off and a lower percent absorption. I am sure Harold and Scot will have the data to either confirm or dispute my suspicion. 

Take care, Rob

January 30, 2020
by rob
Comments Off on Notice of Consent – Annual Mailing Sent to Riparian Homeowners

Notice of Consent – Annual Mailing Sent to Riparian Homeowners

These annual notices were sent via US Mail to all riparian (lake-side) homeowners as required by New York State law. They are a continuation of our annual lake management program, including treatment, dating back over 50 years undertaken when we engaged Pond & Lake Connection as our new lake manager.

Date of Notice: 1/22/2020

Dear Riparian Property Owner:

To control the excessive growth of various aquatic weeds, at Truesdale Lake, The Pond Connection proposes to conduct an application of the aquatic herbicide/algaecide Cutrine Ultra, Green Clean Pro and Clipper.  A copy of these labels can be found at  We anticipate the treatment to occur throughout the summer, only when necessary and will proceed only after the riparian owners obtains a permit for the treatment from the NYSDEC. 

This pesticide application will only occur if sufficient aquatic vegetation is present to warrant treatment and under favorable weather conditions. Prior notification of the exact dates of treatment can be provided by contacting The Pond Connection as listed below.  The pond/lake shoreline will be posted with signs the day of treatment. 

As an affected riparian owner/user, you have the right to consent or object to the restrictions of water use resulting from the proposed treatment. The water use restrictions associated with use of the above pesticides are below:

  • Swimming and bathing are prohibited for: No Restrictions
  • Fishing and/or fish consumption is prohibited for: No Restrictions
  • Livestock watering is prohibited for: No Restrictions
  • Irrigation or spraying of agricultural crops is prohibited for: Cutrine Ultra:N/A, Green Clean Pro: N/A Clipper: 5 Days.
  • Use of water for human consumption is prohibited till: Cutrine Ultra: 200ppb, Green Clean: 50ppb, Clipper: 50ppb.
  • Use of water for domestic purposes is prohibited till: Cutrine Ultra: 200ppb, Green Clean: 50ppb, Clipper: 50ppb.

Human consumption and domestic purposes restriction refers to the water body being used as your primary and sole use of water for drinking and culinary purpose.  Potable water use is not incidental contact with the water such as swallowing a mouthful of water while swimming.

You have twenty-one (21) days to respond to this notice. If you wish to object to the proposed treatment(s), please file a written document stating your objection to the proposed treatment and the water use restrictions resulting from the treatment.

Send your comments to the Bureau of Pesticide Management listed below:

NYS Department of Environmental Conservation, Region 3
Bureau of Pesticide Management
21 South Putt Corners Rd, New Paltz, NY 12561

If you wish further information about the treatment, or wish information on the exact dates of the pesticide application, please contact the following person:

  • The Pond and Lake Connection, 1112 Federal Road, Brookfield, CT 
  • Name of Contact Person: James Gorman
  • Telephone Number: 845-798-9383  Email:

If you do not respond to this notice, your lack of response will be considered consent to the proposed treatment. If you have any questions on the permitting process, please contact the Department representative listed above.

January 14, 2020
by rob
Comments Off on Drawdown Report 12

Drawdown Report 12

These are some of the email reports and communications from Scot Evans from Truesdale Lake, James Gorman from Pond & Lake Connection, and others involved with the project. Putting selected parts up here for all to see what some of the discussion and learning is looking like.

Today, with all siphons flowing, the lake level is 2.3 feet below the spillway ramp and descending. The lake froze completely on December 20th with ice up to three inches thick and 80% of the lake was melted by January 7th, allowing for a much cleaner fifth and final descent to target depth. If we are lucky, the lake will again freeze in January when the siphons shut down with lake level at three feet below the spillway. 

Also today, the dry hydrant intake head became exposed for the fifth time during this season’s drawdown. The Fire Commissioner’s contractor may agree that this Monday through Thursday, 1/13 – 1/16, with above freezing temperatures, would present an ideal opportunity to install an extension in order to lower it vertically at least two feet more.

dry hydrant intake head

And finally, today marks a milestone confirmation of the calculations from our resident mathematician, Harold Ossher, in that the two 12” siphons and one 6” siphon, installed and maintained by James Gorman of P&LC, have demonstrated that they are ideal in size and number for reducing the lake’s level during the 30-year average rainfall of 4.4 inches per month within the three-month drawdown period – October, November and December.

This conclusion is reached from observations in these last two reporting periods, in that all three siphons have been flowing consistently for the past 30 days – WED 12/11 to FRI 1/10 – with inflow from 4.38 inches of rain, which represents one drawdown month.

With all three siphons flowing uninterrupted, the lake’s level increased after each rainfall from 1.3 feet below the spillway up to two and a half inches above the spillway, and it descended during the dry days with a net decrease of 12 inches to 2.2 feet below the spillway. 

DD Month       Rain/SWE    30-year      3-foot below Spillway

2019-2020      inch total    inch AVG    Target Depth achieved

SEP   (dry)         0.6           4.5            1st – Sunday 9/22

OCT  (wet)         7.4           4.6            2nd – Monday 10/7

NOV  (avg)         3.1           4.4            3rd – Tuesday 11/7

DEC  (wet)         6.3            4.1            4th – Friday 11/29

JAN   (dry)    (0.4 to date)    3.7           5th – Friday 1/17

December 2019 was quite wet and matched last year’s December 2018 total of 6.3 inches of rain.

Some of the desired results from the drawdown, like weed tuber destruction and soil desiccation, may be evident as early as the end of next summer. Other long-term benefits, such as silt compaction, will take more time and can be assessed later on. 

In the meantime, lakeside residents have made excellent progress in cleaning up their newly exposed beaches, removing broken glass and other hazardous objects, and disposing of trash, including discarded equipment, at their own expense. 

Many neighbors have sent photos of their newly cleared lakefronts to be included in the Truesdale Lake archives.

This is my final report for the 2019/2020 winter season drawdown. Rob Cummings has compiled all of the drawdown reports and replies in one link on the Truesdale Lake website > 


Daily Observations during this reporting period:

12/23  MON   LG -0.5’          Outflow exceeds inflow. Lake 100% frozen with 3″ ice.

12/24  TUE    LG -0.7’          Outflow exceeds inflow.

12/25  WED   LG -0.9’          Outflow exceeds inflow.

12/26  THU    LG -1.1’          Outflow exceeds inflow.

12/27   FRI     LG -1.3’          Outflow exceeds inflow.

12/28  SAT     LG -1.5’          Outflow exceeds inflow. 0.01” rain

12/29  SUN    LG -1.7’          Outflow exceeds inflow. 

12/30  MON   LG -1.7’           Inflow matches outflow. 0.63” rain

12/31  TUE    LG -1.5’           Inflow exceeds outflow. 0.44” rain

1/1      WED   LG -1.3’           Inflow exceeds outflow. 0.02” SWE

1/2      THU    LG -1.3’           Inflow matches outflow. Lake ice continues to melt.

1/3       FRI     LG -1.5’          Outflow exceeds inflow. 0.07” rain

1/4      SAT     LG -1.7’          Outflow exceeds inflow. 0.11” rain

1/5      SUN    LG -1.7’           Inflow matches outflow. 0.05” rain

1/6      MON    LG -1.8’          Outflow exceeds inflow. 0.01” SWE

1/7      TUE     LG -1.9’          Outflow exceeds inflow. Lake ice 80% melted.

1/8      WED    LG -2.0’          Outflow exceeds inflow. 0.03” SWE. Lake nears target depth.

1/9      THU     LG -2.2’          Outflow exceeds inflow. Siphons perform as calculated.

1/10     FRI      LG -2.3’          Outflow exceeds inflow. Dry hydrant intake head exposed.

Scott, many many thanks for this and all previous reports, and Rob for collecting and publishing them on the website. It’s been great to have such detailed, ongoing information about how the drawdown has proceeded. I also really appreciate your having a found a 30-day period that helped to verify that the calculations were close to matching reality.

Based on our experience this year, so well recorded, I have some thoughts for next year about preventing the lake from rising so much above the 3′ drawdown level so frequently. I look forward to discussing them in due course.

Thanks, Harold

Thank you for sharing this information with me I will pass it along to our contractor and my collogues. The board of fire commissioners has chosen a contractor to do the repairs on the dry hydrant. When the contractor notifies me of a start date I will share that with you. 

Best Regards, Mike Lombardi Fire Commissioner

Scot & Skip, 

The contractor for the Fire District plans to start the repair and extension project for the Truesdale lake dry hydrant tomorrow. If anyone has any questions feel free to contact me. (914) 588-8270.

Best Regards, Mike Lombardi Fire Commissioner

(after extension of dry hydrant)

Hi Mike,

I enjoyed meeting you at the boatyard and observing the final flow test. 
Many thanks to you from all of us for the completed extension and nicely buried and deepened intake section. 
And congratulations on your successful flow test today!


December 28, 2019
by rob
Comments Off on Drawdown: Report 11A

Drawdown: Report 11A

Greetings James,

This is ninth dry day of our break following all that pesky rain.

All your siphons are churning away nicely.

The lake ice continues to melt with rain arriving Sunday night, through Monday. 

The lake level lowered at a rate of two inches per day during this dry spell (18” in nine days).

The 3” ice cap messed up the top of my tenths-graduated gauge, but today, the lake is 1.3 feet below the spillway and descending. 

Enjoy your weekend!


Good news!

December 23, 2019
by rob
Comments Off on Drawdown: Report 11

Drawdown: Report 11

These are some of the email reports and communications from Scot Evans from Truesdale Lake, James Gorman from Pond & Lake Connection, and others involved with the project. Putting selected parts up here for all to see what some of the discussion and learning is looking like.

Summary: This four-week report involved so many environmental changes that I had to wait to complete it until a break in the weather – the dry spell we’re experiencing – now in its third day. We received so much rain this month that the lake level rose 38 inches after receiving five inches of rain and Snow/Ice Water Equivalent (SWE), even with all siphons flowing much of that time.

When flowing, all three siphons draw nearly 12 million gallons of water out of the lake each day, so you can imagine how much water must flow in to continue increasing the lake level even while they are working.
The lake is now frozen, so we can observe what happens next when the water is pulled out from below the ice. If the ice doesn’t melt during the upcoming 40-degree days, it may start to cave in under its own weight through the air spaces up to the three-foot target depth. This may make access to the middle of the lake for ice skating and ice fishing rather challenging. 

On the up side, if the ice cap over the siphons descends with the lake, it may help to prevent the whirlpools above the siphon intakes that form when target depth is near (see photo). 

Siphon Whirlpool beginning to expand

You have probably noticed that the lake rose to its maximum level of three inches above the spillway ramp elevation a few days ago, even with all the siphons flowing. Once again, this demonstrates that we’ll have no difficulty filling the lake back up in the spring as water flows from West Mountain heights down to our oasis.

LG +0.3

The small 6” siphon continued flowing all by itself during the first two weeks of this reporting period. When the lake level rose from target depth to 2.8 feet below the spillway on December 1st (photo below), we requested that P&LC return to restart both 12″ siphons when the lake rose one more foot, which occurred ten days ago. P&LC restarted both 12″ siphons right on schedule – on the 10th & 11th of December – to keep up with the inflow. They will continue working until the 3-foot target depth can be reached for the fifth time.

LG -2.8 on 12-1-2019

While trees are without leaves, I’ll arrange a visit to Ridgefield Academy to take a photo of the lake from West Mountain and post it on NextDoor and in the next report so all can see that we live in a watershed valley.  

Rain Total30 YR AVG3 ft target depth achievedLake freezes completely
SEP 0.6″ 4.5″1st – Sunday 9/22
OCT7.4″4.6″2nd – Monday 10/7
NOV3.1″4.4″3rd – Tuesday 11/71st – Sunday 12/8, then melts
DEC5.3″ (to date)4.1″4th – Friday 11/292nd – Friday 12/20 solid

When December ends in ten days, rain and SWE may match last year’s wet December that totaled 6.33 inches. Today, with all siphons flowing, the lake level is two inches below the spillway ramp and descending.

Daily Observations:

Precip as of Winter Solstice in 2019

TUE     11/26        LG -2.5        Outflow exceeds inflow with all siphons flowing.
 WED    11/27        LG -2.7′       Outflow exceeds inflow with all siphons flowing. 
THU     11/28        LG -2.9’       Outflow exceeds inflow where the west 12″ siphon shuts down naturally.
FRI       11/29        LG -3.0’      Target Depth is achieved where the east 12″ siphon shuts down naturally.
SAT      11/30        LG -2.9’       Inflow exceeds outflow with only the 6″ siphon flowing.
SUN     12/1          LG -2.8’       Inflow matches outflow as Winter Storm Ezekiel approaches.
MON    12/2          LG -2.7’       0.77″ rain where Inflow matches outflow.
TUE      12/3         LG -2.5’       0.20″ rain where Inflow exceeds outflow as coastal low pressure cell 
                                                 moves in with steady light rain.
WED     12/4         LG -2.4’       Inflow exceeds outflow.
THU      12/5         LG -2.3’       Inflow exceeds outflow with salt added to each siphon frozen discharge.
FRI       12/6          LG -2.2’       Inflow exceeds outflow.
SAT      12/7          LG -2.2’       Outflow matches inflow.
SUN     12/8          LG -2.2’       Outflow matches inflow where 100% lake is frozen.
MON    12/9          LG -2.1’        0.37″ rain where inflow exceeds outflow where lake ice completely melts.
TUE      12/10       LG -1.3’        0.88″ rain where inflow greatly exceeds outflow with heavy rain. 
                                                  P&LC restarts both 12″ siphons. (east shuts down)
WED     12/11       LG -1.3’        0.58″ rain where Inflow exceeds outflow after receiving 0.87” rain.
                                                  P&LC restarts east 12″ siphon.
THU      12/12       LG -1.3’        Outflow matches inflow with all siphons flowing well.
FRI       12/13       LG -1.3’        Outflow matches inflow with all siphons flowing.
SAT      12/14       LG -0.5’        1.47″ heavy rain where inflow greatly exceeds outflow and all siphons flowing.
SUN     12/15       LG -0.2’        0.7″ light rain where inflow exceeds outflow with all siphons flowing.  
MON    12/16       LG 0.1’       Level rises over spillway ramp for the first time this drawdown.
TUE     12/17       LG 0.2’’       Inflow exceeds outflow with all siphons flowing.             WED    12/18       LG 0.2’’       Inflow matches outflow with all siphons flowing.
           THU     12/19       LG 0.1’’       Outflow exceeds inflow with all siphons flowing.
           FRI      12/20       LG 0.0’’           Lake level descends to spillway ramp height. 
           SAT     12/21        LG -0.1’’        Outflow exceeds inflow with all siphons flowing.

           SUN     12/22       LG -0.2’’        Outflow exceeds inflow with all siphons flowing.  

This report is set to launch upon the occurrence of Winter Solstice – at 2319 EST.

Happy Holidays to all,

Should we issue a warning to stay off the ice due to the risk of it collapsing as the drawdown continues?


Hi Lara,

Good question and there are two aspects to consider here. 

The first aspect is considering the effect of the drawdown with regard to the ice. The ice cannot support it’s own weight since it is flat and not shaped like an arch. The ice sheet will descend with the lake from the center out toward the perimeter. The air pockets and stress relieving ice breakage will occur in the perimeter areas where the exposed lakebed is already documented. The only risk to the resident is in navigating the broken ice and craters in order to get beyond the exposed lakebed perimeter on the way toward the center for good skating and ice fishing. So the risk for 90% of the lake will be the same as it has always been. Passing along this information may be better than issuing a warning to stay off the ice altogether, unless the board is concerned with potential liability. 

The second aspect is the classic monitoring and reporting of ice conditions so residents can make their own decisions as well as assume the risk for skating or ice fishing. 

Meghan Crystal has posted a question about ice conditions on NextDoor. So regarding your question above, I’ll answer with a post about today’s conditions only. Please let me know if you want to post a caution regarding the future or if you want me to.


November 26, 2019
by rob
Comments Off on Drawdown: Report 10

Drawdown: Report 10

These are some of the email reports and communications from Scot Evans from Truesdale Lake, James Gorman from Pond & Lake Connection, and others involved with the project. Putting selected parts up here for all to see what some of the discussion and learning is looking like.

Summary: The 6” siphon continued flowing during this last two week period and we requested that P&LC restart both 12″ siphons.
On Wednesday 11/20, a Lake Planning Group Meeting was held with John Bergstrom, Robert & Susan Brown, Rob Cummings, Sue Enos, Scot Evans, Lara Gorton, Stephen Macaluso, and Harold Ossher attending.     

James Gorman and crew of P&LC restarted both 12” siphons Friday 11/22 at 10:30 am following the one inch of rain we received two days earlier, where the Lake Gauge started at -2.8 feet and steadily rose 8 inches to -2.1 feet.

With another inch of rain received yesterday, all siphons are flowing and we are currently -2.5 feet below the spillway.

Daily Observations:

TUE     11/12        LG -2.8’       Winter Storm Caleb arrives bringing rain and snow mix totaling only 0.05” liquid precipitation. Lake level rises 0.7”
WED    11/13        LG -2.7′       Inflow exceeds outflow with 6” siphon continuing to flow at 125 CFM. 
THU     11/14        LG -2.7’       Inflow matches outflow
FRI       11/15        LG -2.7’       Inflow matches outflow
SAT      11/16        LG -2.7’       Inflow matches outflow
SUN     11/17        LG -2.7’       Inflow matches outflow
MON    11/18        LG -2.7’       Inflow matches outflow
TUE      11/19       LG -2.5’       Inflow exceeds outflow as coastal low pressure cell moves in with steady light rain.
WED     11/20       LG -2.3’       Inflow exceeds outflow after receiving 0.87” rain. Lake Planning Group Meeting held.
THU      11/21       LG -2.2’       Inflow exceeds outflow.
FRI       11/22        LG -2.1’       Lake is a foot higher above target depth as P&LC arrives to restart both 12” siphons. All flowing at 1,100 CFM.
SAT      11/23       LG -2.4’       Outflow exceeds inflow. Winter storm is approaching from the southwest.
SUN     11/24       LG -2.5’       Storm brings another inch of rainfall today and all siphons are flowing.
MON    11/25       LG -2.4’       Inflow exceeds outflow.

Thanks, Scot, and thanks to James for the timely restart of the large siphons.
Happy Thanksgiving, everyone!
– Harold

November 18, 2019
by rob
Comments Off on Drawdown: Aerial Survey Lake Perimeter

Drawdown: Aerial Survey Lake Perimeter

A friend lent me his drone for an aerial survey of the lake as it is now during the drawdown. I have posted below some of the photos from November 15 when the lake was half frozen on the surface.

The rest (many more than shown below) are in this album online:

November 13, 2019
by rob
Comments Off on Drawdown: Report 9

Drawdown: Report 9

These are some of the email reports and communications from Scot Evans from Truesdale Lake, James Gorman from Pond & Lake Connection, and others involved with the project. Putting selected parts up here for all to see what some of the discussion and learning is looking like.

Summary: Both 12″ siphons shut down: the west 12” on Tuesday night 11/5/19 and the east 12” on Wednesday night 11/6/19. The 6” siphon was the only one flowing most of this week and it was able maintain the lake level following 0.3″ rainfall with a 2 ½” lake level rise. Lake Gauge started at -3.0′ target depth and ended the week rising to -2.8′. 

Two 12″ siphon pipes dry (right) and 6″ siphon pipe energized and flowing (left).
Hoyt Street lake gauge showing around 2’10” below spillway height.

The intake head of the west siphon is 9” below target depth and the east siphon intake head is 17” below target depth. Both developed widening whirlpools above the intakes and this is likely what shut them down. We need to figure out something that eliminates the whirlpools over the intakes. Internal baffles and external fins are two ideas to reduce or eliminate the whirlpools above the intake heads. External fins in second diagram would be easier to construct and less restrictive to the flow. Experiment with this design first.

External fins with the fin “trailing edges” leading out from the siphon intake head.Experimentation will determine minimum number of fins necessary to eliminate a whirlpool – i.e. eight or fewer fins.
Daily Observations:

TUE     11/05        LG -2.9’        All siphons operating with west whirlpool widening. West siphon shuts down that night.
WED    11/06        LG -3.0′        Target depth achieved once again after the October 10th departure from our last target depth achieved.
THU     11/07        LG -3.0’        Both 12″ siphons have shut down. Scot took measurements of these siphons to provide to Cliff Munz, who is working on a large construction project and cannot convert the siphon design to CAD at this time.

FRI       11/08        LG -2.9’        LLR begins with 0.3″ rainfall. 6″ siphon operating at 125 CFM. 
SAT      11/09        LG -2.8’        Inflow continues to exceed outflow 
SUN     11/10        LG -2.8’        Outflow matches inflow with 6″ siphon flowing

MON    11/11        LG -2.8’         As above. Sue Enos schedules Lake Planning Group Meeting for 11/20/19.

Email from Michael Lombardi, South Salem Fire District Commissioner, regarding the dry well on the north end of Lake Truesdale near Indian Lane and the Dam.

Dear Skip, 

The board of fire commissioners is weighing options to repair and extend the dry hydrant pipe in Lake Truesdale. We have the following questions.1. Will the lake draining program be an annual process or is this the only year it will be done. 2. Is the lake going to be drawn down further. 3. When will the lake be refilled. 

Thank you in advance for your assistance feel free to contact me. 

Michael J Lombardi                                                                                                       Fire Commissioner (914) 588-8270

Thank you for contacting us Michael. We will be planning to do the lake drawdown annually as a way to better control weed growth and overall health of the lake. 

The drawdown is at the expected level at this time with only one smaller siphon running to maintain the target depth with expected normal rainfall. 
The drawdown will last until February 1, 2020 – that’s when we will turn off the maintenance pipe. This is the smaller 6″ pipe which we will use to try to keep the lake level 2.5 – 3 feet below the spillway level. 

After then the lake will fill up with winter snowmelt and spring rain. We anticipate it will be back to regular height by May 1, 2020 and likely well before then.

More information on the drawdown is published on the Truesdale Lake web site –

Thanks for your support,
Skip Jahn

November 6, 2019
by rob
Comments Off on Drawdown: Report 8

Drawdown: Report 8

These are some of the email reports and communications from Scot Evans from Truesdale Lake, James Gorman from Pond & Lake Connection, and others involved with the project. Putting selected parts up here for all to see what some of the discussion and learning is looking like.

Summary: Harold Ossher’s conclusion, following his evaluation of watershed research and flow data collected, was to use two 12” siphons plus the one prototype 6” siphon. This proved sufficient to stay ahead of this year’s wet October 8.2” rainfall total. (Average rainfall for October over the last three years is 7.7″ where OCT 2018 was 4.6” and OCT 2017 was 10.3″.)

When drawdown depth is achieved once again, I will gather the measurements of the siphons constructed on scene so that Cliff Munz can revise and convert my design drawing to CAD. 

Thursday 10/31/19 brought us a wicked double cold front for Halloween, delivering 1.01” of rain over 28 hours with strong wind gusts. In advance of the storm, James Gorman of P&LC restarted the west 12” siphon at 0930 EDT ~ providing a well timed response before the rain accumulated, before inflow exceeded outflow and before the two cold fronts passed with freezing temps. All three are flowing again at 1,100 CFM and the cause of the 12” shutdown was not identified. The lake gauge reading at restart was 2.2 feet below the spillway. 

Following the last report, the lake gauge was -2.0’ and ended the week nearly one foot lower at -2.9’ with siphon flow exceeding inflow after the 1.15“ of rainfall we received for the week.

Lake gauge at -2.0′
Last week’s rainfall
Oct 2019 rainfall

Daily observations
TUE   10/29      LG -2.0’     Rob Cummings consolidates all reports, photos & responses to the lake’s website: in order to keep everything out in front of the inevitable questions.

WED  10/30      LG -2.1’     A steep pressure, temperature, & humidity gradient cold front approaches from the west.  THU   10/31      LG -2.2’     James Gorman restarts the west 12″ siphon ahead of the storm.. All siphons flowing.

FRI      11/1       LG -2.1’     LLR from 1.01” rain received. Inflow exceeds outflow. 

SAT     11/2.      LG -2.2’    30° F with first frost of the season. Outflow exceeds inflow for remainder of the week. 

SUN    11/3.      LG -2.4’     A long stick is caught in the east 12″ siphon intake, but it is still drawing water.

MON   11/4.      LG -2.7’     Whirlpool increases in diameter over west 12″ siphon intake which is shallower than the east siphon. This is still flowing but will shut down first.

Good morning Harold,

Here is my precip report for this year which includes JAN through SEP for a total of 37” (plus the 8” we received in OCT).

The report also shows the 30-year average for each month. (The thirty year average for OCT is 4.6” and we received 8.2” this past OCT, making your siphon determination of two 12” + one 6” right on target!)

I listed the links in preference order with your favorite format first.


Many thanks, Scot, great to have this data.
BTW, I was wondering whether fins at and extending a bit beyond siphon intakes, like the bottoms of rockets, would help with the whirlpools? On the other hand, I think we reached target depth with the large siphons still running, so we might not want to keep them going longer.
– Harold

Hi Harold, 
This would very likely work to prevent whirlpools from forming above the perfect circle at the intake heads. I wonder if there exists such an attachment for PVC pipes. Maybe James will fabricate and patent his invention! Here are the baffle diagrams for rocket engine nozzles:

[. images did not download for me 🙁 .]

And you’re right, this would be a future consideration for James to consider for siphon improvements to our next drawdown attempt. 

He luckily installed the 12” intakes deeply enough so that the whirlpools shut them down right at target depth. The deep 6” siphon is still running and will help to keep up with the winter inflow and possibly enough to maintain the lake level close to target depth. 

If we get a lot of NOV rain and if inflow exceeds the effectiveness of the 6” siphon, I’ll ask James to restart the two 12 inchers. 

October 29, 2019
by rob
Comments Off on Drawdown: Report 7

Drawdown: Report 7

These are some of the email reports and communications from Scot Evans from Truesdale Lake, James Gorman from Pond & Lake Connection, and others involved with the project. Putting selected parts up here for all to see what some of the discussion and learning is looking like.

October 29, 2019

Summary: Sunday 10/27/19 brought us the remnants of Tropical Storm OLGA, where we received 1.34 inches of rain in the twelve hours between 4 am and 4 pm.

During the 24 hours after the storm ended, the lake level rose 5″ even with all three siphons discharging a total of 1,100 CFM. Monday 10/28/19, the west 12″ siphon was observed to have stopped flowing; James Gorman was notified.

Mark Vibert of Main St recommended on the NextDoor site that we try to obtain aerial photos of the exposed lakebed during the drawdown target depth of three feet below the spillway deck. Rob Cummings responded and on Tuesday 10/15/19, he brought a borrowed drone over to my place, where we got some impressive aerial shots and video from several altitudes over the lake.

Ideal weather was enjoyed by the drone on this day before the bomb cyclone nor’easter dumped 3.34″ of rain and the lake level rose 17 inches over the next 3 days. Rob remarked that this demonstrates we’ll have no problem quickly refilling the lake this spring.

Today (Oct 29, 2019), the lake gauge is 2.0 feet below the spillway deck.
Rainfall late Oct 2019

Daily Observations
TUE 10/22/19   LG -2.0 feet     Harold Ossher observes 6″ siphon not flowing (cause unknown) and one 12″ siphon still flowing at 500 CFM
WED 10/23/19   LG -2.0 feet    0.45″ rainfall received from weak coastal low
THU 10/24/19    LG -2.0 feet    one 12″ siphon matching the inflow rate
FRI 10/25/19     LG -2.1 feet     James restarts two more siphons and all three are flowing by 0845 EDT at 1,100 CFM
SAT 10/26/19    LG -2.3 feet     Siphon discharge exceeds inflow    
SUN 10/27/19   LG -2.4 feet     TS OLGA delivers 1.34″ rain and inflow exceeds siphon discharge
MON 10/28/19   LG -2.0 feet    LLR 4.8 inches as inflow continued to exceed siphon discharge. Equilibrium achieved about 1700 EDT. West 12″ siphon stopped flowing (cause unknown).

Aerial shots of exposed lakebed:
The three islands named on the interactive map are WAXWING (north), ANT (center) and PIRATE (south).

A new set of islands became visible during the drawdown. I propose that this set be named BOAT PRANG ARCHIPELAGO or LARA’S GALAPAGOS.

Here are a few aerial photos of the lake from the many taken. I’ll post more this week on a NextDoor thread.

Newly exposed islands off of Gilbert Street houses north of the beach property.
Pirate Island (southernmost island) is shown here as Pirate Peninsula with stone wall connecting the island to the mainland.
Dormant Siphons during the September Drought.
North Cove hotspot.
South cove exposed lake bottom.
Dam, north cove, Waxwing Island.
Indian/Gilbert boatyard with dry hydrant that Skip Jahn identified and notified the fire department. They have not yet responded to lengthen the uptake head.
East side of South area and Pirate Island.
Pirate Island showing exposed lake bed.

Thanks Scot for this update

Really interesting to watch how this all unfolds

Thanks again


Yes, thank you, and to you and Rob for the really interesting photos.
I’m not surprised the lake level rose after significant rain despite the siphons. The watershed is so big that there’s no way they can keep pace during periods of peak inflow. But once all of them are running again, the level should go down fairly quickly again.

– Harold

Love the photos! The “Galapagos” is an inspiring bird sanctuary attracting all manner of feathered friends – picture attached. 


View of wildlife exploring and hunting on the newly exposed “Galapagos Islands” off of Gilbert Street.