Truesdale Lake  

South Salem, New York

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 â€“ 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!


Comments are closed.