ASDSO Dam Safety Toolbox

Siphons: Difference between revisions

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Many older dams were not constructed with a means of draining the reservoir. Lowering the reservoir may be needed for temporary construction, for emergency response, or when regular releases aren't needed. Siphons can be a low-cost means of providing a reservoir outlet if one does not exist. The key operational parameters are: (1) the required hydraulic lift cannot exceed the effective local atmospheric pressure adjusted for vapor pressure and frictional losses; (2) the discharge point of the siphon must be lower in elevation than the body of water to be siphoned; (3) the pipe or hose used for the siphon must be designed to operate at less than atmospheric pressures; (4) siphon outlets should only be used when there are no other feasible options; and (5) siphon outlets are difficult to prime.
Many older dams were not constructed with a means of draining the reservoir. Lowering the reservoir may be needed for temporary construction, for emergency response, or when regular releases aren't needed. Siphons can be a low-cost means of providing a reservoir outlet if one does not exist. The key operational parameters are: (1) the required hydraulic lift cannot exceed the effective local atmospheric pressure adjusted for vapor pressure and frictional losses; (2) the discharge point of the siphon must be lower in elevation than the body of water to be siphoned; (3) the pipe or hose used for the siphon must be designed to operate at less than atmospheric pressures; (4) siphon outlets should only be used when there are no other feasible options; and (5) siphon outlets are difficult to prime.


==Siphon Stories==
==Examples==
*[[Siphons when regular releases aren't needed]]
{{Website Icon}} Get answers to some of the [[Common Questions about Siphons]]
*[[Siphoning May Not Always Be Possible]]
*[[Low Pressure During Siphoning Can Collapse Pipe]]
*[[Pump... or Siphon?]]
*[[Siphons can pose Reservoir Level Control Challenges.]]


==Siphon as an Outlet Replacement==
==Trainings==
4 Key Questions that must have a Yes answer:
{{Video Icon}} [[On-Demand Webinar: Design of Siphon Systems]]


#Is the dam small enough and at a low enough elevation so that the use of a siphon is physically possible?
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#Will abandonment of the original outlet works not impact the reservoir's ability to pass the required inflow design storm (dictated by regulatory agencies)?
{{Citations}}
#Is there an alternate means to passively control reservoir level to prevent overfilling?
 
#Can the siphon reasonably be used for emergency drawdown if needed (in combination with pumps in some cases)?
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References
*[https://3.238.206.13/images/f/f2/Simple_Steps_to_Siphoning.pdf Simple Steps to Siphoning]
*[https://3.238.206.13/images/d/d9/Guidelines_for_Use_of_Pumps_and_Siphons_for_Emergency_Reservoir_Drawdown.pdf Guidelines for Use of Pumps and Siphons for Emergency Reservoir Drawdown]
*[https://3.238.206.13/images/9/9c/Drawdown_System_Selection_Flow_Chart.pdf Drawdown System Selection Flow Chart]

Revision as of 05:46, 16 September 2022



Many older dams were not constructed with a means of draining the reservoir. Lowering the reservoir may be needed for temporary construction, for emergency response, or when regular releases aren't needed. Siphons can be a low-cost means of providing a reservoir outlet if one does not exist. The key operational parameters are: (1) the required hydraulic lift cannot exceed the effective local atmospheric pressure adjusted for vapor pressure and frictional losses; (2) the discharge point of the siphon must be lower in elevation than the body of water to be siphoned; (3) the pipe or hose used for the siphon must be designed to operate at less than atmospheric pressures; (4) siphon outlets should only be used when there are no other feasible options; and (5) siphon outlets are difficult to prime.

Examples

Get answers to some of the Common Questions about Siphons

Trainings

On-Demand Webinar: Design of Siphon Systems


Citations:



Revision ID: 3387
Revision Date: 09/16/2022