Modeling a Groundwater Well
Modeling a Groundwater Well
(OP)
How do you model a pump in a groundwater well?
I'm thinking you set a resevoir elevation at the normal water drawdown level and you set the pump elevation at it's actual elevation (ground elevation - pump setting depth).
Our consultant is setting the resevoir below the pump and that creates a negative intake pressure for the pump. That just doesn't seem right even for a model.
Any ideas? Thanks for the help!
I'm thinking you set a resevoir elevation at the normal water drawdown level and you set the pump elevation at it's actual elevation (ground elevation - pump setting depth).
Our consultant is setting the resevoir below the pump and that creates a negative intake pressure for the pump. That just doesn't seem right even for a model.
Any ideas? Thanks for the help!





RE: Modeling a Groundwater Well
RE: Modeling a Groundwater Well
There is the static level, the non-pumping water level.
The pumping level, the level that the well drops to when pump is running.
There are three types of pumps that are used in wells
1)Jet pumps, motor above ground with a suction pipe.
2)Submersibles, pump and motor underwater.
3)Line shaft turbines, motor above pump below.
All pumps have to have the intake below the pumping level.
RE: Modeling a Groundwater Well
It sounds like both you and your consultant are thinking correctly. There would be a negative beginning pressure (NPSH available) and the pumps will have to overcome that, for the reasons you've stated. That value is the amount, as you've stated, "...the normal water drawdown level and...the pump elevation at it's actual elevation...". This sounds like what the consultant's model has done.
The intake has to be below the water, but the pump does not.
For hydraulic analysis, the elevation at which the energy is added to the water is the pump elevation. The elevation at which the potential energy exists is reservoir elevation is the drawn-down water surface. That is the beginning head.
Engineering is the practice of the art of science - Steve
RE: Modeling a Groundwater Well
RE: Modeling a Groundwater Well
ground elevation = 500'
actual pump elevation = 300' (200' deep in well)
actual water pumping level elev. = 350'
This is a submersible pump/motor situation
I would think in the WaterCAD model you set the pump elev. at 300' and the resevoir elev. at 350'.
My consultant is setting the pump at 300' and the resevoir at some lower elev. like 240'
This is just an example, not actual numbers.
thanks for the help
RE: Modeling a Groundwater Well
If that is the case, make sure the motor choosen some type of internal cooling provision. Submersibles often depend on external cooling, and ground water might be a lot colder than the ambient air, or even the air in the well shaft.
Engineering is the practice of the art of science - Steve
RE: Modeling a Groundwater Well
RE: Modeling a Groundwater Well
Well drawdowns are so variable (in my experience anyway) that I don't know how you can model them accurately.
RE: Modeling a Groundwater Well
RE: Modeling a Groundwater Well