I can't answer any better than Cybe. I do remember some mathematical thing
of 100 gallons per 1 inch of width for 1 inches deep of water. Even then I
think experience and playing around are going to pay off better. (In any
other newsgroup that last sentence.....gasp). ~ jan )


On Sat, 27 Dec 2003 15:24:03 GMT
"Steve Shapson" wrote:

I have a pond 25x25 feet by 2 feet depth. A large stream 40 feet long
with a 4 foot height flows into it. How do I figure out what size
underwater pump I will need to make the stream flow fast?

Are there site which help with this math?

Steve Shapson

Forget the math.

There are several things that affect the flow of a stream. Fall ratio,
pump capacity, cross section area of the stream bed, and obstructions,
among possibly others. You have a four in forty fall, not really good
for strong flow. You haven't mentioned the cross section area of the
stream bed, nor any obstructions you may have in the bed. If you have a
pump at all, try it in the stream and see what it's like. Estimate the
flow you want as opposed to the flow you will have. As a helper, maybe
throw a hose in with the pump outflow and see if the increase is
observable. Maybe fill some 5 gallon buckets and pour into the stream
head to estimate the amount of water you will need/time to achieve
what you want. I guess what I'm trying to say is that there is no
substitute for experience /in your stream bed/ to find out what you
want. I'd think about adding several small ponds (wonderful
obstructions!) along that forty foot distance to reduce the total
distance your stream(s) must flow and, at the same time, increasing the
fall ratio. The same thing may be achieved using an occasional
obstruction. Some like the look of a gravel/rock stream bed and it's
pretty easy to adjust your flow thereby. Otherwise, narrowing of the
stream will obviously increase flow rate, but may also require
increasing the stream bed depth. You will also want to consider what
will happen to the stream-held water when the pump is turned off. Left
to itself, a full pond with running stream will overflow when there is
no pump running. One solution is to make an overflow bog area which only
fills when the pump is off. This also encourages turning the pump off
occasionally so the bog plants can get a good watering.

Cybe R. Wizard

See my ponds thru the seasons and/or my filter design:
http://users.owt.com/jjspond/

~Keep 'em Defrosted~
Tri-Cities, WA Zone 7a
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