Alternative Energy Forums

Would someone be so kind as to check my math and give me some input.

I have a dammed stream (read pond) with a 15' dam. Water flows year around. Overflow water comes down through 12' of vertical pipe (unknown dia.) then through a horizontal 24" pipe for approx 15'. Using the "carpenter's square" method, the water comes out 12" and drops 5". It is utilizing about 3" of the 24" pipe.

So using the formula Q = (3.61 A X)/(√Y) = 8759.82GPM where A=cross-sectional area of pipe, X=horizontal distance and Y=vert. dist.
8759.82GPM is for water running out a full pipe.
Mine is using on 3" of a 24" pipe so using a table I found somewhere I got the coefficient of .070
This gives me 613 GPM (or 1.64 cubic ft/sec) with a head of 12'.

(12 * 1.64)/11.8 = 1.66Kw

Can anyone see errors in my thoughts?
Is this 1.66Kw usable or feasible? I am looking to tie into the grid and am about 100yds from the dam site. What type of power loss am I looking at over this distance?

Any and all input in greatly appreciated.
Thanks,
thereverend@hotmail.com