low flow high head hydroelectric generator?

I have a spring on my farm in NE Alabama about 800' feet above the house on the side of Sand Mtn. it is fed to a 1000 gallon holding tank about 100' above the house which supplies all our water. My question is would it be possible to catch the over flow from the holding tank; which is diverted to a pond, to run a hydroelectric generator? The site has about 35' vertical drop from the holding tank to the old grist mill I will be using to house the generator/battery bank were the water can then spill out into my pond (which leaks but thats a different issue). The issue is that of flow rate, the over flow from the tank is about 1/5 of a gallon a minute, is that enough GPM to generate any power with that amount of fall? If not what if I diverted some of the water higher up the mtn. so it had 75' of vertical fall and maybe increased the flow to 1 GPM would that be enough? What do you think would be the minimum flow rate with the amount of vertical fall I have to achieve any substantial output from the hydroelectric generator?

I guess my question would be -why don't you use the larger of the drops to run something like a trolling motor into the storage pond?

That's where you have the most drop and greatest gains.

If you do go with a trolling motor as the generator, the older ones are more durable and efficient. They are ready-made for just this kind of application.

Wasn't this already answered?

If you have 1.5 GPM and 800 feet of head you can conservatively produce 40-45 Watts. You would need a custom-designed turbine to take advantage of such low flow, though.