I have a spring on my property located slightly above my planned building site. I'm not sure of the flow rate but it would probably fill a 2" pipe. I'm new to this geo therm stuff and am wondering if this might be ideal for heating, cooling and possibly drinking. Also couldn't the water be returned to the natural streambed after going through the system? 

Usually the water can be returned.

You need to know the gpm flow of the water, and the temperature of it.

Then you need the heating and cooling loads of your house. From there you can size the system, and see if there is sufficient water flow in the spring. Does the water flow year round?

The flow is fairly constant all year, and I'll do some temp. readings between now and high summer. Does anyone have any low-tech ways to measure flow in a stream bed? I was thinking trying to divert the flow into a wooden channel (three boards nailed together) measure the depth, and the speed of a floating object. Would that give me cubic inches per second? Also there's not much fall to the building site so I was thinking a cistern and a pump.

Kent,

The lowest cost flow checking devise that actually works quite well, get yourself a 5 gallon pail and a stop watch. To figure the flow rate in gallons per minute, gpm, take the measured amount of water, in our case, 5 gallons, times 60, then divide by the number of seconds on the stop watch it took to fill it. For example, if it takes 15 seconds to fill the pail, this is the calculation:

(5 x 60) / 15 = 20 gallons per minute

To make it a little simpler, the 5 gallon pail and time ratio are constant, so you can just take the gallons measured and multiply by 60 for our unit of time, which gives you 300. Now all you need do is use your stop watch to measure the time to fill the pail, and what ever number of seconds it takes divide the 300 by it. Here are a few examples:

If it takes 45 seconds to fill the pail:

300/45 = 6.67 gpm

If it takes 12 seconds to fill the pail:

300/12 = 25 gpm

Hope this helps your flow question,