Todd wrote, on Wed, 29 Oct 2014 13:33:15 -0700:

Right now, telemetry is water spraying out the top of the tank.
And you can see it all over the farm. No binoculars needed!

Out here, we have a simple float that turn off the water *before*
the tank is full:
https://c4.staticflickr.com/4/3876/1...4a418e67_b.jpg

On the outside, we have a "visual indicator" of the water level:
https://c3.staticflickr.com/3/2914/1...a36cde37_b.jpg

Then, we have floating weights, that turn off the water before the
tank runs empty, so that there is always 1/3 of a tank for fire.
https://c2.staticflickr.com/6/5480/1...0794c170_c.jpg

The whole thing is controlled by a set of pump controllers:
https://c4.staticflickr.com/4/3906/1...7712c1c3_b.jpg

Then, there is the booster pump to boost the pressure in the house:
https://c4.staticflickr.com/4/3890/1...7a71d615_b.jpg

So, the control is well known (since all tanks have them).
What you need to concentrate on is the telemetry.