What I would do is run a line from the house. Install a ball valve, solenoid valve and check valve at the house. Pump the water to your pond under the frost line and be done with that part.
As far a level goes.
For a clean, reliable and safe installation, I would use conductivity sensors (switches). They are not mechanical, therefore ice won't mess them up. These would be a single point device, so one for upper level, and one for lower level.
The trick to using level sensors or switches in an open BOW for control of other devices is to use some form of debounce. What I mean by this, is an open BOW is prone to ripples, waves and water activity. A switch or sensor is a dumb device and can not determine if esshup is buzzing around his pond in a boat because Bill Cody told him to do so to break up the dead FA. Need something a bit smarter on the other end to determine what's going on.
Even filling up a tank with a level switch, you still need a debounce. You can chatter the device you are controlling without one, and depending on the device, could shorten its operational life quite considerably.
The simplest form of debounce is to use a timing device. Time delay before any other devices kick in. This determines if it's real. Switch is made for [X] amount of time, then it's OK to proceed.
You can use timing relays and relay logic, but it's much more cost effective to use a PLC.
Quick note on the 2 wire esshup mentioned. It will work, but won't tell anyone how to do this. Way too easy to red neck and get someone killed. Plus, it's not reliable and there is a whole Pandora's Box of potential consequences.
I myself like Ultrasonic sensors. If you get bored, you can open up the electronic chart recorder and watch the wave action
You can also use pressure sensors under water for level. Really complicated and are specifically built for the BOW or vessel.
Just not good at red neck stuff, so you can all disregard any post I submit to.
