Maybe I am not understanding but you essentially want to fill a trough to keep water going on the property right? Instead of mechanical why not rig up a passive system that will only need to be filled by you every few months? I have setups with 200 gallon cattle troughs and float valves. Then I rigged up 2-250 gallon ibc totes and then a shed roof on top with rainwater collection. I actually havent installed the roof on them yet but have all materials sitting and waiting for me to complete. The tanks last 3 months during summer even with pigs knocking water out. I would rather rely on passive systems than anything electronic when you are there on odd weekends...
Edit: maybe I am misunderstanding, you want to pump water out of a tank to somewhere else? If so, the answer was posted, but I wonder why you wouldn't just fill it yourself and then improve the tank some for additional volume. For the cost of the solar pump and install it may be a wash with slightly more effort but more positive impact. Either way, post pics.