Winter Rainwater Storage in Minnesota

Our homestead is entirely reliant on rainwater collection, both for domestic use and irrigation. We have an underground cistern for the house but use 3 above ground 1500 gallon ag tanks for irrigation (along with assorted rain barrels and a dairy bulk tank). The ag tanks, pump, and irrigation lines get drained in the fall after watering out some onto fruit trees and filling water barrels. The dumping of so much water seems so wasteful, especially since we've been having more spring droughts in recent years.  We've been fantasizing about having an underground cistern for irrigation needs to keep water over the winter. But costs and access to a suitable site make that a no go. So I had the idea of putting 12 of the 330 gallon IBC totes above ground, filling them to about 275 gallons, and letting them freeze solid. We found a seller with the tanks we wanted that was able to deliver to us. The original plan was to take off the valves and cap the tanks but that doesn't really sound easy to accomplish. So the latest thought is to use closed cell spray foam to permanently plug the piping stub and drain valve so water can't get in there and crack the fitting.  The totes will be filled with water that would have been dumped in the fall using a transfer pump on top of the tanks and moved back into the irrigation system if needed the next spring. Other than putting a tarp (silage bag scraps that are white on one side) over the "cube farm" to avoid freeze and thaw cycles, is there anything else we're missing? Has anyone else used IBC totes for frozen water storage? If so, specifically how did you deal with the valves?

I recently scored some recycled sliding glass doors from a contractor that was installing new ones in an apartment building I happened to be driving past.  I stopped and asked, and got to take twelve 72X36" glass panels for free.  I'm going to use those for the construction of a greenhouse on the side of my cabin.

I wonder if you could do something the same, building a small enclosure around your totes, with glass facing South, and the other three sides and the roof heavily insulated?  I would design the enclosure such that it could be sealed up in winter, but opened to the air come spring, so the water doesn't get too hot.