Understandably not Pool Forum stuff, but interesting to me...

A half dozen Intex 18'x48" donuts (Easy Set) would provide 33,000 gallons of temporary water storage. These pools support themselves and don't require construction (you do need flat ground - Really flat, less than an inch off flat - flat - flat - no cheating). When each one is depleted it could be folded up and put away. Traditional AG pools don't do well when they're empty - they need the water to keep the walls up but the donuts are supported by an inflateable ring and are OK when partially filled.

These pools are usually sold as a kit for about $500 including ground cloth, cover, filter pump, ladder, and maintenance kit. The pumps aren't much good as pool pumps but will move the water around for you - just not far and not up. You could probably attach some 2x lumber to a ladder to make a ramp for the pups.

You could even run one (last one to use for water) as a clean chlorine pool ( Pool Solutions / Pool Forum will teach you how ) and let the chlorine burn off before you need to use the water.

If you've got the flat ground, you could hang on to 33,000 gallons of water for about $3G. They won't last forever. I ran a 15' Intex donut pool for 3 years and gave it to my neighbor who's just finishing it's 4th year and it still looks good to me. I had a smaller cheaper brand before that and it showed signs of wear after two years ( the ports for the circulation were starting to come apart ).

Good luck! I, for one, would like to know what you do and how it works out.