Can you have a generator, pump and sprinklers/fire hose pulling from your pool?. Seems like 20K gallons could make the area within 100 feet of your house thoroughly soaked?. Maybe that's ridiculous. Have you looked into it?
Edit: 20,000 gal over a circular area of 100 foot radius is 0.6 gal/sq ft. Industrial sprinkler is 150 gpm for 75 ft radius, you could use three such in a triangle centered on the house. 3 x 150 x 60 = 27,000 gal/hour. You could empty that pool in < 1 hour.
http://www.nelsonirrigation.com/products/family/big-gun-sprinklers/big-gun-applications/
75 series costs $685/each
Plus maybe $1,000/each for pump/motor.