Rainwater Harvesting

This is a photo of the inside of a cistern we have on our property. Our household water supply comes from a hand-dug well. The water is quite hard (400+ ppm calcium) and 2-3 ppm iron plus some oxidized iron. We have a water softener to treat the well water but our barns are plumbed directly from the well. I'm not sure this water is the best thing for our animals to drink. My interest in achieving a high level of health for my sheep through proper mineral supplementation may be thrown out of balance by giving them drinking water like this. I'm also wary of using too much well water for the garden so my latest interest is in rainwater harvesting.

This cistern is approximately 1500 gallons. I pumped it out back when we were having water problems in our cellar thinking that perhaps the cistern was leaking through the foundation but that turned out not to be the case. As you can see in the photo, though, water is getting into it from somewhere because it's about half full. The water that I pumped out of it had the slight look and smell of graywater. I'm not sure if that's the result of being stagnant for so long or if there's a drain dumping into it. I need to pump it out again and do a closer inspection.

Besides the cistern, I've got four 55-gallon and six 32-gallon food-grade plastic drums that a friend gave me. I have plans to plumb these together and harvest the rainwater from the greenhouse roof and the white barn roof. If I can get some more clean containers for the right price I can also collect water from the red barn roof. The barn roofs will primarily be used to water livestock and the greenhouse roof will be used for watering the garden, along with the cistern.