Aside from the 'year round' spring fed water there are a few summer time water troughs made up of old bath-tubs people threw away when renovating. The original procedure was to plug the bottom drain and ignore the overflow.
Wow! That's reduced the changing of the waters of horse life from a major hassle to a tiny weeny job. No major back breaking effort. Just a little 'elbow grease' to drain, scrub and refill, with clean and healthy water.