The historic stone dam within Emerald Wash, within the Fountain Hills Desert Botanical Garden, was built by crews from the P-Bar Ranch in the early 1940s. Early on, the dam collected runoff water to serve as a cattle tank as well as attracting wildlife for hunting. There was at one time a ranch line shack near the pond.
Over the years development of the surrounding area, as well as sediment collection, have inhibited the runoff into the wash, leaving the dam containment area dry most of the time.
However, the storm in late September that recorded between two and three inches of rainfall in places around Fountain Hills generated enough rainfall to drain a couple of feet of water into the area behind the dam, which is considered a rare occurrence in recent years.
