Before the cabin was a Short-Term Rental, it was a working cattle ranch.  This trough is one of two on the property.  This side of the mountain around the cabin was fenced to create three separate grazing areas for the cattle.  On from the entrance and then up to the cabin.  And two more above the cabin up to the crest of the mountainside.  

Having cattle in this grazing area meant that you had to open and close the gate at the entrance every time you entered or left the property.