"An interesting feature of these structures is that despite very high visibility" (i.e. often directly on bedrock)
OK, If hundreds of them were built, my gut tells me it had to be something that warranted the effort to build. Something related to survival. Was it a method of capturing precious water? Or confining herds of livestock as mentioned.
Looks like a fish farm to me.
My first thought was if it was wetter back then, perhaps the area would flood once in awhile and these things were built to keep the people and animals and crops(?) from flooding out??