Far as I know, dousing them with water is acceptable as it sometimes brings them out a little better. You know it does rain on them. I just try to get to them when the lighting is better if I can. This area has cameras set up in it which most people may not know about, and no signs saying they are, but I spotted them. Don't know if they're active or just decoys.
They're very interesting images. Info online dates these from as recent as the late 19c to as far as a 1000 year old. So many times that I've driven I80, I would think how old that route going east and west has actually been used by humans. Truckers when I CB back in the late 80s and 90s called it the BIG Road. Before that they built the transcontinental rail road and before that it was the overland route of the pioneers heading to Oregon for land and Gold seekers to California. I would often wonder how long before all that the ancient peoples would have used that same path in transportation across the country. Could have be 10 of thousands of years I'd be thinking.