I get the impression that the water level here is an important clue to these monuments.
Something about the dam being built in 1964 allowing the reservoir to fill and cover the monument, and now in times of extreme drought the photo of the site with water around part of it, seems to me that was how it was at time of construction, built on a jagged peninsular off of the main river.
Clearly the River Targus was of the utmost importance to its builders, They got the stone from it. Travelled on it, Mapped it, A boat people that can navigate Rivers and move stones, interesting.
If only they could make a water level time slide of these sites by checking the soil around them, as I believe the water level is critical to dating them.