Russian forces control the dam and the nearby power plant, which are vital to managing water levels in the reservoir.
A New York Times analysis of satellite imagery over a period of several months also showed that the water level has risen significantly, and now covers sandbars that line the waterway.
In recent days, the reservoir has reached more concerning levels, appearing to actually crest over the top of the dam.
The development is a dramatic turnabout, coming only a few months after water levels in the reservoir had reached a historic low.
Water levels at a reservoir that supplies southern Ukraine with drinking water have reached a 30year high, increasing the possibility of flooding in the area and signaling a lack of regulation.