Rybar has reported that the AFU has moved and is moving forces into Kherson city and Nova Kakhovka. They also mention an S-300 battery that has been moved into the area and is complicating Ru aviation operations. This could suggest a larger operation in the area over the coming weeks.
To be honest, given the evidence above, it does seem to me the much more likely culprit was this ‘semi-natural’ method, but the blame would still fall on Ukraine for having facilitated it by pumping up the Kakhovka reservoir from upstream.