Restoring river water levels can't be done through technical solutions though, they rely on the weather and we can't control that. The European river levels are largely influenced by inland rain, snowfall, and glacier forming/melting; snowfall and rain has been meagre this year, glaciers have been melting and receding for decades now.

This is entirely an ecological and safety concern.

If for the sake or discussion we simplify cooling to four options:

1: just passing river water through a heat exchanger for cooling

2: ingesting river water, using it for cooling, then passing it through a cooling tower before returning it to the river

3: pass the water output from the cooling tower directly back in the cooling loop, only ingest enough water to replace evaporation

4: fully closed loop via direct heat exchange with air

Then 4 is not very viable. But a lot of nuclear plants are stuck at 1 or 2, and each step up the ladder would allow them to operate in worse conditions. This one seems to be at version one