I've said that the energy-water nexus needs the same amount of management as the donut-coffee nexus (i.e., none) because each system can -- and should -- be managed separately for sustainability. This is relatively easy when the nexus refers to commodity ("private good") uses of both resources.
In other words, there wouldn't be a nexus if water companies paid scarcity and externality-adjusted prices for energy --- as they often do --- and energy companies paid scarcity and externality-adjusted prices for water, which they often do not.
...but I just thought of another reason to avoid "nexus" thinking: a tendency to focus too much on what's in the nexus and ignore what's not. Pundits have tried to counter this problem by expanding to the "food-energy-water-climate change" nexus, but they forgot fishing, environment, forests, etc.
It's just a fact that people use water in endless ways that may be too difficult to track, let alone understand or manage. Don't try to understand. Just find a way to limit total demand.
Bottom Line: Studying the energy-water nexus as a means of rationalizing the use of both in society is like studying the goalie-striker nexus as a means of explaining how football games are won.* You end up with data, diagrams... and no clue of how the system works.
* Americans: Like the pitcher-batter nexus...