It wasn't mentioned in the article, but high altitude lakes are perfect for pumped hydro and with enough excess capacity in the system they should be able to mitigate the issue of declining meltwater by pumping water back to the top.
The real competitor is Li-Ion batteries which now cost about the same as pumped storage, and have similar cycle efficiency. Problem is the capacity decline after a few hundred cycles, which is unfortunate if you want to build infrastructure that is low-maintenance and survives decades.
If you are interested in the area, this blog post gives some thoughts to implications [2] though it is a bit outdated by now.
[1] https://www.researchgate.net/figure/Comparison-of-various-EE... [2] https://dothemath.ucsd.edu/2011/08/nation-sized-battery/
https://en.m.wikipedia.org/wiki/Pumped-storage_hydroelectric...