I had to disable ad blocking to get to the article. I turned it back on after through the banner.
Interesting technology. Only issue I see is that they are not at production yet and they believe they will reach a 50% reduction in overall battery costs. If they can do that, then backup batteries may become viable down the road. They are currently too small and expensive from what I've read about the Tesla solution.
Washington is really 2 climates though only 1 is reported on. Western WA (Seattle) gets rain around 300 days a year. Eastern WA is a desert. The water that feeds the generators at Grand Coulee comes from the Columbia which is fed by the Rockies. We had a bit of a drought in Western WA last year or two, but this winter has been one of the wettest on record. Things tend to be cyclical and the El Nino is certainly making my lawn soggy right now. I know that last year spring was pretty dry as the game bird hatch was really good. I hadn't heard that there was a significant difference in the water flow through the dam because of the W. WA drought, but it's certainly possible. Heck, there's a man made lake that expensive homes have been built on which was half empty because the state decided not to divert water into it so you're probably right!