It's easy to integrate wind energy into such a system. When the wind is blowing less water is released to the turbines in the dams. When the wind is not blowing more water is released. This creates some very unnatural river flows but the technology is not complicated.
Most of the world doesn't have these hydroelectric resources so natural gas backs up wind and solar schemes.
At this moment California is getting about 68% of its electricity from renewables, and 22% from natural gas.
California's has a very large hydroelectric capacity, but this is diminished in times of increasingly common droughts.
Wind and solar energy will only prolong our dependence on natural gas and for that reason I frequently say those are the best thing that ever happened to gas industry. Of course the petroleum/gas industry promotes it. That's why you see wind turbines in Texas.
The most serious threat to the fossil fuel industry is nuclear power. Nuclear power is the only energy source capable of displacing fossil fuels entirely.
That explains a lot.
Coal will be the first fossil fuel displaced. That's what happened in France. Nuclear powered France closed its last coal mine twenty years ago.
That's also what caused the current catastrophe in Germany. Their aggressive renewable energy schemes and anti-nuclear policies forced them to import increasing amounts of Russian natural gas and prevented them from quitting coal. That didn't end well, as many had predicted, and it was sooner than expected.