Very simply - vastly increase hydro generation capacity by adding extra turbines to existing hydro powerplants. You can't increase overall amounts of electricit

Very simply - vastly increase hydro generation capacity by adding extra turbines to existing hydro powerplants. You can't increase overall amounts of electricity produced this way because water in dams is finite, but you can increase max power output when needed. This costs a tiny amount compared to digging up dams themselves, displacing businesses and people on the lands to be flooded, buying up land etc. because the footprint of the hydro powerplant doesn't change. In some countries that's a problem because they don't have enough water. Portugal is lucky with that. Water in dams provides seasonal storage of a sort (even if it's never literally pumped up - just used only when necessary, on a high throughput if need be). It will also mean that at daytime and overnight when wind is strong, hydro plants will completely stop. ...In fact, that seems already done. Portugal has 7.6GW of hydro capacity, up from 5GW in 2008. This allows for peak hydro production to cover 1.37 of average and almost entirety of peak electricity consumption in the country. So the answer is very trivial: "when situations like today happen, just use hydro, and don't use hydro in other situations when either wind or solar are available".