We will have to geo engineer large areas, to hold to water longer. Im thinking of storing water, in hidden cisternlakes on mountain tops/hills, drip irrigating the surrounding eco system, repumping rivers bake into the eco system.
A rain water catchment system is quite cheap and nudging people towards investing would make a difference during the summer.
Being from Switzerland we have already massive natural stores of water (Glaciers), but if it gets warmer we will loose them, and our alps would look like the Atlas Mountains in Maghreb, still water but nothing that could fill Lakes.
Not even talking about permafrost and falling-apart mountains.
Won't take long: https://www.nbcnews.com/science/environment/dramatic-swiss-g...