Water is a natural resource. Since our childhood we have heard that water is 70% of the Earth so, why do have lack of water all over the world?
That is because the storage of these resources are not available in most of the countries that is why they have to face water shortage. They donot have dams,reservoirs. And even when it rains the water is not stored.
So the most important thing is to build up these resources. Ok, I have another plan as well. Dig up a big hole and line it up with plastic when it rains you can save a lot of water actually.