There are a few ways to meet the water needs, which I will list below in order to provide you with more variety for your solution.
— Creation of a dam to keep water.
— Fix infrastructure so that water can be retained for longer and a larger amount, too.
— Creation of a pipe or something similar so that it would connect to other waterways/dams so that they can access more water and also store more for when it rains.
Hope this helps!