In The water cycle, written by writers of Khan Academy we see a fairly in depth review of the water cycle. It shows us that much of our water on earth is salt water, when humans need freshwater. On the surface water cycles fast, but as you go underground it slows and takes a lot longer to cycle. They state that the "water cycle is complex and involves state changes in water as well as the physical movement of water through and between ecosystems". This is a key component that needs to be understood about the cycle. The water cycle is also driven by the suns energy. This is when the cycles starts, from evaporation, condensation, precipitation and collection. It is way more complex then this but this is a great article that overviews the importance of the water cycle.
