At any given time, there is about the same amount of water on the Earth. It never changes much. Water has a brilliant way of remaining in a constant cycle. Firstly, water evaporation from the ocean occurs (wind, heat, humidity), and the evaporated percentage travels through the air, before eventually raining down on the land where it then flows back to the ocean through rivers and streams, and the whole procedure starts again. A tiny percentage is lost in the atmosphere as it evaporates too high to return, but this water is replaced by volcanic activity. Did you know that volcanos spew out water that keeps the water cycle stable!
It is fair to say that there is a lot of water on Earth. Something like 1,260 million trillion litres. That is 1,260,000,000,000,000,000,000. However, only about 0.036% of the planet’s total water supply is found in lakes and rivers. That’s still thousands of trillions of litres, but it’s a very small amount compared to all the water available.