We're not losing water to anything. The total amount of water that is on Earth has been the same since the beginning of time. We have great knowledge on how much water is stored in bodies of water, and how much flows into and out of the various components of the water cycle. For example, our colleagues at the US Geological Survey built this amazing chart: https://www.usgs.gov/special-topics/water-science-school/science/water-cycle-diagrams

However, our knowledge is based on long-term averages. Our planet is living and keeps changing as a function of external forces (like energy coming from the sun) and internal forces (like what humans do with the water). So it's always changing. Also, we're now nearly 8 billion people on Earth, whereas we were just 1 billion in the early 1800s.

So: same overall amount of water as ever, many more people than before, and continuing changes in how the water is stored and moves around between, clouds, snow, rain, rivers, lakes, groundwater, and oceans (CD).