Roughly speaking; yes.
We lose a few tons per year from the atmosphere, we gain a few from debris falling onto Earth. But basically you can consider it constant.
The bigger problem tends to be water mixing with other materials so that we can’t readily use it as water. Or components of water being tied up in other materials.
It seems like we have less because of several major factors. 1. Lakes, rivers, and aquifers take a while to filter the water. 2. We have introduced new materials that need to filtered (pollution), in which some of these sources are not capable of filtering. 3. We have a lot more people and demands on these water sources than even a short time ago.
Ergo, same amount of water, harder to get water in the condition you want for your needs.
MKDesign 