How much water do 9 Billion human bodies (@ 80% water) remove from the Earth's 'water system', and to what effect ? Is this significant ?

This idea is to do with Water. So, let's assume there is a finite amount of water on Earth, and it goes around the system from river to sea to rain etc. Now people are 80% water and we expect the Human population to become 9 Billion in the next 50 years, from 1 Billion 100 years ago (?). Now people & other large animals (eg those we eat) are in fact temporary reservoirs of water (i.e. the 80% body mass they take out of the Earth's water system for their lifetime). I'm wondering what effect this decrease of Water will have on the Earth / the environment / the weather ? Has anyone calculated the amount of water there is Vs the amount we're removing in this way ? I'd estimate an average weight of 50kg per person (to cover all ages & sizes). 80% of this is 40kg which is 40 litres of water I suppose. So then we multiply the population increase of 8 Billion in the last 150 yrs and we get 320 Billion litres of water temporarily out of the system - to what effect ?