Firstly, fresh water has to be used with care owing to itsless availability.
"scarcity" is a more appropriate key word to express "less availability"
For example, in countries like India where there is shortage of water, people from the upper strata misuse the fresh water for sake of pools and other water related sports.
... I doubt "strata" is the best word to use there... You mean the people of upper class misuse water for their recreational activities. Isn't it?
Overall, you write very well. Good ideas, sentences, vocabulary and essay structure too. Wish you good luck with IELTS!