The following web sites provide good info on chinch bugs for you to see if that is what you have and what to do about them.
Regarding the salt content of your water that is rather marginal and will stress the grass some. I suggest you contact your County Extension Office about this and see if they have more information regarding what you might be able to do about it if anything.
Thanks for the question. Please stop in again soon!
Q&A Library Searching Tips