Plural

Banu Mathiwater are dirty

That's wrong.
How many ponds are you talking about?

Those ponds' water is dirty.

That is not the natural way to say it.
Say this: The water in those ponds is dirty.

Banu Mathi Those pond's water is dirty or those pond's water are dirty

Is any pond an owner of the water?

AnonymousIs any pond an owner of the water?

The possessive does not always designate ownership.

AnonymousIs any pond an owner of the water?

No, but last year's deficit isn't really the deficit that last year owns either.

Banu Mathi Those pond's water is dirty or those pond's water are dirty

You may mean something as simple as This pond water is dirty.

CJ

CalifJimNo, but last year's deficit isn't really the deficit that last year owns either

Mary's mother is in the kitchen.
Mary doesn't own her mother, either.

That will cost you one month's wages.
The month doesn't own the wages, either.

The relationship between two nouns connected by 's, s' and of can indicate several things, one of which is possession. It is unfortunate we these forms are often labelled 'possessive'. In these four examples, only the fourth denotes possession:

Shakespeare's death
Shakespeare's plays
Shakespeare's wife
Shakespeare's house.