It depends what your lease says about the water bill. If the lease says that you are responsible for paying the landlord for the water and it does not require your landlord to provide you with an itemized bill for the water, then your landlord will probably succeed in getting you evicted. He will need to provide you with a 5-day notice and then file a forcible detainer action. There will be a hearing at which you can present your side to a justice of the peace. You may wish to retain an attorney to represent you at the hearing -- $80-$90/month does seem high for water in your situation.
Assuming the duplex is in the City of Tucson, you will also be charged for sewer and trash in the water bill. My office water/sewer/trash bill runs $60 per month with minimal water usage. You should try one more time to try to work this out with the landlord. If not successful talking to the landlord, you should send a written response to the Notice of Eviction and tender a reasonable amount for the water bill (I suggest $60). Send it certified mail or hand deliver it and bring a copy and proof of delivery to the eviction hearing. You should also contact the Water Department at the City of Tucson to see if they can provide any information to you. If you are not satisfied that the amount you are are billed is correct, then you should appear at the eviction hearing and challenge the basis of the eviction. You should appear the hearing in all events. Do not rely on the landlord telling you that you do not need to appear. Best of luck.
The above "answer" is for discussion purposes only and is neither intended as legal advice nor to create an attorney-client relationship. An attorney-client relationship is not created until after an in person consultation and I agree in writing to provide representation. I am licensed solely in the state of Arizona. You should consult with a knowledgeable attorney in your jurisdiction.