Check the difference in reading.
Secondly check if your water meter is working properly. If it is not working properly Kharma will keep on sending your average bill of QR 150 for water per month + electricity.
I had the same problem for six months. than I went and complained to Kharma about it and after wards its fine.

Kharma customer service centre is open till 8 pm sun - thursday.
hope this will help.