Water clock
Persian water clocks were a practical and useful and necessary tool for the qanat's shareholders to calculate the length of time they could divert water to their farms or Gardens. The qanat(Kariz) was the only water source for agriculture and irrigation in arid area so a just and fair water distribution was very important. Therefore, a very fair and clever old person was elected to be the manager of the water clock called(Mir Aab), and at least two full-time managers were needed to control and observe the number of Fenjans or Pengan(hours) and announce the exact time of the days and nights from sunrise to sunset because share holder usually were divided to the days owners and night owners.