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1 a.m., 7 a.m., 13 p.m., 19 p.m. or from the results of 24 observations

at the time of 1 a.m., 2 a.m., 3 a.m.,... 24 p.m. of the hygrograph.

Average humidity in year is the average of average relative
humidity of all days in the year.

The water level is elevation of the water surface at the
observation place in relation to the sea surface, measured in centimeters
(cm). A system of piles, rulers and self-recording machines are used

to monitor the water level.

Water flow is the amount of water flowing through a cross
section of the river in a unit of time, measured in m³/s. Monthly
average flow is the average value of flow of the days in the month.
Water flow is measured by flowmeters, drifting buoys or ADCP

machines.

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