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Hydrometry (water metrology) is a field dealing with the production of hydrographic data (measurement, data collection), which is essential for the analysis of hydrological processes. More precisely, it is the science of measuring the quantities of standing and moving water. Hydrometry also includes measurements of the size, shape, material, and the amount and quality of sediment transported by water. The main parts of hydrometry are: observation of water levels, measurements of the geometrical characteristics of the beds, measurement of water velocity, yield, sediment characteristics, measurement of wave observations and groundwater characteristics (level, velocity, etc.).

The Hungarian Hydrographic Service regularly measures the following parameters:

  • Water level
  • Water temperature
  • Water speed
  • Water flow
  • Ice conditions
  • Sediment conditions
  • Groundwater level
  • Layer water level
  • Source water flow
  • Hydrometeorological measurements:
    • precipitation
    • snow layer, snow water equivalent
    • air and water temperature
    • relative humidity
    • soil moisture

Measuring instruments and instruments used

The measuring instruments used in hydrographic spatial measurements may be conventional mechanical or analogue instruments, digital recording instruments with data loggers, so-called remote sensing connected with different types (urh radio-wired telephone, mobile gsm or GPRS) transmitter instruments and instruments for special measurement needs. In all cases, the measured data are stored in an on-site electronic data logger, from which they are either copied at the prescribed times (registration) or transmitted to the VIZIG telemetry centre (telemetry) operating the measuring station by some means of communication.

Measuring instruments for measuring surface waters

  • flat water meter

The height of the water surface around the plate with the length unit scale and fixed in the bed can be read on the scale. The height of the zero point of each water meter in Hungary is measured to the level of the Baltic Sea. This makes it possible to compare the relative water levels measured at different water levels.

flat water meter

  • mechanical water level recorder
  • The float on the water rises and falls with the water surface, its vertical movement is continuously drawn by a writing device on a paper tape evenly moved by a clockwork.
  • pressure sensor or float-counterweight analog-to-digital water level gauge

The principle of measurement can be of two types. Mechanically, the water level is measured by the rotation of a disc moved by a floating float on the water, and the degree of rotation is corresponded to the change in water level. The pressure of the water column is measured electronically with a pressure sensor whose output electrical signal is linearly related to the water level. The pressure sensor is placed either in a water immersion probe and the probe is placed below the minimum water level; or they are installed above the highest water level and air is pumped under the water from the sensor through a thin pipe (the end of the pipe is also placed below the lowest water level). In this case, the pressure required to expel the air through the tube is measured.

float-counterweight digital water level gauge


  • digital water level logger
  • digitális water temperature recorder
  • water thermometer
  • rotary vane water speedometer

The rotary vane speedometer measures the number of vane rotations caused by the movement of flowing water at a given measuring point during a predetermined measuring time.From this, by calculating the speed per second, the component of the flow rate in the axial direction of the instrument can be determined by means of the calibration equation for the rotor.

rotary wing instrument with counter

  • induction water speedometer

The induction water speed meter does not contain any moving, rotating parts. The instrument consists of a probe and a display unit. The velocity is determined by measuring the electrical voltage generated in the moving water as a conductor in the magnetic field generated by the induction coil located inside the probe. The voltage measured in the water is proportional to the flow rate of water moving in the close vicinity of the instrument. This ratio is determined during instrument calibration and the function describing it is burned into the instrument evaluation unit, so that the instrument display directly shows the average flow rate in m/s for the preset measurement period.

induction water speedometer

  • ADCP water flow meter

The measurement is based on the determination of the flow cross-section and the water velocity component perpendicular to it. The measurement method is based on moving boat speed measurement. As part of this, the device uses ultrasonic technology to determine the water depth of the vertical under the measuring head, the magnitude and direction of the water velocity per cell distributed with the density depending on the setting of the instrument. It determines the water flow from the sum of the products calculated along the trajectory of the vessel.

ADCP water flow meter

  • depth gauge rod-tape-rope
  • portable measuring tip

A relationship (calibration curve) can be determined between the water flow through the measuring plate and the water level in front of the measuring plate, which is not affected by the suction during the flow. When measuring with a portable measuring plate, the water flow can be determined by calculation or graphically using the water level detected on the measuring plate or the equipment connected to it and the individual verification curve (correlation) associated with the measuring plate.

Measuring instruments used for subsurface measurements

  • measuring whistle, electric water level sensor, ie handheld wellwater level gauges

The measuring devices with a longitudinal scale placed in the well give a light or sound signal when the water level is reached.

handheld wellwater level gauges

  • tape water level indicator

This measurement method is used for regular detection of well water levels. Water level fluctuations move a float in the well that is balanced with a counterweight. The motion of the float is transmitted by a tape or cable to the display of the scan tool.

tape water station indicator

  • water level recorder

The float on the water rises or falls with the water surface, its vertical movement is continuously drawn by a writing device on a paper strip evenly moved by a clockwork.

  • digital water level recorder with pressure sensor

The principle of measurement can be of two types. One measurement principle is to measure the water level of a well using an electric transmitter moved by a float floating on the water. Such a device may be used only in a well of suitable diameter, up to a depth of 20 meters from the surface. According to the other measuring principle, the pressure of the water column is measured with a sensor probe located below the lowest water level, the output electrical signal of which is linearly related to the water level.

water level recording probe with pressure sensor

  • pressure gauge

Measuring instruments for hydrometeorological measurements

  • Hellman system rain gauge

This method of measurement is used to determine the amount of precipitation that has fallen since the previous time of detection.

Hellman system rain gauge

  • precipitator

This measurement method is used to continuously monitor and record the time and amount of precipitation. The precipitator allows the measurement and evaluation of the parts and intensity of the precipitation, with detail depending on the type of clockwork of the instrument.


  • digital automatic tipping precipitometer
  • automatic hydrometeorological measuring station

automatic hydrometeorological measuring station

  • evaporation bath

This measurement method is used when the evaporation of natural or artificial free water surfaces is to be measured. The evaporation of the free water surface in the evaporation measuring bath is measured by measuring the water level at specific times and determining the evaporation for the period between the two water level measurements.

evaporation bath

  • snow density gauge with scale

Snow thickness and water equivalent are measured with a scaled snow gauge. The snow thickness is the value read on the outer mantle of the sampling cylinder pierced to the ground in the intact snow cover, the determination of the snow water equivalent is based on the measurement of the weight of the snow sample highlighted by the sampling roller.

  • air thermometer
  • surface-depth soil thermometer
  • solar radiation gauge
  • wind speed and wind direction gauge

wind speed and wind direction meter

Field data collection tools

  • PSION data terminal
  • field computer

PSION data terminal, field computer

Water flow measurements

Hydrographic spatial measurements include water flow measurements on surface watercourses and canals, which provide important basic hydrological data.

Water flow measurement with ADCP instrument

Rangefinder systems

All 12 Directorates in the country operate one or more telemetry systems. Their headquarters are usually in the headquarters of the regional directorate, possibly in one of the section engineering.

Telemetry systems use state-of-the-art sensing, data acquisition and communication tools. Data arriving at the system center can be graphically and tabularly displayed, processed and transmitted to other processing systems.

telemetry equipment


The purpose of verification is to make sure that the measuring instrument satisfies the requirements which apply to it. Calibration is the set of operations that can be used to determine the relationship between a meter reading and a correct value. In fact, the same operations are performed during authentication as during calibration, the difference is actually administrative in nature. There is a difference in the instruments to be calibrated / calibrated, in the eligibility of the organizations performing the verification or calibration, and there is a difference in the interpretation of the results of the operations. The range of instruments to be verified is contained in legislation (Government Decree 68/2000), while the range of calibration instruments is determined by the user. It is important to know that a measurement with legal effect can only be performed with a measuring instrument that has been certified or verified with a standard of use. The use standard must have a certification or calibration certificate.