Water meters

Water meters

Water meters (gauges) are the instruments intended for measurement of water flow (quantity of the water running through a certain point, i.e. rate of discharge).

Water measuring facilities (gauges) installed in the irrigation network allow more accurate and easy accounting water and distributing it to canals. They are divided into regulating (water meters-regulators) and non-regulating types. Water meters-regulators have devices that allow measuring and at the same time regulating water discharge. Among non-regulating water meters are weirs of different types, flumes, mouthpieces, outlets that can be applied only for measuring flow, water application rates, and calibration of structures.

Water meters-regulators are installed at water distribution nodes, points of water delivery to farms, as well as on permanent on-farm canals, flumes and pipelines.

Tubular water meter-regulator with converging orifices (designs by M.V. Butyrin) measures water discharge up to 1.1 m/s, and with twin-slab type – up to 2.2 m/s. The water meter-regulator consists of headwall face with wing walls and panel structure, a pipe and conically converging water-metering orifice. A well is arranged in order to install the device and rods. The pipes and orifices can be of circular or rectangular section. In the first case, the orifice outlet diameter is equal to d = 0.74 D and length l = D, where D is the pipe diameter.

The orifice is the metering part of the regulator; it creates water pressure difference (Z) that is equal to the difference between the water level in the pipe before the orifice and downstream water level, at water outflow from the structure. At water accounting by using a tubular gauge-regulator, the graph of water discharge against water pressure difference is usually used.

Often, the water meters-regulator is equipped with a flow-rate indicator or flow meter. For this purpose, the well chamber is divided into two parts by a horizontal partition: upper and lower. The upper part is coupled with a pipe, and the lower with the tail-water section. There is a hole in the horizontal partition dividing the well into two parts, where a sensing element is introduced; the sensing element senses the pressure difference in the dynamic flowmeter DRS-60 [in Russian] ДРС-60) or rotary flow meter SVN [in Russian] СВН) and diaphragm water meter of the K.S. Glubshev system.

A VDG-58 [in Russian] ВДГ-58) type automatic water meter has a counting mechanism that continuously shows water discharge per second (in terms of m) and total water volume (in terms of thousand m). The inlet diameter of the water meter orifice is from 7 mm to 222 mm; water discharge ranges from 30 to 1100 l/s depending on the pipe diameter and pressure.

Automatic water meters are installed on devices like a convergent short tube working on conjunction with the pipeline and immediately in the canal bed, in the head wall of the canal.

The SVN-type rotary flow meter indicates water discharge and total water volume supplied to a canal or farm-water user for any time period. The device is installed, similarly to a DRS-60 type dynamic flowmeter, on a water meter-regulator in a special well. It consists of the following parts: an operational connection pipe built in the hole connecting the well with a lower-pressure water meter-regulator; turbine with rectangular screw thread; rod with telescopic insertion piece for changing its length; mechanism (meter) for measuring the rotational speed of the water motor and runoff volume proportional to it. The water motor is rotated by the water flow passing through the connection pipe. The more the discharge of the water meter, the more pressure difference in its water sides, and the faster the water motor rotates. The water motor is connected with the meter by means of the rod and telescopic insertion piece.

Source: Agricultural reclamation / Edited by I.P. Sukharev.
Moscow, “Kolos” Publishing House, 1981.