Installation of Babbitt trough drainage measurement for farmland irrigation

The Bacher measuring tank consists of three parts: an upstream contraction section, a short straight throat, and a downstream diffusion section. The groove bottom of the contraction section tilts downstream, while the inclination direction of the groove bottom of the diffusion section is opposite to that of the throat groove bottom.

Other constant terms need to be experimentally determined, generally as follows:, F=60cm, G=90cm; K=8cm, N--23cm,x=5cm, y=8cm; Depending on the depth of the channel, the height above the upstream water level is 0.1-0.2cm, and generally 1.00 meters can be used. The length of the bottom protection upstream and downstream of the measuring tank is a function of the height H of the tank bottom:

Upstream bottom protection L,=4H;

Downstream bottom protection L,=(6 ^ -8) H;

Meanwhile, due to the high flow velocity in the measuring tank and the significant fluctuations in the water surface in the throat, it is difficult to directly measure the water level in the tank. Therefore, after setting up observation wells on the groove wall, measure the water level with a water gauge. The bottom of the well is 20-25cm lower than the groove threshold. Logging and measuring tanks can be connected with flat metal or concrete pipes, and the centerline of the pipe should be 3cm higher than the bottom of the tank. The upstream water gauge is located upstream of the throat (2/3) from the beginning of the throat, and the downstream water gauge is located 5cm above the end of the throat on the wall of the tank. The zero point of the upstream and downstream water gauges should be level with the height of the groove bottom, and there should be no water leakage in the observation well. The well should be regularly cleaned of sediment and covered with a lid to prevent debris from entering.

The larger the flow in the open channel, the higher the liquid level; The smaller the flow rate, the lower the liquid level. For general channels, there is no definite correspondence between liquid level and flow rate. Because the same water depth and flow rate are also related to the cross-sectional area, slope, and roughness of the channel. Installing a measuring weir groove in the channel, the correspondence between the upstream water level and flow rate of the channel mainly depends on the geometric dimensions of the weir groove, as the gap of the weir or the contraction of the groove is smaller than the cross-sectional area of the channel. The same measuring weir tank is placed on different channels, and the same liquid level corresponds to the same flow rate. The measuring weir channel converts the flow into liquid level. By measuring the liquid level of the water flow in the measuring weir tank, and then reverse calculating the flow rate based on the corresponding water level flow relationship of the measuring weir tank.

·The centerline of the Bacher trough should coincide with the centerline of the channel to prevent water flow from deviating into the Bacher trough.

·After the Bacher trough is filled with water, the flow state of the water should be free flowing. The submergence degree of the Bacher trough should be less than the specified critical submergence degree.

·The upstream of the Bacher Trough should have a straight section greater than 5 times the width of the channel to allow water flow to enter the Bacher Trough smoothly. There is no lateral deviation or the impact force formed by the slope of the channel.

·The Bacher groove should be securely installed on the channel. The connection with the side walls and bottom of the channel should be tight and not leak water. Make all the water flow through the measuring part of the Bacher trough. The measuring part of the Bacher trough is the throat section inside the trough.