Farmland irrigation system water inlet device capable of controlling water quantity

The invention discloses a farmland irrigation system water inlet device capable of controlling water quantity, and belongs to the technical field of farmland irrigation. The device comprises a gate box, a gate top cover, a water passing through hole, a water passing channel, a rotary drum, an adjusting rod, a control iron ring and a filter screen. The interior of the gate box is of a cylindrical cavity structure, and the water passing channel transversely penetrates through the cavity part along the center line of the gate box. The gate top cover is arranged at the top of the gate box; a through hole is formed in the center of the gate top cover; the rotary drum is of a cylinder structure matched with the cavity structure in the gate box and is arranged in the cavity structure of the gate box; the water passing through hole is transversely formed in a drum body of the rotary drum along the diameter of the rotary drum; a lifting rod extends upwards from the through hole; the control ring is arranged on the lif