The utility model discloses a small -size drainage canal that hydraulic engineering used, including the connecting piece that a plurality of equidistance were arranged, it is adjacent two to reach the connection irrigation canals and ditches piece between the connecting piece, the connecting piece is convex, the inboard of connecting piece is provided with convex slot the top position department symmetry of being close to of connecting piece both sides is provided with the plug bush more than two, the plug bush with connecting piece formula structure as an organic whole, the bracing piece has been placeed in the plug bush, the bracing piece is kept away from that one end slope of plug bush sets up downwards, the bracing piece is kept away from that one end of plug bush is provided with a plate body vertical the running through of top of plate body is provided with the through -hole, the plate body passes through the through -hole cooperation has the ground stock, the irrigation canals and ditches piece is semi -circular, the outer ring position department at irrigation canals and ditches piece both ends is provided with the card limit, agree with on the card limit the slot, this device is the transportation easily to can accomplish the drainage fast.