Pump comprising a fluid inlet 16 and outlet 18, a screw member 22 with at least one helical blade rotatable by a fluid flow stream, and a rotatable pump member 30 in communication with the fluid inlet and/or outlet. The pump member may be a Wirtz pump, coil or spiral pump, coil tube pump, or an inner screw member and pump fluid when rotated the screw on the outer surface. The screws may comprise three or more blades. The screw and pump may be coaxial or concentric, and rotatably coupled, the outer screw having a first thread direction, and the inner screw a second, which may be opposing. The outer screw may rotate the pump when in the flow. The thread of the inner screw may generate flow along its longitudinal axis when rotated. The first and second flow directions may be opposed. The inlet and outlet may be spaced apart the longitudinal axis of the body, which may taper/converge towards the outlet. A method and irrigation or flood control system are also claimed. It may be partially submerged in the moving fluid, pump in a horizontal direction, with consecutive pockets of air and water moving along the pump member.
