Abstract: Debris adhering to the outer surface of a barrel-type fish screen is cleared by air bursts from a series of perforated air pipes positioned inside the outer foraminous shell of the screen, the perforations being holes with axes at an acute angle to the screen radius for efficient use of the air. Separately, the conical water collection manifold mounted inside the shell is open at its narrow end, with a valve mounted to that open end to control the opening. The opening prevents reduced water inflow at that end of the manifold, and the valve adjusts the access of the surrounding water to the opening, thereby allowing the manifold to be tuned to more closely approach a uniform distribution of axial water flow along the length of the collection manifold for different ambient conditions.