A rotary sprinkler includes a sprinkler body including a nozzle, a water-deflection plate supported for rotational movement relative to the sprinkler body, the water-deflection plate having one or more grooves configured to cause the water-deflection plate to rotate when impinged upon by a stream emitted from the nozzle; a first brake arranged to slow rotation of the water-deflection plate at all times; and a second brake arranged to further slow rotation of the water-deflection plate as a function of water pressure exerted on the water-deflection plate.