A 6 page report which examines the protocol for aerial spraying of Asulam (for bracken control). The existing operational protocol for spraying by helicopter requires a minimum 50 meter no-spray buffer zone from all surface water bodies, wells, boreholes and springs. This report looks at 1) the science behind the 50 meter buffer zone value; 2) the definition of a "watercourse" in upland catchments that could be used for this guidance.