I'm no hydrologist, but I think it's the same watercourse that emerges from the outflows at the north eastern end of Coate and becomes the Dorcan Stream, feeds Shaftesbury Lake, and ultimately drains into the River Cole up out near South Marston. But it all definitely needs confirming properly, and probably needs a proper source on the various names (I'm definitely less than confident that it really is part of the River Ray).