Rainfall in the catchment generally follows topography with the highest annual rainfall of and above occurring over the high moorland uplands of the Derwent headwaters to the north and west, with the lowest of , in the lowland areas to the north and east. Rainfall totals in the Tame are not as high as would be expected from the moderate relief, due to the rain shadow effect of the Welsh mountains to the west, reducing amounts to an average of for the tributary basin.