rembrandt, just looking at your figures for crop water requirements and am wondering where you got them from. The figures you quote as cotton using, 9megalitre/ha equates to 36" of rain. 1ML/ha the amount you state irrigated canola can be grown with equates to 4" of rain. At present most canola is grown in areas with an annual rainfall of 14", with most of that falling during the growing season. Given the oil yield of canola directly relates to the amount of available moisture, higher yields from canola may require a lot more water than what your figures indicate. There seems to be a trend for cropping canola to move into higher rainfall areas with the growers laying out their paddocks with raised beds to avoid waterlogging. The high cost involved is offset by the higher yields.
