Note: The California Department of Water Resources ETo Zone Map separates California into 18 zones. For this project only 13 zones were looked at in determining ETc. The other zones had very little irrigated agriculture, which was grouped into the closest ETo zone. If you are unsure of your ETo Zone, click on the image to the right for a larger map of DWR zones. NOTE: Zone 4 data is used for both Zones 3 and 4, because it is representative of both zones.