The AWDM was used to determine the annual irrigation demand and irrigated area for each municipality by crop, irrigation system and soil texture. The irrigation demand for these combinations was investigated under three climate scenarios (below). The climate scenarios are designated according to the quantity of growing season precipitation in Metro Vancouver overall. While precipitation is a significant indicator of irrigation demand, it is not the only factor influencing demand and in some instances the precipitation level does not correspond to the level of irrigation demand.
It should be noted that while 2003 represents a dry year for Metro Vancouver overall there is climatic variation among the individual municipalities and 2 of the 5 municipalities received more growing season precipitation in the dry year (2003) relative to the average year (2010). Therefore in some instances irrigation demand in 2010 exceeded that in 2003, specifically the irrigation demand for vegetables in Delta, Richmond and Surrey.
Irrigation systems were grouped into three categories based on efficiency. It should be noted that not all crops are compatible with all irrigation systems. Cranberries and forage are not compatible with drip systems. In some cases forage is compatible with small center pivot sprinkler systems.
An assumption was made in the case that over 90% of the irrigated area of a given crop in a given municipality was under a single irrigation system. In this case it was assumed that the entire crop area was irrigated under a single system. For example, 95% of the blueberries in Delta were reported as drip irrigated therefore it was assumed that all of the blueberries in Delta were under drip irrigation.
When indicated, irrigation demand for cranberries includes water for harvesting and frost protection.