Sources of Irrigated Lands Data
Further literature search on the total irrigated lands in the Philippines; irrigated land usage; and analysis of the annual palay (harvested rice) production, actual yield of palay per season and annually, provided numbers for irrigated rice fields that are rather variant depending on the source of information.
The FAO data used in the graph by PhilRice is readily available online, and is quoted widely in many review and feature articles about rice production and policies relevant to rice resources, including importation for countries, like the Philippines.
The World Bank archive, placed irrigated areas in the Philippines at 9.1-9.2% in 2011-2012. Assuming, about 9.7 million hectares of agricultural land (BASTAT data), that would be less than 1 million hectares of irrigated land.
The National Statistics Office (NSO) data for 2002 more than doubles the number, but it is unclear whether the expanded meaning of the definition of irrigation (e.g., to include water carried by farmers from nearby streams, manual pumps, etc.) would really suffice to provide for rice cultivation.
The National Irrigation Administration (NIA), estimated about 1.7 million hectares of irrigated lands in 2013 (out of the 3.1 million irritable, the latter is less than a third of the 9.7 million agricultural lands). Figure 02 presents the irrigated rice fields (LI) vs the total area of irrigated lands (LTI-NIS) from 2000-2014.