How much less methane does rainfed or drought-prone paddy count than irrigated paddy under the Intergovernmental Panel on Climate Change 2006 tables?

Table 5.12 of the Intergovernmental Panel on Climate Change (IPCC) 2006 Guidelines scales continuously flooded irrigated paddy at 1, regular rainfed at 0.28, drought-prone at 0.25, deep water at 0.31 and upland at 0, with 0.78 for irrigated paddy when the flooding pattern is unknown. Rainfed fields count roughly a quarter of continuously flooded methane.

The scaling factors (Table 5.12)

• Upland, never flooded for a significant period: 0.
• Irrigated, continuously flooded: 1 (error range 0.79 to 1.26).
• Irrigated, intermittently flooded with a single aeration: 0.60. With multiple aeration: 0.52.
• Irrigated, aggregated case, when flooding pattern is unknown: 0.78.
• Rainfed, regular: 0.28. Drought-prone: 0.25. Deep water: 0.31. Aggregated for rainfed and deep water: 0.27.

What the words mean in the table

• Irrigated: fields are flooded for a significant period and water regime is fully controlled.
• Continuously flooded: standing water throughout the season, drying out only for harvest.
• Intermittently flooded: at least one aeration period of more than 3 days during the cropping season, other than the end-of-season drainage.
• Regular rainfed: water level may rise up to 50 cm. Drought-prone: drought periods in every cropping season. Deep water: floodwater above 50 cm for a significant period.

How to use it

Multiply baseline 1.30 kilograms (kg) of methane (CH4) per hectare per day by the factor, then by days of cultivation and hectares (Equations 5.1 and 5.2). The guide asks for at least three baseline water regimes (irrigated, rainfed and upland) and says to use the disaggregated factors whenever you can collect the flooding pattern.

Farm records that settle the choice are irrigation logs and the number of drainage spells. My reading: a canal-fed field drained for more than 3 days mid-season is intermittently flooded; one drained for less is still continuously flooded. A field with water from rain alone is rainfed (the table says water regime depends solely on precipitation).

Reconciling with the water management page

The alternate wetting and drying answer uses the IPCC 2019 Refinement, with its own factors. This page uses the 2006 tables. They differ by edition and are not a mistake on either side. Use one edition throughout a report and say which.

10 hectares each, 115-day season, no amendments, dry pre-season

• Continuously flooded: 1.30 x 1 x 115 = 149.5 kg CH4 per hectare, x 10 = 1,495 kg
• Multiple aeration: 1.30 x 0.52 x 115 = 77.7 kg per hectare, x 10 = 777 kg
• Regular rainfed: 1.30 x 0.28 x 115 = 41.9 kg per hectare, x 10 = 419 kg
• Drought-prone: 1.30 x 0.25 x 115 = 37.4 kg per hectare, x 10 = 374 kg
• In carbon dioxide equivalent at 27: 40,365 kg, 20,990 kg, 11,302 kg and 10,091 kg

Season length and area are example values. 27 is the Sixth Assessment Report (AR6) 100-year warming potential for non-fossil methane. Figures are rounded from the unrounded products.

What Senseible does here

Senseible reads fuel invoices and electricity bills into emission records, so diesel for tractors and power for irrigation pumps show up once uploaded. The fertiliser, residue and field figures on this page come from your own farm records.

• Alternate wetting and drying methane cut
• Flooded fallow before rice: methane factor
• Rice procurement and buyer emissions

Sources: IPCC 2006 Guidelines, Volume 4, Chapter 5, Section 5.5, Equations 5.1 and 5.2 and Tables 5.11 and 5.12, IPCC Sixth Assessment Report, Working Group I, Chapter 7, Table 7.15 (100-year global warming potential: methane of non-fossil origin 27.0, nitrous oxide 273)

Last reviewed 2026-11-05. Factors are from the 2006 edition. Check the table if a buyer or programme names a later edition.