Deep water ecosystem

Irrigated ecosystems

Zones needing supplementary irrigation

Tidal  wetland ecosystem

Irrigated rice ecosystems are those areas that have assured irrigation for one or more crops per year. About 57% of world area under rice (about 43 million ha) area under irrigation. Yield levels achieved are 4-7 t ha^-1 crop^-1. There are three rice environments in this ecosystem, namely, irrigated with favorable temperature, irrigated with unfavorable temperature-tropical zone and irrigated with unfavorable temperature-temperate zone.

The rainfed lowland ecosystem covers 38 million ha or 27 per cent of the rice area of the world. These are rice growing areas with bunded fields. Where water depth does not exceed 50cm for more than 10 consecutive days and the fields are inundated for at least part of the season. No water harvesting/conservation facilities are available on the farm and there is no irrigation water available.