Abstract: The water balance and its efficiency in five rice field ecosystems were studied at the lower reaches plain of Liaohe river from i993 to 1995. The resulls show that there is a significant difference of total water consumptioll among different rice field patterns. Comparing with conventlollal pattern, the improved irrigation and improved irrigation-[ertilization patterns can save 15～23% of itrigatioll water and increase 30% of water efficiency. During the same growing season, each pattern has a similar evapotranspiration, and field stlxicture and control nlanagemen[ have no influence on it. During rice development pened, the difference between field and potential evaPOtranspirations is less than 5%.

Key words: Single-cropping rice, Rice field ecosystem, Water balance, Water efficiency, Evapotranspiration, sand-binding plant, life form, water source, root distribution