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Stable isotope ratios in irrigation water can estimate rice crop evaporation
Author(s) -
Simpson H. J.,
Herczeg A. L.,
Meyer W. S.
Publication year - 1992
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1029/91gl02952
Subject(s) - environmental science , transpiration , irrigation , water use , agronomy , evaporation , arid , paddy field , growing season , crop , hydrology (agriculture) , chemistry , photosynthesis , biology , ecology , geology , geography , biochemistry , geotechnical engineering , meteorology
Irrigated crops provide about one third of world food production, and the total area under irrigation has increased by more than a factor of three since 1950 [Brown, 1988]. Possibilities for further geographical expansion are limited; therefore future production increases are likely to require higher efficiency of water use. Of the major grain crops, lowland rice requires the most water, with total demand per unit area at least twice that for wheat and maize. Stable isotope abundance changes in irrigation water can provide direct indication of integrated evaporation losses exclusive of transpiration and thus provide a new tool to monitor a key parameter relevant to water use efficiency. Large enrichments of deuterium and oxygen‐18 in rice field water compared to initial input water in a semi‐arid region of southeastern Australia indicate high evaporation rates (7 mm day −1 ) during the first month following flooding. This contrasts with semi‐mature rice crops which had small heavy isotope enrichments of field water, indicating low evaporation (<1 mm day −1 ), compared to transpiration (6 to 7 mm day −1 ). Over the entire rice‐cropping season, evaporation accounted for about 40 per cent of total losses to the atmosphere, with transpiration providing the remainder.