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Effects of the introduction of rice on evapotranspiration in seasonal wetlands
Author(s) -
Suzuki Tetsuji,
Ohta Takeshi,
Hiyama Tetsuya,
Izumi Yasuhiro,
Mwandemele Osmund,
Iijima Morio
Publication year - 2013
Publication title -
hydrological processes
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.222
H-Index - 161
eISSN - 1099-1085
pISSN - 0885-6087
DOI - 10.1002/hyp.9970
Subject(s) - evapotranspiration , environmental science , daytime , leaf area index , bowen ratio , latent heat , energy balance , wetland , water balance , eddy covariance , pan evaporation , evaporation , hydrology (agriculture) , ecosystem , atmospheric sciences , agronomy , ecology , geology , geography , meteorology , biology , geotechnical engineering
Land use changes in wetland areas can alter evapotranspiration, a major component of the water balance, which eventually affects the water cycle and ecosystem. This study assessed the effect of introduced rice‐cropping on evapotranspiration in seasonal wetlands of northern Namibia. By using the Bowen ratio–energy balance method, measurements of evapotranspiration were performed over a period of 2.5 years at two wetland sites—a rice field (RF) and a natural vegetation field (NVF)—and at one upland field (UF) devoid of surface water. The mean evapotranspiration rates of RF (1.9 mm daytime −1 ) and NVF (1.8 mm daytime −1 ) were greater than that in UF (1.0 mm daytime −1 ). RF and NVF showed a slight difference in seasonal variations in evapotranspiration rates. During the dry season, RF evapotranspiration was less than the NVF evapotranspiration. The net radiation in RF was less in this period because of the higher albedo of the non‐vegetated surface after rice harvesting. In the early growth period of rice during the wet season, evapotranspiration in RF was higher than that in NVF, which was attributed to a difference in the evaporation efficiency and the transfer coefficient for latent heat that were both affected by leaf area index ( LAI ). Evapotranspiration sharply negatively responded to an increase in LAI when surface water is present according to sensitivity analysis, probably because a higher LAI over a surface suppresses evaporation. The control of LAI is therefore a key for reducing evaporation and conserving water. Copyright © 2013 John Wiley & Sons, Ltd.