Relationship between irrigation conditions and distribution of paddy water temperature under continuous irrigation with running water
2016
Nishida, K. (The University of Tokyo, Bunkyo-ku, Tokyo (Japan). Department of Biological and Environmental Engineering) | Ninomiya, Y. | Uo, T. | Yoshida, S. | Shiozawa, S.
Continuous irrigation with running water (CIRW) experiments during nighttime were conducted in an conventional paddy field, to obtain the relationship between irrigation conditions (amount of irrigation water, irrigation rate and irrigation water temperature) and distributions of the nighttime average water temperature and lowest water temperature. At first, 18 CIRW experiments were conducted under the various irrigation and climate conditions in 2013, 2014, and the water temperature distributions of these conditions were obtained. Then, from the observed temperature, empirical equations were developed for the distribution of nighttime average and minimum water temperature as a function of irrigation water amount and temperature, air temperature and water temperature at the start of irrigation. Predictions of the equations were in good agreement with the observed distribution; root mean square errors (RMSE) for nighttime average and minimum water temperature were 0.47 and 0.62 ℃, respectively. Finally, we calculated the irrigation water requirement and cooling effect of CIRW on paddy water temperature and then found that CIRW using normal irrigation water amount can not provide sufficient cooling effect for a whole paddy field.
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