Improved Valiantzas equation for ET0 prediction in typical Yellow River irrigation district
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DOI:10.7606/j.issn.1000-7601.2018.02.39
Key Words: reference crop evapotranspiration  Valiantzas equation  prediction  Lower Yellow River
Author NameAffiliation
JING Ming Yellow River Institute of Hydraulic Resarch, YRCC, Zhengzhou, Henan 450003, China
Yellow River Irrigation, Drainage and Rural Water Supply Research Center, Xinxiang, Henan 453003, China 
WANG Jun-tao Yellow River Institute of Hydraulic Resarch, YRCC, Zhengzhou, Henan 450003, China
Yellow River Irrigation, Drainage and Rural Water Supply Research Center, Xinxiang, Henan 453003, China 
CHENG Xian-guo Yellow River Institute of Hydraulic Resarch, YRCC, Zhengzhou, Henan 450003, China
Yellow River Irrigation, Drainage and Rural Water Supply Research Center, Xinxiang, Henan 453003, China 
GAO Zi-le Huibei Water Conservancy Science Experimental Station of East Henan Water Conservancy Project Administration, Kaifeng, Henan 475000, China 
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Abstract:
      Selecting the Liuyuankou irrigation area in Henan Province as the representative area, the Valiantzas equation with the air relative humidity (RH) as the input parameter is improved and that based on the characteristic temperature was also established in this paper. Using the multiple regression method, an improved Valiantzas equation with the input of characteristic temperature and daily ordinal number was established, and the accuracy of the model was verified. Compared with original equation, the improved Valiantzas equation had a 12.4% reduction in the relative error and a 37.4% in root mean square deviation. In addition, the correlation coefficient was increased by 13.4%. Therefore, the improved Valiantzas equation could provide basic information about crop water requirement forecast at ten-day scale.