基于FAO-Blaney-Criddle方法的河套灌区参考作物蒸散发量估算

实时灌溉预报是河套灌区管理科学化与信息化的要求，利用天气预报中相对准确的气温数据估算参考作物蒸散发量对实时灌溉预报非常重要，因此需要建立一种基于温度的参考作物蒸散发量估算方法。利用 FAO-Penman-Monteith方法估算河套灌区解放闸灌域历史参考作物蒸散发量，以此作为标准值率定 FAO-Blaney-Criddle 公式中逐旬的修正系数，得到基于温度的参考作物蒸散发量估算方法。结果表明，在作物的生长季（4－9月），FAO-Blaney-Criddle 方法与FAO-Penman-Monteith 方法的估算结果相近。率定期各旬相对误差均<5%，标准误差<0.65 mm/d，验证期各旬相对误差均<9%，标准误差<0.70 mm/d。10 d 滑动平均的参考作物蒸散发量估算精度，Nash 效率系数达到0.75，误差0.5 mm/d 的精确度达到了68%，误差在1 mm/d 以内的准确率达到95%。FAO-Blaney-Criddle 方法可以应用于河套灌区的灌溉预报中。另外，FAO-Blaney-Criddle 方法的参数具有较强的地区差异性，需要针对不同地区的气象数据进行率定和验证。

Calculation of reference evapotranspiration based on FAO-Blaney-Criddle method in Hetao Irrigation district

Abstract: Real-time irrigation forecast is a key step for management modernization in Hetao Irrigation district. Irrigation forecast lies on the prediction of reference evapotranspiration (ET0). A calculating method for ET0 based on air temperature is needed since air temperature is the most accurate and conventional parameter acquired from weather forecast. In this study, FAO-Blaney-Criddle method based on air temperature for ET0 estimation was proposed, and the parameter of the equation was calibrated every ten days in Jiefangzha Irrigation sub-district of Hetao Irrigation district. FAO-Penman-Monteith equation was employed as standard for ET0 estimation. The meteorological data at Linhe climate station, which represented the climate conditions of Jiefangzha Irrigation sub-district, was utilized for calibration and validation of the parameter. The results showed that the estimated ET0 of FAO-Blaney-Criddle method was close to that of FAO-Penman-Monteith method in growing season (April to September) on 10 days scale. The relative error (RE) of the 10 days average ET0 was less than 5%, and the root mean square error (RMSE) was less than 0.65 mm/d in calibration period. And in validation period, RE was less than 9% and RMSE was less than 0.70 mm/d. It was because the correlation between ET0 and temperature was larger in growing season than non-growing season. In April, August and September, ET0 estimation of FAO-Blaney-Criddle method was closer to ET0 estimation of FAO-Penman-Monteith method, compared with that in May, June and July. In the latter 3 months, ET0 was underestimated by FAO-Blaney-Criddle method when ET0 of FAO-Penman-Monteith method was less than 5 mm/d and it was overestimated when ET0 of FAO-Penman-Monteith method was greater than 6 mm/d. For the 10 days moving average ET0, the Nash-Sutcliffe efficiency coefficient (NSE) of estimation of FAO-Blaney-Criddle method was 0.77. Forecasted accuracy with an error less than 0.5 mm/d was greater than 70%, and that with an error less than 1 mm/d was greater than 95%. The same method and parameter was applied at Hangjinhouqi climate station located in Jiefangzha Irrigation sub-district. The NSE of estimation of FAO-Blaney-Criddle method was 0.75. Forecasted accuracy with an error less than 0.5 mm/d was 68%, and that with an error less than 1 mm/d was greater than 95%. Hence, FAO-Blaney-Criddle method is available for the prediction of ET0 as well as irrigation forecast in Jiefangzha irrigation sub-district. When the parameter of FAO-Blaney-Criddle method was employed to estimate ET0 at Baotou climate station located in Hetao irrigation district but a bit far from Jiefangzha irrigation sub-district, theET0 estimation of FAO-Blaney-Criddle method was still reasonable though it was a bit poor than the estimation at Linhe station and Hangjinhouqi station. NSE of estimation was 0.65, forecasted accuracy with an error less than 0.5 mm/d was 52%, and that with an error less than 1 mm/d was 86%. It demonstrates that FAO-Blaney-Criddle method is available in the whole Hetao Irrigation district. It also suggests that the parameter of FAO-Blaney-Criddle method must be different in different places. And when FAO-Blaney-Criddle method is employed to estimate ET0 in the other area, the parameter should be calibrated using the meteorological data in corresponding area.