基于蓝绿水核算的稻田水资源利用效用评价

为了科学区分和评价稻田蓝、绿水资源利用效用，开展了每日蓝、绿水交互迁移过程的试验观测，基于作物全生育期蓝、绿水资源迁移机制，建立了蓝、绿水分解方法和用水效率评价指标体系，揭示了不同降水条件下的稻田蓝、绿水利用表现。结果显示：试验期2015-2018年稻田水资源收入为1 322.9 mm（蓝水占30.7%），其中572.3、246.0和375.2 mm分别以蒸散发、地表排水和田间渗漏的形式流出。全生育期绿水利用效率（GE）、蓝水利用效率（BE）分别为0.425、0.490，干旱年的利用效率明显高于湿润年。净蓝水生产率（BP）和绿水生产率（GP）分别为4.334与2.301 kg/m³，后者受降水影响不大。相较于本文的结果，不考虑蓝、绿水迁移过程的传统方法得到的BE、GP分别高46.2%和29.7%。忽略蓝、绿水交互迁移过程会高估稻田的灌溉效率，同时也会低估降水在作物生长中的贡献。本研究的方法为作物生产水足迹和农田蓝、绿水资源效用评价提供了新路径。

Water use efficiency evaluation in paddy rice field based on blue and green water accounting

In order to accurately differentiate and evaluate the efficiency of blue and green water use in paddy rice fields, the blue and green water differentiation model and water use efficiency evaluation index system were established based on the daily experimental observation of blue and green water interaction migration process during the whole crop season. Blue and green water use of paddy fields in Nanjing, China under different precipitation conditions were revealed. Results showed that annual field water inflow in 2015-2018 was measured to be 1, 322.9 mm (30.7% blue), 572.3, 246.0, and 375.2 mm of which were discharged in forms of surface drainage, evapotranspiration and leakage. Green (GE) and blue (BE) water efficiency in the whole growth period were calculated as 0.425 and 0.490, respectively, both of which were significantly higher in drought years than in wet years. Net blue (BP) and green (GP) water productivity were 4.334 and 2.301 kg/m³, respectively, and the latter was insignificantly affected by precipitation. BE and GP obtained by conventional method were 46.2% and 29.7% higher than those calculated by the proposed method. Field irrigation efficiency would be overestimated and the contribution of precipitation in crop production would be underrated if the interactive blue and green water migration process was ignored. The method and results of this study can provide a new approach for the evaluation of crop water footprint and agricultural blue and green water use efficiency.