| How to objective and quantitative evaluation of irrigation water use efficiency is an important research content of water-saving irrigation. Different scholars had given a number of evaluation indexes. Currently Chinese irrigation engineering specification does not contain water use efficiency and no precise definition as a technical term. Consequently a variety of definition and expression form appears in literature and the practical application,Which are going against intercomparison and causing confusion easily. The properly assessed of irrigation water use efficiency is in urgent need of definite and comparable indicators. This paper calculated water use efficiency under 5 different definitions by DSSAT-CERES-Wheat model simulation. There were farmland total water use efficiency( WUEg), generalized water resources use efficiency(WUEu), crop water productivity(WP),irrigation water use efficiency(WUEi) and real irrigation water use efficiency( WUEti), those are used commonly for irrigation water use efficiency evaluation. The purpose of this article is to quantify the differences, correlation, influence factors and conditions of use of the 5 different water efficiency evaluation indexes. The results of the research have a high value for macroscopic evaluation,decision-making and the proper use of all indicators.The research used Decision Support System for Agrotechnolgy Transfer(DSSAT) CERES-Wheat model constructed irrigated and rainfed winter wheat two scenarios in Xinxiang area of Henan province from 1963 to 2013 and in Huanghuihai area(four typical areas are Tongzhou of Beijing、Shijiangzhung of Hebei Province、Xinxiang of Henan Province and Yanzhou of Shandong Province) from 2003 to2013,results showed that :1. Farmland total water use efficiency and generalized water resources use efficiency, farmland total water use efficiency and crop water productivity, generalized water resources use efficiency and crop water productivity were showing strong positive linear correlation, whose correlation coefficients were greater than 0.8. Farmland total water use efficiency and generalized water resources use efficiency evaluation results agreed well in different sites, the interannual and regional level evaluation.Currently, there is no accepted standard algorithm of effective rainfall. So it was inconvenient to use the generalized water use efficiency. Considering it is recommended to use farmland total water use efficiency and crop water productivity.2. Rainfall of growth period had significant impact on irrigation water use efficiency. Irrigation water use efficiency showed a trend of increase, whereas real irrigation water use efficiency showed a trend of decrease with the increase of rainfall of growth period. The differences between two indexes increased significantly. The use of irrigation water use efficiency was confined to the influence of rainfall, which could not compare with different regions and interannual. Real irrigation water use efficiency had logical definition, represent the total water use efficiency in Huang huaihai area.Acquisition of increased yield in irrigation situation comparison with rainfed is difficult. It is notpractical for irrigation water use efficiency evaluation.3. Pearson’s correlation coefficient(R) were different among variety water use efficiency indices on different site, but in a good positive correlation on regional level. Conclusion was that there were differences among the evaluation results of variety water use efficiency indices on site level and regional level. The evaluation results of WP were the most stable on site level and Farmland total water use efficiency on regional level.4. Farmland total water use efficiency and generalized water resources use efficiency value were close under different hydrological years in the same site. The evaluation results of farmland total water use efficiency and generalized water resources use efficiency had no significant change in different hydrological years. They were consistent among the interannual, site level and regional level. Irrigation water use efficiency decreased gradually with the hydrological year from dry year to wet year. Real irrigation water use efficiency increased gradually with the hydrological year from dry year to wet year.The more different was hydrological of years, the greater differences was in the irrigation water use efficiency. Hydrological year had no significant influence on the total water use efficiency indexes, but had significant influence on the irrigation water use efficiency indexes.5. When irrigation water use coefficient was increased, farmland total water use efficiency and generalized water use efficiency increased significantly. With the improvement of irrigation water use coefficient, differences between the various indicators were decreased, linear relationship between each other tended to be consistent. |
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