Analysis Of Spatial And Temporal Distribution And Influencing Factors Of Irrigation Water Efficiency Evaluation Index In Heilongjiang Province

Water is the basic resource for human survival,and it is also an indispensable natural resource for the development of social and economic development.Heilongjiang province is a big agricultural province,the water use of farmland irrigation ratio accounted for the province's total water consumption is up to 85%.Irrigation water is the main part of agricultural water,the value of utilization efficiency is related to the benefit of food production grain production.Improving the efficiency of irrigation water use is an effective way to alleviate the contradiction between water resources and ensure food security.It is particularly important to evaluate what index is used to evaluate the efficiency of irrigation water.In this study,considering the efficiency of grain absorption and conversion of irrigation water,we selected irrigation water use coefficient and water productivity index respectively to evaluate the efficiency of irrigation water in Heilongjiang province.The main research contents and results are as follows:(1)Taking sampled irrigation districts in Heilongjiang Province as the research object,the temporal trends and spatial distribution of the average irrigation water use coefficient for different scale irrigation areas and the province from 2007 to 2015 were analyzed.Quantitative analysis of factors such as natural climate,engineering conditions,and management levels during the increase of irrigation water use factor was made.The results show that the average irrigation water use coefficient of the province was increasing year by year;from 2007 to 2011,due to the fact that the irrigation districts were in construction period,the irrigation water coefficient of different scales were not stable,and they came to be stable from 2012 to 2015.The irrigation water use coefficient was generally high in the south and eastern,and low in the west and south.(2)In the analysis of spatial variability of irrigation water use coefficient,the fractal theory was applied to the analysis of influencing factors.Horton's water system law was applied to analyze the fractal condition of canal system in irrigation districts and its effect on the irrigation water use coefficient was revealed.The canal system reform schemes for different irrigation districts were proposed.The results showed that the irrigation utilization coefficient of the four levels and three levels irrigation districts first decreased and then increased with the increase of fractal dimension.Among them,there was a positive correlation between the irrigation water use coefficient and the increment of fractal dimension in irrigation districts with area greater than 15 million mu and an area less than 10,000 mu.Contrarily,that in the 1-15 million-mu irrigated areas were relatively negatively correlated.The irrigated districts with less than 50,000 mu of irrigated areas have the greatest potential for improvement.(3)This research calculated the water productivity of rice and grain in Heilongjiang province,and analyzed the temporal and spatial changes.The analysis of the water productivity using rice as the research object indicated the utilization of irrigation water by crops.The grain water productivity could be used as a measure of the amount of irrigation water that can be saved in the regional grain consumption.The results showed that the annual fluctuations of the water productivity of rice and grain crops were large due to the fact that the water productivity determinants included both yield and water use,but the overall trend was upward.From the view of spatial variation,the range and coefficient of variation of rice water productivity and grain water productivity showed a trend of increasing first and then decreasing,and the spatial variation of each indicator value in different cities was different.The overall water productivity of rice was high in the east and west regions,and low in the north and south.The grain water productivity was high in the southwest and central regions and low in the southeast and north regions.(4)Path analysis method was used to analyze the main influencing factors of the spatial differences in water productivity.The LMDI decomposition method was used to derive the decomposition formula of the water productivity variation,and the contribution of climate change and human factors to the change of the water productivity was quantitatively analyzed.The results showed that the average temperature,fertilizer use and irrigation water use coefficient had the greatest impact on grain water productivity.Relative humidity,irrigation water use coefficient and evapotranspiration were the main factors affecting rice water productivity.From 2007 to 2015,the province's grain water productivity increased by 0.166 kg/m~3,and the grain production effect,irrigation engineering effect,irrigation technology effect,and climate change effect were 0.375kg/m~3,-0.372 kg/m~3,0.275 kg/m~3 and 0.110 kg/m~3,respectively.(5)The analysis of the situation of grain production water utilization was based on the water productivity improvement potential indicator and the regionally-saving potential of blue water indicator.Based on the iterative correction principle,comprehensive analysis was made on the irrigation water use coefficient and the water productivity index.The results showed that the comprehensive evaluation model could correct the differences between the results of single method evaluation and make the evaluation results more persuasive.Combined with several evaluation results,the efficiency of irrigation water was highest in Suihua City and lowest in Mudanjiang City during the study period.