Research On Quantitative Method Of Crop Production Water Footprint Based On Hydrological Process

Water resources are important basic resources to support agricultural production.With the development of our country's social economy,the prosperity of industrial activities and the improvement of people's living standards,the demand for water resources is continuously increasing.At the same time,with the implementation of the most stringent water resources management system,the scale of agricultural water was compressed.Therefore,it is vital to improve the efficiency of agricultural water for easing the pressure for water demand.Unquestionably,the scientific and rational evaluation of agricultural water use process is the prerequisite to improve the management level of agricultural water resources and agricultural water efficiency.Water footprint,as a comprehensive index for evaluating water efficiency,can evaluate the type,quantity,efficiency and environmental impact of agricultural water,which can help improve the evaluation and management level of agricultural water.At present,the lack of analysis of the whole process of agricultural water use in the quantification of crop water footprint cannot reflect the hydrological process of agricultural water use in the"diversion-conveyance-irrigation-drainage"link.In this study,based on the water footprint theory,the method of water footprint quantification involving the hydrological process of irrigation area was established with the analysis of the characteristics of the water process of agricultural production.Taking Hetao irrigation district as an example,this method was used to analyze the components and spatial distribution characteristics of water footprint and blue,green and grey water footprint of the crops.The results obtained in this study are as follows:1.The method of water footprint quantification based on distributed hydrological model was established.This study overcame the deficiency of current water footprint quantification method in crop production.In the analysis of water resource utilization in crop production process,the water consumption and loss of irrigation water in the field of"diversion-conveyance-irrigation-drainage"was quantified.Furthermore,the form(liquid water that forms the biological water,evapotranspiration of the plant,and the water that is not returned to the original basin),period(crop growth and non-growth periods),and space(the space extended by field and irrigation system.)of water consumption in the water footprint of crop production were clarified.Based on this water footprint quantification method in crop production,the water footprint quantization method based on hydrological process was proposed from the perspective of regional hydrological cycle to analyze the water consumption of crops.This method considers the water consumption in crop production process such as irrigation water losses in canal and filed,irrigation water consumption in field,green water consumption,and groundwater consumption.Therefore,the water resources utilization of regional crops can be fully reflected.2.The composition and influencing factors of crop blue and green water consumption,and the spatial variation characteristics of the crops produce water footprint and blue and green water footprint in Hetao irrigation district were clarified.The blue and green water consumption in the three crops of spring wheat,corn and sunflower were analyzed by constructing the hydrological model in Hetao irrigation district with established the method for quantifying water footprint of crops.The results showed that the factors that affected the blue water and green water consumption of crops mainly included the characteristics of crops,the climatic conditions of the region and the condition of the canal system.In Hetao irrigation district,the main consumption way of blue water was drainage loss,field evapotranspiration in irrigation water and drainage in the field,and the drainage loss and the field evapotranspiration of irrigation water were accounted for 47.9%and 41.8%of the blue water consumption respectively.The green water is restricted by the natural environmental conditions of the irrigated area,and it has little consumption and is related to the precipitation of the crop.The blue water footprints of the three crops were 1233-2714 m~3/t,820-1588 m~3/t and 1765-4317 m~3/t respectively;and the green water footprints of three crops were 132-197 m~3/t,119-186 m~3/t and 325-538 m~3/t.The green water footprint of the crops was small,and the blue water footprint of the crops was 86%of the water footprint of the crops.The water footprints of the three crops were 1380-2888 m~3/t,942-1774 m~3/t and 2095-4855m~3/t.The blue and green water consumption of the three crops were sunflower>wheat>corn.In spatial distribution,water consumption showed spatial differences in irrigated areas.The eastern part of the irrigated area far from the irrigated area was higher than that in the west,and the south was higher than the north.The highest green water consumption of wheat was in Wuyuan County,while maize and sunflowers were located in the front of the Wulateqianqi County.3.The water footprint and its spatial distribution characteristics of Hetao irrigation districts caused by different pollutants were quantified and evaluated.This study improved the calculation method of water footprint of crop water footprint.The migration and transformation of nitrogen and phosphorus in the field was simulated by SWAT model and the discharge of pollutants was calculated based on the maximum concentration of the local environmental water quality standard;furthermore,combined with crop yield,grey water footprint of crop production was calculated.The results showed that there were significant differences in the spatial distribution of gray water footprint of crop production,and it was influenced by pollutant type,water quality standard and water quality standard of different water bodies.Under the three concentration standards,the water footprints of the crops were also different.The spatial variation of grey water footprint of the three crops was higher than that in the western part of the irrigated area and the lowest in the central area.Based on the agricultural water use process and water footprint theory,this study established the method for quantifying water footprint of crops based on hydrological process.Taking Hetao irrigation district as the research object,this study analyzed the crop production blue,green water consumption and pollutant discharge load in irrigated area;and discussed the spatial variation of water footprint and blue,green and grey water footprint of crop production and its influencing factors.Therefore,this study can provide references for regional water resources management and provide theoretical support for the implementation of the strictest water resource management system in the region.