CALCULATION OF IRRIGATION WATER VOLUME AND EVALUATION OF WATER-SAVING BENEFITS OF FALLOW IN THE NORTH CHINA PLAIN

The North China Plain (NCP) is the main grain-producing region in China, and water shortage is an important factor limiting regional grain production and socioeconomic development. Since 2014, the fallow policy has been implemented in the NCP to reduce winter wheat and expand spring maize planting area. Studying the spatial and temporal distribution of regional evapotranspiration (ET), effective precipitation (PE) and effective irrigation (EI) in combination with crop types can evaluate the water saving benefits of fallow and help the rational allocation of agricultural water. In this paper, spatial calculations and analysis of ET and PE of different crops in the NCP from 2001 to 2016 were conducted based on the 500m spatial distribution rate of PML_V2 remote sensing ET products and precipitation data from meteorological stations, which led to the EI of different time scales in the NCP, and further analyzed the EI of each crop in combination with the planting areas of winter wheat, summer corn and spring corn. The average acreage of water savings under the typical fallow mode of switching from winter wheat-summer corn rotation to spring corn monoculture was compared. The results showed that with the growth of ET of the three crops and the shortage of PE makes the EI show an increasing trend, and the water saving benefit of fallow also shows an increasing trend, with a multi-year average value of 199.3 mm, which provides a scientific basis for evaluating the irrigation water saving benefit of fallow on a regional scale.