Temporal and spatial variations of evapotranspiration for spring wheat in the Shiyang river basin in northwest China |
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| Authors: | Ling Tong Shaozhong Kang Lu Zhang |
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| Institution: | 1. Key Laboratory of Agricultural Soil and Water Engineering in Arid and Semiarid Areas of Ministry of Education, Northwest A & F University, Yangling, Shaanxi 712100, China;2. Center for Agricultural Water Research in China, China Agricultural University, East Campus, Beijing 100083, China;3. CSIRO Land and Water, Christian Laboratory, GPO Box 1666, Canberra, ACT 2601, Australia |
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| Abstract: | The methods for estimating temporal and spatial variation of crop evapotranspiration are useful tools for irrigation scheduling and regional water allocation. The purpose of this study was to develop a method for mapping spatial distribution of crop evapotranspiration and analyze the temporal and spatial variation of spring wheat evapotranspiration in the Shiyang river basin in Northwest China in the last 50 years. DEM-based methods were employed to estimate the spatial distribution of spring wheat evapotranspiration (ETc). Reference crop evapotranspiration (ET0) was calculated with the Penman–Monteith equation using meteorological data measured from eight stations in the basin. Crop coefficient (Kc) was determined from measured evapotranspiration in spring wheat season in the region. The results showed that ETc gradually increased in the upper reaches of the basin in the last 50 years, while the middle reaches showed a significant decreasing trend, and in other regions, no significant trend was found. These changes can be attributed to expansion of irrigation areas and climate change. The multiple regression analysis between ETc and altitude, latitude, and aspect were carried out for eight weather stations and the relationships were used to map ETc for the basin. The spatial variations of ETc were analyzed for three typical growing seasons based their precipitation. Results showed that long-term average ETc over cultivated land was increasing from 270 mm in southwest mountainous area to 591 mm in northeast oasis of the basin, and the relative error between the estimated ETc in spring wheat growing season by reference evapotranspiration (ET0) and crop coefficient (Kc), and the interpolated ETc was within 11.1%. |
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| Keywords: | Evapotranspiration Digital elevation model Geographical information system Temporal and spatial variation Shiyang river basin |
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