Abstract
Irrigation of agricultural land is the main water consumer in the arid and semiarid regions. The accurate time series of daily evapotranspiration (ET) at the field scale is crucial for irrigation water management. Here, we presented an integrated approach to field-scale ET mapping by combing METRIC (Mapping Evapotranspiration at High Resolution with Internalized Calibration) with trapezoidal framework of vegetation fraction and land surface temperature (fv-Trad). This approach fed with Chinese satellite HJ-1 (environmental and disaster monitoring and forecasting with a small satellite constellation) images was used to map daily ET over the desert-oasis irrigation fields in the middle of the Heihe River Basin, Northwest China. The results showed that time series of daily ET derived from HJ-1 were well consistent with the in situ measurements (coefficient of determination (R2) of 0.95, root mean square error (RMSE) of 0.31 mmd–1, mean absolute percentage error (MAPE) of 12.0% at Daman station; R2 of 0.89, RMSE of 0.16 mmd–1, and MAPE of 13.2% at Huazhaizi station). The rapid variation of ET could be precisely captured by HJ-1, especially when rainfall or irrigation events occurred between successive acquisitions of satellite data. Meanwhile, the spatiotemporal variation of monthly ET is closely related to crop growth. Daily ET at field scale will support a variety of local interests in water use and irrigation management for both planning and regulatory purposes.
Highlights
Agriculture heavily relies on irrigation of water drawn from rives or aquifer in arid and semiarid areas
A method combing METRIC with fc-Trad space fed with HJ-1 data was used to convert satellites-retrieved ET on clear days into continuous time series daily ET
This study mapped continuous daily ET distribution in a representative area in the oasis of the Heihe River Basin (HRB) using the METRIC model and 36 HJ-1 images acquired during the growing season of 2012
Summary
Agriculture heavily relies on irrigation of water drawn from rives or aquifer in arid and semiarid areas. Water consumption increases due to booming socio-economy and fast-growing population, which will further deteriorate the water resource status in China [1]. Evapotranspiration (ET), the total amount of land surface evaporation and plant transpiration, is the most active process in the terrestrial hydrological cycle and the major component of energy and water balance in agricultural system. In the north of China, agricultural water consumption accounts for about 70% of total water consumption, and more than 90% of agricultural water is consumed via ET [2]. It is necessary to determine the accurate spatiotemporal ET in irrigated fields for recognizing the crop consumption patterns, evaluating water use efficiency and optimizing irrigation scheduling, especially in the semi-arid and arid areas
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