Evaluation of remote sensing‐based evapotranspiration estimates using a water transfer numerical simulation under different vegetation conditions in an arid area

Abstract

Daily actual evapotranspiration (AET) and seasonal AET values are of great practical importance in the management of regional water resources and hydrological modelling. Remotely sensed AET models and Landsat satellite images have been used widely in producing AET estimates at the field scale. However, the lack of validation at a high spatial frequency under different soil water conditions and vegetation coverages limits their operational applications. To assess the accuracies of remote sensing‐based AET in an oasis‐desert region, a total of 59 local‐scale daily AET time series, simulated using HYDRUS‐1D calibrated with soil moisture profiles, were used as ground truth values. Of 59 sampling sites, 31 sites were located in the oasis subarea and 28 sites were located in the desert subarea. Additionally, the locally validated mapping evapotranspiration at high resolution with internalized calibration surface energy balance model was employed to estimate instantaneous AET values in the area containing all 59 of the sampling sites using seven Landsat subimages acquired from June 5 to August 24 in 2011. Daily AET was obtained using extrapolation and interpolation methods with the instantaneous AET maps. Compared against HYDRUS‐1D, the remote sensing‐based method produced reasonably similar daily AET values for the oasis sites, while no correlation was observed for daily AET estimated using these two methods for the desert sites. Nevertheless, a reasonable monthly AET could be estimated. The correlation analysis between HYDRUS‐1D‐simulated and remote sensing‐estimated monthly AET values showed relative root‐mean‐square error values of 15.1%, 12.1%, and 12.3% for June, July, and August, respectively. The root mean square error of the summer AET was 10.0%. Overall, remotely sensed models can provide reasonable monthly and seasonal AET estimates based on periodic snapshots from Landsat images in this arid oasis‐desert region.

Using bromide data tracer and HYDRUS‐1D to estimate groundwater recharge and evapotranspiration under film‐mulched drip irrigation in an arid Inland Basin, Northwest China

“…Long‐term data about climate data, irrigation practices and soil hydraulic parameters or series of hydrological data are essential for variably saturated flow modelling and calibration (Flint et al, 2002; Lu et al, 2010; Wang et al, 2014). However, these long‐term series are difficult and costly to collect at regional scales (Lian et al, 2018; Lu et al, 2010). In addition to this data limitation, inference of GR and ET at this scale faces difficulties related to obtaining appropriate upscaled soil hydraulic parameters.…”

Spatial and Temporal Evolution Characteristics of Water Conservation in the Three-Rivers Headwater Region and the Driving Factors over the Past 30 Years

“…Vegetation dynamics affect the regional WC through their influence on rainfall-runoff capacity [39] and evapotranspiration [40]. Thus, considering the impact of vegetation dynamics is crucial in quantifying WC services.…”

Impacts of Introducing Remote Sensing Soil Moisture in Calibrating a Distributed Hydrological Model for Streamflow Simulation

“…Several recent researches have turned to soil moisture, evapotranspiration and other hydrological variables as a complement for parameter calibration [5][6][7][8][9][10][11][12][13][14]. Among different surface/subsurface components, soil moisture plays a significant role in the energy and water balance of the hydrologic cycle [15][16][17][18].…”