Abstract
The surface energy balance algorithm for land (SEBAL) is a commonly used method for estimating evapotranspiration (ET) at a regional scale; however, the cloudy and rainy characteristics of subtropical monsoon regions pose a greater challenge for estimating paddy field ET based on remote sensing technology. To this end, a typical subtropical climate region in southern China (Ganfu Plain irrigation system) was selected as the study area. Subsequently, we evaluated the applicability of the SEBAL model for estimating the ET of paddy fields at the daily scale; derived the interannual variation (2000–2017) characteristics of early, middle, and late rice ET; and finally analyzed the spatial distribution patterns of rice in different hydrological years. The results demonstrated that: (1) the SEBAL model estimated ET accurately on a daily scale, with R2, NSE, and RMSE values of 0.85, 0.81, and 0.84 mm/day, respectively; (2) the ET of paddy fields in the irrigated area was higher in July and August and the interannual trend of ET of early rice was not obvious, with a declining trend observed in middle rice and late rice from 2000 to 2009, which was followed by an increasing trend from 2009 to 2017; and (3) variations in the spatial distribution of ET were significant for early and late rice at different precipitation levels and less obvious for middle rice in wet years but significant in dry years. Overall, this study verified the applicability of the SEBAL model for estimating ET in paddy fields in subtropical regions and provided a basis and reference for the rational allocation of water resources at a regional scale.
Highlights
The total precipitation of late rice was the lowest and ranged from 58.9 mm to 401.2 mm. These results indicate that precipitation is abundant in the early rice growing season and less abundant in the late rice growing season, and the total precipitation in the middle rice growing season is between that of early rice and late rice
The results showed that the bias between the estimated by the model and daily results showed that the bias between the ET estimated by the surface energy balance algorithm for land (SEBAL) model and daily referenceET
The SEBAL model was applied to the subtropical climate region of southern China (GFPIS) to assess its rationality and applicability for daily scale estimates of paddy ET and to analyze the spatial and temporal distribution characteristics of early, middle, and late rice evapotranspiration in the Ganfu Plain irrigation system (GFPIS) in different hydrologic years
Summary
Paddy rice is a dominant staple food that feeds over 50% of the population worldwide. Paddy rice needs a large amount of water to maintain high production. Statistics have shown that paddy field irrigation accounts for 80% of agricultural water consumption in southern China [1]. Evapotranspiration (ET) represents the sum of vegetation transpiration and soil evaporation, which is the major component of farmland water consumption, and it includes the amount of evaporation on the ground surface and plant surface and the amount of transpiration that occurs at the plant surface and inside the plant. ET plays a huge role in hydrological cycles and energy balance systems, and represents a crucial link between ecological and hydrological processes; it is a significant
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