Estimation of evapotranspiration and water productivity using surface energy balance on selected irrigated rice areas of Isabela, Philippines
2024
Felipe, A.J.B.
The estimation of evapotranspiration (ET) and water productivity (WP) is crucial for effective water resource management. WP is defined in this study as a ratio of the highest aboveground biomass production (AGBP) to total actual ET (ETa). This study used the Python-based Surface Energy Balance Algorithm for Land (PySEBAL) model to quantitatively assess ET and WP over the NIA Magat River Integrated Irrigation System (MARIIS) Division 4 service areas during dry (DS) and wet (WS) cropping seasons from 2015 to 2023. The PySEBAL model was initially evaluated using eddy covariance data which produced reliable estimates of actual evapotranspiration (ETa) with an R sq of 0.68, NRSME of 0.28, MRE of 0.2, and KGE of 0.67. The model estimated a higher average ETa during WS (5.54 mm/day) compared to DS (4.23 mm/day). On the other hand, higher aboveground biomass production (AGBP) was observed during DS (3851.6 kg/ha) compared to WS (3509.16 kg/ha). Higher WP was also estimated during the DS (0.62 kg/m cu) compared to WS (0.42 kg/m cu). Spatial analysis indicates that areas near the boundary line and built-up areas have lower ETa values, while areas near main and lateral canals have higher ETa values. The distribution of AGBP corresponds with the general cropping calendar in the study area, with higher values observed near the upstream canal areas. Water productivity (WP) varies across the area and shows clear patterns, with lower values observed in areas near the upstream sections of the canal. The results of the study are valuable for management operations and in promoting water productivity and effective water utilization.
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