Assessing evapotranspiration and agricultural droughts at high spatiotemporal scales using metric method in western Thailand | |
| Author | Rijal, Kaushal |
| Call Number | AIT Thesis no.WM-23-11 |
| Subject(s) | Evapotranspiration--Thailand, Western--Measurement Droughts--Thailand, Western Water-supply--Thailand, Western--Management |
| Note | A thesis submitted in partial fulfillment of the requirements for the degree of Master of Science in Water Engineering and Management |
| Publisher | Asian Institute of Technology |
| Abstract | Accurate evapotranspiration estimation is crucial for assessing water availability, irrigation planning, and evaluating climate change impacts on hydrological systems. This study utilizes the METRIC method, a remote-sensing-based approach employing satellite images to estimate daily-scale ET at a high spatial level. The research focuses on Western Thailand provinces from 2016 to 2019, aiming to estimate ET, validate results with MODIS, and assess agricultural drought risk in the region. ET variations were analyzed across different land cover types and agricultural fields, with rice fields exhibiting the highest average monthly ET (191.27 mm/month) and maize fields showing the lowest (64.81 mm/month). Validation of METRIC ET using MODIS data showed satisfactory model performance, with root mean square error (RMSE) ranging from 0.9 mm/day to 1.64 mm/day for 8-day ET values. The model's accuracy was affected during periods with fewer images, particularly during the monsoon season. The ET from METRIC was also utilized for agricultural drought calculation in the study area, with higher drought occurrences observed in 2016 and 2019 compared to 2017 and 2018. Drought severity was influenced by the seasons, with less drought during the monsoon and cool seasons, while the dry season months (March, April, and May) faced mild to severe drought conditions due to high temperatures and increased ET. The highest area affected by drought events occurred in April 2016 (15454.08 m²) and April 2019 (12556.95 m²). The central cropland region faced frequent drought events, with 30.21% of the total area facing severe drought, of which 8.73% were forests and 3.97% were croplands. Out of the total area, no portion faced extreme drought, and 40.14% experienced severe drought. The study area experienced less to no drought intensity, while the western border regions faced moderate to mild droughts (2.03%), with no occurrence of extreme drought events in terms of drought intensity. The ETDI values for representative crop fields were analyzed, indicating that crops faced water-stressed conditions during their growing stages. Rice and cassava crops experienced severe drought scenarios due to insufficient water supply, while sugarcane endured a prolonged but mild drought condition. The application of the METRIC method offers significant advantages in crop water management, enabling daily or weekly study of crop water stress and agricultural drought. This method aids in identifying water-stressed crops and providing real-time evapotranspiration maps. |
| Year | 2023 |
| Type | Thesis |
| School | School of Engineering and Technology |
| Department | Department of Civil and Infrastucture Engineering (DCIE) |
| Academic Program/FoS | Water Engineering and Management (WM) |
| Chairperson(s) | Shanmugam, Mohana Sundaram; |
| Examination Committee(s) | Babel, Mukand Singh;Shrestha, Sangam;Sarawut Ninsawat; |
| Scholarship Donor(s) | AIT Scholarships; |
| Degree | Thesis (M. Sc.) - Asian Institute of Technology, 2023 |