Modeling evapotranspiration in diverse climatic zones of Pakistan using Surface Energy Balance Algorithm for Land (SEBAL) through geospatial technologies

Evapotranspiration (ET) is a key driver of the hydrological and energy cycles, influences directly the vegetation health, surface temperature regulation and the availability of water. Pakistan is a rapidly urbanized and climate vulnerable country, where, it is crucial to understand ET dynamics for sustainable land and water resource management. Landsat 7, 8 and 9 imageries and meteorological data from the Pakistan Meteorological Department were integrated using the Surface Energy Balance Algorithm for Land (SEBAL) in ERDAS Imagine to estimate actual evapotranspiration (ET). Key parameters, including Land Surface Temperature (LST), Normalized Difference Vegetation Index (NDVI), Albedo, and Net radiation, were derived and incorporated to assess spatiotemporal ET variations across Pakistan’s major climatic zones. The spatiotemporal analysis revealed a consistent rise in LST over the years 1989, 1999, 2009 and 2019, accompanied by a decline in NDVI after 2009, decreasing surface albedo, and fluctuating net radiation, indicating intensified urbanization, surface degradation, and altered energy dynamics across Pakistan’s climatic zones. Estimated ET values ranged from 4.67 to 7.33 mm/day, with a pronounced decline in the very high (6.94–7.33 mm/day), high (6.55–6.93 mm/day), and moderate (6.16–6.54 mm/day) ET zones, alongside a substantial expansion of the low (5.77–6.15 mm/day) and very low (4.67–5.76 mm/day) zones by 2019, highlighting extensive vegetation degradation, accelerated urban expansion, and increasing climatic stress across Pakistan’s diverse landscapes. The findings demonstrate the strong applicability and reliability of the SEBAL model for long-term environmental monitoring in data-scarce regions, highlighting its potential not only to guide sustainable urban development and strengthen climate resilience, but also to support integrated land–water management, inform adaptive policy frameworks, and advance scientific understanding of land–atmosphere interactions in the context of Pakistan’s evolving climatic and urban challenges.