Long-Term Trends in Monthly Potential Evapotranspiration across Maharashtra in India during 1991–2020

Abstract

Long-term spatio-temporal trends in potential evapotranspiration were evaluated across Maharashtra by converting long-time daily temperature data into monthly mean temperature. Monthly mean temperature was used for computation of monthly PET by Thornthwaite method. The results revealed a spatially heterogeneous pattern of monthly PET trends. Significant positive trends were observed during February, April, May, October, November, and December in most zones, with May, October and November PET increasing with a slope of (0.031, 0.014 and 0.011). In contrast, January (Z = –0.085) and June (Z = –0.016) months recorded decreasing trend of PET along with reducing slope (-0.002 and -0.001, respectively). At the annual scale, Sub mountain transition zone, western ghat and both Koonkan coastal zones exhibited year round increasing evaporative demand whereas the Central Maharashtra Plateau and parts of Vidarbha exhibited declining or weakly positive trends. The trend analysis reveals a clear and statistically significant increase in potential evapotranspiration across most agro-climatic zones of Maharashtra during 1991–2020, particularly during pre-monsoon and post-monsoon months. This indicates intensifying atmospheric water demand under changing climatic conditions, posing serious challenges for water resource management and agricultural sustainability in the state. This study enhances understanding of spatial–temporal PET variability under changing climate, supporting improved irrigation scheduling and sustainable agro-climatic water and agricultural planning.