Assessing the Long-Term Changes in Potential Evapotranspiration and Its Impact on Agriculture in Lahaul and Spiti, Himachal Pradesh

Long-term variations in Potential Evapotranspiration (PET) are important for evaluating climate changes that affect agriculture in sensitive high-altitude regions. This study examined PET temporal trends from 1951 to 2022 and assessed the agricultural implications for the cold desert district of Lahaul and Spiti in the Indian State of Himachal Pradesh. Monthly PET data were obtained from the CRU TS v4.07 dataset and computed using the FAO Penman Monteith method. Non-parametric statistical tests used to detect seasonal and annual trends were the Mann-Kendall (MK) test, the Modified Mann-Kendall (m-MK) test, and the Innovative Trend Analysis method. Increases and decreases across all seasons were statistically significant, with the strongest negative trend observed during the agricultural season (April–October), with MK Z-values ranging from –6.47 to –2.92 and m-MK values from –12.16 to –2.14. The annual PET declined at a rate of –0.0030 mm/year at Grid Point 1 (Z = –7.04). These results suggest that declining atmospheric moisture demand may reduce crop irrigation requirements. However, changes in evapotranspiration, cropping intensity, and protected cultivation systems might also increase disease susceptibility. The study stresses the need to plan adaptive water and crop management strategies that align with the changing PET scenario.