Impacts and biophysical mechanisms of agricultural water saving on land surface temperature in Northwest China

Abstract

Precise agricultural water regulation and the development of high-efficiency water-saving technologies are crucial for addressing water scarcity in arid and semi-arid regions. However, few studies have investigated the climatic effects and underlying biophysical mechanisms of such large-scale land management practices. In this study, we investigated the impact of large-scale agricultural water saving (AWS) on land surface temperature based on a modified ESM and used an attribution method based on the energy balance equation to analyze the contributions of various biophysical factors. Results indicate that during 1992–2018, the substantial reduction in irrigation water use per unit area has led to decreased latent heat flux and increased sensible heat flux over irrigated croplands. This weakened the evaporative cooling effect previously associated with high-volume irrigation, consequently elevating land surface temperature by approximately 0.2°C on average across the region. Simultaneously, it reduced near-surface air humidity by up to 5 %, mitigating the local warming and moistening trends. Using the derived attribution framework, we quantitatively assessed the relative contributions of different driving factors to this warming effect. The results reveal that the altered distribution of available energy (changed in Bowen ratio, β) within the land surface processes was the primary driver of the increased land surface temperature (+0.25°C). This study demonstrates that with the adoption of more efficient irrigation methods and regional water regulation, the impact of this human management measure on regional climate requires a more scientific assessment to better address the threats and challenges posed by climate change.