Feedback from Human-Natural Land Processes to Indian Monsoon

Abstract:

Increased human intervention in the water cycle of South Asia in the recent period resulted in conversion of the natural system into a human-natural system. Irrigation is one of the major human activities, specifically in agriculture dependant countries like India. In India, the irrigation system is mostly unmonitored and uncontrolled resulting in huge wastage of water. Feedback from such agricultural practices to the Indian monsoon has not been explored extensively in the literature. This attributes to (a) lack of understanding of land-atmosphere feedback in large scale monsoon processes; (b) inaccuracy in the representation of the agricultural season in South Asia, and; (c) limitations in the representation of irrigation and cultivation practices. Majority of the climate models consider the agricultural season to be in the pre-monsoon summer season, which is not the case in reality. In addition, typical irrigation modules used in the models implement controlled irrigation based on soil moisture deficit different from the practices in India, and do not represent the flooded paddy fields in Northern India which account for about 50% of the total crop area. Considering the limitations of state-of-the-art models for Indian scenarios, we developed India specific irrigation modules with representation of paddy fields for the coupled Weather Research and Forecasting- Community Land Model. We find that uncontrolled irrigation shifts the rain band towards North-West Indian sub-continent during the late season and increases the intensity of widespread extreme precipitation over South Asia. Our results not only highlight the feedback from irrigation, but also the potential of changing water management practices over land to perturb large scale Indian summer monsoon precipitation system. This calls for the need to carefully consider the Indian agricultural system in the widely used land-atmosphere models for understanding irrigation feedback to the atmosphere.