Temp-Spatial Heterogeneity of Water Recharge and Its Stable Mechanisms of the Mountainous Rice Terraces in East Asia Monsoon Region

The paddy field water recharge system and the mechanism of its stability are key scientific issues related to reducing the threat to global food security and enhancing the well-being of humans. In this study, we sampled the field water, precipitation, and groundwater in the Hani terrace areas and measured the values of hydrogen and oxygen stable isotopes. The results indicated that precipitation and groundwater were the main sources of terrace water recharge in the Hani terrace area. Spatially, the terrace areas were divided into rain-fed terraces, which were mainly recharged by precipitation, and spring-fed terraces, where groundwater was the primary source of recharge. Temporally, there were two different recharge periods: the rain-fed season (>70% recharge from precipitation) and the spring-fed season (>30% recharge from groundwater). The temporally alternating recharge periods of the spring-fed and rain-fed seasons and the interconnected spatial distribution of rain-fed and spring-fed types were essential to maintain stable water sources in the Hani terraces. Meanwhile, the spatial heterogeneity of groundwater recharge and the timing of agricultural cultivation adjusted the system to some extent. Rice cultivation will be sustainable if the changes in monsoonal precipitation due to global climate change align with the anthropogenic agricultural cultivation cycle, including land preparation, planting, growing, and harvesting. This is the key reason that the mountainous rice cultivation systems of the Hani terraces have lasted for thousands of years under the influence of the East Asian monsoon.