A four-part ecological engine
The Honghe Hani Rice Terraces are an ancient and exceptionally resilient agricultural system, operating continuously for at least 1,300 years. Located on the southern slopes of the Ailao Mountains, the terraces cascade down towards the Hong River, with some slopes containing as many as 3,000 distinct levels. The entire 16,603-hectare area functions as a balanced, gravity-fed hydrological network. This system is built on an integrated, four-part structure of forests, villages, terraces, and the river.
At the highest elevations, from roughly 2,000 to 2,900 meters, are conserved mountaintop forests. These forests act as a natural reservoir, capturing and storing vast amounts of rainfall from the region's subtropical monsoon climate. Just below the forests, between 1,400 and 2,000 meters, the Hani people built their 82 villages. The villages are located to intercept spring water released from the forest catchment. A complex system of channels and ditches then guides this water, along with runoff from the villages, down to the terraces below. The terraces themselves are the center of the system, retaining water and soil. Finally, any runoff drains into the Hong River at the bottom of the valley, where water evaporates, rises, and returns to the mountain forests as clouds and rain, completing the cycle.
Harvesting water from the sky
The design of the Hani system is its ability to harvest moisture directly from the air. The Ailao Mountains intercept warm, moist air from the south, leading to extremely high rainfall of around 1,400 mm annually. This moisture also manifests as a dense fog that blankets the upper elevations. The treetop canopies of the conserved forests function as a massive fog catcher.
As wind drives fog through the leaves and branches, microscopic water droplets collect on the surfaces. This process, known as fog interception, allows the trees to strip significant amounts of water from the air that would not have fallen as rain. These captured droplets coalesce and drip to the ground, recharging the soil and the sandstone aquifers beneath. This stored water is then released slowly into the springs and channels that feed the 392 branch ditches of the irrigation network. This unique water source is so reliable that the vast agricultural system operates without any large, constructed reservoirs. The entire area is a machine that effectively drinks from the clouds.