Doi Chiang Dao in northern Thailand does something most people never notice when they look at it.
Its forests, soil, and limestone terrain work together to soak up water and release it slowly, acting almost like a giant natural sponge.
According to UNESCO’s 2026 study of the Mae Ka sub-watershed, the area functions like a “natural sponge,” absorbing moisture from rainfall and the air and slowly releasing water to surrounding ecosystems and communities.
Researchers studying the area found that the landscape can hold onto both rainwater and moisture from the air, keeping water flowing through the region even as conditions get drier.
This "sponge" effect isn't down to one single feature, it comes from the limestone, soil, and forest cover all working together.
It Starts With Limestone
Doi Chiang Dao is part of a huge limestone landscape in northern Thailand.
The biosphere reserve covers around 85,909 hectares and sits within the Upper Ping River Basin. Its steep karst terrain contains limestone ridges, sinkholes, caves and underground waterways.
When rain falls, water doesn’t run downhill and disappear.
The area’s limestone formations allow water to rapidly infiltrate underground, feeding caves, springs and underground streams. UNESCO notes that these waterways eventually contribute to the Ping River system.
The result is a landscape that can move and store water both above and below the ground.
The Soil Is Part of the System
UNESCO’s recent study collected and analysed soil samples from the Mae Ka sub-watershed to understand how much water the soil can hold and how that changes between seasons.
The results found that the soils have strong water retention capacity and help maintain relatively stable water flow even during periods of drought. UNESCO therefore describes the Mae Ka sub-basin as functioning like a natural reservoir, helping protect both ecosystems and local livelihoods.
In simple terms, rainfall can be captured by the landscape instead of immediately running away. Some of that water remains in the soil and underground systems, then gradually makes its way back into streams and vegetation.
That’s what gives the area its sponge like behaviour.
A Mountain That Helps People Too
Communities around Doi Chiang Dao depend on the Mae Ka stream for domestic water, while agriculture is an important part of the local economy. UNESCO says the reserve’s water systems support both ecosystems and nearby communities.
The wider biosphere reserve is also home to more than 2,000 plant species, around one-fifth of Thailand’s recorded flora, alongside forests, wetlands and numerous caves.
That means the ability to retain and regulate water affects far more than drinking supplies. It helps sustain forests, plants, wildlife and agriculture across the landscape.
What Happens During a Drought?
This is where the sponge analogy becomes particularly useful.
A normal watershed can lose water quickly after heavy rainfall. But a landscape that retains some of that water can continue releasing it after the rain stops.
UNESCO’s findings indicate that the Mae Ka sub-basin can maintain stable flow even during drought periods, demonstrating why the area’s soil and geological systems are important for water resilience.
It doesn’t mean Doi Chiang Dao can create water out of nowhere or prevent droughts. Instead, its natural systems help slow down the movement of water through the landscape.
A Natural System Under Pressure
The system is also vulnerable.
UNESCO says the Mae Ka watershed is increasingly exposed to climate change, making better understanding of its soil and hydrological behaviour increasingly important.
The ongoing monitoring programme is intended to provide data that can improve watershed management, biodiversity conservation and climate adaptation.
That makes Doi Chiang Dao more than a scenic mountain.
Its forests, soil and limestone formations form a connected water system that quietly stores rainfall, feeds streams and supports people living around it.
The interesting thing is, nobody had to engineer the sponge, the landscape was already doing the job.
