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The small water cycle – how rehydrating landscapes makes it rain.

Australia’s agricultural soils today have approximately 50% less water holding capacity than before the arrival of Europeans.

There are multiple ways to fix this problem. For example, we can increase water retention in our soils (involving increased vegetation cover and improved soil health), and we can increase precipitation.

At Mulloon Institute, we apply strategies that increase water retention in our soils which allows plants to thrive – that’s half the problem solved – but how do we increase precipitation?

The small water cycle – what is it?

Mulloon Institute has recently published a series of excellent videos on this issue on this and related topics – VIEW HERE.  

The small water cycle is the process where water evaporates, condenses, and precipitates locally, without traveling long distances. Precipitation includes rainfall, dews, and fogs. In natural, healthy ecosystems including well-managed grasslands, precipitation is captured by vegetation and absorbed into the soil. Plants transpire water vapor back into the atmosphere, which contributes to higher humidity, cooler temperatures, and cloud formation, which can lead to more precipitation in the same area. When this water enters rivers or oceans, it becomes part of the vast, global water cycle that moves water around the entire planet (the “large water cycle”).

Globally, more than 65% of precipitation originates from the land itself, mostly from transpiring plants (small water cycle) rather than oceans (large water cycle). Rehydrating landscapes—that is, restoring their natural ability to retain and cycle water—can reinvigorate the small water cycle, and potentially lead to more consistent and abundant local rainfall.

The small water cycle is highly dependent on vegetative cover, soil moisture, and local topography. When these elements are disrupted—through tree removal or traditional agriculture—the cycle is weakened or even broken.

Traditional farming land use practices can disrupt the land’s natural sponge-like behaviour. When trees are cleared and soils are compacted or stripped of organic matter, the land loses its ability to absorb and retain water. Instead of slowly infiltrating into the ground and replenishing groundwater, rainwater runs off quickly, causing erosion and flooding. This runoff typically carries valuable topsoil, nutrients, and pollutants into rivers and oceans, removing water from the local ecosystem.

As the land dries out, plants struggle to survive, leading to even less transpiration and even less precipitation—a feedback loop that accelerates soil dehydration. Across the world, including in Australia, human intervention has turned fertile, moisture-rich ecosystems into dry, brittle landscapes more prone to droughts, heatwaves, and dust storms.

By prioritising landscape rehydration, we can restore degraded ecosystems, create microclimates that attract and retain rainfall, and build long-term resilience against drought and climate change.

How to rehydrate land

There are various techniques for landscape rehydration including:

  • Planting trees – trees play a central role in the small water cycle. They not only shade and cool the land but also pull water from the soil and release it through transpiration. Integrating trees into agricultural land (agroforestry) increases local humidity and promotes rainfall.
  • Soil regeneration – healthy soil acts like a sponge. Practices such as cover cropping, composting, reduced tillage, and managed grazing help build organic matter, which improves water retention and reduces runoff.
  • Floodplain restoration – floodplains are natural water storage systems. Restoring floodplains slows water movement across the landscape, allowing it to seep into the ground and support plant life.
  • Water retention landscaping (also known as natural infrastructure) – swales, terraces, leaky weirs and other earthworks are used to slow, spread, and sink water into the soil. These simple structures can dramatically improve infiltration in hilly or degraded land.
  • Reconnecting floodplains – allowing rivers to overflow into their natural floodplains during rainy seasons helps recharge groundwater, capture silt and nutrients, reduce erosion, and support biodiversity.

The work of Mulloon Institute utilises all these techniques.

Small water cycle – climate change mitigation

The small water cycle isn’t just a tool for local resilience—it’s also a climate change mitigation strategy.

When landscapes are well hydrated they have a high green leave surface area, they capture CO2, store more carbon (in both soil and biomass), and can moderate extreme temperatures. Conversely, dry, exposed soils and deforested land absorbs heat and on balance release more CO₂ than is captured, exacerbating global warming.

Paradigm Shift in Water and Climate Thinking

The small water cycle is both vital and overlooked.

For decades, mainstream climate and water management strategies have focused on large-scale infrastructure, such as dams and irrigation systems. While these tools have their place, they often overlook the profound role of local ecological processes. What if, instead of spending billions on new dams or maintaining dam infrastructure, we spent this money (or less money) retaining and cycling water in our landscapes with all the significant biodiversity and agricultural co-benefits this brings? Isn’t this a smarter spend of community resources?

Mulloon Institute and the small water cycle

Through our learning and research functions we are teaching our communities about the Small Water Cycle. When you have time, have a look at this great work:

What a privilege it is being involved with the scientists, planners and educators of the Mulloon Institute.

Matt Egerton-Warburton
Chair, Mulloon Institute & Chair, Mulloon Law Committee

 

Photo ©Freepik.