The invisible resource

At the University of New South Wales, we are developing the design of a new satellite. It will have a very unusual capability: it can measure how much moisture is in the first few centimeters of soil. 

When one wishes to account for water resources, the list of assets includes lakes, rivers, streams, reservoirs, and the underground water table. But the additional water to be found in the soils, right at the surface, is a highly significant resource as well. In Australia, for example, a calculation shows that there is as much water in the uppermost layer of Australia’s soils as in all her lakes, rivers and reservoirs. It is also the most crucial to plant life—this is the water that plants actually absorb.

The importance of this invisible resource to the environment cannot be overstated. In addition to the obvious importance to farming, moisture in the soil has many other far-reaching impacts. 

• Soil moisture drives the weather. High moisture in a soil heated by the sun will increase the chance of cloud formation.
• It is a critical factor in determining wind erosion, the source of the huge dust storms that plague Australia and some other nations. Advance warning of dust storm conditions will help protect persons with respiratory conditions.  Knowledge of soil moisture can improve the success of ground cover planting programs for dust mitigation.
• Soil moisture is critical for minimizing water erosion of soils, by watering the plants that stabilize the soils against erosion.
• Knowledge of trends in soil moisture is a key to effective land use planning. Long term changes to soil moisture can force unwanted change; awareness of soil moisture trends can allow for orderly transitions and protect livelihoods. Today, most land use planning maps are static and outdated; real-time knowledge of soil moisture can make advisories more responsive.
• Soil moisture is the key to the health of sensitive ecologies, including wetlands, forests and iconic sites. The effectiveness of water diversion for ecological health and restoration is highly dependent upon the existing soil moisture levels.
• It is critical for broad acre farming and grazing. Soil moisture determines, for instance, how long a grazier may use a particular paddock before having to move her cattle.
• Soil moisture is a key driver for “tipping points” in agricultural settings. If moisture falls below a certain level, a farm may simply crash and be unrecoverable. Only weeds will remain.
• Soil moisture determines the success of carbon storage initiatives. Carbon stored in the root zones is not volatile, so it represents a permanent form of storage. To use this storage technique effectively, water must be conserved in the root zone.

In a subsequent post, I'll discuss why this resource must be measured from space, and what is involved in the process.