New research has led to the development of a model for assessing the best way to install natural barriers for protecting vital groundwater supplies.

Threats to sub-terranean aquifers are one of the major concerns for conservationists and those worried about the long-term environmental impacts of mining and industrial waste. It is also a major concern for people who are opposed to the extraction of underground gas through the injection of chemicals to fracture rocks.

Groundwater sources make up 97 per cent of the Earth’s drinkable water supply, so the need to protect it is obvious. In the effort to maintain clean water supplies for future generations, researchers at The National Centre for Groundwater Research and Training (NCGRT) and University of Technology Sydney (UTS) have developed a model to test the optimal design of ‘store-release covers’ – layers of soil and plants that prevent water from leaking into waste deposits and contaminating the aquifers below.

Building store-release covers is expensive, slow and requires a lot of work, according to team-leader Professor Derek Eamus.

“To build a cover, we have to know what type of soil and plants to use, and how thick the soil layer should be. Also, every site has a different climate, vegetation and soil, so a lot of it is guess work, followed by hundreds of experiments. It can take years and years to optimise the design of a store-release cover.”

To speed up the process the team designed and tested a computer model on three different Australian climates: Perth’s cool, wet winters with hot, dry summers; the monsoonal climate in Darwin; and areas with evenly distributed rainfall across the year in NSW.

“We found that an effective store-release cover has to have enough capacity to store any additional rain that falls in wetter years. The trees have to grow leaves that cover the entire ground, and their roots have to reach the bottom of the soil cover,” Prof. Eamus says, “we don’t want the lower half of the store-release cover to have no roots, because water will gather there and seep through the waste. Also, having more leaves that cover the ground means more water will be used and transpired by the plant.”

“Now we know what makes an effective store-release cover, we can gather the information for these factors, as well as the rainfall average and extremes for any location, to optimise the design of a store-release cover anywhere in the world.”

The study “Design of store-release covers to minimize deep drainage in the mining and waste-disposal industries: results from a modelling analyses based on ecophysiological principles” by Derek Eamus, Isa Yunusa, Daniel Taylor and Rhys Whitley has been published in the journal Hydrological Processes.