What is “perched water” and is it an aquifer?

Review of Key Australian Drilling Standards and Water Bore Licensing Requirements (with a Queensland focus)

This review draws primarily on the Minimum Construction Requirements for Water Bores in Australia, 4th Edition(MCR4), which sets out essential guidelines for water bore drilling in Australia. Here, I’ll refer to it simply as MCR4.

Aquifers and the Curious Case of Perched Water

In MCR4, an aquifer is described as a geological formation capable of storing and transmitting water. These can range from uniform geological units to more complex, layered systems. Each state and territory regulator characterizes aquifers, factoring in local conditions for sustainable management.

Now, here’s where it gets interesting: MCR4 includes “Perched Water” in its definitions, describing it as “unconfined groundwater separated from an underlying body of groundwater by an unsaturated zone, supported by an aquitard or aquiclude.” However, the term “Perched Water” appears only in this definition and nowhere else in the publication. This raises a puzzling question for contractors and consultants: should we interpret this as meaning perched water zones are not to be treated as regional aquifers?

This interpretation is crucial. If “perched water” isn’t classified as an aquifer, then we might not be required to apply the usual aquifer protections, nor adhere to the licensing restrictions for multi-aquifer wells.

The Water Bore Driller’s Licensing Handbook (WBDLH23)

Another reference document reviewed was the Water Bore Driller’s Licensing Handbook WSS/2016/3440 Version 1.04(WBDLH23), dated September 2023. This handbook, issued by Queensland’s Department of Regional Development, Manufacturing, and Water, provides guidance on licensing and skills for drillers. In section 18.1, under Class 1 Skills & Knowledge, it mandates that a Class 1 driller must be proficient in “designing bores in single aquifer systems, with an emphasis on sealing out poorer quality waters and surface contamination.”

While it doesn’t mention “perched” water, it’s tempting to think this might be an indirect reference to perched water zones, as Class 1 drillers are guided to focus on single aquifers without cross-contamination.

Licensed Driller Requirements: Onsite Supervision or On-Camper?

WBDLH23 outlines when a licensed driller must be onsite:

“In Queensland, all water bore drilling activities must be undertaken by, or under the constant physical supervision of, an appropriately licensed driller… It is acceptable for the licensed driller to take a break, provided they are on-site and available to provide direction or take over the work.”

This leads to some amusing yet practical questions. Apparently, a licensed driller could technically supervise from a caravan onsite—maybe even taking a nap! But what counts as “on-site”? Is it enough to be in view of the rig, or on the property? Can they camp a little further offsite if they’re just “a call away”? Clarity on these points would help both the drillers and those responsible for compliance.

What to Do with unexpected Aquifers?

Finally, for those unexpected situations, Queensland’s WBDLH23 provides guidance for drillers who unexpectedly encounter a deeper aquifer or an artesian condition beyond their license class. The document states:

“Drillers who drill into an aquifer system for which they are not licensed… must contact the department as soon as practical for instructions on how to proceed…”

It’s reassuring that, as long as drillers act reasonably and promptly reach out to the department, there should be no penalties for unintentional over-drilling.

A Few Thoughts…

The guidelines for water bore drilling are extensive but leave room for interpretation—sometimes enough to leave drillers scratching their heads. With terms like “perched water” making an appearance only in the definitions and requirements for supervision that almost allow for remote supervision, there’s certainly room for more precise wording. These documents are essential for ensuring safe and sustainable bore construction, but perhaps a little clarification would go a long way toward making compliance straightforward for all involved.