What lies beneath?
Thirty-one soil moisture sensors from Sentek Technologies are being installed as part of the Mulloon Rehydration Initiative’s monitoring program. They are located at Mulloon Creek Natural Farms (Home Farm & Duralla), at Mulloon Farm North and at Palerang and are being paired with approximately half of the 75 previously installed piezometers.
During their installation, the auger being used to drill the holes where the sensors sit have encountered amazing soil profiles. Sometimes as the auger drove down through the soil layers it slowed considerably due to rock, heavy clay, large gravel, water from an aquifer, and even a fine sandy slurry, which we hope to extract using a special tool to remove the slurry as the auger is unable to retrieve it. As a result, a few of the sensor housings are less than the desired 2m depth depending on the subterranean landscapes, with one reaching only 70cm.
Aquifers have also been hit in 10 of the installation sites with some being quite significant, making it difficult to install the bung (plug) at the bottom of the pipe and set it firmly enough to seal the hole as it is hard pushing water back against so much pressure. (See videos below.)
Data from the fully installed sensors will initially be sent to Sentek and then transferred to HydroTerra where it will be stored in the integrated data management system. This data will accessible by the public in due course, via the HydroTerra portal.
The Mulloon Rehydration Initiative is jointly funded through the Mulloon Institute and the Australian Government’s National Landcare Program. The initiative is also assisted by the NSW Government through its Environmental Trust.
Soil profiles
Aquifers
At other times the auger hit a pressurised aquifer which forced water back up the pipe and needed to be pumped out and promptly plugged to prevent further inundation.
Sometimes augers hit aquifers that can be under pressure and force water up into the access tube which then has to be bailed out and promptly plugged to prevent further inundation. Some installations had to be abandoned completely and resituated when rock was encountered too close to the surface.