Aquifers are being affected by domestic, industrial and agricultural contaminates, such as PFAS and micro plastics finding their way into underground water systems. The need to study how these plumes travel through aquifers is of the utmost importance. Overuse of underground water supplies can lead to a lowering of water tables and eventual depletion of groundwater resources. Monitoring of just these two issues alone is becoming increasingly urgent. Groundwater accounts for over 30% of Australia's total water consumption, highlighting its importance as a vital resource. However, current methods used to characterise aquifers are time-consuming and often produce estimates that are unreliable. Ascertaining the characteristics of underground aquifers with any degree of accuracy has always been a problem. In 2022 the CSIRO and Flinders University approached Kremford Pty. Ltd. to implement their scientific advances in sinusoidal wave testing technology. As a group we developed a set of portable field equipment (the Limax) to measure and estimate in ‘real time’ the transmissivity, hydraulic conductivity and storage coefficients of aquifers using sinusoidal analysis. While not new and used in many devices such as magnetic resonance instruments (MRIs) and auditorium sound analysis, the application of sinusoidal analysis to aquifer characterisation is very new. The field equipment consists of an electronically controlled winch connected by cable to solid rods, or slugs, which are lowered via a tripod positioned above the primary groundwater well. Several slug lengths and diameters are available to suit different well sizes. The winch is controlled by equipment that translates the operator’s chosen wave frequency and amplitude into the matching slug sinusoidal vertical travel. This creates a corresponding sinusoidal pressure wave in the connected aquifer that is monitored and recorded by the Limax equipment. Several adjacent wells connected to the same aquifer can be designated as observation wells and like the primary well, monitored using pressure sensors over the same wireless network. These pressure wave readings are recorded and displayed and aquifer parameters estimated in real-time for reporting and controlled via Wi-Fi on an operator’s laptop computer. The pressure sensors in all wells ‘real-time’ water level measurements over the Wi-Fi network at user-specified sample intervals. Calibrated and auto-scaled graphics update at every sample to display the sensor readings along with the current slug position in a visual indication of how the test is proceeding. Global Navigation Satellite System (GNSS) reception is included and provides accurate time and location details to the test. The recorded water level fluctuations from all wells can serve as inputs to aquifer test analysis software. Because the results to date can be copied to the user’s computer at any time, an on-site analysis can present results in near real-time. Typical results include estimates of aquifer transmissivity, storativity, and other important hydraulic properties. Together these provide an accurate and current picture of the aquifer’s hydraulic characteristics. All parameters that specify the slug travel, its sinusoidal period and test length are easily setup on the operator’s laptop, tablet, or smartphone. A variety of excitation sequences are available including single frequency, multiple frequency, and swept frequency. A quick-look capability allows easy verification of what will happen during the test. The operator has instant visual access to time series plots displaying both the current slug position in the well and the outputs from all sensors. This new Limax technology has potential applications in industry, mining, and agriculture. It is an essential tool for governments needing to monitor the health of our groundwater resources.

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