Breaking the Technical Barrier for High Spatial Resolution Monitoring: A Novel Approach to Multi-Level Groundwater Monitoring System Development

Multilevel systems (MLS) enable comprehensive monitoring of groundwater distribution and contamination by observing multiple geologic layers in a single borehole, thereby reducing costs and investigation waste. However, the limited adoption of MLS is due to complex design, lack of flexibility, and accessory incompatibility. This study introduces the HKU Multi-Level Groundwater Monitoring System, or HKU System for short, which provides a flexible and cost-effective approach to constructing MLS. The system comprises PVC pipes and key components (e.g., ports, connectors, and holders) that can be produced through 3D printing. The PVC pipes, constituting over 80% of the system’s materials, are readily accessible from local plumbing suppliers, making it the most cost-effective MLS worldwide. A 5-channel HKU System (⌀60 mm) was showcased to explain the system’s structure and functions, but the specific number of channels and sizes are flexible and can be tailor-made to meet different observation needs. Both groundwater sampling and water level monitoring functions were thoroughly examined in the system installed in a river delta with multilayered aquifers and aquitards in the Pearl River Delta, China. The physiochemical properties of the sampled groundwater were consistent with historical records, ensuring sampling robustness. Finally, an advanced HKU System integrating a universal seal is proposed to further simplify MLS development.