HKU-DHS

Introducing the HKU Depthwise HydrogeoSystem (HKU-DHS)

A Game-Changer in Groundwater Science

In the ever-evolving field of geology, the study of groundwater has long been hampered by a lack of high-resolution data. Now, a new technology developed at the University of Hong Kong (HKU) is set to transform how we monitor and understand this vital resource. The HKU Depthwise HydrogeoSystem (HKU-DHS) offers a suite of low-cost, high-resolution monitoring tools that are changing the game for groundwater investigations worldwide. In this article, we explore the features and benefits of this innovative system and how it is democratizing access to advanced groundwater data.

Background: The need for High-Resolution Groundwater Data

Groundwater is a crucial but often overlooked resource. Its study has traditionally been limited by the high cost and complexity of monitoring systems, leading to a sparse data problem. Conventional monitoring methods, relying on single-depth wells, fail to capture the intricate details of groundwater flow and contamination, which can vary significantly over short vertical distances. This data deficiency hinders our ability to manage groundwater resources effectively and respond to environmental challenges such as aquifer depletion, saltwater intrusion, and agricultural pollution.

The HKU-DHS Solution: A Suite of Innovative Technologies

The HKU-DHS initiative addresses this challenge with a set of eight cutting-edge technologies designed for multi-depth monitoring in diverse hydrogeological settings. These systems leverage 3D printing for key components, reducing costs while increasing design flexibility and accessibility.

  1. HKU Dual Purpose System: This system serves both for water level measurements and groundwater sampling. It features a multi-tube assembly using thin-walled PVC pipes and a new type of seal, the HKUniversal seal, which expands upon contact with water, providing reliable isolation between monitoring depths.
  2. HKU-UW Basic Hybrid System: This system is a combination of HKU and the University Waterloo systems. Designed for use in stable boreholes, this system combines flexible poly tubing with standard PVC pipes for hydraulic head monitoring and water sampling. It is easily manufactured using local materials, making it globally accessible.
  3. HKU-UW Manufactured Hybrid System: This version of the hybrid system has most components manufactured using 3D printing, further reducing costs and shipping requirements.
  4. HKU Groundwater Samplers: These single-purpose systems consist of small-diameter tubes for multi-depth water sampling, ideal for detailed vertical profiling in various geological settings.
  5. HKU Combined System: Combines water level measurement and sampling capabilities, using stiff PVC pipes for miniature wells and flexible polytubes for sampling without disturbing water levels.
  6. HKU Water Wells in Fractured Rock: These systems reduce contamination risks in fractured rock environments by extending steel casings deeper and using HKUniversal seals at multiple depths.
  7. HKU/Geotec System: Designed for geotechnical applications, this system measures water pressure at multiple depths in angled or horizontal boreholes, essential for slope stability and tunnel monitoring.
  8. HKU Miniature Drive-Point Wells: These systems enable high-resolution profiling in shallow settings using small-diameter well points driven into the ground, ideal for areas where conventional drilling is impractical.

Unique-Features and Advantages of HKU-DHS

The HKU-DHS stands out for its unique features and advantages over traditional monitoring systems:

  1. Low Cost and Ease of Manufacture: Many components are 3D printed, and the systems can be manufactured locally using widely available materials, significantly reducing costs.
  2. High Resolution Data: The systems provide depth-discrete measurements, revealing critical features often missed by conventional methods, enabling more precise understanding of groundwater dynamics.
  3. Versatility and Adaptability: HKU-DHS technologies are designed to work in a wide range of hydrogeological settings, from porous media to fractured rock and karst systems.
  4. Open-Source Availability: The HKU-DHS initiative is entirely open-source, allowing anyone to produce and modify the systems, fostering global collaboration and innovation.
  5. Ease of Deployment: The “technology in a box” concept delivers systems in lightweight, portable formats, ready for immediate use or requiring only local, off-the-shelf components.

Applications and Opportunities

The HKU-DHS offers tremendous opportunities for advancing our understanding of groundwater in various fields:

 

  1. Mountain Hydrology: In mountainous regions, where groundwater is poorly understood due to challenging terrains, HKU-DHS can provide high-resolution data on groundwater occurrence and flow, improving water access and management.
  2. Aquifer Depletion and Continental Drying: HKU-DHS can accurately monitor water table positions, essential for assessing aquifer depletion and informing sustainable water management strategies.
  3. Agricultural Impacts: The systems can track the effects of agriculture on groundwater quality, providing real-time data on water levels and salinity, crucial for sustainable farming practices.
  4. Coastal Hydrogeology: HKU-DHS can be deployed as coastal transects to monitor saltwater intrusion and contaminant flux, offering vital data for managing coastal aquifers.
  5. Karst and Cavern Systems: These systems are ideal for studying water pressure and chemistry in karst systems, providing insights into cavern formation and surface contamination threats.
  6. Urban Groundwater and Sponge Cities: HKU-DHS can monitor urban water tables, providing key insights into the effectiveness of green infrastructure in managing urban flooding.
  7. Groundwater Contamination: High-resolution sampling with HKU-DHS can reveal detailed contaminant concentration gradients, enabling more effective risk assessments and remediation strategies.
  8. Mining Industry: The cost-effective and adaptable HKU-DHS systems are well-suited for monitoring complex groundwater systems in mining areas, supporting sustainable water management in these resource-intensive operations.
  9. Groundwater Education: The integration of HKU-DHS into educational programs can enhance students’ understanding of groundwater systems through hands-on experience and high-resolution data.

Conclusion: Democratizing Groundwater Science

The HKU Depthwise HydrogeoSystem represents a significant advancement in groundwater monitoring, offering a cost-effective, high-resolution solution to a long-standing data sparsity problem. Its open-source framework and global accessibility are democratizing access to advanced monitoring tools, enabling researchers, educators, and practitioners worldwide to acquire the detailed data necessary for evidence-based decision-making. As we face increasing water resource challenges, the HKU-DHS initiative is a timely and transformative step towards more sustainable and resilient groundwater management. With its versatile applications and ease of use, this system is a game-changer for geologists and hydrogeologists alike, paving the way for a new era in groundwater science.

References

Chapman, S., Parker, B., Cherry, J., Munn, J., Malenica, A., Ingleton, R., Jiang, Y., Padusenko, G., Piersol, J. 2015. Hybrid Multilevel System for Monitoring Groundwater Flow and Agricultural Impacts in Fractured Sedimentary Bedrock. Groundwater Monitoring & Remediation, 35(1), 55-67.

Cherry, J.A., RW Gillham, EG Anderson, PE Johnson. 1983. Migration of contaminants in groundwater at a landfill: A case study: 2. Groundwater monitoring devices. J Hydrol 63(1-2), 31-49.

Cherry, J.A., and P.E. Johnson. 1982. A multilevel device for monitoring in fractured rock. Ground Water Monitoring Review 2, no. 3: 41–44

Cherry, J.A., B.L. Parker, and C. Keller. 2007. A new depth-discrete multilevel monitoring approach for fractured rock. Ground Water Monitoring and Remediation  27, no. 2: 57–70.

Einarson, M.D. 2006.  Multilevel ground-water monitoring. In  Practical Handbook of Environmental Site Characterization and Ground-Water Monitoring,  2nd ed., chap. 11, ed.  D. Nielsen,  808–848. Boca Raton, Florida: CRC Press.

Einarson, M.D., and J.A. Cherry. 2002. A new multi-level ground-water monitoring system utilizing multi-channel tubing. Ground Water Monitoring and Remediation  22, no. 4:  52–65.

Liang, W; JJ Jiao, Y Liu, S Yu, K HO, X Luo, J Cherry (2025), Breaking the Technical Barrier for High Spatial Resolution Monitoring: A Novel Approach for Multi-Depth Groundwater Monitoring System Development, ACS ES&T Water (in press).

Luo, X., Kwok, K.L., Liu, Y. and Jiao, J., 2017. A permanent multilevel monitoring and sampling system in the coastal groundwater mixing zones. Groundwater, 55(4), pp.577-587.

Meyer, J.R., B.L. Parker, and J.A. Cherry. 2014. Characteristics of high resolution hydraulic head profiles and vertical gradients in fractured sedimentary rocks. Journal of Hydrology  517:  493–507.

Patents

HKU Multi Level Groundwater Monitoring and Sampling System (HKU GM System), Inventors: Jiao JJ, Liang, W, Liu Y, Ho K, Cherry J., (App. No 2024212951878)

HKU Multi Level Groundwater Sampling System (HKU GM System), Inventors: Jiao JJ, Liang, W, Liu Y, Ho K, (App. No 202520168772X)

HKUniversal seal system for wells and devices for monitoring in boreholes, Inventors: Jiao JJ, Ho K, Cherry J., (App. No 2024223031380)

Case studies

Cheng KH, Luo X, Jiao JJ, Yu S. Storm accelerated subsurface Escherichia coli growth and exports to coastal waters. Journal of Hazardous Materials. 2023 Jan 5;441:129893.

Cheng KH, Luo X, Jiao JJ, Yu S. Delineating E. coli occurrence and transport in the sandy beach groundwater system by radon-222. Journal of Hazardous Materials. 2022 Jun 5;431:128618.

Jiao JJ, Wang Y, Cherry JA, Wang X, Zhi B, Du H, Wen D. Abnormally high ammonium of natural origin in a coastal aquifer-aquitard system in the Pearl River Delta, China. Environmental science & technology. 2010 Oct 1;44(19):7470-5.

Liu, Y. et al. Inorganic carbon and alkalinity biogeochemistry and fluxes in an intertidal beach aquifer: Implications for ocean acidification. J Hydro 595, 126036 (2021).

Liu, Y., Not, C., Jiao, J. J., Liang, W. & Lu, M. Tidal induced dynamics and geochemical reactions of trace metals (Fe, Mn, and Sr) in the salinity transition zone of an intertidal aquifer. Science of The Total Environment 664, 1133-1149 (2019).

Liu, Y. et al. Spatial Characteristics Reveal the Reactive Transport of Radium Isotopes (224Ra, 223Ra, and 228Ra) in an Intertidal Aquifer. Water Resources Research 55, 10282-10302 (2019)

Liu, Y., Jiao, J. J., Liang, W. & Luo, X. Using Tidal Fluctuation-Induced Dynamics of Radium Isotopes (224Ra, 223Ra, and 228Ra) to Trace the Hydrodynamics and Geochemical Reactions in a Coastal Groundwater Mixing Zone. Water Resources Research 54, 2909-2930 (2018).

Liu, Y., Jiao, J. J. & Cheng, H.K. Tracing submarine groundwater discharge flux in Tolo Harbor, Hong Kong (China). Hydrogeol J 26, 1857-1873 (2018).

Liu, Y., Jiao, J. J. & Liang, W. Tidal Fluctuation Influenced Physicochemical Parameter Dynamics in Coastal Groundwater Mixing Zone. Estuaries and Coasts 41, 988-1001 (2018).

Liu, Y., Liang, W. & Jiao, J. J. Seasonality of Nutrient Flux and Biogeochemistry in an Intertidal Aquifer. J Geophys Res Oceans 123, 6116-6135 (2018).

Liu, Y., Jiao, J. J., Liang, W. & Luo, X. Tidal Pumping-Induced Nutrients Dynamics and Biogeochemical Implications in an Intertidal Aquifer. J Geophys Res-Biogeo 122, 3322-3342 (2017).

Liu, Y., Jiao, J. J., Liang, W. Z. & Kuang, X. X. Hydrogeochemical characteristics in coastal groundwater mixing zone. Applied Geochemistry 85, 49-60 (2017).

Yu, S., Jiao, J.J., Liu, Y., Luo, M. and Li, H., 2024. Occurrence of CO2 and CH4 and the behavior of inorganic carbon in the groundwater of the Pearl River Delta. Science of The Total Environment, 956, p.177141.

Hydrogeology