Vadose Zone Monitoring System as a Tool for Groundwater Protection

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Abstract

Subsurface monitoring for groundwater protection from pollution hazards has traditionally been based on culling information from the groundwater. This information is usually retrieved from boreholes penetrating the saturated section of the groundwater. Accordingly, the entire path and fate of pollutants transported from land surface through the vadose zone to the groundwater is evaluated from the chemical and physical state of the water which has been sampled from a well. That monitoring procedure is well founded in both scientific studies and through legislative acts which enforce groundwater monitoring for potential sources of pollution. However, this creates a paradox since, by definition, identification of pollution in groundwater means that the groundwater is already polluted. Moreover, since vertical transport in the vadose zone and lateral flow in the groundwater are very slow processes, pollution identification in a well may take years or decades. As a result, the total mass of pollutant that has penetrated the subsurface may be extremely high by the time it has been identified. Finally, pollution identification in a well usually reveals only the edges of a much larger pollutant plume. Accordingly, identification of pollution in the vadose zone right under the pollution source, long before it shows up in the groundwater, should be the key to groundwater protection. The need for real-time information on the quality of percolating water led to the development of a new vadose- zone monitoring system. The new monitoring system is designed to provide continuous measurements of the soil water content and water potential, while allowing pore-water sampling all along the vadose-zone cross section. The installation technique allows monitoring of the vadose-zone cross section under relatively undisturbed soil conditions. The new monitoring system is comprised of special flexible TDR (FTDR) probes, assembled with special vadose-zone sampling ports (VSPs) that function either as deep vadose-zone tensiometers or pore-water sampling devices. The system is adapted for installation in small-diameter boreholes allowing multiple measurements of the soil's hydraulic properties all along the vadose-zone cross section, from land surface to groundwater. This monitoring system has been implemented in several studies on water infiltration and groundwater recharge in different climatic and lithological setups.
Original languageEnglish GB
JournalGeophysical Research Abstracts
Volume32
StatePublished - 1 May 2007

Keywords

  • 1800 HYDROLOGY
  • 1830 Groundwater/surface water interaction
  • 1838 Infiltration
  • 1875 Vadose zone
  • 1890 Wetlands (0497)

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