Development of a watershed-based geospatial groundwater specific vulnerability assessment tool

Area of Science:

• Environmental Science
• Hydrogeology
• Public Health

Background:

• Unregulated groundwater systems are crucial for drinking water but susceptible to microbial contamination.
• Assessing groundwater vulnerability is essential for protecting public health and ensuring safe drinking water.
• Existing assessment tools may not fully capture risks specific to microbial contaminants.

Purpose of the Study:

• To characterize the vulnerability of unregulated groundwater systems to microbial contamination in Georgia.
• To develop and apply a contamination risk screening strategy using watershed characteristics.
• To compare a novel Land Use, Hydrology, and Topography (LHT) model with the U.S. EPA's DRASTIC model.

Main Methods:

• Utilized geospatial overlay/index modeling integrating septic systems, elevation, land use, soil, vegetation, demographics, and livestock data.
• Developed a Land Use, Hydrology, and Topography (LHT) index to assess groundwater pollution vulnerability.
• Validated the LHT model using field data and comparing results with the U.S. EPA's DRASTIC model.

Main Results:

• The LHT model identified higher microbial contamination risk in high to medium vulnerability zones.
• A significant majority of wells (>75%) fell within the medium DRASTIC vulnerability zone.
• The LHT model demonstrated a clearer distribution of well quality across vulnerability zones compared to DRASTIC.

Conclusions:

• The LHT model, incorporating land use and contamination sources, offers a meaningful perspective for groundwater protection.
• The LHT index effectively screens for microbial contamination risks, complementing intrinsic vulnerability assessments.
• Integrating diverse environmental data enhances the accuracy and utility of groundwater vulnerability assessments.