263-2 Impacts of Neighborhood Type, Geology, and On-site Sanitation System on Groundwater Quality

Session: Exploring Groundwater Recharge and Management: Managed Aquifer Recharge and Other Innovative Tools for Water Supply Development and Operations (Posters)

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Access to safe and reliable drinking water remains a significant challenge in many parts of the world, particularly in sub-Saharan Africa. Lusaka, the rapidly expanding capital city of Zambia, relies heavily on a vulnerable karstic carbonate aquifer for its water supply. Approximately 70% of Lusaka’s population resides in peri-urban areas, where access to adequate water and sanitation infrastructure is limited. This has led to widespread groundwater contamination and the persistent transmission of waterborne diseases. This study assesses the quality of drinking water, with a focus on groundwater from 14 residential neighborhoods encompassing both planned urban and peri-urban areas. Key water quality indicators including bacterial contamination, nitrate concentrations, and metal content were analyzed due to their known health risks. Water samples were collected from diverse settings characterized by differences in geology (carbonate vs. schist), sanitation systems (septic tanks vs. pit latrines), and infrastructure (conventional plumbing vs. informal systems). Samples were tested for pH, specific conductance, carbonate, hardness, alkalinity, microbial contamination, and bacterial community composition. Geospatial analysis using ArcGIS Pro was employed to map the distribution of these parameters. Results revealed that nitrate concentrations were elevated across all neighborhoods, with approximately 50% of samples exceeding the World Health Organization’s safe limit of 10 mg/L. However, no clear correlation was found between nitrate levels and other variables. All samples had pH values within the recommended range of 7.0 to 8.5 and were classified as either hard (21%) or very hard (79%) water. E. coli contamination was generally higher in peri-urban areas compared to planned ones. Notably, two planned neighborhoods (Makeni and Meanwood Ibex) with septic systems located near peri-urban areas using pit latrines exhibited significant bacterial contamination, suggesting that hydrogeological factors particularly groundwater flow play a critical role in contaminant transport.

Geological Society of America Abstracts with Program. Vol. 57, No. 6, 2025

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