Sea-level rise drives wastewater leakage to coastal waters and storm drains

Contributed by Trista McKenzie

While sea-level rise (SLR) is frequently associated with surficial flooding and beach erosion, its impact to groundwater is also important. SLR can lead to rising groundwater levels through groundwater inundation, aquifer salinization, and poor coastal water quality. In this study, we investigated the potential for SLR-driven groundwater inundation to compromise coastal wastewater infrastructure such as cesspools and fractured sewer lines. This was accomplished through a field-based geochemical study in Honolulu, Hawaiʻi using spring tides as a proxy for future sea levels. We focused on two potential pathways for this to occur: (1) direct groundwater inundation of wastewater infrastructure, which subsequently flows to the coastal ocean, and (2) indirect inundation of wastewater infrastructure through storm drain backflow. Groundwater discharge was monitored using radon, a naturally occurring groundwater tracer, over half tidal cycles. In addition, pharmaceuticals and dissolved nutrients were collected from groundwater, surface water, and storm drains at low, mid, and high tides. Groundwater discharge and pharmaceutical concentrations fluctuated with tides indicating tidally driven groundwater inundation and wastewater discharge. This study presents some of the first field-based evidence for groundwater inundation of coastal wastewater infrastructure, demonstrating that SLR is already leading to negative impacts to coastal water quality and environmental health.

This work has been published in Limnology and Oceanography Letters: https://aslopubs.onlinelibrary.wiley.com/doi/full/10.1002/lol2.10186

Citation: McKenzie, T., Habel, S., Dulai, H., (2021). Sea-level rise drives wastewater leakage to coastal waters and storm drains. Limnology and Oceanography Letters. doi: 10.1002/lol2.10186. 

Datasets:

McKenzie, T., S. Habel, H. Dulai (2020). Honolulu King Tide Study: Raw sample dataset, HydroShare, https://doi.org/10.4211/hs.efecc49323cf4a57a8068890889e259f

McKenzie, T., S. Habel, H. Dulai (2020). Honolulu King Tide Study: Radon Time Series, HydroShare, https://doi.org/10.4211/hs.14cc6984035d4fb4aa4e653e1625d0bd

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