Turbidity Plume Forecast : Ala Wai, Oʻahu


Caution: The model below is experimental and no promise of accuracy is implied for the plume position and turbidity values.

Ala Wai Turbidity Plume Animation

This animation shows the predicted turbidity from the Ala Wai canal, Honolulu, Oʻahu. It is updated daily at 11:30 AM HST.

After a significant storm event, large amounts of runoff from the land can enter coastal waters. This storm water runoff, often referred to as “brown water”, can contain pollutants and contaminants, including sewage, harmful micro-organisms, and chemicals from residential, commercial, and recreational sources.

Turbidity is a measure of water clarity and can serve as an indicator to determine the severity of a storm event. A high turbidity level means an increased number of tiny solids are suspended in the water column. The Turbidity Plume Model simulates a possible plume advection and dispersion at the Ala Wai Canal as a result of a storm event.

Different water quality samples showing turbidity gradient

The plume position and turbidity values are determined using the results from the ROMS Ocean Circulation Model configured for Waikīkī. The model also takes near real-time river runoff and turbidity measurements for the Ala Wai canal into consideration, along with waves (SWAN) and atmospheric (WRF) model forcings.

The results could indicate the fate of large discharges from the Ala Wai due to heavy rains or other events and the generation of a coastal “brown water” plume. Please visit the State of Hawaiʻi Department of Health (DOH) Clean Water Branch (CWB) for more information on storm water runoff.

The model data were generated as part of an academic research project, and the principal investigator, Brian Powell, asks to be informed of intent for scientific use and appropriate acknowledgment given in any publications arising therefrom. The data are provided free of charge, without warranty of any kind.

For additional model output data from the Regional Ocean Modeling System (ROMS), please visit the PacIOOS Currents Forecast, Salinity Forecast, and Water Temperature Forecast or find more data on PacIOOS Voyager.

Note: This example is an extreme event that typically occurs every few years.

The animation below serves as an example of a high rainfall event in December 2011, resulting in a large turbidity plume off the coast of Waikīkī. The movement and lifespan of the turbidity plume through time depends on oceanic and atmospheric conditions. Examples of a few mechanisms that can affect the turbidity plume are: tidal currents, freshwater outflow, as well as wind speed and direction.

Ala Wai Turbidity Plume Animation