Combining DHI’s Coastal Receiving Environment Scenario Tool with Auckland Council’s Freshwater Management Tool
DHI’s team in New Zealand and Auckland Council’s Healthy Waters department carried out a contaminant assessment of the inner and outer Waitematā Harbour using a coupled FWMT-coastal hydrodynamic model. Continuous time series for 80 sub-catchments were fed to a wave and tide-forced hydrodynamic model to predict the transport and fate of stormwater contaminants, including Total Nitrogen (TN), Total Phosphorus (TP), Total Suspended Solids (TSS), Total Copper (TCu) and Total Zinc (TZn).
A catchment-to-coast connectivity matrix was developed between FWMT inflows and sub-domains within the model domain. With this approach, Auckland Council could estimate the contribution of freshwater-derived contaminants to the coastal receiving environment at close to 100 sub-estuary/harbour domains within the inner and outer Waitematā Harbour.
Based on the connectivity matrix, an online Coastal Receiving Environment Scenario Tool (CREST) system was developed to allow Auckland Council to view the baseline model results and compare them against agreed thresholds for each contaminant. The tool can then evaluate whether load reductions in the catchments would translate to improved coastal water quality.
The solution allows Auckland Council to independently view the link between source and sink, run cost-effective what-if scenarios and access the data 24/7 globally through a digital portal. With its user-friendly interface, the solution facilitates collaboration and stakeholder engagement anytime and anywhere.