Catchment flow and water quality forecasting

An overarching objective of eReefs is to develop a modelling framework linking the agricultural and land management activities in catchments that drain into the GBR to water quality and ecological responses. eReefs is developing a series of marine hydrodynamic and biogeochemical models that are intended to be used in hindcast, near-real time or forecasting mode (i.e. predicting conditions a few days ahead). These marine models require riverine inflows and associated concentrations of fine sediments, speciated nutrients and carbon at each time step as boundary conditions. For forecasting and near-real time applications, the use of monitoring data is not possible and a combination of models will be required to produce input series of streamflow and associated sediments and nutrients.

The marine hydrodynamic forecasting capability will require at a minimum a streamflow forecast and ideally a catchment load forecast. A short-term streamflow forecasting system for Australia has been developed collaboratively by CSIRO and the Bureau of Meteorology through the Water Information Research and Development Alliance (WIRADA). All hydrological modelling is undertaken using the Short- Term Water Information Tools (SWIFT) which integrates real-time observations of rainfall and stream flows with numerical weather prediction (NWP) model rainfall forecasts and continuous hydrological modelling. The system produces streamflow forecasts at hourly time steps with lead times of up to 9 days. This provides ‘sentinel’ type information for emergency service managers.

In the first phase of eReefs, within the Fitzroy Basin, CSIRO have demonstrated a possible combination of models based on a semi-distributed hydrological model to produce streamflows coupled with a set of generalised additive models to predict water quality constituents, therefore providing on-the-fly scenario modelling capacity.

In the second and third phases of eReefs, the Bureau of Meteorology is further developing and will operate catchment forecast models for priority eReefs catchments and these forecasts will be delivered on daily basis to the marine models. The additional target catchments are to be selected through a consultative process with all key stakeholders. Priority will be given to catchments of significance for the hydrodynamic modelling of the reef, particularly those that yield substantial water volumes and pollutant (sediment and nutrient) loads.