Modelling helps us determine what happened, or forecast what might happen in our dams.
What is reservoir modelling?
Reservoir modelling uses computer software to explain and forecast how water in lakes moves around under the surface.
Reservoir models use detailed underwater mapping of the hills and valleys under a lake's surface (bathymetry), and information about wind, air temperature, water temperature, rainfall run-off and water quality at various locations in the lake.
Computer software reproduces the physical, chemical and biological processes that occur in a lake and uses this information to create three dimensional models. These models can then explain and predict water movement under the surface under different conditions.
The models are checked for reliability by comparing their predictions against actual monitoring data for temperature and water quality at various locations for extended periods of time.
Why is modelling important?
Modelling is used to investigate what happened, or forecast what might happen, to water in Sydney's major water supply dams under different conditions.
Understanding reservoir dynamics through modelling and forecasting what changes in water quality can be expected, and when, allows WaterNSW to plan ahead and ensure it supplies the best quality water to customers.
How does WaterNSW use reservoir models?
During periods of heavy rainfall, catchment run-off carrying eroded soil, other nutrients and pollution may move around at different levels and locations of a lake, depending on the temperature and meteorological conditions. Reservoir models can help forecast changes in water quality from run-off, allowing WaterNSW to draw water from different depths, or from an alternate water supply.
At other times, reservoir modelling can be used to forecast when a lake may cool down enough to de-stratify, which causes variable water quality throughout the lake. Also, models can help explain the reasons why particular water quality changes occurred and help WaterNSW be better prepared in the future.