The Office of Water uses a range of modelling techniques to understand how our river and groundwater systems behave. The resultant models help predict what will happen in a variety of scenarios, including water sharing, compliance and the effects of climate change, and factors that affect water availability.

The complexity of modelling approaches can vary from very simple conceptual models through to very detailed and data rich approaches. Models can be applied at scales varying from very small scale specific sites or study levels, through to regional scales. The utility of any of these models is constrained by basic limitations in our knowledge and the availability of data to build the model. Models cannot generate knowledge; they only combine what we know into useful forms.

Surface water model for water sharing and management

The main surface water model used for water sharing and management is the Integrated Quantity and Quality Model (IQQM). IQQM has been developed to assess the impacts of different management strategies on all water users. The models have been developed to simulate the major hydrological processes in river valleys along with relevant management rules. These models have been calibrated to match reservoir levels, diversions and flows over the calibration periods. The models are set up in such a way as to reproduce the average long term behaviour of the river system for planning purposes and not specifically to reproduce individual daily flow behaviour in any particular year, or to forecast any future year.

IQQM models have been developed for most inland river basins and some coastal river valleys. The models can be used to obtain a range of information on simulated river system behaviour ranging from average summary statistics to specific event or sequence details.

These models are used in different water management areas such as:

Groundwater models

A regional groundwater model has been established to investigate, audit and derive sustainable yield estimates for the state's groundwater systems. The model has been used in water sharing plans, land and water management plans together with monitoring of groundwater use throughout the state.

Stacked water source model

A conceptual MODFLOW groundwater model methodology was used to represent a stacked water source system to study the impact of groundwater pumping on water availability. The impacts have been studied in a variety of scenarios in the report, Impact of groundwater pumping on stacked water sources (PDF 633 KB).

Climate and hydrological modelling

The effects of climate variability and climate change have been a particular focus of the Office. We have used a range of climate and hydrological modelling approaches to help translate estimates of rainfall and evaporation changes from climate change scenarios into impacts on the surface water regimes of river basins across NSW.