SIMRAT-XL is an MS Excel implementation of the key computational algorithms from the SIMRAT Salinity IMpact Rapid Assessment Tool. It provides a rapid assessment of the salinity impacts arising from the application or removal of water on land at some distance from the aquifer discharge.

As no detailed modelling or calibration is required, SIMRAT-XL can be used to quickly assess the relative merits of applying or removing water on different parcels of land.

Conceptually, SIMRAT moves rainfall and applied water excess vertically through the soil zone to the aquifer using wetting or drying functions. In the aquifer, the Unit Response Equation is used to esimate the aquifer discharge at some point remote from the area of application. Allowance can be made for the loss of salt to floodplain processes, or partial connectivity of the aquifer to a river.

SIMRAT can be applied to a wide range of physical situations provides some basic assumptions are met.

For the River Murray, SIMRAT-XL provides a separate results page which assesses impacts at Morgan using both EC and $ units.

The target group includes land and water managers along the River Murray from Nyah to Lake Alexandrina, and in the Lower Darling River downstream of Weir 32. Other users would include:

• researchers who may wish to utilise the core algorithms for catchment scale applications, and
• developers who may wish to undertake a preliminary assessment of the impacts of irrigation or other developments on salinity.
• people interested in aquifer discharge at locations outside the lower River Murray provided the basic model assumptions can be verified.

As a Rapid Assessment Tool, SIMRAT has been developed to be as conceptually simple as possible while retaining the ability to predict salinity impacts to a reasonable level of precision and conservatism. Basic hydrogeological knowledge is all that is required to run SIMRAT-XL. Before running SIMRAT-XL it is recommended that users become familiar with the basic model assumptions and limitations as provided in the comprehensive companion documents. It is recommended that expert hydrogeological knowledge is sought to review data inputs and interpret model outputs appropriately.

• Impacts of water trade.
• Impacts of changes in water use efficiency.
• Impacts of changes in land use on infiltration rates (eg revegetation)
• Impacts from environmental watering.

Advantages:

• Rapid assessment of potential salinity impacts.
• No modelling required.
• Consistent approach across State boundaries.
• Rapid comparison of the salinity effects of applying water to different areas.
• Robust simplifying assumptions.

Disadvantages:

• Detailed modelling of individual sites is not undertaken. For final design of new irrigation schemes local models are recommended.
• Simplifying assumptions may be inappropriate in some areas.