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Image ModifiedLASCAM is a Rainfall runoff model plugin.Adapted  Adapted and re-written as a C# plugin for Source IMS framework by Joel Hall, Water Science Branch, Department of Water, Western Australia, 23/06/2011. Originally developed by Neil Viney and Murugesu Sivapalan, Centre for Water Research, University of Western Australia, 1996-2002

Maintained by eWater and will be incorporated as a core Source Rainfall runoff model in an upcoming production release.

General Info

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LASCAM was developed with the aim of predicting the impact of land use and climatic changes on the daily trends of streamflow and water quality in large catchments ove over long time periods. It was developed as a lumped, conceptual model, using sub-catchements catchments as basic building blocks. Typical subcatchmetn sub catchment sizes are 1 - 10 km2, although much larger subcatchments can be used.

LASCAM hydrology is built around three interconnected subsurface stores, the A store representing the near-stream aquifer system and riparian zone, the B store representing the permanent deeper groundwater system, and the F store representing an intermediate unsaturated infiltration store. These represent typical accumualations accumulations of soil water in duplex profiles where a shallow, gravelly or sandy and highly permeable A horizon overlies a clayey, less permeable B horizon.

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- Sivapalan, M., Ruprecht, J.K., and Viney, N.R., 1996. Catchment-scale water balance modeling to predict the effects of land use changes in forested catchments. 1. Small catchment water balance model. Hydrological Processes, 10(3), 413-428 - Viney, N.R., Sivapalan, M., 1996. The hydrological response of catchments to simulated changes in climate. Ecological modeling, 86, 189-193- Viney, N.R., Sivapalan, M., 2000. Modelling catchment process in the Swan-Avon River Basin. Hydrolgoical Processes.

- Viney, N.R., Sivapalan, M., 2000. LASCAM: The large scale catchment model - user manual. Version 2. Research Report WP1392NV, Cenre Centre for Water Research, Unviersity University of Western Australia, Nedlands.

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Saturation excess runoff (Dunne mechanism) is generated on variable SOURCE areas which are saturated prior to rainfall, or which become saturated during the course of the rainfall. This variable contributing area is predicted as a function of the current level of the perched aquifer storage.
Infiltration excess runoff (Hortonian mechanism) is modelled in two ways: i) direct runoff from impervious areas in urban areas; and ii) infiltration capacity of the surface soil layer, which is assumed to depend on vegetation cover and land use. Any precipitation in excess of the infiltration capacity and the direct runoff is assumed to run off.
The infiltrating water, on the other hand, is assumed to percolate vertically to the bottom of the surface soil layer where it encounters the less permeable clayey horizon. However, due to the high permeability of the A-horizon soils, this percolation is assumed to occur rapidly enough, insofar as not requiring a more sophisticated model for the percolation process.

Subsurface runoff generation
The model assumes that subsurface runoff is generated at the top of the clayey B-horizon by both infiltration excess and saturation excess processes. Subsurface saturation excess runoff (q_sse) is generated on variable SOURCE Source areas, which are saturated due to the presence of a perched water table. Subsurface runoff by the infiltration excess mechanism (q_sie) is estimated using a modified version of the catchment-scale infiltration capacity equation developed by Robinson and Sivapalan (1995). This equation relates the catchment scale infiltration capacity to the state of the infiltration store F and to the value of the water deficit in the groundwater store.

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Differences between LASCAM 2.0 and LASCAM for SOURCESource
The LASCAM hydrological routine was adapted and re-written as a C# plug-in for SOURCE IMS framework Source by the Water Science Branch, Department of Water, Western Australia. Some minor changes were made to the code to integrate the hydrology to the SOURCE FrameworkSource framework. These changes included:

• evaporation from throughflow (e_g) is calculated
• total evapotranspiration (e_t) includes evaporation from throughflow (e_g) (to satisfy mass balance)
• initial store parameters abar, bbar and fbar have been removed , and replaced by the half full stores (see the function initStoresFull() in Appendix B)
• the default parameters are different to the literature, and are based on a calibration from Nambeelup Brook, WA
• LAI and potential evaporation are entered as a time-series at the same time-steps the rainfall (the original code calculated EP, and LAI was a monthly function of an annual value)
• no store disaggregation equation is used to initialise the stores
• no separate LAI for the riparian zone (as this can be done from within SOURCE IMS framework Source if desired)

The code was tested for completeness using the nUnit test program , and validated against the original LASCAM modelling results for the Nambeelup catchment, which was modelled as part of the Peel Harvey Nutrient Modelling project (Kelsey et al, 2010).

 
 

 

Source Code

Source code available here: available https://bitbucket.org/ewater/source.communityplugins/src/master/LASCAM/.