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Lumped Arid/Semi-arid Model (LASAM) simulates infiltration and surface runoff (two important components of the hydrologic cycle) based on Layered Green-Ampt with redistribution (LGAR) model

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NOAA-OWP/LGAR-C

Catchment Arid/Semi-arid Model (CASAM) for streamflow simulation

CASAM (formerly known as LASAM) is a catchment scale hydrolgic model originally designed for arid or semi arid areas, in which the partitioning of precipitation into infiltration and runoff is important. CASAM is composed of a vadose zone model, which is Layered Green & Ampt with redistribution (LGAR) and represents a layered soil matrix, and a nonlinear reservoir which is filled via a simple formulation for preferential flow. LGAR is a model which partitions precipitation into infiltration and runoff, and is designed for use in arid or semi-arid climates. LGAR closely mimics precipitation partitioning results simulated by the Richards/Richardson equation (RRE), without the inherent reliability and stability challenges the RRE poses. Therefore, this model is useful when accurate, stable precipitation partitioning simulations are desired in arid or semi-arid areas. LGAR in Python (no longer supported) is available here.

CASAM is theoretically a skillful catchment scale hydrolgic model in the event that precipitation partitioning into infiltration and runoff is the most important process for streamflow generation in a given catchment. Nonetheless, CASAM also includes a nonlinear reservoir so that some water stored in the catchment can contribute directly to streamflow (currently, we assume soil water does not directly contribute to streamflow).

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Published papers: For details about the model please see our manuscript on LGAR (weblink).

Build and Run Instructions

Detailed instructions on how to build and run CASAM can be found here INSTALL.

  • Test examples highlights
    • simulations with synthetic forcing data and unittest (see build/run).
    • simulations with real forcing data (see build/run)
    • CASAM coupling to Soil Freeze Thaw (SFT) model (see instructions)

Model Configuration File

A detailed description of the parameters for model configuration is provided here.

Calibratable parameters

A detailed description of calibratable parameters is provided here.

Nextgen Realization Files

Realization files for running CASAM (coupled/uncoupled modes) in the nextgen framework are provided here.

Getting help

For questions, please contact Ahmad (ahmad.jan(at)noaa.gov) and/or Peter (peter.lafollette(at)noaa.gov), the two main developers/maintainers of the repository.

Known issues or raise an issue

CASAM is a newly developed model and we are constantly looking to improve the model and/or fix bugs as they arise. Please see the Git Issues for known issues or if you want to suggest adding a capability or to report a bug, please open an issue.

Getting involved

See general instructions to contribute to the model development (instructions) or simply fork the repository and submit a pull request.

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Lumped Arid/Semi-arid Model (LASAM) simulates infiltration and surface runoff (two important components of the hydrologic cycle) based on Layered Green-Ampt with redistribution (LGAR) model

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