HydPy-GA (Green-Ampt)

The members of HydPy-GA calculate surface water infiltration into soils based on the simplifying Green-Ampt assumption of “piston-like” wetting fronts. Opposed to purely volume-based approaches, they consider the influence of rainfall intensity on infiltration and, thus, the potential generation of surface runoff. Hence, one might prefer them when dealing with short but intensive (often convective) rainfall events. However, Green-Ampt methods are also usually more demanding regarding computational effort and the required geodata and are more sensitive to data uncertainties. Compared with numerical approximations of the Richards equation, they are less flexible (e.g. because of neglecting soil heterogeneities) but more stable and efficient (as they rely on relatively simple ordinary instead of highly-stiff partial differential equations).

So far, ga_garto is the only HydPy-GA member usable as a stand-alone model. It implements GARTO, a “Green-Ampt infiltration with Redistribution” model that “incorporates features from the Talbot-Ogden infiltration and redistribution method” (Lai et al., 2015). It should outperform simpler Green-Ampt approaches when simulating complex rainfall events that include significant low-intensity subperiods.

Hydrologically, ga_garto_submodel1 works like ga_garto, Technically, it is a submodel that can hook into larger main models like lland_dd to include (additional) surface runoff due to infiltration excess into simulations.

Available models:

• ga » HydPy-GA (base model)
• ga_garto » HydPy-GA-GARTO (main model for calculating the Green-Ampt / Talbot-Ogden infiltration with redistribution)
• ga_garto_submodel1 » HydPy-GA-GARTO-Sub1 (submodel for calculating the Green-Ampt / Talbot-Ogden infiltration with redistribution)