About the model...

The SoilWaterApp uses a daily water-balance model based on the HowLeaky model.

Water balance models describe the dynamics of water in agicultural systems and consider impacts of a range of management options, soil type and weather on infiltration, runoff, plant available soil water, evaporation, transpiration and deep drainage.

Calculations are performed on a daily time step using inputs of rainfall, pan evaporation, temperature, planting and harvest dates and soil residue cover. Parameters describing soil water and infiltration and drainage characteristics, soil evaporation and erosion are retrieved from a database.

Evaporation is estimated from the evaporative demand (pan evaporation) soil moisture content and soil cover (crop and residue or stubble). The model calculates surface runoff as a function of rainfall, soil water content and surface cover. Deep drainage is calculated when the soil is above field capacity, and further rain occur. 

Further documentation is available in the Library and and Lnks section on these www pages.