Modeling infiltration using time-to-ponding and a storm generator approach

Soil productivity is largely determined by the biological, physical, and chemical properties and processes in concert with climate and resource management inputs. Mathematical or physical models are effective for describing the influences of soil erosion and management systems on long-term productivity. Research on developing and applying a functional model of infiltration into a soil profile under rainfall or irrigation conditions is important in both hydrology and agriculture. To provide a rational basis for infiltration prediction during rainfall or irrigation, a nonlinear model was used in this study to calculate cumulative infiltration based on time-to-ponding approach. The cumulative infiltration amount at ponding is a function of water application rate, saturated conductivity, saturated soil water content, antecedent soil water content, and macroscopic capillary length. Soil management practices such as crop types, tillage methods and surface residue cover also influence soil properties and infiltration capacity.; To make this infiltration model functional for strategic applications where it is difficult to obtain or use short-period rainfall data, a relatively simple storm generator was used to generate daily precipitation and to disaggregate it into a discrete number of storms of varying intensity patterns. The generated outcome distribution of rainfall was used as input to the physically based time-to-ponding model.; A field study was conducted on a loamy sand (Eutric Glossoboralf) soil in Michigan with corn and potatoes under various tillage, surface residue, and wheel traffic conditions to determine values of the soil properties needed for the infiltration model. Time-to-ponding was observed for various water application rates using a sprinkling infiltrometer under a variety of soil management situations. Time to ponding curves were established for each management combination of crop, tillage and wheel traffic conditions.; The time-to-ponding approach appears to be a good infiltration predictor under complex rainfall patterns and different soil management conditions. Using the ponding curves, with known soil hydraulic properties, the point source (or localized) runoff are predictable under any type of rainfall or irrigation patterns. This point source runoff is a critical input for the assessment of water erosion.