A Study of Flooded and Rain Infiltration Relations With Surface Ponding

The non-linear partial differential equation (combination of Darcy\u27s law and continuity equation) has been used in this investigation to predict the flooded infiltration through soils possessing appreciable amount of clay and initially drier than its field capacity. One of the most important assumptions made in solving the differential equation is that the capillary conductivity-moisture content relationship is unique for each initial moisture content computation due to the different reaction of clay minerals with different initial moisture contents. Mathematical equations were also derived to predict: The rate of the wetting front advance, prior to the occurrence of surface ponding, taking into account the effect of initial soil moisture content and rate of water application. The time at which surface ponding takes place under different rain (sprinkler) intensities by utilizing the intake rate curve obtained under flooded infiltration. The derived equations enable us to estimate a definite period of time, during which a field can be sprinkled at a given application rate, beyond which if sprinkling continues runoff will take place, and to estimate the accumulative rain (sprinkler) uptake at the time of surface ponding. The theory was tested and firmly supported by the results of a multipurpose laboratory experiment conducted on samples of a Nibley silty clay loam soil packed into columns to a density of 1.25 gm/cm3

A Theoretical Study of Infiltration into Range and Forest Soils

More than 400 rainfall simulator experiments were examined to detect which soil properties could be used to computer infiltration time relationships. Three theoretical equations were tested to determine their efficacy for calculating infiltration time relationships from soil and site characteristics. It was shown that both the modified Green and Ampt and Fletcher equations could by successfully used. Darcian type equations were developed on laboratory type samples which would show the relations between soil, solution and rainfall properties and infiltration. These latter equations have not been tested on undisturbed soils but give excellent agreement between measured and computed values for time before flooding and infiltration time relationships