Modeling Effect of Depth on Furrow Infiltration

In contrast to borders, water depth in furrows has a primary influence on infiltration. If flow depth remains relatively constant everywhere and infiltration parameters are measured at that depth, volume infiltrated per unit length computed in a mathematical model of furrow flow depends only on the time of stream arrival. But, a significant depth gradient results in error unless the variable depth is incorporated into the infiltration computation. Six different schemes are considered. The most complicated assumes that infiltration into every element of wetted perimeter at a section depends on the time that element has been wetted. Less complex schemes assume that volume infiltrated per unit length at a station depends on time of stream arrival there and, in order of increasing crudeness, local wetted perimeter, local top width, upstream wetted perimeter, upstream top width, top width at normal depth for the give inflow. Comparisons of computed results with field measurements of upstream depth, advance, and cumulative volume infiltrated with time lead to the tentative conclusion that use of current local wetted perimeter is the most satisfactory approach.