A distribution function approach to water flow in soil macropores based on kinematic wave theory

Kinematic wave theory is adapted to gravity-driven flow in narrowly defined macropore groups. The frequency distribution of macropore conductance, b (dimensions L T −1), is obtained by superimposing the predicted drainage hydrographs from the individual groups of macropores and matching predicted outputs to observed drainage hydrographs. The time period over which this concept applies is limited to about 1.5 times the duration of the water input to the soil surface. The drainage hydrographs from four different soils, using three different measuring devices, were analyzed accordingly. The analysis suggests that between 10 −2 and 0.2 of the input is required to supply water to the macropore system, while a parameter controlling losses to the matrix varies over only a small range.