COMPUTATION AND PLOTTING OF INFILTRATION ADVANCE ISOCHRONES FOR ANY SOURCE

The position and rate of change of the advance front due to surface wa ter spreading on a flat surface is computed using a two-step approach. The size of the spreading pool is first calculated using a volume bal ance equation. The geometric shape of the pool area is then approximat ed using potential theory. This is simplified by using distributed poi nt sources to represent the source. A combination of both techniques a llows isochrones of the advance front from any source to be predicted. Site specific advance front velocity values are calculated from the c onstructed isochrones. An equation is also presented for the general r ate of change of the pool area. Isochrones families, for a number of d ifferent shaped sources, are presented as is a discussion on the const ruction of streamlines. The isochrones lines are also used to define l ines of constant infiltration opportunity time and constant cumulative infiltration. The combined technique offers a foundation on which to later add many of the processes associated with water spreading on the surface.