Volume balance and flow rate considerations were used to develop an equation for the radial rate of advance of irrigation water. The equation is applicable to radial flow from bubblers, sources near the edge of a basin, or other situations in which the primary flow direction is radial from the source. Examples are given for the use of the equation in designing the spatial and temporal characteristics of an applied slug of water. A technique is presented to allow equations associated with previous strip irrigation analyses to be transformed for use in radial irrigation analyses.