Illinois State Water Survey Bulletin 70 and Bulletin 71 and Circular 173 data contains synthetic rainfall time-distribution curves for heavy rainstorms in the Midwestern United States. This information comes from Circular 173 (Huff1990). Rainfall time-distribution curves are used for runoff computations related to the design and operation of runoff control structures.

Time-distribution curves are divided into four categories, corresponding to first-, second-, third- and fourth-quartile storms. Time distributions are represented as cumulative fractions of the storm rainfall depth and the storm duration.

The Bulletin 70/71 data contains median (exceedance probability of 50%) curves. The Circular 173 data gives the curves for exceedance probabilities of 10% and 90%.