Many of the more than 2,200 storm-water basins on Long Island, N.Y., having runoff and infiltration characteristics similar to those of a basin studied in North Massapequa are potential sites for returning large volumes of reclaimed water (highly treated waste water) to the ground-water reservoir. By use of a finite-difference method of calculation, formulas were devised to calculate changes in basin storage at various time intervals from the start of storm inflow, with and without addition of reclaimed water. The North Massapequa storm-water basin was the prototype design used to test several methods of water application. Calculations using various infiltration rates, storm durations, and storm-return periods indicate that several methods of applying reclaimed water to storm-water basins on Long Island would be feasible. (Woodard-USGS)