A tank model consisting of three tanks was developed for prediction of runoff and sediment yield. The sediment yield of each tank was computed by multiplying the total sediment yield by the sediment yield coefficients; the yield was obtained by the product of the runoff of each tank and the sediment concentration in the tank. The sediment concentration of the first tank was computed from its storage and the sediment concentration distribution (SCD); the sediment concentration of the next lower tank was obtained by its storage and the sediment infiltration of the upper tank; and so on. The SCD, caused by the incremental source runoff (or the effective rainfall), was obtained by the theory of the instantaneous unit sediment graph (IUSG) and a sediment routing function. Using the SCD, the sediment yield was computed from the tank model as well as by the IUSG model. The sediment yield obtained from the tank model was then compared with that from the IUSG model. Finally, the tank model was verified on an upland watershed in northwestern Mississippi. Springer Science + Business Media, Inc. 2005.