 The Soil Conservation Service Curve number, SCSCN, approach is widely used as a simple method for predicting direct runoff volume for a given rainfall event. This approach involves selecting CN parameter values corresponding to various soil, land cover, and land management conditions from tables, or estimating the CN value from measured rainfall runoff data, if available. Previous researchers have indicated that the CN values calculated from measured rainfall runoff data vary systematically with the rainfall depth. Therefore, they suggested the determination of a single asymptotic CN value observed for very high rainfall depths to characterize the watershed's runoff response. In this paper, the hypothesis that the observed correlation between the calculated CN value and the rainfall depth in a watershed reflects the effect of soils and land cover spatial variability on its hydrologic response is being tested. Based on this hypothesis, the simplified concept of a two CN heterogeneous system is introduced to model the observed CN rainfall variation by reducing the CN spatial variability into two classes. The behavior of the CN rainfall function produced by the simplified two CN system is approached theoretically. This article was authored by J. D. Vallianzas and K. X. Suleys. We are article.tv. Links in the description below.