Rainfall-runoff co relationship can be carried out within a purely analytical framework based on observations of the inputs and outputs from a catchment area. In this study an attempt has been made to develop a similar co relationship for Lower Mahi Basin, situated in the Western Part of India. Rainfall data for the important rain gauging sites was considered for a period of 10 years. Runoff depth was calculated using the SCS-CN method. Utilizing both the parameters, a rainfall-runoff co relationship was obtained using the regression equation.