K.D. GHARDE AND D.M. MAHALE 13 Bioved, 23(1) : 13–18, 2012 Modeling of erosivity index from rainfall data of south Konkan region K.D. Gharde and D.M. Mahale College of Agril. Engg & Tech., Dr. Balasaheb Sawant Konkan Krishi Vidyapeeth, Dapoli, Ratnagir (MS) Received October 30, 2011 and Accepted January 2, 2012 ABSTRACT : Agricultural Research Station (ARS), Mulde Dist. Sindhudurg is characterizes with its unique biodiversity, high intensity rainfall, flash flood, slope (7 to 35 %) and average annual rainfall ranging from 3000 to 4500 mm. It is southern part of konkan situated in 16°42’N latitude and 73°2’ E longitude and at an elevation of 17 m from MSL with majority of soil lateritic type with steep slope in shadow of severe soil erosion. Thirteen years rainfall data recorded by automatic rain gauge was collected from Hydrometeorology, ARS, Mulde. This collected data was analyzed for every storm to determine erosivity indices and characteristics of rainfall parameters. The indices were developed for rainfall with all intensities and with intensity ³8 mm/hr, 10 mm/hr, 12 mm/hr. Intensity with ³8 mm/hr was found as threshold intensity and was used for further analysis. Average annual erosivity for ARS Mulde was 11189.186 MJ-mm/ha hr. The month July was contributing mostly in annual erosivity index followed by month June and August. Daily erosivity index has given significant relationship with daily rainfall and I 30 of the day with coefficient of determination as 0.95 and 0.68, respectively. For KE³8 mm/hr, an erosivity value is 6962.15 MJ-mm/ha.hr of the ARS Mulde. Key Words: Erosivity, rainfall, threshold intensity, rainfall intensity. Soil, water and vegetation resources are nature’s gift to mankind. These are the basic resources con- tinuing to exert over-riding impact on agricultural production. Twenty per cent of land sustains 60% world’s population that exploited the natural resources (soil, water and vegetation) and that disturbed eco- logical balance. Therefore, efficient utilization of water resource and conservation of soil are impor- tant for sustainable agricultural production. In India the soil erosion is taking place at the rate of 16.35 tones per ha per annum, which is well above the per- missible limit of 4.5 to 11.2 tones per ha (Dhruva Narayan and Ram Babu, 1983). The amount of soil detached by rain depends on the intensity of rain, or its detaching capacity, char- acter of soil or its detaching ability and the protec- tive cover present (Hudson, 1965). Erosive capacity of raindrops results from three factors, amount and intensity of rainfall, diameter of rainfall, and the ve- locity of the drops as they strike the soil (Foster et al., 1980; Uson and Ramos, 2000). Rainfall kinetic energy is directly related rainfall intensity and depth of rainfall. This detaching capacity of the rainfall or the ability of rainfall to cause erosion has been quan- tified in the form of rainfall erosivity factor. This rain- fall erosivity factor ‘R’ which is defined as the ability of rainfall to cause erosion appears in the Universal Soil Loss Equation (USLE) developed by Wischemeir and Smith (1962). The Konkan region is situated along a coastal belt of Arabian sea with length 720km and width 35- 50 km. Rainfall and slope are causing irreparable damage in the form of very severe soil erosion rang- ing from 10-12 tones per ha per year to 30-33 tones