Determination of the Best Rainfall Erosivity Index in Fars Province and its Zoning

The water erosion is as one of the important issues in agriculture and watershed management. researchers, through different studies are looking for ways to minimize it. Rainfall erosivity index is the most important factors affecting on soil erosion and is a function of the rain physical properties. Various index have been developed to quantify the rainfall erosivity factors. The choice of appropriate indicators is important due to ecological conditions. This study has been carried out in Fars province to estimate rainfall erosivity index according to the relationship between quantity-based indicators of erosion and erosivity factor introduced by Whichmeier and Smith, (EI30) and to zone by using different geo statistics and deterministic methods. Investigation of the regression relations showed that Fournier index was as a suitable indicator for the province with r=0.80. In the next step, erosivity factor (R) was calculated for stations without rain recorder. Finally, the method of radial basis function (RBF) with tapes thin due to higher r value and lower RMSE and MAE was chosen as the best interpolation method. According to the temporal and spatial distribution erosivity factor in Fars province, the maximum amount of erosivity factor was observed in north and the lowest was in east and north east of province. Also, 44% of province area has medium erosion and 10% is subjected to high erosion.