Study of Rain Erosivity Index of West Azarbaijan Province for Rain Iso-Erosive Mapping

Rainfall erosivity is one of the major factors of soil erosion that expressed as some indices. The objective of this study is to determine the appropriate rainfall erosivity index in West Azarbaijan in relation to soil loss at the erosion standard plates. After recording the rainfall amounts in a certain time periods, erosivity indices calculated and appropriate index was selected for the area. Selected index calculated through available indicators such as Modified Fournier, annual rainfall and average maximum daily rainfall in stations without rainfall Intensity statistics and the best index was obtained. To provide the Iso-erosive map, geostatistics based interpolation methods were used by cross validation. Results showed that AWT IMAGE were the best correlated with soil loss than other erosivity indices. The results also showed the modified Fournier index had a significant correlation at 95% with EI30. The error of the co-kriging method when compared to the IDW, Ordinary kriging, Universall kriging and spline methods declined by 10.57%, 0.71%, 4.6% and 0.67% respectively but due to the unstability of the EI30 data, Spline Interpolation method is well fitted for rain erosivity index. The annual value of this index obtained between 200 and 700 MJ mm ha h. Prepared map presence of rain erosion index decreased from West to East of the province.