Roles of SAR and EC in Gully Erosion Development (A Case Study of Kohgiloye va Boyerahmad Province, Iran)

Gully erosion is a serious problem of land degradation in pasture land of Sothern Iran. To study thecauses of gully erosion initiation, the Abgendi Watershed with the highest amount of gully erosionwas selected as a semi-arid area in Iran. In this area, 35 gullies were randomly chosen and theinfluences of SAR and EC, as the indexes of alkalinity and salinity on gully erosion, wereinvestigated. The role of sodium in calculating SAR, and the effective role of sodium to soildispersing, It can increase the susceptibility of soil to water erosion. Moreover, concentration ofsoluble salts (are measured by electrical conductivity), such as sodium cations are attached to eachsoil clay particle in the arid and semi-arid areas. To accomplish this study, soil sampling from headcutand gully walls in two depths of 0-30 cm (top layer) and 30cm to the bottom of gully (sub-layer)was carried out. One main objective of the present study was to determine the effects of these twochemical factors on gully erosion development. Based on gullies volume (as a dependent variable),the gullies were classified into four groups and were compared in terms of EC and SAR. The resultsindicated that the gullies with volume of more than 200 m3 (big gully group), in comparison to thegullies with volume less than 50 m3 (very small gully group), have greater EC and SAR. The amountsof EC and SAR of big gully group were significantly higher than very small gully group. Moreover,for the purpose of further analysis, the gullies were classified and compared in terms of EC and SAR.The results indicated that there is a significant difference between gullies volume groups in terms ofEC and SAR as well. The gullies with EC > 8 dS/m and SAR > 8, compared to the gullies withEC < 4 dS/m and SAR < 4, have significantly greater volume and length.

Keywords:

Gully erosion , Sodium absorption ratio (SAR) , Electrical conductivity (EC) , Semi-arid area , Kohgiloye va Boyerahmad Province