Determination of the Most Important Soil Factors in Runoff Production in Different Land uses in Gachsaran Formation

Natural ecosystems have their own order and balance unless they are disordered under the influence of a foreign force, which unfortunately, human have caused disordering in many watersheds by unconsumed exploitation of some of its elements. One of the most main of its results is run off production that resulted to increasing flood production and erosion and soil poverty. Gachsaran Formation is one of the most important erodible formations in Iran. This formation has about 1600 meters of thickness and in terms of petrology includes salt, anhydrite, colorful lime marls and some shale. Therefore, scientific research on runoff and erosion of Gachsaran Formation is essential, which is one of the main objectives of this study.

In this research for determination of the most important factors in runoff production of various land uses in Gachsaran formation studied a part of the gypsum mountain watershed in Izeh Township. It has 1202 hectares area. This investigation in order to determination of the relationship between produced runoff by rain simulator with some soil physicochemical characteristics like percent of very tiny sand, sand, clay, silt, pH, Ec, soil moisture, Calcium Carbonate and organic materials in different land uses of Gachsaran formation done. Then run off samples in 6 points and with three replicates in Gachsaran formation in the precipitation intensities of 0/75, 1 and 1/25 millimeter in minute in range, residential and agricultural land uses using rain simulator done. In order to investigate efficacious factors in runoff production, sampling was done in 0-20 centimeters of soil layers and also the same number of runoff. In order to do statistical analysis used EXCEL and SPSS software.

The most important soil factors in runoff production were identified by multi regression. The results showed that runoff production in different land uses at different intensities had significant differences. In this study, it was shown that the recognition of the soil parameters is very important in increasing and decreasing runoff in Gachsaran formation.

  Regression models showed that clay and calcium carbonate had the highest role in increasing and decreasing runoff of different land uses among the measured factors in Gachsaran Formation.