Comparing of the Runoff and Sediment of Different land uses in Gachsaran and Aghajari formations under Rain simulation

Sediment Production in catchment area subject to very much factors, the one of these factors are not correct use of the lands. Environmental characteristics such as amount and intensity of precipitation, the degree of slope and accumulation of aqueducts in production of runoff and sediment is effective. Sediment production in a watershed depends on several factors, one of the most important of which is inappropriate and unprincipled use of lands. Different environmental issues also have different effects on sediment production. Aghajari formation consists of gray and brown calcareous sandstone, gypsum red marl, and siltstone. Its main section spreads from Omidiyeh to the Aghajari oil field and it has a thickness of 2965 meters. Gahsaran formation has a thickness of about 1600 meters. A viewpoint of lithology is consisting. Statistical studies in the mentioned regions show that the absolute maximum air temperature is 46 °C, the absolute minimum temperature is -6.7 °C and the annual temperature average is 20.8 °C. The annual rainfall average is 636 mm.

In order to investigate sensitivity to the erosion and sediment yield the various land uses of Aghajari and Gachsaran deposits, part of Margha and Kuhe Gach watersheds areas in Izeh Township was elected. This investigation to determine productivity runoff and sediment in 6 points and three times replicates in Gachsaran formation and in 7 points and with three times replicates in Aghajari in the various intensities of precipitation 0.75, 1, and 1.25 mm in minute in three land uses range, the residential and agricultural lands to help kamphorst rain simulator do. These experiments were carried out in Aghajari and Gachsaran formations at the end of spring and after harvesting in agricultural lands, and in order to create homogeneous conditions for rainfall simulation, there was no vegetation at plot level in Aghajari and Gachsaran formations. In this study, samples were randomly identified and harvested. Also, all information related to different studies in the studied watershed including climate and geology were used in this study. Spss and Excel software were used to perform all statistical analysis.

Comparing runoff and sediment in two formations showed that in the low intensities of precipitation formation type in runoff and sediment has more interference. Whatever precipitation increases, the difference to at least it seems. It is also recommended that due to the high erosion and sedimentation of these two formations, reservoir of large dams is not located in these two formations because at a very short distance or the reservoirs of these dams are filled with sediment. Or they become so salty that they cause huge damage to downstream areas or cause dangerous landslides in the dam reservoir, which will eventually lead to dam breakage and ultimately devastating floods by pushing large volumes of water into the dam body.

In addition, research results showed that erosion and sediment rates in land uses of Gachsaran formation is more than Aghajari formation land uses due to Ec and more distance gypsum hardpan than soil surface. However, two formation of viewpoint run off rates proximately had similar trend. The results also showed that due to high erosion and sedimentation of these two formations, reservoir of small and large dams is not located in these two formations.