mohsen padyab; Sadat Feiznia; Hasan Ahmadi; Ardeshir Shafei
Abstract
Evaluation of changes present in soil and water resources due to operation implement of floodwater spreading is necessary to assess their positive or negative resultant effect. Rate of the internal sediment to diversion spreader channels, surface sedimentation and aggregation of the spreading field depth ...
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Evaluation of changes present in soil and water resources due to operation implement of floodwater spreading is necessary to assess their positive or negative resultant effect. Rate of the internal sediment to diversion spreader channels, surface sedimentation and aggregation of the spreading field depth are most important effective attributes on the yield of floodwater spreading systems. These factors can change physical and chemical properties of studied field, as, by measuring of the infiltrate depth sedimentation of can achieve influencing depth of floodwater. To determine the effect of flooding spread on the sediment infiltrate rate in the field depth of Gachsaran floodwater spreading, from 0-15, 30-15, 30-45 and 45-60cm of the soil surface of spreading field and control were sampled. Granulometry of all samples was done using dry sieve and hydrometric analysis and then percent of the sediment grains with size of less than two millimeters were subjected to analysis of variance (ANOVA) by Duncan t-student test for 80 sampled samples. Results showed that deep entering of the sediments into drilled profiles to 30-45cm was completely distinct which can affect on the soil physical and mechanical properties. However, after the 30-45cm depth, the impact of floodwater spreading was minimal. The infiltration of each studied layer is the most important feature which will change from surface to the depth of spreading belts, so that by increasing infiltrated fine particles in the depth and blocking pores, the soil layers are clogged and in result reduce the infiltration rate, sharply. This state was more remarkable in the spreader belts surface. Furthermore, by depositing the sediments in the surface (0-15cm depth), an impermeable and earthen layer is created which prevent from infiltrate the particles and even water into soil depth. Generally, with determine of the deposited sediment level in the spreading belts and also its deep infiltrate rate can provide effective and practical decision to improve efficiency and easy maintenance of the floodwater spreading systems or even not use this method.
Mohsen Padyab; Sadat Feiznia; Hassan Ahmadi; Ardeshir Shafei
Abstract
Small precipitation with temporal and spatial variation of rainfall is the main responsible factors on flood occurrence in arid and semi arid regions. Floods in their regions usually contain high concentration of sediments which when they are deposited on the surface of lands, they change the properties ...
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Small precipitation with temporal and spatial variation of rainfall is the main responsible factors on flood occurrence in arid and semi arid regions. Floods in their regions usually contain high concentration of sediments which when they are deposited on the surface of lands, they change the properties of soils of the area. In this research, the effect of floodwater spreading on physic-chemical characteristics of soil in Gachsaran floodwater spreading station, after 12 years of floodwater spreading, is investigated. For this purpose, soils and sediments were sampled from 0-15, 15-30, 30-45 and 45-60 centimeter depths, from the flood spreading and representative (without floodwater spreading) fields. Samples were analyzed for following proportion: percentages of clay, silt, sand and gravel, pH, EC, percentage of lime, anions and cations. The result have show that the amounts of clay, silt and sand have increased, chemical properties have changed slightly and among the chemical properties, pH and percentage of lime have higher change so that pH decreased and lime increased in floodwater spreading field respect to the representative field. It is concluded that due to floodwater spreading, physical properties of the field underwent considerable amount of changes and gravelly texture has changed to less gravelly texture. The surface soil has undergone more changes and from the surface to the depth, change of physical and chemical properties becomes negligible.
