Flood-spreading effects on the chemical properties of the soil: a case study of the Tasuj station, Iran

چکیده مقاله

Floods impact the quality of soil in the flood area and affect the success or failure of the flood-water spreading plan. An important issue is related to the changes of soil properties after a flood spreading event. The objective of this paper is to determine whether the flood spreading system at Tasuj station in east Azerbaijan, Iran, has caused inappropriate chemical alterations of soils. One question is whether the flood spreading system was constructed at an inappropriate location such that it could lead to unintentional consequences. For this purpose, composite soil samples were taken from three flooded areas, from three grids in each flooding area, and from two depths. Two soil samples were also taken from a control area (totally 20 composite samples). Soil chemical characteristics including electrical conductivity, pH, concentrations of bicarbonate, chloride, sodium, calcium, and magnesium ions, and the sodium adsorption ratio (SAR) in the flooded areas were measured. Results showed that because of calcareous, gypsum, shale, and marl formations in the first flooded area (especially its first grid), dissolution of solutes of these formations increased the concentration of ions in the runoff (especially sodium and chlorine, to 19.50 and 21.90 mmol (charge) L^-1, respectively). These high ion concentrations caused the electrical conductivity of runoff increased significantly (up to 2.03 dS/m) compared to the other areas. High amounts of lime in the soil caused increasing buffering capacity of the area soil, as a consequence the flood spreading did not cause significant changes to the soil pH and showed only 0.3-0.2 differences (insignificant) in the first flooded area compared to other areas. Based on these observations, it is concluded that the flood spreading system was constructed at an appropriate location so that it will not cause detrimental effects to the chemistry of the soil. There is a minor problem associated with salts in the initial parts of flooded area. This issue can be mitigated by cultivating plants resistant to salinity and drought and by adding modifiers.