Kharazmi Journal of Earth Sciences

Kharazmi Journal of Earth Sciences

Investigation of the dominant flow system in the Nekarood karst basin

Authors
narges nabizadeh chamazcoti
Gholam Hossein Karami
azizollah taheri
ramazan ramazani omali ramazani omali
10.22034/KJES.2024.10.2.107741
Abstract
The Nekarood basin is located in the north of Iran and has an area of 2275 km2 . In the Nekarood Basin, the majority of limestones include thick bedded and massive limestones of Lar Formation and Cretaceous limestones, and there is also a lesser amount of limestones of the Elika, Dalichai and Ruteh Formations. Various features such as the amount of outcrop, thickness and lithological characteristics of karst rocks and their relationship to other lithologies on a regional scale are the geological controls on karst development. Among these factors, the thickness and lithology of the existing formations in the studied area are of great importance, in such a way that if the outcropping limestone is thick bedded and massive, the karstification process is very high. In order to investigate and analyze parameters such as the hydrograph and recession curve of the basin’s springs, discharge coefficient, type of flow system (conduit and diffuse), determination of the source of recharge, and water quality of the springs, physical and chemical characteristics of the springs (discharge, electrical conductivity, temperature, etc.) were analyzed. In the Nekarood basin, four karst springs, Jezi, Espeo, Kao Cheshmeh, and Senbi have relatively high discharge rates and were selected for detailed study. The analysis of temporal variations in discharge indicates that the spring discharge is significantly dependent on regional precipitation. When precipitation exceeds 15 mm, which is sufficient to recharge the aquifer, the spring water flow increases after a relatively short time delay. Furthermore, the analysis of temporal variations in electrical conductivity of the karst springs shows that electrical conductivity decreases as discharge increases. This indicates that as the karst aquifer is recharged and the proportion of recharged water increases, the dilution process reduces the dissolved salts in the aquifer water, leading to a decrease in electrical conductivity. Analysis of the recession curves of the springs revealed that the recession curve for all selected springs is multi-slope, and the discharge coefficients range from 10-3 to 10-2. Considering that the coefficient of discharge variation and the recession coefficients are relatively high in all four karst springs, it can be concluded that the dominant flow system in this karst aquifer is of the conduit-diffuse type.
Keywords
Karst spring
dominant flow system
Nekarood
Subjects
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Kharazmi Journal of Earth Sciences
Volume 10, Issue 2 - Serial Number 20
December 2024
Pages 538-556