Hydrology
hojat miranimoghadam; Gholam Hossein Karami; Rahim Bagheri
Abstract
Gonabad area is an arid region where 19.5 mcm of groundwater is annually extracted from 26 qanats. Six major qanats were sampled for hydrochemical and isotopic analyses to determine the origin and flow mechanism of the groundwater.The total dissolved solids vary from 524 to 2375 mg/l. The dominant water ...
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Gonabad area is an arid region where 19.5 mcm of groundwater is annually extracted from 26 qanats. Six major qanats were sampled for hydrochemical and isotopic analyses to determine the origin and flow mechanism of the groundwater.The total dissolved solids vary from 524 to 2375 mg/l. The dominant water types are Na+-Mg2+-HCO3- and Na+-Cl-. The groundwater is saturated with regard to carbonate minerals and under-saturated with regard to evaporate minerals. This means that the composition of the groundwater is highly controlled by the dissolution of carbonate rocks. The deuterium and oxygen 18 isotopes signatures demonstrate the meteoric origin of the groundwater and the flow mechanism is direct infiltration of precipitation before evaporation through fractures in the limestone formations and infiltration of surface water in the coarse grain alluvial cones at the south of the plain. The groundwater recharge originates from an area between 2000 to 2700 m a.s.l. The groundwater of these qanats has depleted stable isotopes in the wet season due to recharge through the infiltration of precipitation and has enriched stable isotopes in the dry season due to recharge through the return flow of qanats and springs used for agricultural activities in the south of the basin.
