Identifying the recharge and salinization mechanisms of the Shekastian saline spring in southern Iran.

Abstract

To identify the recharge, and the salinization mechanisms of Shekastian saline spring, appearing via thin limestone layers on the Shekastian stream bed, southern Iran, a comprehensive study was conducted using multi-tracing approach. Hydrochemical tracing indicated that the halite dissolution is the main salinity source for Shekastian spring. Similar to surface waters, spring salinity is amplified by evaporation during dry season, indicating that recharge comes from surface waters. The temperature of the spring water varies hourly, which is another sign that surface waters recharge the spring. Applying the discharge tracing method at two low-discharge times in two consecutive years by precise longitudinal discharge monitoring of the Shekastian stream above and below the spring site revealed that the main source of recharge for the Shekastian saline spring is water escape via thin limestone layers, located on a stream bed above the spring site. Results of isotope tracing indicated that Shekastian saline spring is recharged from evaporated surface water, subjecting to CO2 gas along subsurface flow path of recharging water. Geologic/geomorphologic evidences, supported by results of hydrochemical tracing, revealed that halite dissolution of Gachsaran evaporite formation by spring recharging water is the main salinization source for the Shekastian saline spring. To avoid salinization of Shekastian stream by Shekastian saline spring, draining the spring recharging water at downstream vicinity of spring recharging stream by building an underground interceptor drainage system is suggested, in which resulted in flow stopping the spring.