The Role of Qazvin Central Marsh Interceptor Drain in Controlling Shallow Groundwater Salinity

Qazvin salt marsh open interceptor drain has been designed and implemented to either prevent or reduce the risk of salinity expansion to its upstream fertile lands. This paper is intended to assess results of the data gathered from the monitoring system around the drain. To monitor the effect of the drain on water table level and on the shallow groundwater quality، 99 observation wells (in 9 sections perpendicular to the drain) were constructed. Water table levels were measured and samples taken on a monthly basis. Chemical analysis of the samples throughout the year showed chemical changes resulted from the existence of the drain. The drain performance was evaluated as positive since it resulted in a discharge of brine with a salinity of around 200 dS. m-1. The results showed that the construction of inceptor drain stopped movement of saline water towards fresh water aquifer to some extent by increasing the groundwater hydraulic gradient as due to a lowered water table of about one meter. The subsurface water salinity decreased to an extent of 13. 6 percent throughout the first year. Obviously the decrease was not observed as even in all the observation wells. The performance of the drain was finally evaluated as positive during the first year of its operation.