Evaluation of the Spatio-Temporal Variability in River and Groundwater Interactions, an Example from South West of Iran

River - groundwater interaction is one of the most common types of surface water and groundwater exchanges that occur in alluvial aquifers. These interactions are variable with space and time and received great attentions in recent years. In this research, the natural tracers such as 222 Rn, natural heat and common water quality characteristics were applied to evaluation of the river- groundwater interactions. The study area is Chamgolak area that is located in the northeast of the Andimeshk city in the south west of Iran. The Dez River is the major surface water body that interacts with groundwater in this area. The temporal and spatial variation of water exchanges between the river and groundwater were evaluated in this research. For this purpose, some common water quality parameters such 222 Rn, temperature, electrical conductivity (EC) and nitrate were measured in 2012- 2013 water year. The temporal variation patterns of common water quality parameters shows that the river recharge water influences the groundwater quality, so that the amounts of electrical conductivity (EC), temperature and nitrate show a notable decrease in river adjacent wells especially in wet period. "The spatial pattern of nitrate concentration shows that the topographic conditions of the Dez River channel also influence the rate of river - groundwater interactions, so that the maximum water exchanges between river and groundwater occur in the convex part of the Dez River meander near the Chamgolak town. This study show that the Dez River has a losing nature and recharges the groundwater but with rates that is vary temporally and spatially.