Three-Dimensional variably- saturated simulations of groundwater flow and salt water intrusion using a numerical model (Case study: Tavabe- Arsanjan, Fars province, Iran)

Tavabe-e-Arsanjan, Iran, is one of the oldest agricultural areas in the world and is suffering from the progressive salinization of basin groundwater due to crop irrigation activities as well as the progressive intrusion of salt water from the adjoining highly saline Tashk Lake. The objective of this study is to use a three-dimensional variably-saturated variable-density hydrologic model to investigate the progressive salinization of the regional groundwater flow system due to agricultural irrigation activities, as well as the continued encroachment of the highly saline saltwater intrusion front emanating from Tashk Lake into the aquifer. First, Inverse method is used to estimate the hydraulic conductivity, porosity and the fraction of precipitation which infiltrates as well as the fraction of irrigation water that recharges the water table. In the course of the numerical simulation of the salt water intrusion in the area, various aquifer parameters, including boundary condition, were identified with the model until satisfactory agreements between modeled and observed values of water level and chloride concentration were obtained. Comparison between observed and simulated values showed good agreement between the simulated and observed water table elevation. Overall, one could conclude that groundwater flow and the solute transport model performs satisfactorily with regards to results. More importantly, the model could be used to predict future changes in water levels and chloride concentrations of the groundwater when controlling of the salt water intrusion are taken into account. Several management scenarios were chosen to represent the likely range of effects that could be encountered at Tashk Lake, and provide some information about the behavior of the lake system and possible impacts under a variety of operating conditions.

Keywords:

Groundwater modeling , salt water intrusion , Tavabe-e Arsanjan area