Simulating the impact of subsurface dam construction on the change of nitrate distribution

The use of subsurface barriers can be suggested to harvest the underground flows during the dry seasons. Groundwater levels at the south of Shahrekord plain has fallen strongly because of immoderate discharge and decreased the quality of water by urban wastewater entrance. The solute transport modeling was conducted to evaluate the impact of subsurface dam construction on flow treatment and urban water quality using numerical simulation. The hydraulic conductivity and specific yield has been calibrated in both steady-state and transient conditions during 15 months over the time period 2007–2008. The southern outlet of plain was selected to study the simulation of underground dam then a horizontal-flow barrier set in this location with mean hydraulic conductivity about 0.5 m/day. The solute transport model was calibrated and verified by monthly measured data of nitrate concentration before and after the dam construction. Longitudinal dispersivity and distribution coefficient was estimated 5 and 0.0001, respectively. The results show that the central parts of aquifer are responsible for raising the groundwater levels in the measured piezometers located about 4.5 km in upstream with 13 km² area on the upstream side of dam structure. Quality model predictions don’t show considerable difference in nitrate concentration.