Field study and iron reactive simulation in riverbank water supply well fields

摘要

The quality of groundwater pumped out by riverbank water supply well fields often tends to decrease due to infiltration of water from surface reservoirs. A similar situation is the case for an investigated reservoir located in the central Russian Federation. Water intakes are located at the bank of a river whose level has been raised by >3 m since the construction of a water reservoir in this river. Numerical flow simulation shows that 70-90% of groundwater is replenished by water from the reservoir. Monitoring of the groundwater quality shows that iron concentration is higher than the maximum admissible value for drinking water. We have been involved in the project aimed at identifying and locating sources of iron in groundwater coming from the intakes. At the initial stage a series of field experiments was performed, such as chemical tests of groundwater, reservoir and near-bottom water, as well as sampling of aquifer rock and bottom sediments. Eventually, the most probable source was found -high content of iron minerals in bottom of the reservoir. The process of dissolution of iron minerals due to reservoir water infiltration through bottom sediments into the aquifer was simulated by PHREEQC-based numerical model.