Pump-and-treat (P&T) techniques are among the most commonly applied methods for groundwater contamination remediation. This study develops a groundwater flow model and a solute transport model using MODFLOW and RT3D to design and optimize P&T strategies for a polluted chemical park in northern China. Five scenarios were analyzed to evaluate the effects of well placement and pumping rates on remediation performance. Simulation results indicate that the existing number of extraction wells is inadequate to meet remediation targets. While increasing the pumping rate of individual wells accelerates remediation, it also increases the total extracted water volume. Similarly, higher extraction rates in heavily contaminated areas shorten remediation times but lead to greater water extraction. The findings demonstrate that numerical modeling can effectively optimize P&T designs, enabling the minimization of water extraction volumes while achieving remediation objectives within the required timeframe.

Unconfined aquifers beneath piedmont pluvial fans are widely distributed in front of mountains and proper for water supply with pumping wells. However, the catchment zone and capture zones of a pumping well in such an unconfined aquifer is not well known. We develop a preliminary simplified model where groundwater flows between a segmental inflow boundary and a discharge boundary of constant head. The catchment zone is delineated from numerical simulation via MODFLOW and MODPATH. Results are expressed with dimensionless variables and lumped parameters to show general behaviors. Sensitive analyses indicate that there are 4 types of the catchment zone according to different connections to the boundaries. The shape of the catchment zone is quantitatively analyzed with typical shape factors. Capture zones with respect to special travel times are identified from travel time distribution in the catchment zone. The modeling results can be applied in the design of water supply wells and delineation of protection zones at a site with similar hydrogeological conditions.