Groundwater is a key water resource, with 45.7% of all drinking water globally beingextracted from 15groundwater. Maintaining good groundwater quality is thus crucial to secure drinking water. 16Micropollutants, such as pesticides, threaten groundwater qualitywhich can be mitigated by 17biodegradation.Hence, exploringmicrobial communities in aquifers used for drinking water 18productionis essential for understanding micropollutantsbiodegradation capacity.This study aimed 19at understanding the interaction between groundwater geochemistry, pesticide presence, and 20microbial communities in aquifers used for drinking water production. Two groundwater monitoring 21wellslocated in the northeast of The Netherlands and at 500 m distance from each other were sampled 22in 2014, 2015, 2016 and 2018. In both wells, water was extracted from five discrete depths ranging 23from 13 to 54 m and used to analyze geochemical parameters, pesticide concentrations and microbial 24community dynamics using 16S rRNA gene sequencing and qPCR. Groundwater geochemistry was 25stable throughout the study period and pesticides were heterogeneously distributedat low 26concentrations (μg/L range). Integration of the groundwater chemical and microbial data showed that 27geochemical parameters and pesticides exerted selective pressure on microbial communities. 28Furthermore, microbial communities in both wells showed a more similar composition in the deeper 29part of the aquiferas compared to shallow sections, suggesting vertical differences in hydrological 30connection. This study provides initial insights into microbial communitycomposition and distribution 31in groundwater systems in relation to geochemical parameters. This information can contribute for 32the implementation of bioremediation technologies that guarantee safe drinking water production 33from clean aquifers.