Technical Abstract: The benefits of water table management (WTM) practices on groundwater quality were investigated by conducting field experiments at Iowa State University's research centers in Ames and Ankeny, USA, during the crop growing seasons of 1989-91. Water-table depths of 0.3, 0.6 and 0.9 m were maintained in the field lysimeters at the Ames site, and variable water- table depths were maintained in a subirrigation field at the Ankeny site. Groundwater samples were collected from various depths to evaluate water quality by analyzing NO3-N and pesticide concentrations in groundwater. The lowest NO3-N, atrazine, and alachlor concentrations in groundwater were observed at shallow water-table depths of 0.3-0.6 m. Chemical concentrations in groundwater generally decreased with increased depths and time during the growing season under all WTM practices. Results of this study indicated that WTM practices can be used to substantially reduce the chemical concentrations in groundwater for environmental benefits.