This document presents a study that uses Bayesian Regularized Neural Networks (BRNN) to model groundwater levels in the Mahabad aquifer in Iran. The study area and data collection process are described. Five factors - precipitation, evaporation, temperature, streamflow, and previous month's groundwater level - are used as inputs to the BRNN model to estimate current groundwater levels. The results show the BRNN model performs excellently with low errors and high accuracy and determination values. Previous month's groundwater level and streamflow are found to be the most important predictors of current groundwater levels.