The present study aimed to analyze groundwater level changes in the Dorud-Borujerd plain and to identify trend change points and structural transformations in aquifer behavior. Unlike conventional studies that merely rely on linear trend detection, the novelty of this study lies in the triple integration of non-parametric change-point tests, statistical distribution change analysis, and their spatial interpretation to reveal the aquifer's transition from a stable regime to an unstable one. For this purpose, data from 25 piezometric wells were analyzed using the modified Mann-Kendall test (with autocorrelation removal), the Pettitt test, statistical parameter analysis before and after the break, and the two-sample Kolmogorov-Smirnov test. The findings indicated that 72% of the wells exhibit a declining trend, but only two wells (Borujerd University and Kivareh) show a statistically significant trend at the 95% confidence level. The Pettitt test revealed a significant change point for 64% of the wells within the 2007–2009 period; the remaining 36% of the wells experienced a later trend change during 2010–2020. Analysis of statistical characteristics before and after the break showed a sharp increase in variance (up to 13,838%) and a shift in skewness toward severely negative values (up to 875%) in the post-break period. The Kolmogorov-Smirnov test also confirmed a significant change in data distribution for 76% of the wells. These findings suggest that the Dorud-Borujerd aquifer has transitioned from a relatively stable condition to an unstable regime characterized by severe fluctuations and a concentration of data at low extreme values. Spatial analysis of the Mann-Kendall Z statistic revealed that the western part of the plain experienced the greatest fluctuation, with the Borujerd University well showing the most severe decline and the Kivareh well showing the greatest increase; this spatial heterogeneity is attributed to differences in local recharge conditions, anthropogenic withdrawals, and lag in hydrogeological response.