<p>Low-permeability fractured rocks, which are the bedrock of many regions worldwide, show highly complex and varied drawdown-time trends when pumped due to their extreme heterogeneity and anisotropy. Understanding their behavior is essential for operational choices, such as using of wells for water supply. This study examines Miocene dacitic-andesitic rocks, comparing rock mass characteristics with pumping test results to provide useful insights for the sustainable management of wells and the long-term preservation of groundwater resources. To achieve this, comprehensive investigations, including analysis of rock mass fracturing, core main technical properties, groundwater level monitoring and nine single-well pumping tests, were conducted on a test site. Results show that the dacitic-andesitic aquifer is extremely heterogeneous at the scale relevant for well design and pumping assessment. The heterogeneous pumping responses observed are due to the continuity and spatial distribution of discontinuities, their dispersed orientation, the presence of discontinuous volcanic breccia and the intercalations of quartz veins, dikes or filled fractures within the rock mass. In this complex environment, the temporal evolution of drawdown and recovery is a more crucial indicator for sustainable planning pumping, than the hydrogeological parameters values derived from conventional pumping test interpretation. Consequently, the duration of pumping tests becomes a critical factor, as it allows the identification of successive flow regimes and provides insight into the scale-dependent transmissivity of the aquifer. This finding has direct implications for the management of highly heterogeneous volcanic and low-permeability fractured aquifer, allowing to accurately assess the sustainable yield and appropriate usage timing of wells.</p>