The Buzău river alluvial fan – a groundwater modeling approach to sustainable exploitation
Abstract: Knowledge of groundwater resources is a key challenge for hydrogeologists, especially due to a continuous increase in demand for drinking water. This paper aims to investigate the consequences of overexploitation of the phreatic aquifer from the Buzău River alluvial fan and to assess alternatives operating programs related to achieving a sustainable groundwater exploitation. The study was achieved using data (groundwater level and general information from 97 hydrogeological boreholes) from the National Institute of Hydrology and Water Management, Romania, and collected in the field between July 18-19, 2017 (river stages for Buzău and Călmățui). The aquifer data was statistically analyzed and the obtained results allowed the design of a conceptual model for the hydrostructure and a mathematical model for the groundwater flow, using the FREEWAT software. Continuous exploitation of the phreatic aquifer through the catchment fronts that supply the city of Buzău (Crâng, Zahăr I, and Sud fronts) was simulated using the hydrodynamic model, in a transient regime. The maximum allowable flows were defined for each hydrogeological borehole that exploits the phreatic aquifer, using the mathematical model (values between 4.0 and 19.0 l/s). The exploitation of these flows was performed for 10 years, with time steps that allowed an analysis of the depression cone extension and drawdown value after 90 days, 180 days, one year, and five years of continuous pumping. After ten years, the resulting depression cone reached a diameter of 9.8 km and the groundwater level decreased with a maximum of 8.26 m, in a hydrogeological borehole. For stationary simulation (which is not influenced by the time parameter), it was observed that pumping with the maximum allowable flows resulted in a drawdown that exceeds one-third of the water column, which indicates overexploitation.