The extreme well‑loss component of drawdown in two deep artesian wells in Israel

The drawdown of water levels in pumping wells encompasses two main components: aquifer loss and well loss, the latter primarily arising from turbulent and nonlaminar flow conditions. This study aimed to analyze the drawdown characteristics of two deep artesian wells in Israel, measuring depths of 1,397 m and 878 m, to determine the significant impact of well loss in relation to aquifer loss. Methodologically, step-drawdown tests were conducted to evaluate the relationships between these components, while detailed measurements of flow velocities and head pressures were recorded. Results indicated that a striking 96–99% and 82–90% of the total drawdown for the respective wells was attributed to well loss, leading to low well efficiencies that decreased as flow rates increased. Moreover, each activation of the artesian flow caused immediate observable jumps in head pressure, highlighting unusual dynamics compared to typical well behavior. Turbulent flow conditions, confirmed by high Reynolds numbers within the well casings, along with significant frictional head losses identified through the Darcy-Weisbach equation, contributed to the high levels of well loss observed. This phenomenon presents critical implications for the engineering and management of deep artesian wells.