A new approach to the step-drawdown test

Abstract

In this paper a new approach to perform step-drawdown tests in presented. Step-drawdown tests known so far are performed strictly keeping the value of the pumping rates constant through all the steps of the test. Current technology allows us to let the submerged electric pumps work at a specific revolution per minute (rpm) and allows us to suitably modify the rotation velocity at every step. Our approach is based on the idea of keeping the value of rpm fixed at every step of the test, instead of keeping constant the value of the discharge. Our technique has been experimentally applied to a well and a description of the operations and results are thoroughly presented. Our approach, in this peculiar case, has made possible to understand how actually the discharge Q varies in function of the drawdown s_w. It has also made possible to monitor the approaching of the equilibrium between Q and s_w, using both the variation of Q and that of s_w with time. Moreover, we have seen that for the well studied in this paper the ratio Q/s_w remains almost constant within each step.