Abstract: The dimensioning of a ground water well is obtained by investigating the yield characteristics of the ground water region by conducting a series of pumping runs using an observation tube in stepwise pumping cycles of short time intervals (15 seconds to 20 minutes), and measuring the hydrostatic height of the water of each run, finding the yields as a function of the level drop. The yield of the production well, compared with the yield of the observation tube, is found from the ratio of the strainer sections and observation tube, using a predetermined empirical factor corresponding to the different sizes of the strainer. In the case of ground water deposits at very great depth, the yield may be explored by an inverted method in that water is pumped into the ground and the hydrostatic pressure is measured with different pumping rates.