Abstract: Complicated seepage problems can be solved satisfactorily with simplified mathe mate solutions if correct explanations are made for seepage flow net.In this paper, a detailed description is given on an easy method which uses weighted mean streamline length to simulate the local additional resistance for three dimensional flow problems of partially penetrating wells in confined and unconfined aquifers, thus simplifying the solutions for complicated seepage problems.Formulas （21） and （22） for calculating the discharge of partially penetrating wells are not only simple but also accurate as compared with approximate calcula-t-ing formulas at home and abroad.