The purpose of the paper is to describe a procedure for the hydrologic computations necessary to river basin studies. For this paper hydrology is defined as the science dealing with water, its properties, phenomena and distribution, especially with reference to water on the surface of the land, in the soil and underlying rock, and in the atmosphere. This definition implies that quantity and quality are hydrologic factors that are inseparable for a complete analysis of existing data. However, it is proposed herein to separate the computations by obtaining and analyzing data on quantities of flow, and later superimposing quality data upon the quantity analysis to determine flow and storage needs for water quality control. (Author Modified Abstract)