Excerpt from the report Preface: This publication provides basic long-term data on the variability and dependability of an area's natural rainfall supply potential. In addition to providing a better understanding of the precipitation phenomena of an area, the data will also aid in the development of water resource management plans for the area. For example, the need for supplemental irrigation can be derived; adequacy of precipitation for municipal and industrial water supply can be determined; and the design and management of reservoir storage for flood control or low-flow augmentation can be estimated. These data will also be used in research work in the evaluation of projects or operations in a given area.