This Public Works Technical Bulletin (PWTB) provides an overview of rainwater harvesting for Army installations. Rainwater "harvesting," or the capture of rainfall runoff from roofs or similar hard surfaces that would normally escape to storm sewers or overland flow, provides a high quality source of water that can be used to extend an installation's water supply. This alternative allows beneficial use of water and helps meet a number of recent policy requirements. This bulletin presents a brief history of rainwater harvesting; a review of policies and regulations; guidelines that may play a role; and a summary of institutional barriers. Guidelines are also presented on how to develop an active rainwater harvesting system including design factors, user considerations, materials, implementation, and operation and maintenance (O&M). Additionally presented are representative economics, examples of local requirements, and military experience with lessons learned. This document does not attempt to provide an exhaustive treatment of every aspect of rainwater harvesting; rather, it means to present sufficient information to encourage greater consideration of the necessity and benefits of incorporating this option on installations. Application of the guidelines presented in this bulletin will provide installation personnel with the information to properly determine the applicability of rainwater harvesting for their installations.