Aakaashepani (आकाशेपानी) is a user-friendly and interactive Android application that provides an enabling environment for the installation of a rainwater harvesting system. With the help of this application, users can calculate the optimal tank size required for household need in a few easy steps with their fingertips. In addition, it maps the nearest vendors from where people can purchase the installation parts and provides other technical and financial aspects of rainwater harvesting systems specific to the household site. This application incorporates the information of local precipitation pattern, structures and dimensions of roofs and their runoff coefficients including households’ water requirements. The algorithm of the application dynamically adjusts to the users’ input considering the water availability, demand and potential storage. This application is currently limited to Karnali River Basin, Nepal, but, being freely available and highly customized to the local context of the Himalayan basin, it is of great significance to build adaptive capacity of the local people.