Author(s)

J. W. Male & M. S. Kennedy

Abstract

The increased emphasis on sustainability has resulted in an effort to reduce the reliance on municipal water in favor of the use of collected rainwater. This paper addresses the reliability of rainwater collection and use for residential buildings. It describes a procedure that utilizes a water balance based on the amount of collected rainfall, household demand, and storage tank capacity. The probabilistic nature of rainfall is incorporated by establishing weekly exponential distributions based on historical data. These rainfall distributions are used in a Monte Carlo simulation along with characteristics of the residential system (catchment area, storage tank size, household demand, etc.). Results show that along with the size of catchment area, the storage tank capacity is critical in determining the reliability of the system. The procedure is illustrated with data from Portland, Oregon. Keywords: rainwater harvesting, reliability, residential water supply. 1 Introduction With increasing water rates, a growing number of homeowners are considering the use of rainwater to help lessen the reliance on municipal water. While the practice is more common in other countries, it is far from widespread in the U.S. In addition, water supply utilities are also looking for ways to reduce water use and forestall the need for capacity expansion. Judicious use of rainwater has the potential to address both concerns. The intent of this paper is to assess the potential use of rainwater for domestic purposes in Portland Oregon, paying particular attention to the reliability of rainwater collection. 1.1 Previous work The use of rainwater has been addressed by a number of individuals and organizations, but usually from the practical viewpoint of design. There are a

Keywords

rainwater harvesting, reliability, residential water supply.