Geographic Information System Mapping Tool for Rainwater Harvesting in the United States

Abstract

The Rainwater Harvesting Tool is a publicly available web-based geographic information system tool. It was developed using geospatial analysis in combination with historic zone improvement plan (ZIP) Code–level monthly average precipitation and evapotranspiration data across the US to help select potential locations for harvesting rainwater. Rainwater harvesting can provide a key alternative water source for a variety of uses, including landscape irrigation, vehicle washing, cooling tower make-up, dust suppression, and toilet flushing. Rainwater harvesting can help to diversify water sources for institutional, commercial, and residential buildings and offset the use of treated potable water. This tool aims to help organizations strategically target locations in which to implement rainwater harvesting systems. The metric used in the tool is called the rainwater harvesting potential, which is a normalized metric. The rainwater harvesting potential describes the amount of rainwater that reasonably can be collected and stored at a specific location. This metric was used to rank areas delineated by ZIP Codes across the US from lowest to highest to show the relative availability of rainwater for harvesting. Two mapping layers are included in the tool: a layer that shows the general year-round rainwater harvesting potential, and a layer that specifically shows the potential for harvesting rainwater to supply irrigation water. The Rainwater Harvesting Tool allows users to view the overall trends across the US and view the data at a scale at which the ZIP Code boundaries are clearly delineated. The tool can be used to help organizations with buildings located in multiple regions to strategically identify where to install rainwater harvesting systems and prioritize locations that may be optimal for rainwater harvesting. The Rainwater Harvesting Tool is a web-based geographic information system tool, which is free and available to the public. The tool presents the rainwater harvesting potential across the US to help determine locations that are potentially good candidates for harvesting rainwater and capable of meeting the water demands of institutional, commercial, and residential buildings. Rainwater can supply water for irrigation, cooling towers, vehicle washing, toilet flushing, and so forth, and offsets the use of treated potable water. The tool contains two mapping layers. The first shows the general potential for capturing rainwater and indicates the relative ability of a given location to collect rainwater throughout the year for beneficial use. The second identifies areas with favorable precipitation patterns for collecting rainwater during the irrigation season. The Rainwater Harvesting Tool provides interactive functions within a single browser session. Users enter specific locations (by ZIP Code), and the tool outputs a relative rank of the harvesting potential. The amount of rain potentially harvested each month also is provided. This portfolio planning, decision support tool can be utilized by organizations to target locations that are most conducive for rainwater harvesting across many locations.