What does this CALCULATOR do? The purpose of this spreadsheet is to aid the user in evaluating the Rainwater Harvesting approximate potential for a given site. Instructions are provided in the green column on the left that help with step-by-step procedures. The user can look up and enter rainfall information for a specific location in Clackamas County, and then can add specific information for the amount of roof area that is available, the size or potential design size of the water storage units, and some information regarding rough estimated watering needs. For the entered information, the spreadsheet estimates the water volumes that are collected, stored, and used on a monthly basis. It does this by using standardized monthly rainfall distributions and rough estimated monthly watering rates. This spreadsheet calculates the largest useful storage size by several methods and also calculates the amount of landscape that can irrigated by the design storage size and recommended storage size.
Click here to download the rainwater harvesting calculator.