Continued Operation of a 25-Raingage Network for Collection, Reduction, and Analysis of Precipitation Data for Lake Michigan Diversion Accounting: Water Year 2009

Abstract

A dense raingage network has operated in Cook County since the fall of 1989 to provide accurate precipitation measurements for use in simulating runoff for Lake Michigan diversion accounting. This report describes the network design, the operations and maintenance procedures, the data reduction and quality control methodology, a comparison of rainfall amounts obtained via analog chart and data logger, and an analysis of precipitation for Water Year 2009 (October 2008–September 2009). The data analyses include 1) monthly and Water Year 2009 amounts at all sites, 2) Water Year 2009 amounts in comparison to patterns from network Water Years 1990–2008, and 3) the 20-year network precipitation average for Water Years 1990–2009. Also included are raingage site descriptions, instructions for raingage technicians, documentation of raingage maintenance, and documentation of high storm totals.