Monthly Data (commencing Jan 1989) comprising physical measurements, chemical and bacteriological analyses, and periphyton observations from 77 National River Water Quality Network (NRWQN) sites for the purpose of environmental assessments and monitoring of long term trends. The NRWQN has been funded up until June 2011 by the Foundation for Research, Science & Technology (FRST) through NIWA's Nationally Significant Database: Water Resources & Climate programme. Commencing July 2011, continuation is via NIWA Environmental Information/Monitoring programme core funding.