Physical, chemical and biological monitoring of water quality in estuaries within the Northland region for Northland Regional Council. Sampling sites are currently located in the Whangarei Harbour (WH), Bay of Islands (BOI) and Kaipara Harbour (KH), past data includes Hokianaga and Whangaroa Harours. Sampling frequency = 2monthly + 3 event driven sampling each year following heavy rainfall (WH, BOI), monthly (KH). Sampling began in 1986 (WH, BOI) and 2009 (KH) and is ongoing. Number of sites = 41 total currently. Since the start of the programme some sites have been dropped and some new sites have been added. Number of replicates = 1 per site. Measured variables = Water quality: salinity, DO%, DOmg/l, temp (YSI meter), Enterococci, faecal coliforms (Internal lab), TP, DRP, NNN, NH4, Turbidity (External lab), secchi, water depth (recorded in field). Sampling protocol & QA = Internal field monitoring manual and QA procedures. Water samples taken from top 0.5m of water column and sampling conducted at random tidal states, giving a more representative picture of water quality over time (WH, BIO) or high water (KH).