Water samples were collected by both AIMS and CSIRO in the Herbert River catchment 10-15 days before the Cyclone Sadie flood. During the flood event, the John Row Bridge was the only site continuously accessible through the peak flow. Independent concurrent sampling was carried out by AIMS and CSIRO at the John Row Bridge, allowing for comparison of the different sampling and analytical methods used by each agency. Time-series sampling commenced 10 h before the flood peak (approximately 13 h after the initial rise began) and continued for two and a half days, covering most of the flow event. Following the Cyclone Sadie flood, sampling was continued at this and other sites at lower frequency for a further three weeks, which included a second, smaller flood event. Surface water samples were collected at bridges, in clean plastic containers, from the mid- or deepest point of the river. At sites where bridge access was restricted, the sampling container was thrown out into the main flow of water and retrieved by rope.Water samples were analysed to determine: dissolved inorganic nitrogen (DIN)= (NH4+NO2+NO3), dissolved inorganic phosphorus (DIP)=PO4=orthophosphate; silicate; total dissolved nitrogen (TDN); total dissolved phosphorus (TDP); particulate nitrogen (PN); particulate phosphorus (PP); suspended sediment; potassium; and salinity. pH was also measured.Concentrations of dissolved organic nitrogen (DON) and phosphorus (DOP) were calculated as the difference between the total dissolved and dissolved inorganic nutrients. Water discharge in the Herbert River was monitored at two flow gauging stations, one located immediately upstream of the John Row Bridge (116001E) and the other at Gleneagle on the upper Herbert (116004C).
