Low oxygen blackwater events are a common and sometimes natural occurrence in the Murray River’s lowland systems during flood events. Some blackwater events are severe and can cause large scale mortalities in fish and other aquatic organisms. These events can be extensive in size and affect more than one State. The NSW Office of Water, as leading authority for water management in NSW has an interest in monitoring such events and where possible advises on flow adjustments to minimise the adverse effects caused by low oxygen concentrations in the rivers. To be able to manage future blackwater events more effectively, the NSW Office of Water has installed real time DO sensor technologies integrated into the existing Hydrometric network in blackwater affected areas. This paper discusses the trial of 10 DO sensors during an extensive 2011-2012 blackwater event.