An innovative, federally funded project, through the Commonwealth Environmental Water Office, is investigating how to balance water needs for the environment with those of human populations and agriculture in The Murray-Darling Basin (MDB) in eastern Australia. The MDB produces around half of Australia’s food but suffers consistently from insufficient water. A major objective is the measurement and assessment of responses of ecological indicators, including fish, vegetation and stream metabolism, to planned and stochastic stream discharge events. Such knowledge will greatly benefit management of scarce water resources (timing, duration and magnitude of watering actions). Four years of stream metabolism data has now been collected from two to six sites in each of seven sub-catchments of the MDB. This talk will present some highlights in the findings thus far and explore the use of metrics derived from rates of gross primary production, ecosystem respiration and flow to discern the effects of environmental watering actions. In general, stream metabolism rates are at the lower end of the international spectrum and are constrained by both nutrient bioavailability and light climate (high turbidity).