We investigated stream metabolism in the Murrumbidgee River in relation to delivery of environmental water under the Commonwealth Environmental Water Office (CEWO) Long–Term Intervention Monitoring (LTIM) project (2014-19). An open‐system, single-station diurnal oxygen change method was used to determine the daily rates of gross primary productivity (GPP) and ecosystem respiration (ER) at two in-channel sites (Narrandera and Carrathool) between spring and autumn. The two in-channel sites were more than 100 kilometres apart and in reaches with contrasting hydrology due to flow extraction and diversions. Overall, the GPP rate varied in the range 0.03-13.58 mg O2 L-1d-1 and the ER rate in the range 0.06-26.82 mg O2 L-1d-1 (n=1382). A bivariate plot of the annual median GPP:ER ratios against the annual median flow rates (n=5) showed a site-specific negative relationship between them. The stream metabolism response to river flows seems to be complex. Site-specific factors may play an important role in regulating the GPP, ER and their ratio in the Murrumbidgee River.