Live Oral Presentation delivered remotely as part of National Virtual Conference AFSS Conference 2020

Stream metabolism in the Murrumbidgee River (#17)

Tsuyoshi Kobayashi 1 2 , Benjamin J Wolfenden 2 3
  1. Science, Economics and Insights Division, Department of Planning, Industry and Environment, Lidcombe, NSW
  2. Institute for Land, Water and Society, Charles Sturt University, Albury, NSW
  3. Regional Operations Group (South Branch), Department of Planning, Industry and Environment, Albury, NSW

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.