Poster Presentation World Lake Conference 2025

The carbon footprint of irrigation canals and storages: a case study of the Murrumbidgee Irrigation Area. (#229)

Jackie R Webb 1 , Emily Armstrong 2 , Hayley Dryza 3 , David Dodemaide 2 , Rebecca Lester 2
  1. School of Agriculture and Environmental Science, University of Southern Queensland, Toowoomba, QLD, Australia
  2. Centre for Regional and Rural Futures, Deakin University, Geelong, VIC, Australia
  3. Centre for Regional and Rural Futures, Deakin University, Griffith, NSW, Australia

Irrigated agriculture has created high densities of artificial waterbodies, such as dams and artificial lakes for water storage and canals for water conveyance and drainage. Global studies suggest that small artificial waterbodies are widespread emitters of carbon dioxide (CO2) and methane (CH4). Agricultural surface waters such as irrigation channels and storages are recognised as an anthropogenic system by the IPCC that should be accounted for in national emission inventories, yet data is extremely limited for irrigated landscapes. On the other hand, storages and canals can store carbon (C) through sedimentation of eroded soil from farm fields and organic matter generated internally from aquatic primary production. Although this process of sediment deposition is generally viewed as a functional nuisance to water storage capacity and conveyance, they may represent an unexpected ecosystem service through carbon storage that needs to be considered for C footprint assessments.

The aim of the study was to carry out a scoping investigation of sediment carbon storage and GHG emissions in canals and storages to evaluate if the irrigation water network holds potential for carbon offsets. Four spatial surveys of canals and storages within the Murrumbidgee Irrigation network were carried out to capture different water conditions associated with seasons. 

At the time of sampling, 60% of sites were emitting CO2, 100% were emitting CH4, and only 45% were emitters of N2O across all surveys. Summing emissions from all three GHGs, the median total CO2 equivalent emissions across the irrigation network was 2.53 t CO2-eq ha-1 y-1. The average C burial rate was 8.67 t CO2-eq ha-1 y-1, which is comparable to the global average C burial rate of 10.65 t CO2-eq ha-1 y-1 for reservoirs. Eight out of the 15 sites had a negative carbon footprint, meaning that the associated GHG emissions were not large enough to offset the gain in sediment C burial. Overall, the carbon footprint was negative for the drainage channels (-0.71 t CO2-eq ha-1 y-1), supply channels (-17.02 t CO2-eq ha-1 y-1), and storages (-0.99 t CO2-eq ha-1 y-1). These preliminary results demonstrate that some irrigation waters have the potential to be used as carbon offsets if GHG emissions are kept in check. This study represents the first known field research to measure GHG fluxes and carbon burial from artificial waterbodies in the irrigation sector.