Evaluating Use of Environmental Flows to Aerate Streams by Modelling the Counterfactual Case
- 209 Downloads
This paper evaluates an experimental environmental flow manipulation by modeling the counterfactual case that no environmental flow was applied. This is an alternate approach to evaluating the effect of an environmental flow intervention when a before-after or control-impact comparison is not possible. In this case, the flow manipulation is a minimum flow designed to prevent hypoxia in a weir on the low-gradient Broken Creek in south-eastern Australia. At low flows, low reaeration rates and high respiration rates associated with elevated organic matter loading in the weir pool can lead to a decline in dissolved oxygen concentrations with adverse consequences both for water chemistry and aquatic biota. Using a one dimensional oxygen balance model fitted to field measurements, this paper demonstrates that increased flow leads to increases in reaeration rates, presumably because of enhanced turbulence and hence mixing in the surface layers. By comparing the observed dissolved oxygen levels with the modeled counterfactual case, we show that the environmental flow was effective in preventing hypoxia.
KeywordsEnvironmental water Hypoxia Reaeration Dissolved oxygen Counterfactual case
This research was supported by the Commonwealth Environmental Water Office, Australia and was undertaken as part of a broader environmental monitoring program led by the Murray Darling Freshwater Research Centre (MDFRC). The project was also supported by the Australian Research Council (Project DP130103619). The project benefited from advice provided by Dr. Gavin Rees (MDFRC) and Geoff Earl (Goulburn Broken Catchment Authority).
Compliance with Ethical Standards
Conflict of Interest
The authors declare that they have no competing interests.
- ANZECC (2000) Australian and New Zealand guidelines for fresh and marine water quality. Australian and New Zealand Environment and Conservation Council and Agriculture and Resource Management Council of Australia and New Zealand, Canberra, Australia, p 103Google Scholar
- Gualtieri C, Doria GP (2008) Gas-transfer at unsheared free-surfaces. In: Gualtieri C, Mihailovic DT (eds) Fluid mechanics of environmental interfaces. CRC Press, Boca RatonGoogle Scholar
- Gualtieri C, Gualtieri P (1999) Statistical analysis of reaeration rate in streams. Int. Agric. Engrg. Conf. (ICAE ‘99), Pechino, ChinaGoogle Scholar
- Gulliver JS (2011) Air-water mass transfer coefficients. In: Thibodeaux LJ, Mackay D (eds) Chemical Mass Transfer in the Environment. CRC Press, Boca RatonGoogle Scholar
- Koehn J (2007) The loss of valuable Murray cod in fish kills: a science and management perspective. In: Lintermans, M., Phillips, B. (eds) Management of Murray Cod in the Murray-Darling Basin: Statement, Recommendations and Supporting Papers. Proceedings of a Workshop held in Canberra, ACT, 3–4 June 2005 Canberra. Murray-Darling Basin Commission and Cooperative Research Centre for Freshwater Ecology, pp 73–82Google Scholar
- Mallin MA, Johnson VL, Ensign SH, MacPherson TA (2006) Eutrophication of Freshwater and Marine Ecosystems. Limnology and Oceanography 51(1):690–701Google Scholar
- Nilsson C, Malm Renöfält B (2008) Linking flow regime and water quality in rivers: a challenge to adaptive catchment management. Ecol Soc 13(2):18Google Scholar
- Parker GW, DeSimone LA (1992) Estimating reaeration coefficients for low-slope streams in Massachusetts and New York, 1985–1988, Water-Resources Investigation Report. U.S. Geological SurveyGoogle Scholar
- Rees G (2006) Ecological implications of azolla sp. proliferation events in the lower Broken Creek. Victoria. Report by the Murray-Darling Freshwater Research Centre, Wodonga, AustraliaGoogle Scholar
- Rees G, Hall K, Baldwin D, Perryman SE (2007) The lower Broken Creek: aspects of water quality and growth of Azolla species Murray-Darling Freshwater Research CentreGoogle Scholar
- Skinner D (2012) Sediment resuspension and water quality during declining water levels in a shallow lake: a case study of Lake Alexandrina. University of South Australian, South AustraliaGoogle Scholar
- Vervuren PJA, Blom CWPM, de Kroon H (2003) Extreme flooding events on the Rhine and the survival and distribution of riparian plant species. J Ecol 91:135–146Google Scholar