No abstract

Climate change is predicted to affect the future supply and demand for water resources. Current water-management practices may not adequately cope with the impacts of climate change on the reliability of water supply, flood risk, health, agriculture, energy generation and aquatic ecosystems. Water managers can adapt to climate variability by structural change, such as increasing the size or number of dams, building desalination plants and transferring water between catchments; however, a broader set of alternatives with multiple beneficial outcomes for society and the environment should be explored. We discuss how modifying dam operations, ‘dam reoperation’, can assist with adaptation to climate change and help restore ecosystems. The main operating purpose of a dam (e.g. flood management, hydropower or water supply) will influence dam reoperation strategies. Reoperation may require integration across sectors or involve multiple dams, enhancing benefits such as water supply or hydropower while simultaneously achieving ecosystem restoration. We provide examples of lessons learned during extreme scenarios (e.g. floods and droughts), where operational flexibility has been demonstrated. We contrast structural climate-change adaptation strategies (e.g. building new dams) and their resulting detrimental environmental outcomes with dam reoperation, which can maximise benefits for ecosystems and society.

No abstract

Experimental data for the decay of acrolein approximated first order kinetics. The reaction continued to completion in local waters but in buffered solution (pH 5.1-8.6) an equilibrium was reached after reaction of about 92% of the acrolein. It is proposed that data presented on the effects of pH on decay of acrolein may be used as a conservative estimate of dissipation rates in water where non-target organisms are at risk. In flowing water in two channels the 8 to 10 fold discrepancy between observed and predicted rates of dissipation was attributed to major losses in volatilization and adsorption. A relatively non-volatile reaction product (which gave a positive reaction with dinitrophenylhydrazine) accumulated initially but dissipated rapidly, probably by microbiological processes, when acrolein concentrations fell below about 2 to 3 ppm.

Chemical analysis and sensory assessment of river waters from the Murrumbidgee and Murray Rivers showed geosmin is an important odor compound. Experiments in culture using Anabaena circinalis isolated from the Murrumbidgee River, New South Wales, Australia showed that changes in chlorophyll per unit dry weight resulting from alterations in light intensity were paralleled by similar changes in geosmin/dry weight such that geosmin concentration was correlated with chlorophyll a over an extreme range of light conditions. A.circinalis was a prolific producer of geosmin, but a substantial proportion of the total geosmin was often retained intra-cellularly and released on sonication or treatment with copper. Therefore water treatment processes should avoid cell lysis.