Novel methods for managing freshwater refuges against climate change in southern Australia. Supporting Document 1: Evaluating the utility of cold-water releases (“shandying”) for enhancing the resilience of riverine species
Authors: Courtney R. Cummings, Ty G. Matthews and Rebecca E. Lester
This report presents a literature review examining the current and future utility of coldwater releases (shandying) from large dams as a method for providing cooler water for aquatic life so they may persist in warmer climates. In addition, natural resource managers were contacted about current and future management plans to assess the use of cold-water releases as a deliberate strategy. At the time of the survey, no managers were undertaking cold-water releases to moderate high water temperatures because current management had focused on minimizing potential negative effects of cold-water releases rather than considering potential positive outcomes. However, this study indicates that there is also the potential for positive impacts of cold-water releases, should they be appropriately managed. There are substantial knowledge gaps that need to be filled before the strategy can be seriously considered by managers, other than as a test case. This report recommends three key steps to start filling important knowledge gaps: 1) collect fine-scale temperature data in a range of Australian stream systems to identify the location and use of thermal refuges; 2) develop in-stream temperature models to enable the potential impact of releases to be simulated and validate these with experimental releases; and 3) collect information on the thermal migration cues of Australian fish as a starting point for considering the release of cold water to encourage fish migration. Until these and other key knowledge gaps are filled, the technique of releasing cold-water to influence in-stream temperatures is unlikely to be feasible.