Impact of critical flow events on biota of regulated streams

Abstract

The primary approach to the evaluation of IFIM's predictive ability was to: - Establish IFIM hydraulic assessment transect sites in key locations downstream of Hydro dams; - Develop habitat preference curves and weighted useable area (WUA)- discharge (Q) curves for dominant invertebrate taxa at those sites, as well as for diversity and total abundance; - Schedule a single shut-down event for the Derwent River (downstream of Cluny dam), the King River (John Butters Power Station) and the Ouse River (Lake Augusta) and monitor spill events for Derwent River (Clarke dam), Forth River (Paloona dam) and the Mersey River (Parangana and Rowallan dams); - Conduct quantitative sampling of invertebrates within study reaches and at unregulated 'control' sites, on at least 3 occasions prior to each shut-down or spill event, and on at least 3 occasions following each event; - Develop hypotheses describing the likely change in abundance or diversity of invertebrates at each site due to each flow event, based on the degree of change in WUA at each site caused by the flow event. The hypotheses were based on the premise of either: 1. a decrease in habitat availability (at either low or high flows) sufficient to cause a decrease in abundance of individual taxa; or 2. an increase in habitat availability sufficient to facilitate increase in abundance. - Formally test these hypotheses using ANOVA on the monitoring data, in a BACIP (before-after-control-impact paired) design, with site x time interaction as the test statistic. - Use the results of these tests to describe the success of IFIM in predicting the effects of low events.