Caenid mayflies (riffles) and oligochaete worms (pool edges) are generally typical of the upland regulated Snowy River. Other studies have also found greater densities of Caenidae mayflies in regulated rivers compared to unregulated rivers. Reduced high flows and constant low flows in the upper Snowy River are likely to have favoured high densities of worms through the buildup of silt and organic matter in the pools. Nichols et al. (2006) and Petts et al. (1993) also found greater densities of segmented worms associated with soft sediments and coarse organic debris in response to river regulation. Chironomids were also numerically dominant in riffles sampled in the regulated Snowy River. This response has been found in many other studies of regulated rivers and has been attributed to an increase of periphytic growth in riffles that increased overall habitat area and food availability.