Lake Corangamite in western Victoria, Australia, is the largest permanent lake on the Australian mainland. Its levels and salinities fluctuated naturally until recently. Since about 1960, its major inflow creek has been diverted for management purposes and lake levels have fallen and salinities risen. The changes have been most profound since 1980. Since 1980, salinity has risen from ∼35g/L to >50g/L, water levels have fallen by nearly 2m, and many islands have become peninsulas or have disappeared. The major effect has been a change in the composition of the biota from one that is characteristic of lakes in the region of moderate salinity (>35g/L) to one that is characteristic of more saline lakes (50-100 g/L). In particular, Austrochiltonia subtenuis (Amphipoda), Coxiella (Gastropoda), Galaxias maculatus (Pisces) and Ruppia (macrophyte) have almost disappeared. The loss of these species has greatly decreased the value of the lake to the avifauna in particular and as a natural resource in general.
The changes to Lake Corangamite resulted largely from the diversion of the inflowing waters from the Woady Yaloak Creek, the major influent stream, into the Barwon River. The diversion scheme, undertaken by the Rural Water Commission of Victoria, was implemented mainly to minimize the possibility of flooding of land adjacent to the lake. The environmental consequences of such diversion were not fully considered. The paper documents the physico-chemical and biological changes that occurred up to 1992, and discusses issues of conservation and management interest associated with the changes. Changes in the level of Lake Corangamite and associated limnological features accord with the pattern observed in many salt lakes worldwide.