Geography
The river originates at Lake St Clair and flows south over a distance of 187 km to New Norfolk and the estuary portion extends a further 52 km out to sea. Flows average in range from 50 to 140 cubic metres per second. Mean annual flow is 90 cubic metres per second.
The large estuary forms the Port of the City of Hobart – often claimed to be the deepest sheltered harbour in the Southern Hemisphere; some past guests of the port include the HMS Beagle, carrying Charles Darwin, in February, 1836, the USS Enterprise and USS Missouri. The largest vessel to ever travel the Derwent is the 113,000 tonne, 61 metre high, ocean liner 'Diamond Princess', which made its first visit in January 2006. At points in its lower reaches the river is nearly three kilometres wide, and as such is the widest river in Tasmania. Until the construction of several hydroelectric dams between 1934 and 1968, it was prone to frequent flooding. There are more than 20 dams and reservoirs used for the generation of hydro-electricity on the tributaries of the Derwent River, including on the Clyde River, Dee River, Jordan River, Nive River, Ouse River, Plenty River and Styx Rivers. Seven lakes have been formed by damming the Derwent and Nive tributary for hydroelectric purposes: Lakes Meadowbank, Cluny, Repulse, Catagunya, Wayatinah, Liapootah and King William. Further other dams and diversions add to this complex scheme. A substantial part of the dam construction work was performed by Polish and British migrants after World War II. The State of Tasmania is now attempting to diversify its over reliance on power from hydroelectricity, specially considering the low storage capacity of the overall Hydro system.
Read more about this topic: River Derwent (Tasmania)
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