Lets look the "definitions" of these two phrases,
these are not an exact definitions,
different organizations and so called experts interpret and define them differently
Sustainable energy is energy obtained from a source which is not expected to deplete during the timeframe relevant to the human race.
Renewable energy is energy obtained from a source where the energy is replenished during a relatively short cycle.
Major hydro power is renewable but not sustainable.
usually major hydro power projects involved building a reservoir which would occupy a large area of land, this may change the natural environment so much that there could be long term effects such as change in rainfall etc, so whether the dam could replenish its energy for a long period of time (such as the end of humanity) is questionable. hence major hydro power is not considered renewable.
but then again this is debatable
because there are major hydro projects which have not gone bad... it all depends on how nature adopts to the change i guess...
well take the upper kotmale project.
it would change the environment but if its going change in a way that would effect rainfall which replenishes water to the reservoir for a long period of time is debatable.
so major hydro in general is not a sustainable source of energy but its renewable.
other types of renewable sources such as wind, small hydro, solar PV (solar cells) and solar thermal (solar powered hot water etc), geo thermal energy etc are all sustainable energy types
Referer : http://www-formal.stanford.edu/jmc/progress/cohen.html
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