Complex sentence: The lake was officially opened on Saturday 24th April 1982 at a weekend long event that attracted 7000 spectators with the rowing course hosting a regatta attended by 188 crews and representing 80 South Island rowing clubs.
Split into simpler sentences: The lake was officially opened on Saturday 24th April 1982. There was a weekend long event which attracted 7000 spectators with the rowing course hosting a regatta attended by 188 crews and representing 80 South Island rowing clubs.