Townsend, who reportedly missed the men’s 100m freestyle on the opening day as his entry had not been processed, won gold and silver on Wednesday's second and final day.
The 28-year-old Olympic gold medallist won the men's 200 metres freestyle in 1:43.31 ahead of Australia's Robert Hurley who finished second in 1:43.93. Fellow Australian Tomasso D'Orsogna touched third in 1:44.49.
Townsend, who has won medals at all seven legs of the series this season, also secured silver in the 200m individual medley, clocking 1:53.30.
Daiya Seto won gold to stretch his overall series lead, setting a Japanese national record of 1:52.48, with countryman Kosuke Hagino taking third in 1:53.76.
The last of eight World Cup legs will be held in Singapore this weekend.