The Waikato in the North Island is the The longest river in New Zealand with a length of 425 km (264 mi). The Whanganui is the longest navigable river at 290 km (180 mi). The Clutha River in the South Island is the largest river by volume. The Rakaia River has the longest bridge in the country with a 1,757 metre (5764 feet) span. New Zealand has over 180,000 kilometres (11,1847 miles) of rivers.