Claiming the land
Like Māori, the first European settlers used rivers for exploration and transport. Some major rivers such as the Whanganui and Waikato were used as routes for military conquest, and later as supply lines for isolated settlements.
Rivers were often a source of danger for the unwary. There were so many deaths on river crossings that drowning became known as ‘the New Zealand death’. Once bridges were built, perceptions changed and rivers were no longer seen as barriers.
In the 1860s, after the gold rushes in California and Australia, New Zealand also had a gold boom. As well as boosting the nation’s population and wealth, the rushes shaped relationships between settlers and some significant river landscapes.
Mainly in Otago and on the West Coast of the South Island, rivers yielded deposits of alluvial gold. The gold was panned, then sluiced. Later in the century, gold dredges did the work, scooping up millions of tonnes of river gravel and boulders. This altered the landscapes of both regions.
In the 19th century, gold-mining companies in the North and South islands were allowed to designate rivers as ‘sludge channels’, to discharge debris from gold recovery work. Using rivers to dispose of sewage and waste from farming and industry also became common, and it is still a problem.
The flood threat
Most rivers have steep gradients, but some, especially in the North Island, flowed over gently sloping plains. On the river flats, settlers tried to tame rivers by building drainage works, ports, and flood control systems. Upstream they felled bush, ploughed land and introduced grazing animals, increasing the natural rate of erosion. This led to greater runoff of water, and more sediment being deposited along the lower reaches and flood plains of rivers.
Hazards could develop – for instance, a riverbed could build up between stopbanks until the water level was higher than the surrounding countryside. In heavy rain, serious flooding occurred. Flooding is a growing threat for many rivers that have been modified.
With recreational fishing in mind, 19th-century acclimatisation societies introduced rainbow and brown trout and quinnat salmon. Today there are trout in most New Zealand rivers. The fisherman’s gain was at some cost to native fish, which were preyed on by trout.
One of the effects of hydroelectric power schemes was the creation of artificial lakes. Dams have formed eight lakes along the Waikato River: Aratiatia, Ōhakuri, Ātiamuri, Whakamaru, Maraetai, Waipapa, Arapuni and Karapiro. They have recreational value. Karapiro, for example, is used for international rowing competitions.
Salmon were systematically introduced by the government for their commercial value. Eventually they were confined to the Rakaia in mid-Canterbury and, to a lesser extent, to some other South Island rivers.
After early schemes in the 1920s, the use of rivers to generate electricity gained pace. Between 1945 and the mid-1970s, New Zealand expanded its electricity generation capacity almost tenfold, mostly through hydroelectric schemes.
By the 1970s many of the country’s major rivers, such as the Waikato, Tongariro, Waiau and Waitaki, had been dammed. Hydroelectric developments were seen as desirable because they produced power from a renewable resource. But they had an impact on water levels in rivers, and sometimes submerged natural features such as waterfalls.