Mining of the extensive Waikato coalfields began at Huntly in 1876. Production increased steadily until the 1960s, followed by fluctuations depending on economic conditions. Waikato coal is sub-bituminous ‘brown’ coal, less prized than the bituminous coal found on the South Island’s West Coast. It was used for domestic and commercial heating for most of the 20th century. Production leapt after 2000, mainly to provide fuel for the Glenbrook steel mill at Waiuku and the thermal power station at Huntly.
There have always been pockets of radical political activity in Waikato, because of the presence of large industries employing immigrant workers from countries with strong union traditions such as Britain. In September 1942 a strike by Huntly coal miners created a rift in the wartime coalition cabinet and led to the nationalisation of the mines. Strikes at the Kinleith pulp and paper mill, notably one lasting three months in 1980, also stirred up controversy.
Most coal was mined underground at Huntly until 1915, when mines opened on the west side of the Waikato River. During and after the Second World War, to boost production, opencast mining began near Huntly and Maramarua.
In the 2010s an estimated 2 billion tonnes of coal remained, mostly more than 300 metres below the surface. The main mining companies were Glencoal Energy and the state-owned enterprise Solid Energy New Zealand, which went into liquidation in 2018.
In 1913 the Waihi Gold Mining Company built a dam at Horahora on the Waikato River, which the government bought in 1919 as part of a plan to manage electricity supply. Another dam was completed at Arapuni in 1929. These power stations also supplied Auckland, the Bay of Plenty and Rotorua.
Growing demand for electricity in the late 1930s created shortages, inspiring a state hydro dam construction programme. The Waikato River was ideal for development because it had a steep fall, narrow gorges, the highest and most stable flow of any North Island river, and massive storage capacity in the form of Lake Taupō. From the 1940s a chain of hydro dams was built on the river. By the mid-1960s they produced nearly half of New Zealand’s power. In the 2010s Waikato hydro dams belonged to Mighty River Power and, along with the company's geothermal and gas power stations, generated 15–17% of New Zealand’s electricity.
Once hydro development peaked, thermal generation, using river water for cooling, was investigated. The first major thermal station was opened in 1958 at Meremere, using local coal. Because soft Waikato coal created too much ash, the station closed in 1991. Another thermal station designed to use coal and gas opened at Huntly in 1983. To reduce emissions and improve efficiency, owner Genesis Energy installed a combined-cycle gas turbine generator in 2007. New Zealand’s largest power station, Huntly generated about 20% of the country’s electricity in the 2010s.
Forestry and wood processing
In 1905 timber company Ellis and Burnand, which had cutting rights over areas of King Country native forest, established its headquarters in Hamilton. It became one of New Zealand’s largest timber-milling enterprises before being sold to Fletchers in the 1960s. The Taupo Totara Timber Company, which logged native forests west of Lake Taupō in the early 20th century, built a light railway line to its Putaruru mill and a mill at Kopakorahi (near present-day Kinleith).
As native forests dwindled, the focus shifted to exotic forestry. South Waikato pumice lands were unsuitable for farming, because cobalt deficiency in the soil caused a stock illness called bush sickness. Exotic trees were planted there and on hill country at Maramarua, north Waikato from 1925 to 1935.
These plantations began maturing in the 1940s, and in 1954 New Zealand Forest Products opened the Kinleith pulp and paper mill. More timber mills were built in south Waikato, and later wood-processing and treatment plants opened in or near Hamilton, and south-east of Te Aroha.
More exotic forests were planted in south Waikato from the late 1960s to the mid-1980s and in north Waikato in the 1960s. In 2010 approximately half of the South Waikato district was forested, but the logging industry was declining. In 2001 it employed 627 people in south Waikato; by 2013 the number had dropped to 330.
The same was true of wood processing. The Kinleith mill expanded in the 1960s and 1970s, but when government market-protection policies ended in the 1980s it became less profitable. Despite modernisation programmes, there were redundancies from the 1980s to the 2000s. The Carter Holt Harvey mill at Putaruru closed in 2008.