A Directory of Wetlands in New Zealand
A Directory of Wetlands in New Zealand WAIKATO CONSERVANCY Lower Waikato River and Estuary (10) Location: Rangiriri, 37°26'S, 175°08'E; centre of delta, 37°21'S, 174°46'E. The Lower Waikato River is approximately 34 km southwest of the city of Auckland at Port Waikato and 72 km south of the city of Auckland at Rangiriri, North Island. Area: Lower Waikato River, c.3,500 ha (56 km from Rangiriri to Port Waikato); estuary c.588 ha. Altitude: Sea level to 10 m at Rangiriri. Overview: The Waikato River, between Rangiriri and Port Waikato, passes through large areas of mineralised swamp and shallow lakes, and finally discharges through a diverse delta habitat to the sea. It provides habitat for a range of threatened bird species, and supports New Zealand's largest eel fishery. Physical features: The site comprises the Lower Waikato River from Rangiriri downstream for about 56 km to Port Waikato at its mouth. The basement rocks of the Waikato Region are comprised of Mesozoic "greywacke-type" rocks that have undergone extensive alteration to form dissected fault blocks around the perimeter of the Waikato catchment. During the early Tertiary, coal measures with associated freshwater and shallow marine sediments were laid down, although today many have been removed by erosion. Following this period, a series of several different phases of volcanism occurred. As a result of extensive sediment deposition at this time, the Waikato River, which previously flowed out to the Firth of Thames, changed course to flow out into the Hamilton Basin, bringing much sediment with it and causing extensive deposition and creating small lakes and swamps.
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