Waingaro River (Waikato)

The Waingaro River is a river of the Waikato region of New Zealand's North Island. It flows generally southwest from its origins near Glen Afton and Glen Massey, west of Ngāruawāhia, to reach a northern arm of Raglan Harbour (see 1:50,000 map). Its main tributary is Kahuhuru Stream, which Highway 22 follows for several kilometres. Tributaries total about 170 km. At Waingaro it is fed by a hot spring.

Geology
The lower river flows over Puaroan age (about 150 million years ago), blue-grey Puti siltstone.

Pollution
The Waingaro River is one of the largest sources of sediment in Whaingaroa Harbour, partly because it is 99 percent unfenced.

Pollution has been worsening for phosphorus, though nitrogen has improved, as shown in this table of important (i.e. slope direction probability over 95% and RSKSE over ±1% pa) improvements, or deteriorations (-) in relative seasonal Kendall slope estimator (RSKSE) trends (monthly records are flow-adjusted using a Lowess curve fit with 30% span.) - Turbidity is also poor.