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Wairau River

The Wairau is a large braided river and is the largest river in the Marlborough region. Its catchment accounts for 25% of the entire Marlborough Region. It starts in the high alpine ranges between the Spenser Mountains and the St Arnaud range and flows for 257km from source to sea. Catchments located on the north banks of the Wairau have a wet climate and are dominated by native forests, south bank catchments have a dry climate and are dominated by pastoral hill country farming, exotic forestry and viticulture. 

Tributaries of the Wairau River are used to generate hydroelectric power with further hydroelectric schemes planned for the future.


Water quality is generally good but there is some deterioration in water quality in the lower reaches. Recent trend analysis carried out by NIWA shows that nitrogen levels are increasing in the lower reaches, whilst phosphorus levels are increasing in the upper reaches.

The Wairau is important for groundwater recharge in the lower plains, where irrigation from groundwater is in high demand. Blenheims drinking water supplies are dependent on groundwater quality in the lower Wairau plains. Stock access to rivers and streams, septic tanks and irrigation are some of the pressures on the sub-catchments of the Wairau, particularly in the lower catchment. A number of spring fed streams arise within the Wairau catchment, including Mill Stream and Spring Creek.

Sites 15

Monitored sites in the Wairau River catchment

...retrieving sites.

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