Hurunui River Catchment

The Hurunui is considered of high conservation value, and is noted for its trout and salmonid fishery value. The river is also used extensively for other recreational activities such as kayaking, sailing, jetboating and swimming. A diversity of landuses are represented; the upper catchment is largely pristine beech forest and low intensity pastoral hill farming. The middle catchment is predominantly grazed pasture and woody native vegetation, whereas the Culverden/Amuri Basin is intensively farmed with sheep, beef, dairying and plantation forestry the predominant landuse.

Two main irrigation schemes operate in the catchment; the Waiau scheme, which became operational in 1980, and the Balmoral scheme, which became operational in 1985. The increased availability of irrigation water has also been associated with major shifts in landuse in Culverden Basin, particularly the conversion from sheep and beef to dairying. Although there has been some shift from border-dyke to spray irrigation, the former method is still widely used in the Basin. 

Long-term water quality data (since 1989) are available for upper , middle and lower Hurunui, as well as more recent data (since 2005) for sites on tributaries within the Culverden Basin (Waitohi, Pahau, Dry Stream and St. Leonards Stream). State and trend analysis over the last ten years indicates that water quality in the upper catchment to middle catchment at state highway 7 is predominantly good, with concentrations of nutrients and E. coli at levels considered unlikely to encourage nuisance algal growths or to impact on recreational and aesthetic values.

In contrast, tributaries of Culverden Basin have exhibited high nutrient and E. coli levels; these largely reflect the intensification of landuse that has occurred since the later 1980’s and early 1990’s, and the poor management of wipe-off water from border-dyke irrigation. Although E. coli, nitrate, dissolved reactive phosphorus and turbidity breach guideline values in all tributaries of the Culverden basin, there has been some improvement in dissolved phosphorus in a few sites due improved management management of wipe-off water and conversion to more efficient spray irrigation techniques.

Although water quality in the lower Hurunui River at state highway 1 is generally acceptable, occasional breaches of guidelines for faecal contaminants and nutrient levels are largely due to the contribution from the Culverden Basin tributaries upstream. Breaches of nutrient guidelines do not appear to cause nuisance algal growths except under during the summer months under low flow and elevated temperature conditions.