Waters of the western springs catchment, Auckland

Abstract

Aquifers occur in basalt deposits infilling valleys in the Western Springs catchment of Auckland City, and they discharge into small streams incised along the edges of major lava flows. Total run‐off from the area is >0.261 m³·s⁻¹. Analyses by standard methods of twelve subsurface and surface waters show that flowing groundwaters have a low level of pollution (dissolved oxygen x = 7.6 mg·l⁻¹, abuminoid nitrogen x = 0.038 mg·l⁻¹, and total solids x = 188 mg·l⁻¹). Surface waters and stagnant groundwater have high, but varying levels of biological activity. Although much of the dissolved solid content of all the waters (e.g., Ca²⁺, Mg²⁺, Na⁺, K⁺, SiO₂) is consistent with the chemistry of the rocks of the catchment, particularly the glassy volcanic tuffs, for surface waters various sources of pollution also make significant contributions (e.g., leaking sewers, sewage overflows, combustion of fossil fuels, fertilisers, zoo animals). Apart from its iron level, the moderate volume (∼.0.13 m³·s⁻¹) of flowing groundwater is of suitable quality for domestic, industrial and irrigation needs.