Waikakaho River Gravels Aquifer

The Waikakaho River is a Northbank tributary of the Wairau River located between Kaituna and Tuamarina.

It is a narrow river valley incised into the schist ranges, and infilled with alluvium, which forms an aquifer.

Recent drilling has shown the gravels are deeper than first thought, being in excess of 30 metres in some places. This means there is greater storage than initially believed, although much remains to be learnt about the capacity of the aquifer.

The conceptual diagram below represents the latest understanding of the Waikakaho River Catchment and how surface water interacts with groundwater.

The existence of groundwater relies on continued Waikakaho River flow. Without recharge from the river channel, the aquifer would quickly drain.

The undulating nature of the underlying schist means that river channel flow is intermittent. Where the basement rock is close to the surface, channel flow occurs. Conversely, where gravel deposits are thicker, channel flow is lost below the surface.

Water demand is still relatively low except over summer. Water is used for a variety of purposes including drinking, crop irrigation and stock supply.