Kaihoka Lakes

The Kaihoka Lakes are a pair of shallow coastal lakes near Whanganui Inlet in northwest Nelson. The lakes formed due to the accumulation and subsequent landward movement of wind-borne coastal sand dunes, and occupy an area characterised by a sequence of large, established sand dunes.

The dominant westerly winds of the region drive the movement of sand from the nearby ocean coastline east toward the Kaihoka Lakes. The continued eastward advance of large wind-formed dunes has blocked the course of minor valleys, limiting drainage and encouraging the development of swamps. Over time, these consistently wet areas have developed into the dual Kaihoka Lakes system. All inflows and outlets for the Kaihoka Lakes are ephemeral. Water accumulation primarily occurs from rainfall and seepage. Both lakes have a peat mud bottom, so water loss is dominantly from evaporation, with water residence times typically less than 12 months for both lakes.

Though absolute dating of the lakes has not been undertaken, scientists estimate that the lakes are less than 6,000 years old. Prior to 4000BC, the residual effects of the preceding ice age meant that sea level was significantly lower than it is today. The stabilisation of sea level approximately 6,000 years ago limits the ages of the lakes – prior to this time, the movement of sea level would have inhibited the accumulation and migration of the dunes.

As you approach the lakes in your vehicle, observe the strongly-windswept trees which grow out of the dunes. What does this tell you about the dominant wind direction in the area? Does this align with what you think caused the Kaihoka Lakes to form?

At the Kaihoka Lakes turnoff, continuing approximately 1 kilometre up the gravel road will reveal a view of large unvegetated dunes surrounding the lakes. These dunes are the modern equivalent of the vegetated, permanent dunes which now surround the Lakes.