Wetland Restoration

Wellington's fragile wetlands


Upper dam reservoir

The Sanctuary encompasses the headwaters of the Kaiwharawhara Stream catchment, which has its outlet into Wellington harbour through Ngaio Gorge.

In 1870, the stream was dammed at the lower end of the valley to create a 5ha, 500m long lake. In 1906, a second dam was built 1km further up the valley. This, together with forest clearance and urban development downstream along the length of Kaiwharawhara Stream, has resulted in serious disturbances to the original freshwater stream habitat.

Despite considerable work downstream to improve the habitat, the underground mid-section is unlikely to ever be restored back to a quality charactersitic of an unmodified stream. Given this disturbance, and the need to retain the two historic dams in the stream, our objectives for restoring the freshwater ecosystem need to focus on a more realistic goal than restoration of the stream to its pre-human state.


	Kaiwharawhara Stream

Our restoration goal is to have a diverse range of freshwater habitats, flora and fauna representative of the Wellington Ecological District. The stream has been permanently impounded in two places by the dams, so we will regard this as if it were due to a natural event such as a landslip restricting migration of aquatic species. The small size and steep nature of the valley will constrain our restoration options, but wetlands and lakes are non-existent in the Wellington peninsula and are regionally rare, so our lakes, wetlands and streams will be increasingly important as our objectives are met.

The outcome will be the establishment of a range of wetland fauna and flora that would otherwise be rare or absent in the Wellington region.

Wetland habitat zones

To assist with the management and restoration of wetlands in the Sanctuary, four habitat zones have been identified. These are: upper freshwater streams (requiring little or no management), the upper lake (Roto Mahanga) and margins, central freshwater streams, and the lower lake (Roto Kawau) and margins.

The Keith Taylor Lakehead Restoration project

The southern shoreline of the lower lake (Roto Kawau) has been modifed to establish a shallow marginal habitat suitable for a range of wetland plants. Once these become established, it will be an important feeding area for wetland birds. Considerable planting has been undertaken around the margins, and artificial islands established near the head of the lower lake.


Head of Lower Reservoir before restoration work		Fish ladder & new wetland

Behind a new weir the terrace has been flooded to create the Taylor Wetland, a new habitat for waterfowl and fish. To promote the movement of fish between the lower lake and the Taylor Wetland, a fish ladder has been constructed that joins the stream and wetland to the lower lake.

There is a history of summer algal blooms occurring in the lower lake, resulting in an unpleasant smell and unsightly algal scum. While this is a natural event, there may be some management actions that could be undertaken to reduce the frequency and severity of these blooms, so research is underway to understand contributing factors (such as nutrient input or impacts of exotic fish).

Artificial islands and viewing hides have been installed by the Lions Club of Karori at the upper lake (Roto Mahanga) to increase the diversity of habitat for waterfowl and provide viewing opportunities for the public. Considerable effort has gone into control of exotic plants and planting of native wetland shrubs and grasses around the lake edge and on the artificial islands.