Our fragile wetlands
Our restoration goal is to have a diverse and representative range of freshwater habitats, flora and fauna.
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 the lower lake. In 1906-08 a second dam was built 1km further up the valley. This, together with forest clearance and urban development along the Kaiwharawhara stream, has resulted in serious disturbances to the original freshwater stream habitat.
To assist with the restoration and management of wetlands in the sanctuary, four habitat zones have been identified. There 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.
Lower Lake wetland restoration
Lower lake wetland (foreground) and lower lake
The southern shoreline of the lower lake has been modified to establish shallow habitat suitable for a range of wetland plants. This is an important feeding area for wetland birds such as brown teal and scaup and fish. Considerable planting has been undertaken around the margins, and artificial islands established. To promote the movement of fish between the lower lake and the wetland, a fish ladder has been constructed that joins that stream and wetland to the lower lake. Karori Sanctuary Trust is grateful to the Keith Taylor Charitable Trust for making this wetland development possible.
Native fish tank and display
In addition to this development a native fish tank and interpretation about freshwater ecosystems is located here.
The lower lake suffers from algal blooms in the summer, resulting in an unpleasant smell and algal scum. While this is a natural event, there may be some management actions that can be undertaken to reduce the frequency and severity of these blooms.
Research is being conducted by Cawthorn Institute and Waikato University to understand the impact that exotic fish have on this phenomena.
Upper lake wetland restoration
Brown teal at home on an artificial island on the upper lake
Thanks to the Lions Club of Karori, artificial islands and viewing hides have been installed at the upper lake to increase the diversity of habitat for waterfowl and help the public view species such as scaup and brown teal. Considerable effort has gone into controlling exotic plants and planting native shrubs and grasses around the lake edge and on the artificial islands.