Lake Waikare and the Whangamarino Wetland

Lake Waikare is the Waikato’s largest lake, lying to the south-east of Te Kauwhata. It covers 3,442 hectares, with inflow from the Waikato River through the Te Onetea Stream at Rangiriri and the Matahuru stream to the south, and discharge into the Whangamarino Wetland.

It was once the centre for a thriving sailing and boating club, and locals recall spending school sports days swimming in the lake.

The lake was lowered in 1965 for flood control and this seriously affected the natural hydrology. Agricultural runoff, vegetation clearance and pest fish have caused poor water quality and the lake is extremely turbid, being very shallow for its large surface area. Additionally, the large number of koi carp is proving a pest in this, as in other Waikato lakes.

Due to the low light environment it is difficult for aquatic vegetation to establish, which would help stabilise the sediments. Wetland area surrounding the lake has declined by 67% since 1963 (Barnes, 2002).

Lake Waikare currently receives discharge of fully-treated water from the Te Kauwhata wastewater treatment ponds but the Waikato District Council has announced plans for this to cease in the early 2020s.

Lake Waikare suffers regularly from algal blooms, and the trophic state of Lake Waikare has worsened since 1993, with increased N and P and suspended sediment loads and decreased clarity. Chlorophyll A concentrations have remained stable, and this has been attributed to light limitation of algae due to the high suspended sediment concentrations. The high density of koi carp are also contributing to the status of the lake.

 

Restoration Action

Lake Waikare is a difficult case for restoration due to its large catchment and surface area, shallow depth and continued inflows from wastewater treatment ponds.

Macrophyte re-establishment would help reduce high suspended sediment loads and internal nutrient loading. However, macrophytes would be extremely difficult to establish due to 1) high suspended sediment loads restricting light penetration for macrophyte growth, 2) high wind exposure resulting in an unconsolidated lake bed, 3) risk of Egeria densa (Brazilian waterweed) becoming dominant and collapsing due to high nutrient availability.

Waikato-Tainui currently is working on a restoration plan for the Raupatu areas of the lake shore and will work with interested parties to review the overall lake quality.

Information sourced from a variety of locations, including Lake Ecosystem Restoration NZ

How to get there

Turn off SH1 at Te Kauwhata, onto Te Kauwhata Road, head for the village and drive straight through, (or stop for coffee!).  When you come out other side you will be on Waerenga Road; follow this for approx. 5 minutes and you will go over a bridge over a stream – the Longswamp Canal which is the main egress for Lake Waikare into Whangamarino wetlands.

Take the next right onto Waikare Road. The first access point is a couple of kms along on the right- Ruahine Road and this will take you to the water’s edge at the NW corner of the lake. If you travel on past Ruahine Rd for approx. 5km you will come to the second good access point, this is the old sailing club, now abandoned.  Waikato District Council and the community plan to restore this area in the future.

 

Whangamarino Wetlands

The second-largest wetland in the North Island, covering 7,290 hectares between Meremere and Te Kauwhata, the Whangamarino Wetland encompasses peat bog, swampland and river systems.

The dominant vegetation is mānuka and wire rush, with moss and lichen species. Threatened plants include water milfoil, the swamp helmet orchid (Anzybas carsei), and clubmoss.

Threatened bird species, including the grey teal, the spotless crake, the North Island fernbird and around 25% of New Zealand’s population of Australasian bitterns live in the wetland. Eighteen species of fish include the black mudfish.

 

In 1961 the lower Waikato–Waipā flood protection scheme caused water levels to drop by more than 1.5 metres. As part of wetland restoration, a weir was constructed on the Whangamarino River in 1989 to maintain minimum water levels. The Department of Conservation controls animal and plant pests, which include the highly invasive alligator weed.

The wetlands are controlled by weirs from Lake Waikare, and a concrete/steel barrier which operates at Oram Road just before the Whangamarino enters the Waikato again just south of Meremere

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