Lake Koromatua: One of 1000 community restoration projects

Lake Koromatua, Waikato

I always find it interesting to ask volunteers how many hours they estimate they’ve put into their restoration projects. Hamilton Fish & Game Assn. members, Keith, John and Murray, average 4000-6000 hours annually between them for restoring Lake Koromatua.

I joined the Waikato branch of Forest & Bird for an outing to the 6.5 hectare lake, tucked away off a farm road just 5km from the edge of Hamilton. The lake is perched on the edge of what was once the extensive Rukuhia peat dome, one of 11 major peat formations in the Waikato basin. It’s one of a meandering chain of more than 30 peat lakes, formed over 17,000 yrs ago as the Waikato River changed its course.

Keith and Murray became involved with the lake during the resource consent process for the Temple View Sewerage ponds in 1998. Then, the hyper-eutrophic lake was expected to dry out within 10-14 years. Why? No weir. Grey willow encroaching along with blackberry, honeysuckle, gorse and woolly nightshade. Possums, rats and cats feasting on native wildlife and damaging native flora. Part of the rationale for beginning such a project was that duck shooters, according to Keith, traditionally move on to another lake when the conditions are no longer suitable for sport. Adopting a restoration mind set was seen as a necessity given the finite number of lakes in the region to choose from.

The first step towards restoring the lake was installing a weir to raise the water level by 0.5m. With farm drains diverting into the lake to increase water availability, silt traps were also created to manage the nutrient and sediment loads. Given the size of the area to be restored, 8 management zones were developed based on the different biophysical characteristics of each. Glyphosate was liberally used – sprayed manually and by helicopter to combat willow in particular. Manuka and kanuka were planted create shelter for frost sensitive species such as tawa, titoki, mahoe, five finger, wineberry and various coprosma species. Between 3000 and 3500 plants are grown annually by fellow members and family from locally sourced seed.

Although dedicated pest control has given plants a far greater chance of survival – evidenced by thick undisturbed carpets of native seedlings, Keith highlights: “…we would be years ahead of where we are if we had started trapping the first year that we began the project”. Controlling pests is also likely to have helped native birds, such as banded rail and spotless crake gain a stronger foothold in the wetland.

However, the group have no data on bird species and population changes, highlighting the difficulty of enlisting skilled volunteers for conducting basic monitoring. Uniquely, Lake Koromatua is free of pest fish such koi carp and gambusia that are commonly found in the majority of the region’s peat lakes. Instead, black mudfish burrow into the soft peat to aestivate (a fishy form of hibernation) during dry periods.

I queried why they weren’t enlisting more volunteers given the work load – however, managing large numbers of volunteers can be a job in itself. The new Health and Safety legislation also places a greater onus on volunteer coordinators should anything go wrong on site.

So, how are decisions made? Although other peat lakes nearby are also being restored, many with similar hydrological and pest plant and weed issues, each lake has its own characteristics. Decisions are made by consensus and both Keith and John highlight the importance of information sharing between projects, for example, on landcare networking days which bring together community restoration groups from throughout the region. Their approach is also highly adaptive, in other words, it’s learning by doing. Between the four of them, I’m sure there’s an entire manual on peat lake restoration waiting to be written.

Who knows how many community-led restoration projects are currently underway in New Zealand. Lake Koromatua is likely to be one of thousands. It was a privilege to gain an insight into the technicalities of restoring such a degraded site, and to see what can be achieved by a handful of dedicated folk who have put so much energy into reviving another one of the region’s precious peat lakes.

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