Botany Field Trip - Wainuiomata Catchment
17 December 2000
This was our lucky day - planned in a hurry after the club got the welcome news from Wellington Regional Council staff that we could send the first group into the recently opened valley. The new Access Plan provides for one group of up to 20 people to visit the valley for a day, each month accompanied by rangers in the ratio of 1:10.
The trip began at the Water Treatment Plant where WRC Ranger Gareth Cooper gave us a detailed, interesting briefing on conditions of access, the significance of the Valley’s ecosystem, and information about the region’s water supply. Club members’ interest in the valley was shown by the numerous questions asked during the briefing, and the discussions with Gareth, and rangers Fraser Oliver and Owen Spearpoint.
The 8000 ha Wainuiomata-Orongorongo Water Collection Area is of national importance, being the best example of lowland podocarp forest in the lower North Island. The treatment plant, opened in 1993, produces up to 60 million litres of high quality water per day, supplying a quarter of the water used by greater Wellington.
Gareth said that in 1999, the treatment plant was shut down for 6 weeks so that possums in the valley could be killed, and during the roar, members of the public shot deer. Goats and pigs remain a problem – we heard a goat in the east branch.
We were required to keep to the road during our 4km walk up the valley, and to remain within earshot of each other. The valley floor north-east of the decommissioned Morton Dam was a mass of Cortaderia fulvida, a toetoe, its gracefully curved flower stalks nodding in the breeze. The first 2km upstream of the dam were through regenerating forest once farmed by the Sinclair family. We saw numerous species of native herbaceous plants, rushes, sedges, grasses, orchids, ferns, lianes, shrubs and trees during 5 hours in the valley. To help us to learn the names of plants not familiar to us, and to refresh our memories about plants we knew, we each had a copy of a list of 136 species compiled during a 3 hour walk along the same road in 1997. The regenerating forest kept us busy for two hours, but it was the immensity of the northern rata, rimu, matai, kahikatea, totara and miro trees which held us spell-bound. To be among such large living organisms is a very special experience, enhanced for us because it was so close to home, yet for so long inaccessible.
Sharp eyes helped us to add Parsonsia heterophylla, a liane, and Libertia sp., a native iris, to the list as well as nine more weed species. We saw a paradise duck, and, near the start of the climb towards beech forest, we heard an NZ falcon, both additions to our list. The revised lists will be sent to Wellington Regional Council and the Department of Conservation.
Everyone enjoyed the day botanising in first the regenerating forest, and then the magnificent pre-European forest. We agreed that pest animal control and pest plant control must be given top priority as a matter of urgency, to restore the ecosystem and to protect the drinking water produced by it.