The price of chemical spraying.
by Trevor Reeves
In 2001, the Waipori generating scheme using the Mahinerangi reservoir, is due for re-licencing. This will coincide with all of the Clutha schemes and in fact, all others around the country. This is to fulfil the requirements of the Resource Management Act 1991. At present, the scheme is controlled by the conditions of the Dunedin City Corporation Empowering Act 1924, the year the main Waipori dam was built. This was amended in 1927, 1930 and 1944. This document was a lot more comprehensive than the 1955 water right empowering the Roxburgh dam, which was simply one page long and allowed the Electricity Corporation to virtually do what it liked!
As well as allowing the owners of Waipori, the DCC, comprehensive powers to raise the lake, use the water as it liked, the 1924 right restricted the DCC in many areas. Principally, that nothing should interfere with riparian rights – that is, fishing rights from the riparian strip, or people's right to safely use the water for amenity purposes such as boating.
To assist in the proper control and protection of the reservoir environment, an operating regime was agreed to whereby the reservoir was allowed to fill at certain times during the year with the effect of controlling weed, gorse and broom. This equitable arrangement also allowed the DCC to generate electricity sufficient for the city of Dunedin's needs and to draw on the national grid (controlled by the Department of Electricity) when there was insufficient storage available outside the operating regime that had been agreed to.
In 1998, the Waipori scheme was sold by the DCC under the electricity legislation promoted by the National Government, whereby the DCC had to divest itself of the Waipori generation if it wanted to hold on to its lines company. Transpower bought the scheme and is now preparing to apply for a new consent in late 2001 to operate the dams.
Because the requirements of the RMA are generally a lot more stringent than the previous planning authorities, Transpower hired consultants and commenced a series of "stakeholder" meetings. A stakeholder being a person, group or company that either owned land there, or used the lake as an amenity for various activities such as boating and fishing.
During those meetings and the reports that came out of them, it transpired that Transpower, locked into a different regime than the DCC, due to the freeing up of the electricity market, where looking to put in place a different operating regime for generation. Whereas Waipori generation used to be for the purposes of supplying electricity for Dunedin residents and supplying to the National Grid on a reciprocal basis, with profits being viewed in the context of amenity, conservation values as well as electricity supply, things had changed completely. Trustpower can supply only 33% of its own customers (as against Contact Energy, for instance, which has a lot more generation than retail customers). This means that Trustpower, in winter, where demand is highest and storage normally at its lowest, draws down heavily on its available storage so as to be able to supply as many of its own customers as it can. The price advantage is obvious – it means they don't have to buy on the New Zealand Electricity Market for a certain block of their electricity at prices which are much higher that the cost of generation from their own scheme.
This is one of the bad features with the now, deregulated electricity market, where environmental and efficiency concerns come second to individual operators' requirements to maximise profit. We saw this last year, where dams in the South Island were allowed to spill water to waste while North Island fossil fuel and thermal generation was going full bore.
The history concerning Lake Mahinerangi (which is a larger lake than Lake Dunstan, behind the Clyde dam) as far as weed control and chemicals are concerned, has not been good. From 1960 – 1980, there had been a nine-fold increase in chemical residues due to the amount of "super" being applied. Since then, considerably more has been applied, particularly by Landcorp which owns most of the farmland around the reservoir. In an effort to control gorse and broom, due to prolonged lowering of the reservoir, Tordon and Grazon was applied by helicopter, resulting in erosion, noxious weeds, dead fish and lobsters and increasing amounts of slime. Also wilding pines.
There are new areas in Otago and throughout New Zealand that will grow nothing at all. This is a result of over-excessive chemical use, as confirmed by Agrispray at East Taieri. There has been no monitoring of Lake Mahingerangi for quite some time – certainly since 1980. For most of the year, in recent times, the reservoirhas been drawn down low, even in periods of high rainfall and greater inflow. As soon as the reservoir rises, therefore, Transpower draws it off to supply its customers for commercial advantage.
Transpower's response to Stakeholders' concerns as to the quality of the environment around the reservoir and their properties, was to commission a report from Murray Harris, consultants, and Ryder Consulting Ltd. This report, completed in April, had as its main thrust, the methods of control of the environment around the lake by chemical spraying. The consultants said that, by and large, the cost for such weed control should be borne by others, not itself, as those people owned or used the land in question.
This would be done by groups such as Task Force Green, Conservation Corps Volunteer Groups, and Fish and Game, Otago. Of all the control methods mentioned, only one was regarded as the primary method of eradication, and that was the use of "approved' herbicides using helicopters and spot spraying, with mechanical clearing and ground cover improvement – planting etc, being secondary tools. Of the $351,000 budgeted for the next five years, only $66,000 would be provided by Trustpower, who would be by far the principal user of the resource.
Therefore, for Trustpower to be able to maximise it profits from generation, by using the inflows and storage capacity of the reservoir to their ultimate to suit their purposes, private owners' resources plus public funds (DOC had been picking up the major share of the tab in past chemical spraying) would be asked for. The net result would be a rapid degradation of the entire environment over a period of many years, so that in the end there would be only a concrete dam and a dustbowl. Already, erosion caused by continuing low reservoir levels has caused mud and sludge, banks breaking into the reservoir (particularly around the old cemetery there), and dead fish life. Also, replanting of various special species such as floodproof native grasses would be under threat from chemical residues through over-spraying.
In the Journal of Pesticide Reform (Oregon, USA) there is considerable detail as to the short and long term effects of the use of Tordon and Grazon (Dow Chemicals). These are the trade names for Picloram. Tests showed contamination of groundwater from Picloram, which is persistent and highly mobile in soils.. It causes danger to crops and is highly toxic to fish. There are ample case studies detailed that show this, and other dangers of Picloram. Picloram herbicides are hazardous to the eye and the immune system. These sprays have been used over the riparian strip (lake's edge) in the past by DOC and there is plenty of evidence of fish kill over that time.
In the May/June issue of Soil and Health (NZ) there is an article, "Pesticides and the Principal of Minimum Harm" covers the effects of unrestricted and sustained spraying, of the kind that is being suggested for the Mahinerangi environment.
In the consultants' report the method of control using fluctuation of lake level at certain times in the year, and planting of native grasses resistant to inundation to control weed growth, such and broom and gorse was not costed. The reason given is that it would interfere with Trustpower's operating regime, which would not agree with such periodic inundation. Trustpower were asked to monitor the reservoir, or ask their consultants, Ryder Consulting Ltd to do so, during recent high levels of inundation to close to the maximum level, to assess the effects of the resulting weed control. They refused. They said that periodic inundation was not an option for them. They also said that such control methods would not be supported by the other stakeholders. This is not true. Their consultation was such that the residents of the Mahingerangi fishing village were not told of the stakeholders' meetings and those others who were were not adequately informed about the methods and options available.
Mark Nelson, of Fish and Game, said at the second Stakeholders' meeting that he wanted Trustpower to go away and sort out an operating regime for their generation which would allow the traditional periodic inundation of the lake edges to control weed growth, then come back and tell us about it. This move was well supported at the time by all present. Trustpower have since stuck to their plan to control weed growth by chemical means. A plan, briefly mooted by them, to lay large matting over the area to stop anything growing, was abandoned no doubt due to the cost. They would not agree to any modification of their operating regime.
We consider this resource consent process as very important to establish consistent and sustainable methods of land management practice within the requirements of the Resource Management Act. We consider the effects of Trustpower's operating regime to be far too adverse on the local environment (let alone downstream in the Taieri, through released chemical residues) to be permitted.
Return to:
Home Page
