No.04 2003

Environment Watch on CD: promoting healthy farm and forest streams
The six Environment Watch CDs (NIWA Information Series No. 37–42) provide education resources for use by community groups, environmental educators, and secondary schools. The series is based on the TV3 programme No. 8 Wired produced by the Gibson Group.

Fresh Water New Zealand: problems, processes, and priorities
13–14 November 2003, the University of Auckland
Organised by the Royal Society of New Zealand, and sponsored by NIWA and the Science Subcommission of the New Zealand National Commission for UNESCO, this conference is a major forum on the serious problems facing freshwater in New Zealand. Tensions and conflicts are increasing. Supply is limited and demand is growing. Water quality is also a problem. Overriding both is the way we manage water through law and government.

Lake Taupo – keeping it clear for future generations
Oblique view of Lake Taupo.
Chlorophyll-a concentrations at 2–3 week intervals since 1994.
The mass of nitrated that has accumulated in the lower layer of the lake by the end of the stratification period.
The time to take action to protect the water quality of New Zealand’s largest lake is now – before the lake shows further signs of water quality decline.
In every story of lake decline, and there are depressingly many such stories from around the world, there are always 'if onlys'.

Lake Taupo: a national jewel in a state of change
Lake Taupo is the largest lake in Australasia, with a surface area of 610 km2 and a water volume of over 60 km3. Such water volumes have long response times. The groundwater aquifers in the catchment add to the response time. There have been significant land developments in the Taupo catchment during the last 50 years, and there is little doubt that the lake is changing as a result.

Outlook for water resources in spring 2003
Dry conditions in eastern New Zealand at the beginning of September were alleviated by good early spring rainfall. The National Climate Centre’s rainfall outlook for October–December 2003 is for normal or above normal rain in the west, and normal or below normal rain in the east. We expect normal or above normal flows for this period in rivers in the west, and normal or possibly below normal in the east. Groundwater levels in parts of the eastern South Island are likely to be normal to below normal.

Water resources in winter 2003
River flow
River flows for winter were below normal for much of the country, especially in the central North Island and the east of the South Island. For some rivers in the Manawatu-Wanganui and Otago regions, these are the lowest winter flows on record.

Managing Lake Taupo water quality
Lake Taupo is a large, near pristine lake, highly valued for its crystal blue waters and dramatic vistas.
Taupo’s excellent water quality is derived from extremely low levels of plant nutrients and phytoplankton. Unlike many other lakes, the availability of nitrogen, rather than phosphorus, limits phytoplankton growth in Taupo – so increased nitrogen flows from rural land use and urban growth in the catchment promote phytoplankton growth, threatening the high water quality of the lake.

A new riparian management tool
The map shows how easy it would be to control stream temperature by using riparian planting.
Management of riparian areas exerts a strong influence on the health of streams and downstream water bodies. Management of riparian vegetation and stock access influences stream temperature and plant growth; sediment, pathogen, and nutrient levels; food webs; and physical habitat.
The importance of these various functions of riparian areas varies greatly depending on stream and land characteristics and the local waterway management issues.

How long does it take for nutrient enriched groundwater to travel from farms to Lake Taupo?
The age of groundwater in the Lake Taupo catchment has been estimated for Environment Waikato by Geological and Nuclear Sciences, who measured concentrations of the cosmogenic isotope tritium, and two anthropogenic tracers: chlorofluorocarbons (CFCs) and sulphur hexafluoride (SF6). These analyses tell us when the water was last in contact with the atmosphere, and the proportions of 'young' and 'old' water in a sample.