Water quality in the Upper Clutha is “excellent,” the best in Otago, according to a ‘state of the environment’ report on river and lake water quality in the region.
The study reports on the state of water quality on a site-by-site basis, relative to nationwide targets specified in the National Policy Statement for Freshwater Management 2020.
It also assesses water quality trends at each site where there is sufficient data, and across Otago as a whole.
General Manager Strategy, Policy and Science Gwyneth Elsum said the information in the report was valuable for the Otago Regional Council (ORC) and the wider community as it updates knowledge of water quality across Otago.
“This report largely reflects the patterns we have seen in the past, which tell us that water quality is best in the headwaters and at higher elevations, but it suffers at sites in smaller, low-elevation streams that drain pastoral or urban catchments,” she said.
“That spatial pattern of water quality in Otago will inform the development of our new Land and Water Regional Plan, which divides the region by catchment into freshwater management areas.
“This information will also support ORC and the community to implement other water quality improvement initiatives,” Elsum said.
The report does not analyse the drivers for water degradation trends, due to the lack of detailed information that ORC currently holds on land use and land management changes at a local or catchment scale. ORC recently formed a new science team to develop its knowledge in this area.
The ‘State and Trends of River and Lake Water Quality in the Otago Region 2000-2020’ report states, on the Upper Clutha and upper reaches of the Wakatipu:
In the Upper Lakes Rohe (rohe describes the territory or boundaries of iwi (tribes)) water quality is generally very good, as it should be. Of the NOF (National Objectives Framework) attribute state, the Rees and Dart are below the national bottom line for turbidity, but this is a natural state due to glacial melt-water.
Despite very good compliance with the E.coli attribute, four sites are below the national bottom line; Bullock Creek is an urban stream running through the Wānaka township with a large population of wildfowl, these and stormwater are likely to be the reason behind the poor grade.
The Makarora and Rees are large rivers, with catchment areas largely in national parks. It is likely that the poor water quality is very localised, and possibly reflects the quality of tributaries running over the flats. The same can be said for Quartz Creek that runs over the flats before entering Lake Wānaka.
In summary; for the majority of sites across the Upper Clutha reporting region, water quality is excellent and the best in Otago.
Nutrient concentrations stimulating algae growth are low, other than in Bullock Creek where periphyton (chlorophyll) is below the national bottom line.
Trend analysis for rivers showed an ‘exceptionally unlikely’ improvement for NNN (nitrogen) in the Matukituki .
Trend analysis for lakes showed the outlets of Lakes Hāwea, Wānaka and Wakatipu had ‘exceptionally unlikely’ or ‘extremely unlikely’ improving trends for turbidity, but ‘virtually certain’ improving trends for NNN.
Read edition 1023 of the Wānaka Sun here.