Trends in river water quality in the Waikato region, 1993-2017 / prepared by: Bill Vant.
By: Vant, W. N [author.].
Contributor(s): Waikato (N.Z.). Regional Council (2011- ) [issuing body.].Material type: BookSeries: Waikato Regional Council technical report (2011): 2018/30.Publisher: Hamilton [New Zealand] : Waikato Regional Council, 2018.Description: 1 online resource : colour illustrations.Content type: text Media type: computer Carrier type: online resourceSubject(s): WATER QUALITY | RIVERS | WAIKATO | NEW ZEALAND | WAIKATO RIVER | ENVIRONMENTAL MONITORING | ESCHERICHIA COLI | NITROGEN | WATER QUALITY MANAGEMENTHoldings: ELECTRONIC Online resources: TR 2018/30 Waikato Regional Council website | NIWA document server | National Digital Heritage Archive Open Access
|Item type||Current location||Call number||Copy number||Status||Date due||Barcode|
|WELLINGTON ONLINE||ELECTRONIC||1||Not for loan||395971|
Archived by the National Library of New Zealand in PDF.
Hypertext links contained in the archived instances of this title may not be functional.
Includes bibliographical references.
1. Introduction -- 2. Methods -- 2.1 Datasets analysed -- 2.2 Statistical analyses—general approach -- 2.3 Seasonal Kendall trend slope -- 2.4 Slope direction probability -- 2.5 Flow adjustment -- 2.6 Flow records -- 3. Results and discussion -- 3.1 Waikato River -- 3.2 Other rivers and streams -- 4. Conclusions.
River water quality generally changes over time. Ongoing increases or decreases over a period of years or decades are called “trends”; these will either amount to improvements or deteriorations in water quality. The water quality of more than 100 river sites in the Waikato region has been monitored for more than 25 years, so we are therefore well-placed to assess trends over that period. This is the fifth in a series of trend reports that have been prepared by WRC every five years.
This latest report shows a mixed picture of changes in water quality over the past 25 years: many records of river water quality have been stable (i.e. no change in average conditions); some records have shown important improvements; and yet others have shown important deteriorations.
This report shows that we continue to see increases in nitrogen concentrations in many of the region’s river, although the rate of increase has tended to slow over the past 10 years. In the south-eastern part of the region, increases are likely to continue for some considerable time in the future due to storage of nitrogen-rich waters in the large underground “aquifers” or natural reservoirs of groundwater found there.
By contrast, a pleasing—if somewhat unexpected—finding is that since 1998, concentrations of the faecal microbe E. coli have declined at about one-quarter of the sites where it has been monitored. The average rate of improvement was a relatively-high 4% per year.