2. Bill Vant, Waikato Regional Council
Water quality, 1: Rivers
Bill Vant, Waikato Regional Council

3. Outline Variables Council’s river water quality network Flow
Changes moving downstream
Sources of contaminants
Condition and trend

4. Variables: “a huge number”
NZ Drinking Water 2005: standards for contaminants
ANZECC 2000: guidelines for 250 ecological toxicants in water
USEPA (1998) identified “an estimated 87,000” potential endocrine disruptors

5. Key types of variables Major ions: Na, K, Ca, Mg, SO4, Cl, HCO3
Plant nutrients: various forms of N and P
Inorganic suspensoids, e.g. silt particles
Microbes: viruses, bacteria, protozoans, plankton
Metals (e.g. As, Cd, Cu, Hg, Zn)
Pesticides & other synthetic organics

6. Council’s river water quality network
Waikato River—10 sites, others—100 sites
monthly intervals
>20 variables (“general water quality”)
physical: temperature, conductivity, visibility
chemical: pH, oxygen, nutrients, geothermal
biochemical: BOD, chlorophyll a
microbiological: faecal coliforms, E. coli, enterococci
Waikato—since 1980; others—since 1990

8. Conductivity @ Otamakokore, raw

9. Otamakokore

10. Otamakokore, conductivity vs flow

11. Conductivity @ Otamakokore, raw and flow-adjusted

13. Salinity (March 2012, high tide and low river flow)
Piako

14. Turbidity
Piako

15. Nitrogen in rivers and land use

16. Sources of N and P, 2000-09 (kg/ha/yr)
Nitrogen
Phosphorus

17. Condition and trend

19. A typical record

20. Whangamarino: ecological health variables

25. Trend analysis, using non-parametric statistics
slope (“seasonal Kendall slope estimator”)
= median (Ji - Ji-1, Ji - Ji-2, … , Fi - Fi-1, …)
p-value (“seasonal Kendall trend test”)
= +ve slopes cf. ve slopes

31. Summary: current condition
excellent in places, poor in others—but not dire
conditions are often “at least satisfactory for desired uses”
differences between zones (e.g. Coromandel cf. Lowland Waikato)
these broadly reflect differing intensity of land use

32. Summary: trends
Waikato River: some improvement (ammonia, chlorophyll); some deterioration (turbidity, nitrogen)
Other rivers: some improvement (ammonia), some deterioration (nitrogen)
Pastoral agriculture likely to be the cause of much of the increase in nitrogen