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

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

Variables: “a huge number” NZ Drinking Water 2005: standards for 140 contaminants ANZECC 2000: guidelines for 250 ecological toxicants in water USEPA (1998) identified “an estimated 87,000” potential endocrine disruptors

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

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

Conductivity @ Otamakokore, raw

Flow @ Otamakokore

Otamakokore, conductivity vs flow

Conductivity @ Otamakokore, raw and flow-adjusted

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

Turbidity Piako

Nitrogen in rivers and land use

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

Condition and trend

A typical record

Whangamarino: ecological health variables

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

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

Summary: trends 1993-2012 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