Nitrate Testing Three Years On:

August 2021 to July 2022

, Nitrate Testing Three Years On:
Selwyn River at Coe’s Ford. Ford closed,15 m3 /sec following winter rains August 10, 2021

NZFFA water testing NO3-N mg/L Year Three 2021 t0 2022

, Nitrate Testing Three Years On:

Ecosystem health

The August 2020 “bottom line” for nitrate DIN for rivers (virtually the same as NO3-N) is 2.4 mg/L

The bottom line for lakes is 700 to 800 mg / m3 [1.80 mg/L = 1,800 mg / m3]

Surface waters exceeding this bottom line are recorded in red since August 2020

The apparent improvement in the Selwyn River nitrate results simply reflects the relative proportion of groundwater to water from surface flooding, (i.e. When the upper and lower Selwyn River flows are connected).

The increased nitrate results along the Lower Lake Road probably reflects markedly increased flows from recent rains and no take up by plants during a cold part of the year. In the summer most of these drains are dry or are reduced to a trickle.

Ecologist agree that ecosystem health begins to become affected by direct nitrate toxicity from 0.6 to 1.0 mg/L NO3-N

There are no precise limits due to a lack of studies and the influence other water quality parameters such as pH, Hardness, dissolved O2, etc..

Aquatic invertebrates are lost first, then amphibians, then early life stages of fish such as trout.

A Canadian Government sponsored study (2010) found Lake Trout and Whitefish eggs and fry become affected from 2.90 mg/L

The Canadian Government has adopted a bottom line for nitrate of 3.0 mg/L to protect salmonid fish as a result.

A recent peer reviewed study (2020) found no nitrate sensitive invertebrates in the MIC index in 19/20 Canterbury streams.

, Nitrate Testing Three Years On:
Cycling the banks of the Hallswell River
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2 Responses to Nitrate Testing Three Years On:

  1. " Chinook" says:

    What great work by NZ Federation of Freshwater Anglers. The question is where is Fish and Game? Where is the Department of Conservation who are charged with advocating for and protecting native fish? If the invertebrates disappear then so do native fish and trout and young salmon descending down river to the ocean.

  2. Jim Brodhead says:

    I agree with “Chinook”. Government including the Ministry of Health is in denial.
    The Department of Conservation is not interested even though native fish are at risk. Cabinet ministers are not interested, too involved in government’s social engineering it seems.

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