Indicator 2.6.10

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System

Water Type

Feed Dependent

Species

Indicator 2.6.10

by Contact on 8 October 2026

Requirement

The UoC shall, after the determination of the water quality baseline, conduct monitoring of the water quality parameters listed below, following the method outlined in Appendix 8 (8.8):3434An exemption applies if the mean of Secchi Disk (SD) depth calculated over any rolling two-year period remains ≥10m. – Total Nitrogen (TN); and, – Total Phosphorous (TP); and, – Dissolved Oxygen (DO); and, – Secchi Disk (SD) depth; and, – Chlorophyll-a (Chl-a).

How Do I Interpret This Requirement?

  • Quarterly monitoring ensures the UoC can capture any seasonal or inter-annual variations in the data collected.

  • Measurements should be timed to coincide with, or immediately follow, annual turnover events when the waterbody is not permanently stratified (holomictic).

  • The UoC should calibrate equipment used to measure DO, TN, TP, SD and Chl-a according to the technical specifications of the equipment.

  • The UoC should conduct measurements of the parameters in-situ.

  • Samples may be sent for laboratory analysis, however variability with sample maintenance during transit can lead to inconsistent results. This is particularly evident with DO and Chl-a samples.

Evidence of Implementation

  • Documentation outlining the sampling plan to conduct quarterly monitoring and that is in accordance with Appendix 8 (8.8).

  • Quarterly monitoring data has been collected and submitted to the ASC Water Quality Calculator. Data should be submitted at least annually.

  • Evidence that quarterly monitoring data has been timed with annual turnover events (where applicable).

  • That equipment to measure DO, TN, TP, SD and Chl-a has been calibrated according to technical specifications.

Auditors Should Confirm

  • The sampling methodology to conduct quarterly monitoring is in accordance with Appendix 8 (8.8).

  • The UoC has conducted quarterly monitoring of the water quality parameters and submitted data to the ASC Water Quality Calculator at least annually.

  • Evidence has been provided demonstrating the UoC has calibrated equipment to measure DO, TN, TP, SD and Chl-a in accordance with the technical specifications.

Useful Resources

  • Paerl, H.W., Scott, J.T., McCarthy, M.J., Newell, S.E., Gardner, W.S., Havens, K.E., Hoffman, D.K., Wilhelm, S.W. and Wurtsbaugh, W.A., 2016. It takes two to tango: when and where dual nutrient (N & P) reductions are needed to protect lakes and downstream ecosystems. Environmental science & technology, 50(20), pp.10805-10813.

  • Information on the appropriate use of Secchi Disks can be found here: ‘What is a Secchi disk’, accessed November 22, 2023: <https://www.nalms.org/secchidipin/monitoring-methods/the-secchi-disk/what-is-a-secchi-disk/>

  • Example of a method for Chl-a measurements made using ethanol extraction followed by spectrophotometric measurement at wavelengths 665 and 750nm (using accredited methods: EPA method 445.0: Method 445.0 In Vitro Determination of Chlorophyll a and Pheophytin ain Marine and Freshwater Algae by Fluorescence, accessed November 22, 2023: https://cfpub.epa.gov/si/si_public_record_report.cfm?Lab=NERL&dirEntryId=309417

  • Cost effective example for measuring using in-situ Chl-a using a field spectroflurometer include the FluoroSense handheld fluorometer manufactured by Turner Designs and the YSI handheld meter with EXO1 (#599080) or EXO2 (#599201) sondes.

  • Hamdhani, H., Eppehimer, D.E., Walker, D. and Bogan, M.T. (2021) Performance of a Handheld Chlorophyll-a Fluorometer: Potential Use for Rapid Algae Monitoring. Water, 13, 1409: https://doi.org/10.3390/w13101409

  • Kuha, J., Järvinen, M., Salmi, P. and Karjalainen, J. (2020). Calibration of in situ chlorophyll fluorometers for organic matter. Restoration of Eutrophic Lakes, 847, 4377-4387: <https://doi.org/10.1007/s10750-019-04086-z>