Revision of the 1996 South African Water Quality guidelines: development of risk-based approach using aquatic ecosystems responses

Prof. O.N. Odume, Dr N. Griffin, Dr P. Mensah, Mr D. Forsyth

Sponsor: Water Research Commission
Collaborators:  Dr L. Ncube, Ms E. van Niekerk

April 2020–December 2023

This research project focuses on the revision of the 1996 South African water quality guidelines for freshwater ecosystems, with a view to developing risk-based guidelines operationalised through a software-based decision support system. The final system will have spatially specific guidelines for a greater number of parameters than the 1996 guidelines. This approach follows the revision of water quality guidelines for other water users in South Africa.

The imperatives for the project arise out of the realization that the 1996 water quality guidelines have limitations in several important areas: i) non-alignment with approaches to water resource protection; ii) not being sufficiently risk-based; iii) lacking internal coherence between guidelines for different users; iv) not reflecting the full range of critical water quality variables such as persistent organic pollutants (POPs), pesticides and endocrine disrupting compounds (EDCs), despite local and international research regarding these variables. The project intends to address these shortcomings through the development of a multi-tier decision support system (DSS) allowing for risk identification, analysis and management. The overarching aim of the current project is to review and develop an electronic-based decision support system (software) able to provide both site-specific and generic risk-based water quality guidelines for South African aquatic ecosystems.

Production of risk-based guidelines will be data based, and data on responses of taxa to stressors as well as data on ambient spatially specific water quality will be required to generate suitable guidelines. The project has gathered 219 442 toxicological results from international databases, as well as 332 084 water quality records from regularly monitored sampling points around the country.

The project team attended a planning workshop in Maputo where considerable progress was made in the design of three tiers. Tier 1 is conservative and guided by multitaxon toxicological responses; Tier 2 is site-specific and modified to reflect local water quality, and Tier 3 was being refined.

The software tool for guideline derivation has been developed and is currently being refined. Using a database of toxicological responses, Tier 1 guidelines simply produce ecological category boundary values for 25 inorganic, 45 organic and 26 pharmaceutical compounds. Tier 2 guidelines produce locally appropriate (at ecosystem Level 2 scale) risk-based guidelines, using either water quality data or macroinvertebrate data to generate an estimate of risk. Tier 3 guidelines are issue-based, and allow a user to explore aspects of the risk scores generated by the other tiers.

Last Modified: Tue, 06 Aug 2024 14:57:12 SAST