Project title: South African Water Quality Guidelines for Freshwater Ecosystems - Version 2
Link to DSS: Decision Support System (Version 1) for the implementation of the South African Water Quality Guidelines for Freshwater Ecosystems - Version 2
The 1996 Water Quality Guidelines for Aquatic Ecosystems are widely used in South Africa, and even beyond the borders of the country. They have also aided the management of water quality in the country, including being used for education purposes. However, they have been criticised for four fundamental reasons. First, they have been criticised for not being explicitly risk-based and not taking an explicit risk approach in their development and implementation. An important implementation outcome of not being risk-based is what has been referred to as over- or under-protection. In this regard, current guidelines are being used as trigger value, above which an action, usually corrective one, needs to be taken, and below which all is assumed to be fine, and no action may be taken. Second, they are largely generic, and not site specific (with the exception of a few variables such as conductivity, pH, total dissolved solids, water temperature) or do not consider the spatial variability that naturally impacts water quality. Third, the 1996 guidelines were developed prior to the promulgation of the National Water Act, as a result, the guidelines do not reflect the thinking informing the various resource directed measures (RDM). For example, the current guideline for freshwater ecosystems follows the trigger value approach (target water quality range), which is not very helpful given that the Department of Water and Sanitation (DWS) approach accords water resources different levels of protection e.g., Class I, II, III and Ecological Categories A-D, with descriptive and quantitative Resource Quality Objectives (RQOs). Fourth, since the 1996 guidelines were published, much research has been undertaken locally and internationally in the field of water quality and new and emerging pollutants of concern. There is thus a need to update the guidelines to reflect new science in the field.
The hard-copy, paper-based 1996 guidelines were deemed as not supporting rapid decision making processes and were not easily updatable. To this end, the stakeholders in the sector recommended the development of an updatable software-based decision support system (DSS) that allows rapid decision making regarding the risk posed by pollutants of concern. A multi-tier approach was also recommended for the revision of the guidelines.
The following were the aims of the project:
The revised Guideline follows a multi-tier approach, Tiers 1- 3, where Tier 1 are generic guidelines developed mainly using toxicological data, generated through an SSD curve (species sensitivity distribution). The guidelines at Tier 1 are generic, conservative and are similar to the 1996 Guidelines, but with reference to the Ecological Categories A – F. The guidelines are thus aligned with the Ecological Categories. Tier 1 guidelines are developed for 23 inorganic salts; 42 organic compounds; and 26 pharmaceuticals. Temperature guidelines defer to the work of Rivers-Moore and Dallas.
Tier 2 guidelines are derived at ecoregion level II to account for spatial variability within the country. By developing guidelines for each level II ecoregion within the country, the spatial variability driven by several factors such as climate, physiography, geology and soils as well as altitude, are thus accounted for in the revised guidelines. In addition, guidelines at Tier 2 are developed for both physico-chemistry and macroinvertebrate response, thus accounting for community-based effect of the ecosystem to water quality change. The physico-chemical variables for which guidelines have been developed at Tier 2 were driven mainly by available data within the current DWS water quality monitoring networks. As such, some ecoregion level II were data-rich, whereas others were data-poor.
Tier 3 assessment is triggered when an unacceptable risk is suspected based on the results of Tiers 1 and 2. Tier 3 provides a means for a site-specific water quality risk assessment by collecting detailed site-specific information. A key feature of Tier 3 assessments is that they are event/scenario-based. The reasoning behind this approach is that improving water quality implies a focus on the event/scenario driving water quality change. For the purpose of Tier 3 assessment, risk is conceptualized as a measure of the likelihood (probability) of an event/scenario/issue occurring and its adverse effects or consequences as well as the associated uncertainty.
The Guidelines are implemented within an updatable software-based decision support system (DSS) flexible enough to allow for rapid decision making regarding the risk posed by pollutants of concern. The DSS interface allows for easy navigation. As the Guidelines are software-based, they are easily updatable, support educational and research purposes and can also facilitate rapid decision making. Crucially, the revised guidelines can also support water quality licensing and similar imperatives.
Last Modified: Fri, 19 Jan 2024 12:46:47 SAST