4.3 APPLICATION OF THE PROBFLO APPROACH
4.3.1 Step 1: Vision exercise
The importance of having clear water resource management objectives for a regional scale risk assessment is imperative as it directs all components of the assessment. Although the purpose of the risk assessment is to evaluate endpoints that are exposed to relatively different risks from sources and stressors in different regions of the study area, in the context of risk pathways, an understanding is needed of what managers or stakeholders deem important in the region and what should be tested in an assessment. To achieve this, it is considered good practice by Integrated Water Resource Management strategies, regional management plans and
frameworks, national legislation and E-flow assessment tools to establish clear goals or visions for the study area that will direct the use and protection of water resources (Poff et al., 2010;
King and Pienaar, 2011). This vision should be established within a legislative context so the RQO determination procedure (DWA, 2011) was implemented to provide a narrative and numerical description of various ecosystem features required to achieve the balance between the use and protection of the water resources in the study area and provide a documented vision.
However, in the absence of a catchment scale Water Classification Study for the Thukela River and Estuary, the vision established for the lower reach of the Thukela River has only been used in the development of endpoints for this assessment. These endpoints would be useful for the future RDMs required for the comprehensive protection of the water resources in the whole catchment but in the interim would facilitate the sustainable use and protection of water resources for the region.
A summary of the procedural steps followed for this case study to establish the vision and develop the endpoints are provided below.
• Delineate the Integrated Units of Analysis (IUAs) and Resource Units (RUs): In this case, the region was divided into two IUAs. The first being the freshwater part of the lower reach of the Thukela River and the second, the Thukela Estuary. Three spatial levels for resources were considered for RQO determination in this case study:
o Regional (IUA) scale assessments for the rivers in the study area.
o Resource Unit scale assessments that were aligned to sub-quaternary catchments and existing Reserve determination sampling sites were considered for the rivers and estuary in the study area.
The RU delineation procedure initially involved the identification of sub-quaternary reaches of rivers in the study area. The sub-quaternary reach of V50D-03903 for the Thukela River was the only applicable sub-quaternary for the assessment (DWS, 2014).
This included the Thukela River and estuary from the upstream edge of the study area to the mouth of the Thukela River. Unfortunately, available data did not include the delineation of the socio-ecologically important eMandeni Stream that is a focus of the assessment and represents a location where the quality and associated use of water resources in the study area changes. As such, the eMandeni Stream and its associated catchment was delineated and used to separate RUs in the assessment (Figure 4.3). The number and spatial extent of RUs selected for the assessment can be associated with the biophysical nodes that can inform a future formal Water Resource Classification study for the region. The delineation procedure involved the use of Geographical Information System (GIS) spatial ecosystem data.
Figure 4.3: Map of the Resource Units determined for the study area
• Establish a vision for the catchment and key elements for the IUAs: In this phase, existing preliminary RQOs from a Draft Thukela River Estuary Management Plan (INR, 2014b) and available water resource use and protection information were considered. Stakeholder workshops were also held, that highlighted the importance of flows in the Thukela River and estuary to maintain the wellbeing of the Thukela Bight.
The vision selected to direct this assessment is adaptable and based on local and regional applicable legislation and policies. The vision for the assessment simply states:
o Maintain the current (2017) ecological wellbeing of the structure and function of the ecosystem, which includes biodiversity and key ecosystem process maintenance.
o Maintain a sustainable balance between the use and protection of water resources, including an environment that is safe and clean and promotes sustainable use for the benefit of all stakeholders.
• Prioritise and select RUs and ecosystems for RQO determination: In this step, RU’s in the study area were prioritised and sites within each RU that have previously been used as Ecological Water Requirement (EWR) sites or sites for routine monitoring were selected to represent the study area (Figure 4.3).
• Prioritise sub-components for RQO determination, select indicators for monitoring and propose the direction of change: Sub-components prioritised for RQO development in this assessment included water quality, quantity and habitat components and a series of biological components. They were used to establish the endpoints for the assessment, that represent the current balance between the use and protection of water resources that should be “maintained or improved”.
• Develop draft endpoints for the assessment: The endpoints selected for the assessment include a range of use and protection ecosystem indicators including:
Resource protection indicators:
o Maintain riparian vegetation wellbeing: this ecological endpoint represents an important component of the ecological wellbeing of the aquatic ecosystems of the Thukela River and eMandeni Stream. Risk to the maintenance of the wellbeing of the riparian ecosystem will inform the components of the vision to maintain the biodiversity and ecosystem processes of the study area.
o Maintain fish community wellbeing: similarly, this ecological endpoint represents an important component of the ecological wellbeing of the aquatic ecosystems of the Thukela River and eMandeni Stream. Risk to the maintenance of the wellbeing of the fish communities will inform the components of the vision to maintain the biodiversity and ecosystem processes of the study area.
o Maintain macroinvertebrate community wellbeing: similarly, this ecological endpoint represents an important component of the ecological wellbeing of the aquatic ecosystems of the Thukela River and eMandeni Stream. Risk to the maintenance of the wellbeing of the invertebrate communities will inform the components of the vision to maintain the biodiversity and ecosystem processes of the study area.
Resource use indicators:
o Maintain supply of natural products: in the study area the supply and maintenance of the existing quality of fish from the river and vegetation from the riparian zone for food and materials, as well as sand were selected to represent the natural product supply for the assessment. These endpoints must be maintained for the benefit of local communities to achieve the sustainable use and protection vision of the rivers in the study area.
o Maintain opportunities and environmental quality for recreational activities: the maintenance of the quality of the ecosystem to limit threats to human health and access and opportunities for recreation in the study area must be maintained.
This will contribute to the achievement of the vision of the study area, namely;
to promote the use of and access to the study area as well as sustainably use the environment.
o Maintain water for abstractors: the socio-economic value of the rivers in the study area, associated with the abstraction of water for urban and peri-urban communities, agriculture and industry must be maintained. This will contribute to achievement of the sustainable use of water resources in the study area for the equitable benefit of all users.
o Maintain effluent assimilative capacity of the environment: the water borne waste removal service of the rivers in the study area is of great value to the users and regulators of the rivers in the study area. To achieve the vision of the assessment that includes, “sustainable use for the benefit of all stakeholders”
the assimilative capacity of the rivers is a suitable ecosystem indicator for the assessment that must be carefully managed.