Resource Directed Measures for Protection of Water Resources: River Ecosystems

R29:USING ECOLOGICAL MANAGEMENT CLASSES TO DERIVE INTEGRATED RESOURCE QUALITY OBJECTIVES AND THE ECOLOGICAL RESERVE FOR WATER RESOURCES

Senior Author:Dr Heather MacKay, Department of Water Affairs and Forestry

Editors:Lizette Guest, Guest Environmental Management

Version:1.0

Date:24 September 1999

Appendix R29:

Using Ecological Management to derive integrated Resource Quality Objectives and the Ecological Reserve for Water Resources

First draft written in January 1999, following discussions during the Crocodile River pilot test in November 1998 (also included in version 1.0 Rivers specialist manual, Appendix R29).

Note to readers: Readers need to be familiar with the generic RDM methodology as described in the RDM Integrated Manual, and with the procedures described in the specialist appendices to the Rivers RDM manual. In the next draft of this document, considerably more detail and numerical examples will be included.

R29.1Background

It is important to note that, in this document, the classification system referred to includes only the prototype ecological component of the full management classification system. The other components of the classification system, which include classes and associated rules for basic human needs and for water users, will be covered in version 1.1.

R29.1.1Framework for setting resource quality objectives and the Reserve

The framework for setting the Reserve and resource quality objectives for water resources will be based on a nationally applicable management classification system. The following issues represent the departure point for the future design, development and implementation of a classification system for water resources in South Africa. These requirements have guided the preliminary design of the classification system, and the development of procedures for classification and setting of objectives.

  • There will be different levels of protection, and not all water resources can or should be given the same level of protection. Resources will be grouped into classes representing these different levels of protection. Specific issues associated with each class are likely to include the level of protection or of risk of damage to the water resource; the instream flow, quality, habitat and biotic conditions required; the water-related and land-based impacts which may be allowed, limited, controlled or prohibited; the standards to be met for waste discharges and other impacts on water resources.
  • Resource quality objectives will be set for each water resource. Resource quality objectives are a rigorous numerical or descriptive statement of the requirements for a given level of protection, corresponding to the class which is assigned to the resource.
  • Objectives have four components, in order to encompass use-related water quality requirements and ecological functions of water resources: water quantity, water quality, habitat integrity and biotic characteristics. The resource quality objectives for a particular water resource include the provisions of the Reserve (i.e. basic human needs and environmental) and use-related quality requirements.
  • Classification and resource quality objectives must eventually be extended to cover all water resources, i.e. rivers, lakes and reservoirs, wetlands, groundwater bodies, estuaries.
  • The process of assigning a class to a specific water resource, and setting appropriate objectives, will be a consultative one, aimed at reaching consensus amongst stakeholders on the level of protection which is acceptable for the resource. This consultative process must address long term protection requirements as well as accounting for economic and social issues, in deciding how to balance protection for long term sustainability with short to medium term development needs.

R29.1.2Purpose of a classification system

The protection-based classification of water resources is intended to provide:

  • a nationally consistent basis for setting resource quality objectives;
  • a clearly understood, accepted and consistent basis for assessing proposed impacts on water resources and deciding whether these impacts are acceptable or unacceptable;
  • a stable planning, regulatory and management framework, which will remain in place for an agreed time period before review, and within which decision making and development can take place.

R29.1.3Classes and levels of risk

Each class within the classification system represents a different level of risk of irreversible damage to a water resource, ranging from negligible risk (the highest level of protection) to high risk (the lowest level of protection). The risk here refers to risk of irreversible damage to the structure and function of the aquatic ecosystem, since it is assumed that structure and function of the ecosystem are what give it resilience, and the capability to sustain ongoing utilisation within certain limits.

It is assumed that the four major components of an aquatic ecosystem must all be addressed to ensure protection of structure and function, i.e. the water quantity, the water quality, physical and biological aspects), the habitat and the biota. This is why the definition of resource quality in the Water Act includes all of these four components:

``resource quality'' means the quality of all the aspects of a water resource including –

  • the quantity, pattern, timing, water level and assurance of instream flow;
  • the water quality, including the physical, chemical and biological characteristics of the water;
  • the character and condition of the instream and riparian habitat; and
  • the characteristics, condition and distribution of the aquatic biota;

The water quantity, water quality and habitat aspects are the primary drivers of the aquatic ecosystem; the biotic characteristics are usually dependent on the interaction between the three primary drivers (stressors), and the biotic characteristics tend to be used as the principal indicators of the healthy functioning (or otherwise) of an ecosystem.

The risk of irreversible damage to an aquatic ecosystem relates to the overall integrated risk due to stresses on the ecosystem arising from changes in the driving factors or stressors. The resource quality objectives which are then set with the intention of maintaining the level of risk/protection associated with an assigned class must have three characteristics:

  • they must be set in an integrated way, allowing for the combined and inter-dependent effects of the stressors;
  • they must allow for the high variability in natural hydrological, chemical and biological conditions which is observed within South Africa;
  • they must be implementable, measurable and verifiable.

Table 4.1 is drawn from an earlier discussion document, and formed the preliminary framework for developing the concepts of classification and integrated resource quality objectives.

R29/1

Department of Water Affairs and Forestry, South Africa

Version 1.0: 24 September 1999

Resource Directed Measures for Protection of Water Resources: River Ecosystems

Table 1. Proposed framework for deriving integrated resource quality objectives. From MacKay HM (1998). Towards a classification system for water resources in South Africa. Proceedings of the WISA Conference, Cape Town, May 1998.

Class
/ Water quantity / Water quality / Instream habitat / Riparian habitat / Biota
A / Natural variability and disturbance regime: Allow negligible modification. / Negligible modification from natural. Allow negligible risk to sensitive species. Within Aquatic Ecosystems TWQR for all constituents. / Allow negligible modification from natural conditions. Depends on the instream flow and quality objectives which are set. / Allow negligible modification from natural conditions. Control of land uses in the riparian zone in order to ensure no modification (e.g. no disturbance of vegetation within set distance from banks) / Negligible modification from reference conditions should be observed (based on the use of a score or index such as SASS).
B / Set instream flow requirements to allow only slight risk to especially intolerant biota. / Use Aquatic Ecosystems TWQR and CEV to set objectives which allow only slight risk to intolerant biota. / Allow slight modification from natural conditions. Depends on the instream flow and quality objectives which are set. / Allow slight modification from natural conditions. / May be slightly modified from reference conditions. Especially intolerant biota may be reduced in numbers or extent of distribution.
C / Set instream flow requirements to allow only moderate risk to intolerant biota. / Use Aquatic Ecosystems TWQR, CEV and AEV to set objectives which allow only moderate risk to intolerant biota. / Allow moderate modification from natural conditions. Depends on the instream flow and quality objectives which are set. / Allow moderate modification from natural conditions. / May be moderately modified from reference conditions. Especially intolerant biota may be absent from some locations.
D / Set instream flow requirements which may result in a high risk of loss of intolerant biota. / Use Aquatic Ecosystems TWQR, CEV and AEV to set objectives which may result in high risk to intolerant biota. / Allow a high degree of modification from natural conditions. Depends on the instream flow and quality objectives which are set. / Allow a high degree of modification from natural conditions. / May be highly modified from reference conditions. Intolerant biota unlikely to be present.

R29/1

Department of Water Affairs and Forestry, South Africa

Version 1.0: 24 September 1999

Resource Directed Measures for Protection of Water Resources: River Ecosystems

R29.2Translating and assigned Management Class into Numeric Resource Quality Objectives

R29.2.1Development of the framework

This is Step 6 in the generic RDM process, and by far the most technically demanding. To develop a procedure for carrying out step 6, a number of problems have to be addressed.

The first problem is that measures for assessing the overall state of an aquatic ecosystem tend to be those which integrate the effects of multiple stressors, for example a habitat integrity index, or an invertebrate index (such as SASS). However, resource managers cannot undertake practical everyday system management on the basis of indices or biotic characteristics: everyday management is at the level of stressors - water quantity, water quality and habitat. The indices of biotic integrity can then tell us how well we have done in protecting ecosystem structure and function, subsequent to management of flow, quality and habitat. So, while indices are useful integrated measures of the effects of past management actions, they need to be "unpacked" in order to develop operational rules for managing the stressors to achieve future management goals (such as a particular assigned class).

Secondly, the interactions between the stressors themselves and then the responses of the biota to these stressors are complex and also subject to a degree of inherent uncertainty (as most ecological processes are). So far, many of the interactions are only partly or poorly understood. Even where the nature of the interaction is understood, we are a long way from being able to integrate, quantify and then predict the effects on the biota of multiple stressors. Presently, the use of expert judgement, supported by systems models and laboratory or field data where available, is accepted as a way to derive numerical objectives for stressors such as water quantity, water quality and habitat, which are intended to achieve a broad (usually qualitative) goal or class for biotic integrity.

Thirdly, objectives need to be site-specific in most cases, since a numerical objective which provides a certain level of protection in one region of the country may not provide that same level of protection in another region where the hydrological and geochemical conditions are quite different.

(Note: These concepts of risk, ecological resilience and integration of multiple stressors are dealt with in other documents, as well as being the subject of a current Water Research Commission project, so they will not be covered in great detail here. References to follow in the next draft of this document.)

As discussed in the RDM Integrated Manual, a number of tools for deriving objectives were available when the RDM project began in 1997. The Building Block Methodology allows the derivation of objectives for flow in a river in order to maintain a particular level of protection of the ecosystem. The South African Water Quality Guidelines for Aquatic Ecosystems provide procedures for setting instream water quality objectives for protection of freshwater aquatic ecosystems. The Habitat Integrity Assessment procedures, while they have been used mainly as assessment tools, can also be utilised to some degree to set descriptive objectives. However an integrated process for using these tools together, taking account of the interactions of multiple stressors, does not yet exist. So far, the tools have been applied independently of each other, with only the Habitat Assessment taking some account of the effects of other stressors, because habitat itself has considerable dependence on flow and water quality characteristics.

This document outlines a proposed procedure for deriving integrated resource quality objectives on the basis of an assigned ecological management class. Recognising that quantification of all the interactions in an aquatic ecosystem is not possible at this stage, the procedure is intended to represent a formal and structured way to incorporate available data and expert judgement into a consistent and transparent framework - essentially an expert system approach. Within this framework, it is easier to see where interactions have actually been quantified, where expert judgement has been used in the absence of data or quantitative relationships, where the primary uncertainties are, and what the estimated overall level of confidence is in the final resource quality objectives.

The initial framework was developed during a pilot test of the reserve procedures at the Crocodile River, Nelspruit, in November 1998. The inputs of the RDM project team to this development are gratefully acknowledged.

R29.2.2Worked example

A numerical worked example will be included in version 1.1, using the Crocodile River data. For now, it seems that a non-quantitative and somewhat simplistic worked example may be the best way to explain the framework of the Step 6 process.

Table 4.2 is the starting point for the explanation. The explanation is given in terms of a river ecosystem, but the principles should be applicable to estuaries and wetlands also. Across the top of the table are the four major ecosystem components which are addressed in resource quality management and resource quality objectives: biota, habitat, flow and water quality. The same four aspects are considered throughout the generic RDM procedure, and particularly in

  • Step 3 (reference conditions),
  • Step 4 (present status assessment),
  • Step 5 (selection of ecological management class ) and
  • Step 6 (quantify Reserve and resource quality objectives).

The first column in Table 2 lists each of these steps. Their relevance to the explanation will hopefully become clear. The table is blank to begin with.

R29/1

Department of Water Affairs and Forestry, South Africa

Version 1.0: 24 September 1999

Resource Directed Measures for Protection of Water Resources: River Ecosystems

Table 2. Blank table showing framework for setting reserve and resource quality objectives. The Steps in the first column refer to the steps in the generic RDM procedure

Biota / Habitat / Flow / Water quality
Invert-ebrates / Fish / Veg / Instream / Riparian / Mainten-ance / Drought / Floods / Toxics / Nutrients / System variables
pH / Temper-ature / Dissolved oxygen / TDS / TSS
Step 3
Reference conditions
Step 4
Present status assessment
Step 5
Assigned ecological manage-ment class
Steps 6 & 7a
Numerical Reserve & Resource Quality Objectives

R29/1

Department of Water Affairs and Forestry, South Africa

Version 1.0: 24 September 1999

Resource Directed Measures for Protection of Water Resources: River Ecosystems

Reference conditions

Let us assume that this is an exercise to set the reserve and resource quality objectives (RQOs) for the Example River. If we follow the generic RDM procedure, we will undertake steps 1 and 2. So we will have delineated the geographical (upstream and downstream) boundaries of the resource unit for which the reserve and RQOs are to be determined, and we will have identified the ecoregional type of that resource unit. Knowing the ecoregional type, and perhaps undertaking some other work in the region, will allow us to fill in the first row of Table 2 for reference conditions. Some cells in the row could contain numerical data, such as concentrations of certain water quality constituents or monthly flows to be expected under unimpacted reference conditions. Other cells might contain more descriptive data, such as the characteristics of the instream habitat (e.g. braided stream, or riffles and pools). Reference conditions for biota might be in the form of indices or descriptive statements. See Table3.

Present status assessment

The assessment of present status is usually carried out by a team of specialists, who address all the various ecosystem components. In this example, the components have been broken down into sub-components as follows (with reference to Table 3):

  • Biota: assessments of invertebrates, fish and vegetation status, relative to reference conditions (as described in the RDM Integrated Manual)
  • Habitat: assessments of instream and riparian habitat, including both physical structure and vegetation, relative to reference conditions
  • Flow: assessments of maintenance flows, drought flows, flood flows relative to reference conditions
  • Water quality: assessments of toxic constituents, nutrients and system variables (which are again broken down into pH, water temperature, dissolved oxygen, TDS and TSS).

The present status is assessed in terms of a degree of change from reference conditions. Guidelines for these assessments can be found in the specialist appendices in the specialist manuals.

The breakdown of the four major components of resource quality to the levels indicated above and in Table 3 was considered necessary by the RDM team. Integration to any higher level led to loss of information for practical management purposes, and so no higher indices or "super-indices" were utilised. Each of the sub-component stressors acts in a way sufficiently independent of other sub-component stressors (or perhaps in a way which can be sufficiently resolved from the effects of other sub-components) to warrant being addressed separately, rather than being integrated into an index. Additional sub-components may be added (e.g. amphibians) should this be considered necessary in further development and testing of the framework.