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A PRELIMINARY ECOREGION CLASSIFICATION SYSTEM FOR SOUTH AFRICA
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Resource Directed Measures for Protection of Water Resources: River Ecosystems
R23: DETERMINATION OF RESOURCE QUALITY OBJECTIVES FOR HABITAT INTEGRITY
Ssenior Author: CJ Kleynhans & L Hill, Institute for Water Quality Studies, Department of Water Affairs and
Forestry
Editor: Heather MacKay, Department of Water Affairs and Forestry
Lizette Guest, Guest Environmental Management
Version: 1.0
Date: 24 September 1999
M:\f_rdm_october\rivers\version 1.0\riv_appR23_version1.0.doc
Department of Water Affairs and Forestry, South Africa R23/1
Version 1.0: 24 September 1999
Resource Directed Measures for Protection of Water Resources: River Ecosystems
Appendix R23:
Resource Quality Objectives: Determination of Habitat Integrity
Objectives
R23.1 Introduction
The purpose of resource quality objectives (RQOs) is to establish clear goals relating to the resource quality of
the relevant water resources. Where resources for instance need a high level of protection, a strict set of
objectives that will represent a low risk of damage, will be set. There is an implicit understanding that once the
management class (A, B, C or D) of a water resource has been decided, the objectives for protection of basic
human needs and ecological integrity take precedence in cases where the objectives for other uses, or for
impacts, may conflict with the requirements for protection.
Resource Quality Objectives have four critical components, to cover each of the aspects necessary for
protection:
requirements for water quantity, stated as flow requirements for a river reach or estuary, and/or water level
requirements for standing water or ground water, and/or requirements for groundwater level in order to
maintain spring flow and base flow in rivers and other ecological features;
requirements for water quality (chemical, physical, and biological characteristics of the water);
requirements for habitat integrity, which encompass the physical structure of in-stream and riparian
habitats, as well as the vegetation aspects;
requirements for biotic integrity which reflect the health, community structure and distribution of aquatic
biota.
These RQOs must further:
be quantifiable, measurable, verifiable, and enforceable; and
ensure protection of all components of the resource, which make up ecological integrity.
The aim of this discussion is to propose an approach to the derivation of objectives for the habitat integrity
aspect of the RDM for rivers. This could then act as a generic model for deriving habitat objectives for wetlands
and estuaries. Taking the integrated aquatic environment as a basis for management, these objectives cannot be
set independently from the other mentioned components of ecological integrity. It will therefore be necessary,
together with the objectives set for the other components (water quality, water quantity and biota), to derive
integrated resource quality objectives for a water resource.
R23.2 Methodology
R23.2.1 Approach
The perceived resource quality conditions of each ecological management class are described in Table 1.
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Resource Directed Measures for Protection of Water Resources: River Ecosystems
Table 1: Description of perceived conditions for each ecological management class for rivers
Management class Description of perceived conditions
A Modifications to the natural abiotic template should be negligible to small. The
characteristics of the resource should be determined by unmodified natural
disturbance regimes. Human induced risks to the abiotic and biotic maintenance of
the resource should be insignificant. The supply capacity of the resource will only be
used within limits that represent a negligible impact on the resource.
B Largely natural with few modifications; only a small risk of modifying the natural
abiotic template and exceeding the resource base should be allowed. Although the
risk to the well-being and survival of especially intolerant biota (depending on the
nature of the disturbance) at a very limited number of localities may be slightly
higher than expected under natural conditions, the resilience and adaptability of biota
must not be compromised. The impact of acute disturbances must be totally
mitigated by the presence of sufficient refuge areas.
C Moderately modified; a moderate risk of modifying the abiotic template and
exceeding the resource base may be allowed. Risks to the well being and survival
and intolerant biota (depending on the nature of the disturbance) may generally be
increased with some reduction of resilience and adaptability at a small number of
localities. However, the impact of local and acute disturbances must at least partly
by mitigated by the presence of sufficient refuge areas.
D Largely modified; large risk of modifying the abiotic template and exceeding the
resource base may be allowed. Risks to the well being and survival of intolerant
biota (depending on the nature of the disturbance) may generally be allowed to
increase substantially with resulting low abundance and frequency of occurrence, and
a reduction of resilience and adaptability at a large number of localities. However,
the associated increase in the abundance of tolerant species must not be allowed to
assume pest proportions. The impact of local and acute disturbances must at least to
some extent be mitigated by refuge areas
In order to set habitat integrity objectives on a national level, it is the level of risk and levels of protection that
are potentially applicable rather than numerical objectives (resource quality specifications). In only a few cases
would it be practical to set numerical objectives for a specific class that would be applicable to all rivers of that
class wherever they were in the country (e.g. for toxics). An objective which posed only a slight risk to a
particular ecosystem in one geographical region may result in a much higher risk in another geographical region,
depending on the resilience of the adapted ecosystem, the background quality of the water, and the natural flow
regime.
The extent, distribution, type and integrity of instream habitat is strongly dependent on the water quantity and
water quality objectives which are set. However, objectives must be derived for other factors (see Table 2) that
influence instream habitat and riparian habitat. For example, where excessive soil erosion in the catchment
increase instream sedimentation rates to an unacceptable level, the regulation of the impacts of land use
practices may also be an aspect of the water environment objectives. Another example of instream habitat
modification is through the impacts of sand mining or gravel extraction, and objectives will be set to regulate
these impacts and subsequent rehabilitation.
The riparian habitat is more at risk from land use practices, such as construction, river diversion, ploughing on
riverbanks and urban development. Numerical or narrative objectives would be set which would ensure the
appropriate extend, distribution, type and integrity of riparian habitat, in order to maintain an acceptable level
protection for biota which rely on the habitat.
In Kleynhans (1996), criteria considered indicative of habitat integrity (Table 2) were selected on the basis that
anthropogenic modification of their characteristics can generally be regarded as the primary causes of
degradation of the habitat integrity of the river.
Department of Water Affairs and Forestry, South Africa R23/3
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Resource Directed Measures for Protection of Water Resources: River Ecosystems
Table 2: Criteria used in the assessment of habitat integrity
Criterion Relevance
Water abstraction Direct impact on habitat type, abundance and size. Also implicated in flow,
bed, channel and water quality characteristics. Riparian vegetation may be
influences by a decrease in the supply in water.
Flow modification Consequence of abstraction or regulation by impoundments. Changes in
temporal and spatial characteristics of flow can have an impact on habitat
attributes such as an increase in duration of low flow season, resulting in low
availability of certain habitat types or water at the start of the breeding,
flowering or growing season.
Bed modification Regarded as the result of increased input of sediment from the catchment or a
decrease in the ability of the river to transport sediment. Indirect indications
of sedimentation are stream bank and catchment erosion. Purposeful
alteration of the stream bed, e.g. the removal of rapids for navigation is also
included.
Channel modification May be a result of a change in flow that may alter channel characteristics
causing a change in marginal instream and riparian habitat. Purposeful
channel modification to improve drainage is also included.
Water quality modifications Originates from point and diffuse point sources. Measured directly or
agricultural activities, human settlements and industrial activities may
indicate the likelihood of modification. Aggravated by a decrease in the
volume of water during low or no flow conditions.
Inundation Destruction of riffle, rapid and riparian zone habitat. Obstruction to the
movement of aquatic fauna and influences water quality and the movement of
sediments.
Exotic macrophytes Alteration of habitat by obstruction of flow and may influence water quality
and increase turbidity. Dependent upon the species involved and scale of
infestation.
Solid waste disposal A direct anthropogenic impact which may alter habitat structurally. Also a
general indication of the misuse and mismanagement of the river.
Indigenous vegetation Impairment of the buffer the vegetation forms to the movement of sediment
removal and other catchment runoff products into the river. Refers to physical
removal for farming, firewood and overgrazing.
Exotic vegetation Excludes natural vegetation due to vigorous growth, causing bank instability
encroachment and decreasing the buffering function of the riparian zone. Allochtonous
organic matter input will also be changed. Riparian zone habitat diversity is
also reduced.
Bank erosion Decrease in bank stability will cause sedimentation and possible collapse of
the riverbank resulting in a loss or modification of both instream and riparian
habitats. Increased erosion can be the result of natural vegetation removal,
overgrazing or exotic vegetation encroachment.
The severity of certain modifications (Table 3) (from Kleynhans, 1996), will therefore, have a detrimental
impact on the habitat integrity of a river, the emphasis being on the qualitative interpretation of the habitat
quality, size, diversity, variability and predictability as influenced by various anthropogenic modifications.
Department of Water Affairs and Forestry, South Africa R23/4
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Resource Directed Measures for Protection of Water Resources: River Ecosystems
Table 3: Descriptive classes for the assessment of modifications to habitat integrity
Impact class Description
Negligible Negligible impact, or the modification is located in such a way that it has a negligible
impact on habitat quality, diversity, size and variability.
Small The modification is limited to very few localities and the impact on habitat quality,
diversity, size and variability are also very small
Moderate The modifications are present at a small number of localities and the impact on habitat
quality, diversity, size and variability are also limited
Large The modification is generally present with a clearly detrimental impact on habitat
quality, diversity, size and variability. Large areas are however not influenced
A generic modification impact table for instream habitat (Table 4) and for riparian habitat (Table 5) are
subsequently derived and this is regarded as a first step towards quantitative resource quality specifications
(RQSs).
Table 4: A modification impact table for instream habitat
Management Class Unacceptable Modifications Allowed Modifications
A Exotic macrophytes Resulting cumulative impact of the following must
Solid waste disposal be negligible or small:
Channel modification
Water abstraction
Inundation
Flow modification
Bed modification
Groundwater
B Exotic macrophytes Resulting cumulative impact of the following must
Solid waste disposal be small:
Channel modification
Water abstraction
Inundation
Flow modification
Bed modification
Groundwater
C Exotic macrophytes Resulting cumulative impact of the following must
Solid waste disposal be moderate:
Channel modification
Water abstraction
Inundation
Flow modification
Bed modification
Groundwater
D Exotic macrophytes Resulting cumulative impact of the following must
Solid waste disposal be less than that defined as large:
Channel modification
Water abstraction
Inundation
Flow modification
Bed modification
Groundwater
Department of Water Affairs and Forestry, South Africa R23/5
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Resource Directed Measures for Protection of Water Resources: River Ecosystems
Table 5: A modification impact table for riparian habitat
Management Class Unacceptable Modifications Allowed Modifications
A Increased bank erosion Resulting cumulative impact of the following must
be negligible or small:
Removal of indigenous
vegetation within the Channel modification
riparian zone
Water abstraction
Exotic vegetation
Inundation
encroachment
Flow modification
Solid waste disposal
Groundwater
B Increased bank erosion Resulting cumulative impact of the following must
be small:
Removal of indigenous
vegetation within the Channel modification
riparian zone
Water abstraction
Exotic vegetation
Inundation
encroachment
Flow modification
Solid waste disposal
Groundwater
C Increased bank erosion Resulting cumulative impact of the following must
be moderate:
Removal of indigenous
vegetation within the Channel modification
riparian zone
Water abstraction
Exotic vegetation
Inundation
encroachment
Flow modification
Solid waste disposal
Groundwater
D Increased bank erosion Resulting cumulative impact of the following must
be less than that defined as large:
Removal of indigenous
vegetation within the Channel modification
riparian zone
Water abstraction
Exotic vegetation
Inundation
encroachment
Flow modification
Solid waste disposal
Groundwater
R23.3 Conclusions
Given that numerical objectives would only be applicable on a site-specific or resource-specific basis (except in
a few cases), the process of setting RQS for a reach in question will require that:
The following procedures are in place or established (in terms of the intermediate determination of the
reserve (DWAF, 1999)):
Ecological typing
Reference condition
Ecological importance and sensitivity
Present Ecological Status
Ecological Management Class (for water quality, flow , biota and habitat)
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Resource Directed Measures for Protection of Water Resources: River Ecosystems
The following are known:
the type of authorisation/license that is applied for (e.g. discharge or abstraction, etc.);
the potential impact of the proposed development (e.g. informal settlement) or activity (e.g.sand
mining) on the habitat integrity;
the sensitivity of the system to specific forms of anthropogenic impacts (e.g. erosion potential,
gradient, etc.);
that the proposed development or activity complies with the agreed management class of the river.
Example of RQO for habitat and biotic integrity will be provided in the reports on the Crocodile River and
Pienaars River pilot tests.
References
Department of Water Affairs and Forestry. 1997. White Paper on a National Water Policy for South Africa.
Department of Water Affairs and Forestry, South Africa.
Department of Water Affairs and Forestry. 1998. The National Water Act. Governement Gazette, No. 19182,
South Africa.
Kleynhans, C.J. 1996. A qualitative procedure for the assessment of the habitat integrity status of the Levuvhu
River (Limpopo system, South Africa). Journal of Aquatic Health 5:41-54.
MacKay, H (ed.). 1999. Resource-Directed Measures for the Protection of Water Resources. Department of
Water Affairs and Forestry, Report No.: N/0000/00/_/REH0299.
Department of Water Affairs and Forestry, South Africa R23/7
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