Ecosystem Guidelines for Environmental Assessment

FRESHWATER
INCORPORATING MINOR DRAINAGE LINES TO STREAMS AND LARGE
RIVERS, AND EPHEMERAL, SEASONAL AND PERMANENT SYSTEMS
FRESHWATER
ECOSYSTEMS: RIVERS
Liz Day and Nancy Job
What are the key ecological “drivers” in terms of
maintaining ecosystem function, pattern or structure
Water quantity and flow regime - including surface and groundwater sources.
Water quality.
Geomorphological processes (erosion and sedimentation).
Biological processes, affecting biotope quality and availability (e.g. algal abundance).
Upstream/catchment processes.
What are the key challenges affecting management
Maintenance of hydrological regimes and the implementation of effective Instream Flow Requirements
(IFR) for river systems. The limitations in terms of accuracy and methodology of the Department
of Water Affairs and Forestry's present Ecological Reserve Determination should be clearly understood
and reflected in a conservative approach to implementation of any particular reserve.
Maintenance of natural or near-natural water quality, and improvement of water quality in degraded
systems.
Maintenance of natural (or sustainable, in an altered environment) erosion and sedimentation
processes.
Maintenance of biological and hydrological linkages throughout the catchment and seasonal or
permanent links with groundwater and wetlands.
Maintenance of specific habitat quality and availability.
Maintenance of genetic integrity (including biodiversity).
Co-ordination of management interventions at a catchment scale so as to maximise the potential for
achieving and sustaining all of the above objectives.
Integration of ecological and social objectives, so that improvement in one sphere is not at the
expense of the other.
What are the key issues, vulnerabilities and threats
Catchment hardening (loss of wetlands and natural drainage patterns; loss of natural habitat at a
catchment level leading to increased volume and rate of runoff).
Fragmentation/loss of biological corridors and natural connectivity through inter alia diversion and
in-filling of riverine wetlands.
Direct loss of aquatic habitats (including diversion, canalisation and dredging, and loss of associated
floodplains) due to encroachment of developments.
Removal or degradation of indigenous vegetation in the system.
Over-abstraction from:
- surface water
- groundwater
Impoundment.
ANDREW BROWN
74 : FRESHWATER ECOSYSTEMS - RIVERS