by Nelisiwe Khusi | Maps created by: Yaaseen Bodhanya
The GCBR has established a river health monitoring program for rivers within the region. The program’s primary aim is to collect continuous river health data to assess the long-term trends and raise awareness about the status of rivers and aquatic life within the GCBR region.
Perennial rivers are rivers that flow throughout the year, whereas non-perennial rivers are rivers that do not flow continuously throughout the year. A Catchment (synonyms: drainage basin, watershed) is an area of land where all flowing surface water converges to a single point, such as a river mouth, or flows into another body of water, such as a lake or ocean (DWS, 2011). Understanding how surface water drains and the areas where it collects is vital for effective water resource planning. This helps identify water source areas, manage water quality, and plan for water supply and infrastructure.
1.1 Freshwater systems within the GCBR region
The GCBR covers approximately 3.2 million hectares of terrestrial and marine surface area, covering 44% of the Breede-Gouritz Water Management Area. There are three primary catchments within the region, namely J, H, and K. J is the largest primary catchment in the region. Primary catchments are further subdivided into secondary, tertiary, and quaternary catchments. There are 11 secondary catchments with over 150 perennial rivers, and the main rivers within the GCBR region are Breede, Gourits, and Olifants. These river systems are vital as they provide the necessary resources to support economic development and social well-being while maintaining essential ecosystem goods and services for conservation, tourism, coastal fisheries, and residential developments (BGCMA, 2017).
Moreover, they are home to various fish species, some of which are endemic to the region; this means they are not found anywhere else in the world. Most of these species are listed as either Endangered, Critically Endangered, or Vulnerable and face a risk of extinction, making the conservation of these river systems even more critical. Ongoing research is revealing high levels of genetic diversity within isolated populations of many species and presents evidence that the current taxonomy vastly underestimates the diversity of freshwater fishes within the region (Weyl et al., 2014; Pool-Stanvliet et al., 2017; Jordaan et al., 2020; CapeNature, 2024)
1.2 Threats Faced by our Freshwater systems
Rivers within the GCBR region are prone to negative impacts from various human activities and natural occurrences. Significant alterations to river channels and riparian zones, such as channelisation and riverbank modifications, can disturb natural flow patterns and habitat structures, leading to habitat degradation and loss of biodiversity (fynbosfishtrust.org, 2020; Jordaan et al., 2020; CapeNature, 2024).
Invasive Alien Species Infestation
Invasive alien species of both flora and fauna pose a significant threat to river ecosystems by outcompeting indigenous species, altering habitat dynamics, and disrupting ecosystem balance. These invasions result in the loss of indigenous biodiversity and destabilise ecosystem functions. Invasive Alien fish species such as trout, bass, carp and catfish compete with indigenous species such as Cape galaxias, Cape kurper, and Heuningnes redfin minnow for food and habitat or prey on them (fynbosfishtrust.org, 2020; CapeNature, 2024)
Natural Channel Impacts
Flood events such as the September 2023 Western Cape floods severely modify river channels, particularly altering aquatic habitats. The dense growth of invasive alien plants exacerbates the impact of floods on river channels and results in extensive scouring of the channels. While floods are natural processes essential for maintaining river health, their frequency and intensity can be exacerbated by human-induced factors such as poor land-use practices, leading to increased risks to human communities and river ecosystems.
Addressing these challenges requires an integrated approach linking sustainable land-use planning, habitat restoration efforts, invasive species management, effective flood risk management strategies, and stakeholder engagement. Through the Gouritz Resilient Rivers Project, the GCBR actively clears invasive alien plants, chips biomass, and mulches for alien seed suppression. Additionally, it implements soil erosion controls, rehabilitation, and revegetation using indigenous species, establishing and maintaining ecological corridors in the GCBR through landscape rehabilitation, and promoting sustainable land-use practices by supporting farmers and landowners. These projects have significantly benefited the region’s river systems. The introduction of the river health program for continuous monitoring allows us to gather data to make informed decisions regarding managing and protecting these river systems. By understanding the dynamics of river systems and their interconnectedness with surrounding ecosystems, we can work towards maintaining the integrity and resilience of these environments for current and future generations.
2. The importance of Monitoring rivers within the Gouritz Cluster Biosphere Reserve
Ecosystem Health:
Rivers are essential to ecosystems, providing habitats for numerous species of plants and animals. Monitoring river health allows us to assess the overall health of these ecosystems and identify any potential threats or disturbances.
Water Quality:
Rivers are a vital source of freshwater for ecosystems and communities. Monitoring water quality parameters such as pH, dissolved oxygen, nutrients, and pollutants helps ensure that water resources remain safe for consumption and support healthy aquatic life.
Biodiversity Conservation:
Many species of plants and animals rely on rivers for survival. Monitoring rivers helps us understand how changes in river health may impact biodiversity, allowing for targeted conservation efforts to protect vulnerable species.
Human Health:
Humans depend on rivers for drinking water, agriculture, industry, and recreation. Monitoring rivers helps identify potential risks to human health, such as contamination from pollutants or pathogens, allowing for appropriate management and mitigation measures to be implemented.
Climate Change:
Rivers are sensitive indicators of climate change, with alterations in flow patterns, temperature, and precipitation affecting river ecosystems. Monitoring rivers provides valuable data for understanding the impacts of climate change on freshwater resources and ecosystems.
Resource Management
Rivers support various economic activities such as fishing, agriculture, tourism, and transportation. Monitoring rivers helps inform sustainable resource management practices, ensuring the continued availability of ecosystem services and economic benefits.
References
BGCMA. 2017. Catchment Management Strategy for the Breede-Gouritz Water Management Area. [Internet]. Available from: https://cer.org.za/wp-content/uploads/1999/12/BGCMA-draft.pdf. [Accessed: 11 March 2024].
CapeNature. 2024. What a landowner should know about the FACT SHEET INDIGENOUS FISH of the Cape Floristic Region: DIVERSITY, THREATS AND MANAGEMENT INTERVENTIONS. [Internet]. Available from: https://www.capenature.co.za/uploads/files/Indigenous-Fish-Fact-Sheet-English.pdf. [Accessed: 11 March 2024].
DWS. 2011. The Groundwater Dictionary: A Comprehensive Reference of Groundwater Related Terminology. Pretoria, South Africa
fynbosfishtrust.org. 2020. THE FYNBOS FISH TRUST CONSERVING FRESHWATER FISHES and their habitats in South Africa’s Cape Fold Ecoregion Biodiversity Hotspo. [Internet]. fynbosfishtrust.org. Available from: https://fynbosfishtrust.org/fynbos-fish/. [Accessed: 11 March 2024].
Jordaan, MS, Chakona, A and Van der Colff, D. 2020. Protected areas and endemic freshwater fishes of the Cape Fold Ecoregion: missing the boat for fish conservation? Frontiers in Environmental Science 8 502042.
Pool-Stanvliet, R, Duffell-Canham, A, Pence, G and Smart, R. 2017. The Western Cape Biodiversity Spatial Plan Handbook. CapeNature, Stellenbosch, South Africa.
Weyl, OLF, Finlayson, B, Impson, ND, Woodford, DJ and Steinkjer, J. 2014. Threatened endemic fishes in South Africa’s Cape Floristic Region: A new beginning for the Rondegat River. Fisheries 39 (6): 270-279.