3. Freshwater Systems in South Africa: Comprehensive Study Notes

Introduction to Freshwater Systems in South Africa

Sylvia Earle Quote: "No Water, NO LIFE, NO Blue, NO GREEN."
Social and Economic Goals: Water is an essential requirement for achieving various goals. These include: - Efficacy and economic efficacy. - Equity. - Environmental impacts. - Fiscal impacts. - Political and public acceptability. - Sustainability and administrative feasibility.
Legal Custodianship: The Minister acts as the custodian of water resources in South Africa.
National Water Resources Strategy: Under this strategy, all water resources in South Africa are protected. The specific level of protection applied depends on factors such as: - Human demand. - Ecological value.
Resource Management: There are constant trade-offs between the use, development, and protection of rivers.

Rainfall and Water Availability in South Africa

Average Rainfall: The average rainfall in South Africa is less than $500\,mm$ per year.
Regional Variations: - Driest areas: Western parts of the country receive less than $200\,mm$ per year. - Wettest areas: Some parts receive more than $2500\,mm$ per year.
Geographical Disparity: Water is not always located where it is most needed; for example, Gauteng has high demand but limited local supply.
Evaporation: South Africa suffers from high evaporation rates, which complicates water storage and security.
Natural Water Bodies: South Africa has very few natural lakes and is heavily dependent on rivers, built dams, and groundwater.

Dams and Interbasin Transfer Schemes

Storage Capacity: Approximately half of the annual rainfall in South Africa is stored in dams.
Government Infrastructure: There are $550$ government dams storing approximately $37,000 \times 10^6\,m^3$ .
Impacts of Dams: - Positive attributes: Flood reduction, sediment deposition, and the ability of aquatic plants to reduce nutrient and toxin loads. - Negative attributes: Dams act as artificial barriers that prevent the free movement of biota and create deep, deoxygenated, sterile zones.
Operational Challenges: - Evaporation: Many dams are shallow with large surface areas, leading to high evaporation loss. - Siltation: Sediment settling reduces the water-storing capacity of dams over time.
Interbasin Transfer Schemes (IBTs): These schemes move water from high-supply areas to low-supply areas. - There are currently $7$ operations in use, with $8$ more planned. - Orange-Fish River Scheme: This is the largest scheme. It moves water from the Gariep Dam through tunnels and channels to the Sundays and Fish Rivers in the Eastern Cape. - Other Major Schemes: Tugela-Vaal and Lesotho Highlands-Vaal Schemes.

Water Use and Management Structures

Per Capita Availability: Water availability in South Africa is $1200\,m^3$ per capita per annum.
Water Stress: Despite a complex network of dams and transfer schemes, the resource is under stress due to economic demands and population growth.
Water Management Areas (WMAs): South Africa is divided into $19$ WMAs responsible for the planning and management of water resources.
Major Water Users: - Irrigation and urban use are the two largest consumers. - Other users include mining, rural demand, afforestation, and power generation.
Critical Management Areas: - Olifants River: This river has the highest demand in the country and stopped flowing for the first time in history in $2005$ . - Other critical WMAs include Inkomati, Mvoti, and Umzimkulu.

Supply and Demand Management Factors

Current Adequacy: In $2006$ , the Department of Water Affairs and Forestry (DWAF) reported that water resources would only be adequate until $2025$ .
Factors Influencing Water Supply: 1. Semi-arid climate with low rainfall. 2. Erratic rainfall patterns. 3. High runoff areas being geographically distant from high demand areas. 4. Limited availability of poor-quality groundwater. 5. Invasive species that consume more water than native species. 6. Decreased water quality rendering it unsuitable for certain uses.
Factors Influencing Growth in Demand: 1. Population growth rate. 2. Rapid urbanization. 3. Economic development. 4. Demands for basic or higher levels of service. 5. Requirements for sustaining or rehabilitating ecological systems. 6. National drive to produce drinkable water for the entire population. 7. Ineffective structures, including pricing structures.

Wetlands: Definition, Value, and Threats

Official Definition: Wetlands are "areas of marsh, fen, peatland or water, whether natural or artificial, permanent or temporary, with water that is static or flowing, fresh, brackish or salt, including areas of marine water the depth of which at low tide does not exceed six metres." They may also incorporate adjacent riparian and coastal zones, and islands or bodies of marine water deeper than six metres at low tide lying within the wetlands.
Ecosystem Productivity: Wetlands are among the most productive ecosystems, providing billions of dollars in essential services to the global economy.
Food Web Support: - They provide food in the form of particulate organic matter, microbes, and plants (phytoplankton, macrophytes). - Dead organic matter breaks down into small particles fed on by aquatic invertebrates (zooplankton, insects) and vertebrates (juvenile fish), which in turn support larger amphibians, birds, fish, reptiles, and mammals.
Ecosystem Services: - Supporting: Global water cycle, nutrient cycling, and primary production. - Provisioning: Food (fish, crabs), raw materials (reeds, timber), genetic resources, water supply, medical resources, power generation, and horticultural products. - Cultural: Sacred natural sites, recreation/aesthetics, tourism, and cultural monuments. - Regulating: Carbon sequestration, water purification, flow rate regulation, coastal protection, waste decomposition, atmospheric equilibrium, sediment trapping, and groundwater recharge.
Global Cycles: Wetland microbes and plants are integral to global cycles for carbon, water, nitrogen, and sulfur. They also moderate climate conditions.
Threats to Wetlands: - Human activities and overexploitation. - Approximately $87\%$ of known inland wetland systems have been lost globally. - Conversion to rice paddy fields in Asia accounts for a loss of about $5000\,km^2$ per year. - IUCN Red List Data: Of over $19,500$ wetland-dependent species, approximately $25\%$ are threatened with extinction. $25\%$ of inland wetland-dependent species are globally threatened, and $6\%$ are critically endangered.

Wetland Monitoring

Importance of Monitoring: Essential to evaluate the success of restoration and rehabilitation efforts and to help environmental managers make informed decisions.
Types of Monitoring: - Chemical Monitoring: Testing water and sediment. - Habitat Monitoring: Reviewing vegetation, hydrology, and subsurface flow. - Biological Monitoring: - Active Biomonitoring: Using specific organisms to test for environmental changes. - Passive Biomonitoring: Observing existing populations of fish, vegetation, aquatic macro-invertebrates, and diatoms.

Freshwater Pollution: Definitions and Eutrophication

General Definition: Degradation of water quality measured by physical, chemical, and biological criteria, judged against the intended use or health impacts.
National Water Act (1998) Definition: "Pollution means the direct or indirect alteration of the physical, chemical or biological properties of a water resource so as to make it less fit for any beneficial purpose of which it may reasonably be expected to be used, or harmful or potentially harmful to the welfare, health or safety of human beings, to any aquatic or non-aquatic organisms to the resource quality or to the property."
Eutrophication: The enrichment of water with nutrients, specifically nitrates and phosphates. - Process: Nutrient increase leads to excessive growth of macrophytes and microscopic plants (algae and cyanobacteria). - Consequence: Oxygen depletion occurs, leading to mass fish deaths. - Primary Causes: 1. Inefficiency in sewage treatment and sanitation. 2. Use of unregulated phosphate-containing household detergents. 3. Excessive use of fertilizers in agriculture. - Effects Chain: Increased nutrients $\rightarrow$ Algal blooms/Macrophyte growth $\rightarrow$ Increase in Biological Oxygen Demand (BOD) and $CO_2$ $\rightarrow$ Changes in photic zones $\rightarrow$ Loss of aquatic diversity.

Acid Mine Drainage (AMD)

Chemical Process of AMD Formation: - Step 1: Ferrous Sulphide reacts with Water ( $H_2O$ ) and Oxygen. - Step 2: Oxidation of Ferrous Sulphate in the presence of Thiobacillus sp. creates Ferric Sulphate and acidic water. - Step 3: Ferric Sulphate in acidic water generates $Fe^{3+}$ and $SO_4^{2-}$ ions. Reaction with water generates Ferric Hydroxide and a large amount of acid ( $H^+$ ions).
Environmental Impacts: - Sediments in rivers and dams act as a sink for heavy metals. - When AMD reduces the pH of river water, these heavy metals are released from the sediment into the water column. - Lowered pH increases the toxicity of certain metals to aquatic biota.

Persistent Organic Pollutants (POPs)

Characteristics: Toxic chemicals that adversely affect human health and the environment. They are persistent and can be transported globally by wind and water.
The "Dirty Dozen" POPs: 1. Aldrin: Crop insecticide (corn, cotton). 2. Chlordane: Crop insecticide (vegetables, citrus, cotton, potatoes). 3. DDT: Crop insecticide (cotton). 4. Dieldrin: Crop insecticide (cotton, corn). 5. Endrin: Crop insecticide (cotton, grains). 6. Heptachlor: Insecticide (termites and soil insects). 7. Hexachlorobenzene: Fungicide for seed treatment. 8. Mirex: Insecticide (termites, fire ants). 9. Toxaphene: Insecticide (livestock and crops). 10. PCBs (Polychlorinated Biphenyls): Industrial chemicals used in transformers, heat exchange fluids, paint/plastic additives. Also produced by combustion. 11. Dioxins: Unintentionally produced during combustion (waste burning, industrial processes) and found as contaminants in herbicides. 12. Furans: Unintentionally produced during combustion.

Heavy Metals and Metalloids

Definition: Elements with an atomic density greater than $4\,g\,cm^{-3}$ .
Common Examples: Copper ( $Cu$ ), Cadmium ( $Cd$ ), Zinc ( $Zn$ ), Lead ( $Pb$ ), Mercury ( $Hg$ ), Arsenic ( $As$ ), Silver ( $Ag$ ), Chromium ( $Cr$ ), Iron ( $Fe$ ), and Platinum ( $Pt$ ) group elements.
Key Characteristics: - Non-biodegradable: They do not break down in the environment. - Bioaccumulation: Concentrations increase in living organisms over time. - Biomagnification: Concentrations increase as they move up the food chain. - Toxicity: Many are toxic or carcinogenic even at low concentrations, inducing multiple organ damage.
Sources: - Natural: Rock weathering, volcanic eruptions, wind-blown dust, aerosols. - Anthropogenic: Mining, fossil fuel combustion, metal processing, pesticides, inorganic fertilizers, sewage sludge, batteries, and detergents.
Biological Impacts: Accumulation in organs leads to oxidative damage, endocrine disruption, and immune system depression in phytoplankton, zooplankton, amphibians, and fish.

Microplastics in Freshwater Systems

Definition: Plastic particles smaller than $5\,mm$ .
Categories: - Primary Microplastics: Purpose-manufactured beads. - Secondary Microplastics: Fragments broken down from larger plastic items.
Distribution and Accumulation: - Microplastics can sink and accumulate in deep-sea or freshwater sediment. - A conservative estimate suggests $14 \times 10^6$ tons of microplastics reside on the ocean bed. - Environment influences distribution, though dams often act as sinks, limiting long-distance transfer.
Microplastics as Vectors: Pollutants in the environment bind to the surface of microplastics. - They carry metals such as $Cd$ , $Hg$ , $Pb$ , $Cu$ , and $U$ . - Color Correlation: Darker plastics tend to have higher $Pb$ levels; redder plastics tend to have higher $Cd$ levels.
Research Challenges: Lack of standardized sampling methods or reporting units makes comparing results across different studies difficult.

South African Case Studies

Citizen Science in Groundwater (Limpopo): - Villages: Ga-Komape and Ga-Manamela. - Residents were trained to capture groundwater data on smartphones and upload it to a website for government access. - Outcome: Increased "water literacy" among villagers and tribal authorities.
Loskop Irrigation Scheme: - Concerns over whether farmers bear the cost of poor catchment management. - Farmers spend approximately $R73.4 \times 10^6$ per year to mitigate eutrophication and algae-related problems.
Cyanobacteria and Food Safety: - Common toxin-producing genera in SA: Microcytis, Anabaena, and Oscillatoria (Planktothrix). - Toxins produced include microcystins, nodularins, saxitoxins, and cylindrospermopsin. - Plants irrigated with infested water can take up and bioaccumulate these toxins, posing a health risk to humans upon ingestion.
Dam Analysis (2019–2020): - Study sites: Roodeplaat and Hartebeespoort dams. - Algal biomass estimated using Chlorophyll-a levels, which ranged from $49.86$ to $177.54\,\mu g/L$ . - Both dams are categorized as hypertrophic (Chlorophyll-a > 56.00\,\mu g/L).