Water is a critical resource necessary to support social and economic development. Economic growth and, in particular, the growth of urban and peri-urban areas, however results in declining water quality which threatens water-dependent industries. In developing countries this is a particular concern due to the rapid rate of urbanisation and the limited financial resources and technical capabilities to adequately maintain and upgrade wastewater treatment works. This is particularly relevant in catchments with a high dependence on export-orientated agriculture. This study considered water quality risks in the Breede River catchment as an area which experiences significant urban and peri-urban growth, focusing on economic risks associated with declining water quality, estimates of the costs needed to rehabilitate existing wastewater treatment works, and alternative strategies such as the use of artificial wetlands, the rehabilitation and protection of natural wetlands, as well as the clearing of invasive alien plants. A major conclusion is that the financial risk associated with a declining economy and social instability outweighs the costs that will be needed for rehabilitation of existing treatment plants. Together with more pronounced fluctuations in precipitation anticipated with climate change, these risks due to declining water quality are likely to increase in future with continued urban and peri-urban growth.
In the South African National Water Act (NWA, No 36 of 1998), the ecological Reserve is defined as the quality and quantity of water required to ensure appropriate protection of water resources, so as to secure ecologically sustainable development and use. Aquatic ecosystems are recognised as the core location of water resources, and although considerable progress has been made in developing methods for quantifying environmental flow requirements, this paper describes and discusses the first agreed method for quantifying environmental water quality requirements in an ecological Reserve assessment. Integration of flow and water quality is emphasised, and is based on the philosophy that environmental flows should be motivated to provide ecologically important flow-related habitat, or geomorphological function, but should not be motivated to solve water quality problems by dilution. Water quality is multivariate, and not all variables can be considered in an ecological Reserve assessment, but core water quality variables include: system variables (salts, dissolved oxygen, turbidity, temperature), nutrients (phosphate, nitrite, nitrate) and toxic substances (those listed in the South African Water Quality Guidelines for Aquatic Ecosystems, including toxic metal ions, toxic organic substances, and/or substances from a chemical inventory of an effluent or discharge). In addition, biological indicator data (e.g. SASS data), chlorophyll-a (e.g. phytoplankton and periphyton data) and toxicity test data may be used. For each variable, a concentration range or response is linked to a class within a water resource classification system, where classes range from minimally to severely modified. There are five main stages in the environmental water quality method:• Initiate study and determine scope of assessment.• Delineate water quality sub-units.• Select sites and collect data and information.• Determine benchmarks, including generic boundary values (literature-based concentrations related to classes); the unimpacted, natural or reference condition; the present ecological state; and the contribution of water quality to the overall ecosystem importance and sensitivity. • Provide quantified and qualitative water quality objectives for each ecosystem health class, and each variable in each resource unit. These steps are integrated with environmental flow assessment procedures. After environmental flows have been recommended to achieve a selected level of protection (class), flow-concentration relationships are modelled, and the likely water quality consequences of modified flows are provided to resource managers, who then decide on whether to allocate water for dilution and/or to address the pollution problem directly using source controls.
By 2050 it is predicted that 67% of the world population is expected to be living in urban areas, with the most rapid levels of urbanisation taking place in developing countries. Urbanisation is often directly linked to the degradation of environmental quality, including quality of water, air and noise. Concurrently, the climate is changing. Together, the negative impacts of climate change and urbanisation pose significant challenges, especially in developing countries where resources to mitigate these impacts are limited. Focusing on the Berg River Catchment in South Africa, which is experiencing increasing levels of urbanisation, the impacts of climate change, the ‘wicked problem’ of service delivery to the historically disadvantaged within a developing country, persistent infrastructure backlogs, and where high unemployment is prevalent, this paper explores the increasing water quality risks due to climate change and rapid urban development and the likely direct and indirect economic impacts that this will have on the agriculture sector, which is a key contributor to the regional and national economy. The results give support to the need to invest in risk mitigation measures including the provision of basic services, the upgrading and maintenance of wastewater treatment plants and investing in ecological infrastructure.
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