Water Research Commission

In many of the geotechnical engineering problems, particularly analysis of dam-foundation structures, the water flow induced forces have to be taken into consideration in order to arrive at a more realistic solution. The water flow induced forces viz. seepage forces and hydrostatic forces, which can be calculated from the seepage analysis, mainly depend upon the flow properties of the media. For analysis of flow through dam foundation with seams or faults, a new joint element formulation has been suggested to simulate flow through joints. By using the joint element, results of the seepage analysis of a dam-foundation with sub-horizontal seams have been presented. With the calculated water flow induced forces from the seepage analysis, elastic and elastoplastic behaviour of a dam–foudation system with seam have been compared.

The purpose of this study was to determine the influence of stakeholders on smallholder mango production in Limpopo Province, aiming to increase the effectiveness of this influence. Purposive sampling of the population of 374 smallholder mango producers with a plot size of ±4.7ha was used. Primary data was collected from the smallholder producers using a structured questionnaire designed to include selected variables on stakeholder interactions and influence. Key stakeholders included the Limpopo Department of Agriculture and Rural Development (LDARD), the South African Mango Growers Association (SAMGA), the Agricultural Research Council (ARC) and the National Agriculture Marketing Council (NAMC). The LDARD provided broad support, mainly farm management and marketing information (57%), SAMGA provided production (fertiliser application and spraying) information (86%), ARC provided research information (92%), while NAMC provided market information (59%). Interactions with the producers were mainly through LDARD meetings (11%) and visits (41%), SAMGA meetings (70%) and visits (23%), ARC meetings (12%) and emails (9%), and NAMC meetings (10%) and visits (11%). Lack of transformation and budgetary constraints were the main challenges limiting smallholder mango production. The study is crucial for efficient resource deployment and the maximisation of impact from development initiatives, especially in our country, which faces severe budgetary constraints and associated austerity measures.

Wetlands in hypersaline environments are especially vulnerable to loss and degradation, as increasing coastal urbanization and climate change rapidly exacerbate freshwater supply stressors. Hypersaline wetlands pose unique management challenges that require innovative restoration perspectives and approaches that consider complex local and regional socioecological dynamics. In part, this challenge stems from multiple co-occurring stressors and anthropogenic alterations, including estuary mouth closure and freshwater diversions at the catchment scale. In this article, we discuss challenges and opportunities in the restoration of hypersaline coastal wetland systems, including management of freshwater inflow, shoreline modification, the occurrence of concurrent or sequential stressors, and the knowledge and values of stakeholders and Indigenous peoples. Areas needing additional research and integration into practice are described, and paths forward in adaptive management are discussed. There is a broad need for actionable research on adaptively managing hypersaline wetlands, where outputs will enhance the sustainability and effectiveness of future restoration efforts. Applying a collaborative approach that integrates best practices across a diversity of socio-ecological settings will have global benefits for the effective management of hypersaline coastal wetlands.

Wetlands in hypersaline environments are especially vulnerable to loss and degradation, as increasing coastal urbanization and climate change rapidly exacerbate freshwater supply stressors. Hypersaline wetlands pose unique management challenges that require innovative restoration perspectives and approaches that consider complex local and regional socioecological dynamics. In part, this challenge stems from multiple co-occurring stressors and anthropogenic alterations, including estuary mouth closure and freshwater diversions at the catchment scale. In this article, we discuss challenges and opportunities in the restoration of hypersaline coastal wetland systems, including management of freshwater inflow, shoreline modification, the occurrence of concurrent or sequential stressors, and the knowledge and values of stakeholders and Indigenous peoples. Areas needing additional research and integration into practice are described, and paths forward in adaptive management are discussed. There is a broad need for actionable research on adaptively managing hypersaline wetlands, where outputs will enhance the sustainability and effectiveness of future restoration efforts. Applying a collaborative approach that integrates best practices across a diversity of socio-ecological settings will have global benefits for the effective management of hypersaline coastal wetlands.

IntroductionThe water-energy-food (WEF) nexus has evolved into an important transformative approach for facilitating the timely identification of trade-offs and synergies between interlinked sectors for informed intervention and decision-making. However, there is a growing need for a WEF nexus tool to support decision-making on integrated resources management toward sustainable development.MethodsThis study developed a geospatial web-based integrative analytical tool for the WEF nexus (the iWEF) to support integrated assessment of WEF resources to support resilience building and adaptation initiatives and strategies. The tool uses the Analytic Hierarchy Process (AHP) to establish numerical correlations among WEF nexus indicators and pillars, mainly availability, productivity, accessibility, and sufficiency. The tool was calibrated and validated with existing tools and data at varying spatio-temporal scales.ResultsThe results indicate the applicability of the tool at any spatial scale, highlighting the moderate sustainability in the management of WEF resources at various scales. The developed iWEF tool has improved the existing integrative WEF nexus analytical tool in terms of processing time and providing geospatial capabilities.DiscussionThe iWEF tool is a digital platform that automatically guides policy and decision-making in managing risk from trade-offs and enhancing synergies holistically. It is developed to support policy and decision-making on timely interventions in priority areas that could be showing signs of stress.

Water hyacinth (Eichhornia crassipes) is a potential accumulator of water pollutants in aquatic ecosystems, and its presence in water systems can affect water quality. This study used different field measurements and laboratory tests of Lake Water to determine the impact of water hyacinth phytoremediation capacity. A total of eight sampling stations used for the two lakes; Lake Koka and Lake Ziway. Sampling stations were selected from sites infested with water hyacinth (low, medium and high) and non-water hyacinth aquatic plants during wet and dry seasons to compare the effects of plants on water quality in the two lakes. All the sampled stations had various human interventions. The water samples were tested for the selected physico-chemical properties namely phosphate, nitrate, pH, electrical conductivity (EC), Biological oxygen demand (BOD5), temperature, and heavy metals (Chromium (Cr), Lead (Pb), Cadmium (Cd), Zinc (Zn), and Copper (Cu). These water quality variables were compared by means of ANOVA. Despite the COD of Lake Ziway, this study found no significant (p > 0.05) variation in the concentrations of Cu, EC, pH and temperature between wet and dry seasons in either lake. Variations in Zn concentration and other physico-chemical parameters (EC, BOD, COD, nitrate, phosphate) between low, medium and high levels of water hyacinth were significant in both lakes (p<0.05). Water hyacinth has shown significant phytoremediation nature during wet and dry seasons. The lowest average heavy metal, phosphate, and nitrate concentrations; and significant pH and temperature variations were observed in Lakes Koka and Lake Ziway, among water hyacinth and other grass-infested sites.

This chapter summarizes the successes and challenges of catfish farming in the small-scale industry in Southern Africa. Given that capture fisheries have been declining steadily over the years in many countries, aquaculture is generally expected to grow to meet demand. However, catfish production in most Southern African countries is low. This is despite the region having the most suitable temperature for the culture of freshwater fish species. In Southern Africa, catfish farming is one of the most important components of inland aquaculture, and it is mainly dominated by the small-scale sector. Production in the small-scale sector is affected by several constraints, which affect the profitability of the sector. These challenges include, among others, quality of production systems, supply of quality fingerlings, feeds, management of diseases, education and training of farmers, marketing and development of products, access to finance, research capacity, extension services, and, to some extent, regulatory frameworks and policies. The chapter proposes interventions that are needed to improve the production of catfish in Southern Africa. For instance, there is a need for the small-scale sector to move from intensive to advanced culture systems, such as recirculating aquaculture systems and integrated aquaculture systems, such as aquaponics, in order to boost catfish production.

Food demand in Africa continues to outstrip local supply, and the continent currently spends over US$35 billion annually on food imports to supplement local deficits. With the advances in agronomy and breeding, commercial crops like maize (Zea mays) and soybean (Glycine max) in the region are under threat from climate change, decreasing rainfall and degraded lands. Unlike commercial crops that are generally adapted from other regions, underutilized indigenous crops are uniquely suited to local environments and are more resilient to climatic variations and tolerant to local pests and diseases. This study, done in Limpopo Province, South Africa, identifies optimal areas for cultivating Bambara groundnuts (Vigna subterannea), an indigenous crop suitable for arid and semi-arid regions. The aim is to promote the production of underutilized indigenous crops at a large scale with fewer resources, while still meeting local demand and reducing the food import budget. Suitability maps are delineated using a multicriteria decision method in a Geographic Information System (GIS). The procedure is important for diversifying farming systems, making them more resilient (to biotic and abiotic stresses and climate change) and more successful at enhancing water, food and nutritional security. With the province's limited water and land resources for agriculture expansion, promoting indigenous underutilized crops is a pathway to reduce water allocated to agriculture, thereby enhancing drought resilience and ensuring water, food and nutritional security. Large tracts of degraded agricultural land deemed unsuitable for adapted crops, and which may require costly land reclamation practices, can be used to cultivate underutilized crops that are adapted to extreme local conditions.