Civil Engineering June 2021 | Vol 29 No 5

Civil Engineering June 2021 43 S edimentation rates in South Africa are extremely high and pose a serious threat, alongside increased water demands in the region. In the last year, some of the country’s dams have experienced up to 90% sedimentation, leading to storage capacity losses of between 10% and 30%. To assist in addressing these chal- lenges, the Department of Water and Sanitation (DWS) has appointed the Water Research Commission (WRC) to develop the National Siltation Management Strategy for Large Dams in South Africa, more commonly known as the NatSilt Programme. The programme represents a collaborative, transdisci- plinary approach to tackle the wide spec- trum of dam sedimentation and storage capacity challenges in South Africa. It was officially launched during a two-day virtual WRC NatSilt Symposium in May under the theme Protecting our source water systems . The event brought together stakeholders across the sectors of water and sanitation and environmental management. Leonardo Manus, Acting Deputy Director General: Infrastructure Operations & Maintenance at DWS said, “We have established our whole economy and livelihood around these majestic dam structures, but we can so easily lose them if you don’t apply proper management procedures to keep them in that state. STRIVING FOR EFFICIENCY, EFFECTIVENESS AND SUSTAINABILITY “The NatSilt Programme will provide the department with tools and intelligence to make appropriate, site-specific decisions regarding each dam instead of having a blanket approach. Where sedimentation occurs to such an extent that it has to be dealt with, we will create a business model that will not be to the detriment of those who are dependent on the dam. To minimise costs to the downstream users in that specific catchment, we need to find alternatives to expensive methodologies and dredging models deployed to keep any dam operating,” said Manus. The NatSilt Programme thus aims to ensure that bulk water resource infra- structure is managed in an efficient, ef- fective, and sustainable manner to ensure economic growth, social development, and poverty eradication. It is initiated and funded by the DWS through its Infrastructure Build Operate and Maintenance branch, which is respon- sible for asset management and infrastruc- ture maintenance of 276 government water schemes in the country, including 321 large state dams that make up more than 90% of the country’s total storage capacity. Dr Shafick Adams, Executive Manager: Water Resources and Ecosystems at the WRC, said some of the pressing water challenges requiring mitigation and ad- aptation include those related to climate change, extreme weather variability, van- dalism of infrastructure, operation and maintenance issues, and user behaviour, among others. Managing and prolonging storage availability of dams by limiting silting of dams is one of the strategies to ensure water security into the future. “These challenges require an institu- tional and governance response that is not only focused on getting more water to people, but also protects and manages our dam assets effectively. That includes considering land use planning. In most cases the dam is the symptom of the problem, rather than the problem itself. Upstream behaviour, coupled with poor land use, is usually responsible for the unnatural release of sediment into a dam,” said Adams. The key deliverables of the NatSilt Programme are to develop: Q Q A dam basin siltation management operations model Q Q A sustainable dredging business model/s Q Q A dam basin classification decision- making tool Q Q Capacity building Q Q A step-by-step comprehensive im- plementation plan and piloting of the draft strategy, models and tools Q Q A pilot plan potentially rolled out in three government water schemes. There are four sub-projects that will syn- chronise across the NatSilt Programme: Sub Project 1 will focus on the develop- ment of a siltation management strategy; Sub Project 2 will focus on dam engi- neering and socio-ecological systems; Sub Project 3 will explore sustainable dredging of dams; and Sub Project 4 will investigate and implement training and capacity development. The NatSilt Programme will be under- taken over three phases within three years and is expected to conclude in 2023. The first phase will involve conceptual and strategic development, and research and assessments, followed by practical piloting of the decision-making tools, models and concepts in Phase 2. Phase 3 will see the culmination of the programme and appli- cation of learnings to revise the strategy and adapt the models and tools.  NatSilt Programme launched to tackle dam storage challenges As a water-stressed country, South Africa is expected to reach a 17% deficit of water by 2030. The country has a history of building dams to address water security needs and to provide essential bulk water supply to its population. However, the construction of dams does come with disadvantages. For more information visit: https://wrcnatsilt.org.za Watch a video summary of the NatSilt Programme here: https://youtu.be/7BOtiQlMm6o