Abstract
Reservoirs play a critically important role in supplying water for human uses. However, sedimentation limits storage capabilities and increases risk for aging infrastructure. The objectives of this paper are to synthesize both general sediment management strategies and past sediment management efforts in Taiwan in order to identify the barriers to more effective sediment management in reservoirs globally. A review of the broader literature and six Taiwan case studies was conducted to examine the characteristics, limitations, costs, and effectiveness of different sediment management strategies. Results highlight how social barriers play an important role in limiting reservoir sustainability, particularly the crisis-response approach to addressing sedimentation and the low priority for sediment management relative to competing objectives, such as tourism. Technical barriers are driven primarily by the engineering and costs of retrofitting existing dams and site conditions that may inhibit particular practices at any given site. Results also highlight tradeoffs in the effectiveness, costs, and time efficiency of various sediment management strategies in restoring storage capacity. The high sediment loads and rapid filling of reservoirs in Taiwan provide early insight into the management issues that are emerging worldwide, and these results emphasize the need for proactive engineering and management of sediment in reservoirs globally.
Highlights
Accumulation of sediment can reduce reservoir life and, long before storage capacity is significantly affected, can interfere with functions of the reservoir [1]
Reservoir Objectives are defined as Municipal and Industrial (M&I), Irrigation (IR), Industrial (ID), Hydropower generation (HP), Recreation (R), Sediment Control (SC), and Flood Control (FC)
When viewing the six case study reservoirs through the perspective of the sediment management framework of Annandale et al [8] (Table 5), we found that some sediment management strategies were more commonly applied, such as reducing sediment yield from the catchment, sediment trapping above the reservoir, modifying dam operating rules, and hydraulic scour near outlets
Summary
Accumulation of sediment can reduce reservoir life and, long before storage capacity is significantly affected, can interfere with functions of the reservoir [1]. While many large reservoirs were designed with dead storage sufficient to accommodate 100 years of sediment accumulation [2] and some large reservoirs could store centuries worth of incoming sediment before filling up completely [3], such long sedimentation horizons are rarely the case in areas with high sediment yields. The efficiency and feasibility of strategies vary according to their compatibility with operations at individual reservoirs, those with carryover storage, synchrony with natural sediment supply, water demand for each unit of sediment managed, effectiveness in maintaining reservoir capacity, and ability to meet necessary infrastructure and hydraulic conditions, among other factors (Table 1). Taiwan’s dependence on reservoir storage and its high sediment yields mean management of reservoir sediment is important (Figure 1, Table 2), as clearly identified by Hwang [22].
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