Sustainable sediment management in reservoirs and regulated rivers: Experiences from five continents

Abstract

By trapping sediment in reservoirs, dams interrupt the continuity of sediment transport through rivers, resulting in loss of reservoir storage and reduced usable life, and depriving downstream reaches of sediments essential for channel form and aquatic habitats. With the acceleration of new dam construction globally, these impacts are increasingly widespread. There are proven techniques to pass sediment through or around reservoirs, to preserve reservoir capacity and to minimize downstream impacts, but they are not applied in many situations where they would be effective. This paper summarizes collective experience from five continents in managing reservoir sediments and mitigating downstream sediment starvation. Where geometry is favorable it is often possible to bypass sediment around the reservoir, which avoids reservoir sedimentation and supplies sediment to downstream reaches with rates and timing similar to pre-dam conditions. Sluicing (or drawdown routing) permits sediment to be transported through the reservoir rapidly to avoid sedimentation during high flows; it requires relatively large capacity outlets. Drawdown flushing involves scouring and re-suspending sediment deposited in the reservoir and transporting it downstream through low-level gates in the dam; it works best in narrow reservoirs with steep longitudinal gradients and with flow velocities maintained above the threshold to transport sediment. Turbidity currents can often be vented through the dam, with the advantage that the reservoir need not be drawn down to pass sediment. In planning dams, we recommend that these sediment management approaches be utilized where possible to sustain reservoir capacity and minimize environmental impacts of dams.

Examining Storage Capacity Loss and Sedimentation Rate of Large Reservoirs in the Central U.S. Great Plains

“…Consequently, finding locations with optimal geography, hydrology, topography, and geology for building new dams in the same region can be challenging [81]. For these reasons, along with other prohibitive logistical factors (e.g., economic, legal, and regulatory), new large impoundment construction currently is considered an unlikely option for Kansas as it seeks to ensure a future water supply for its citizens and industries.…”

Evolution of Two Urbanized Estuaries: Environmental Change, Legal Framework, and Implications for Sea-Level Rise Vulnerability

“…With water quality becoming less of a problem, the medium-to long-term strategies of dam removal, or at least the integration into existing dams of functional fish passages [71] and other measures, may in time allow the return or stabilization of anadromous fish stocks, and allow for a more sustainable sediment management [112,113]. This later aspect would likely be of crucial importance in enhancing wetland resilience in face of the increased rates of SLR, expected towards the end of the century, as the sustainability of wetlands appears to be strongly connected with the maintenance of a good sediment supply [54,58,90,91,[95][96][97].…”

Turbulence study in the vicinity of piano key weir: relevance, instrumentation, parameters and methods

“…However, it destabilizes sediment continuity, because flow velocity is reduced due to the increased water depth (Bai and Duan 2014;Fan and Morris 1992). Due to the restricting nature of sediment downstream, it is deposited directly upstream of a weir (Kim et al 2014;Kondolf et al 2014). As sediment from upstream normally moves downstream with flowing water, the geographical features are changed and hydro-ecological habitats are subsequently affected.…”