Can Reservoir Regulation Along the Yellow River Be a Sustainable Way to Save a Sinking Delta?

Abstract

 The impact of reservoir regulation along the Yellow River on delta evolution was systematically evaluated  The man-made experiment through reservoir regulation along the Yellow River did mitigate delta erosion by scouring the lower river bed  With sediment coarsening of lower riverbed, bed scouring through reservoir regulation is not a sustainable way to nourish delta lobe Abstract Today's deltas are impacted negatively by 1) accelerated subsidence (e.g. from ground fluid extraction), 2) global eustatic sea-level rise, and 3) decreased sediment supply, which increasingly starves these landforms of sediment necessary to sustain their footprint. This growing vulnerability threatens many mega cities that have developed due to the rich resources offered by deltas, and therefore urgently calls for efforts to maintain sustainability. The Yellow River of China is classic example of such a landform under threat and which requires human intervention to maintain its resilience. Since 2002, the Yellow River Conservancy Commission has enacted an annual water and sediment regulation scheme (WSRS) by coordinated operation of three large reservoirs in the main stream. Here we evaluate the efficiency and sustainability of this man-made experiment on delta evolution. The impulsive delivery of muds and sands, within ~20 day intervals (averaged duration of the WSRS), did indeed move the present Yellow River delta from a destructive phase to an accretion phase. With continuous scouring, however, the downstream riverbed erosion efficiency has decreased, due to coarsening of surface bed material sediment. Concomitantly, sediment delivery has decreased, resulting in the present delta once again entering an erosive (destructive) phase, since 2014. From a perspective of delta restoration, the WSRS on the Yellow River is effective but potentially unsustainable. Restoring delta resilience necessitates ©2020 American Geophysical Union. All rights reserved. an enhanced, coordinated effort, relying upon new sciences advances, rather than simply assuming channel scour will address the sediment deficit of the delta.

Controls on Organic Carbon Burial in the Eastern China Marginal Seas: A Regional Synthesis

“…Sedimentation rate, another well‐established control of OC burial in coastal systems (e.g., Bao et al., 2018; Blair & Aller, 2012; Cui, Bianchi, Jaeger, et al., 2016), has been altered by many changes in the Anthropocene such as land‐use, precipitation gradients, eutrophication, and damming. In fact, the Eastern China Marginal Seas (ECMS), which has historically been fed by some of the most sediment‐rich rivers in the world, has been disproportionality altered by such human activities (e.g., Moon et al., 2020; Wu et al., 2020) ‐ due to profound economic growth in the region (He et al., 2014). The ECMS provides prolific gradients of change for exploration, and thus offers a unique set of natural laboratories to investigate these questions.…”

Spatiotemporal Changes of Coastline over the Yellow River Delta in the Previous 40 Years with Optical and SAR Remote Sensing

“…The analysis in Figure 13 shows that the sediment discharge has a great contribution to the change of estuary area with a correlation of 0.615. Therefore, the impulsive delivery of muds and sands indeed transforms the present YRD from a destructive phase to an accretion phase [57]. However, this study shows that the contribution of sediment transport to the change of the estuary is not the only dominant factor.…”

“…Due to the coarsening of the surface bed material sediments, the erosion efficiency of the downstream riverbed has reduced. Since 2013-2017 in Figures 9 and 10, continuous scouring and reduced sediment transport have caused the current delta to re-enter a phase of erosion and destruction [57]. The previous study has shown that erosion of the abandoned delta lobes can sustain the supply of sediment to remote offshore depocenters, even after decades of declining river sediment discharge [58].…”

A Tale of Two Deltas: Dam-Induced Hydro-Morphological Evolution of the Volta River Delta (Ghana) and Yellow River Delta (China)

“…Furthermore, the shifting of the river course in the Yellow River Delta could enhance the progradation of the delta at the river mouth (Figure 6a-d) due to the relatively low sediment accommodation space at the nearshore area, i.e., the "Course Shift Bonus" proposed by [81]. Currently, although the Yellow River Delta is likely to keep prograding at the river mouth [43], the progradation could be unsustainable due to the functional degradation of the WSRS [51,82], suggesting a potential erosion of the delta under the projected continuous decrease of sediment load in the foreseeable future. Nevertheless, the potential shoreline retreat in the Yellow River Delta could possibly last for a while and transition to a new quasi-equilibrium as has already happened in the Volta River Delta [19,28].…”