Recent changes in the sediment regime of the Pearl River (South China): Causes and implications for the Pearl River Delta

Abstract

Riverine sediments have played an important role in the morphological evolution of river channels and river deltas. However, the sediment regime in the many world's rivers has been altered in the context of global changes. In this study, temporal changes in the sediment regime of the Pearl River were examined at different time scales, that is, annual, seasonal, and monthly time scales, using the Mann–Kendall test. The results revealed that precipitation variability was responsible for monthly and seasonal distribution patterns of the sediment regime and the long‐term changes in the water discharge; however, dam operation has smoothed the seasonal distribution of water discharge and resulted in decreasing trends in the annual, wet‐season, and dry‐season sediment load series since the 1950s. Due to the different regulation magnitudes of dam operation, differences were observed in sediment regime changes among the three tributaries. In addition, human activities have altered the hysteresis of seasonal rating curves and affected hysteresis differences between increasing and decreasing water discharge stages. Sediment supply is an important factor controlling river channel dynamics, affecting channel morphology. From the 1950s to the 1980s, siltation was dominant in river channels across the West River and North River deltas in response to the sediment increases; however, scouring occurred in the East River deltas due to sediment reduction. Significant erosion occurred in river channels in the 1990s, which was mostly due to downcutting of the river bed caused by sand excavations and partly because of the reduced sediment load from upstream. Although sand excavations have been banned and controlled by authority agencies since 2000, the erosion of cross sections was still observed in the 2000s because of reduced sediment caused by dam construction. Our study examines the different effects of human activities on the sediment regime and downstream channel morphology, which is of substantial scientific importance for river management.

Assessing the Effects of the Hong Kong‐Zhuhai‐Macau Bridge on the Total Suspended Solids in the Pearl River Estuary Based on Landsat Time Series

“…Understanding factors causing this trend behind the scene is crucial for better interpreting the transport of sediment in the PRE, the remediation of local marine ecosystems related to potential damage caused by contaminated sediment, and the protection of marine protected areas. Different factors affect TSS in the PRE, such as soil erosion (Dai et al, 2009; Liu et al, 2018), meteorological and hydrological conditions (Chen et al, 2017; Zhao et al, 2018), dam constructions (Dai et al, 2008; Wu et al, 2012), and sand mining (Hu et al, 2010). These effects have already been comprehensively deciphered in previous studies.…”

Coral reef diversity losses in China’s Greater Bay Area were driven by regional stressors

“…The Pearl River outflow is highly turbid from high levels of sediment, another known coral stressor ( 57 , 58 ). Although sedimentation has been decreasing due to upriver damming over the last 50 years ( 59 , 60 ), low light continues to limit primary productivity in western waters ( 61 ). Extensive land reclamation throughout the 1980s increased silt loads and caused a documented loss of 40% of coral cover in two marine embayments ( 47 ).…”

Erosion-deposition patterns and depo-center movements in branching channels at the near-estuary reach of the Yangtze River

“…channel improvement works, and sand excavation) (Kuang et al, 2014;Zheng et al, 2018;Dai and Ding, 2019), and Coriolisinduced circulation in estuarine areas (Wang et al, 2013;Li et al, 2011Li et al, , 2014. Dams modulate runoff discharge in rivers worldwide and can drive the morphological evolution of braided reaches, as demonstrated by many inland rivers (Petts and Gurnell, 2005;Graf, 2006;Han et al, 2018;Alcayaga et al, 2019;Mendoza et al, 2019; and estuarine areas (Warne et al, 2002;Sloff et al, 2013;Zhu et al, 2017;Liu et al, 2018;Zhou et al, 2018), noting that tidal discharges are relatively stable at the yearly time scale (Horrevoets et al, 2004;Jiang et al, 2012a;Zhu et al, 2017). For fluvial braided reaches, shrinking or developing trends of branching channels are often aggravated or interchanged after dam impoundment, caused by changes in unidirectional flow dynamics driven by the altered runoff discharge (Han et al, 2018;Zhu et al, 2019).…”