Abstract High Mountain Asia contains the largest volume of glacier ice outside the polar regions, and contain the headwaters of some of the largest rivers in central Asia. These glaciers are losing mass at a mean rate of between –0.18 and –0.5 m water equivalent per year. While glaciers in the Himalaya are generally shrinking, those in the Karakoram have experienced a slight mass gain. Both changes have occurred in response to rising air temperatures due to Northern Hemisphere climate change. In the westerly influenced Indus catchment, glacier meltwater makes up a large proportion of the hydrological budget, and loss of glacier mass will ultimately lead to a decrease in water supplies. In the monsoon-influenced Ganges and Brahmaputra catchments, the contribution of glacial meltwater is relatively small compared to the Indus, and the decrease in annual water supplies will be less dramatic. Therefore, enhanced glacier melt will increase river flows until the middle of the twenty-first century, but in the longer term, into the latter part of this century, river flows will decline as glaciers shrink. Declining meltwater supplies may be compensated by increases in precipitation, but this could exacerbate the risk of flooding.

The Pearl River Delta with its network system and estuarine bays is unique and one of the most complicated large-scale estuarine systems in China. In this paper, a long-term morphodynamic model is developed to simulate the long-term morphological evolution of the Pearl River Delta. The concepts of long-term model calibration and verification are discussed. The paleo–estuary bay topography formed in the last interglacial period is reconstructed and serves as an initial and boundary condition of this model with time steps of 100 yr. Events of shorter duration are ignored. The driving forces and control factors considered in the long-term delta evolution include representative tides, sediment supply from the Pearl River system, sea-level variation, sediment condensation rates, and neotectonic movement. Deposition rates and total deposition volume are investigated and determined and then used to calibrate the model. Core data with 14 C dating at 30 locations are used to verify the model output with satisfactory results. Approximately 1700 collected cores are carefully analyzed to justify the model-simulated evolution processes. Morphodynamic analysis is conducted to justify and explain the output of the model on delta evolution and deposition modes. The study also provides more temporal and spatial details to the delta development originated from the effects of the morphodynamic structures, such as bidirectional jets and the “men” system. The model confirms that the complicated morphology, e.g., the rocky islands in the shallow estuarine bays, is one of the important factors affecting the long-term evolution of the Pearl River Delta.