China has many lakes, marshlands and rivers. Due to their uneven geographical distribution and varied degrees of salinity, their exploitable freshwater resources are limited. In the wake of the highspeed growth of nat...China has many lakes, marshlands and rivers. Due to their uneven geographical distribution and varied degrees of salinity, their exploitable freshwater resources are limited. In the wake of the highspeed growth of national economy in recent years, human infringement upon their natural settings has been increasingly intense, leading to the degeneration of China's lacustrine ecosystems and the degradation of their surrounding environments. Lakes are shrinking and becoming more saline. In arid and semi-arid inland areas, some of them have even disappeared. In addition, lake water pollution and eutrophication in densely populated areas are getting worse, resulting in serious water shortages in some places. Silt deposition in lake basins, water surface shrinkage caused by hectic and irrational reclamation for farmland, the prevalence of flooding and water-logging calamities and ecosystem depletion caused by predatory exploitation of fishery resources, all of these have become restrictive factors in regional sustainable development. The author of this article suggests measures for the protection and sustainable exploitation of limnetic settings in China.展开更多
Estuarine projects can change local topography and influence water transport and saltwater intrusion.The Changjiang(Yangtze)River estuary is a multichannel estuary,and four major reclamation projects have been impleme...Estuarine projects can change local topography and influence water transport and saltwater intrusion.The Changjiang(Yangtze)River estuary is a multichannel estuary,and four major reclamation projects have been implemented in the Changjiang River estuary in recent years:the Xincun Shoal reclamation project(RP-XCS),the Qingcao Shoal reclamation project(RP-QCS),the Eastern Hengsha Shoal reclamation project(RP-EHS),and the Nanhui Shoal reclamation project(RP-NHS).The effects of the four reclamation projects and each project on the saltwater intrusion and water resources in the Changjiang River estuary were simulated in a 3D numerical model.Results show that for a multichannel estuary,local reclamation projects change the local topography and water diversion ratio(WDR)between channels and influence water and salt transport and freshwater utilization in the estuary.During spring tide,under the cumulative effect of the four reclamation projects,the salinity decreases by approximately 0.5in the upper reaches of the North Branch and increases by 0.5-1.0 in the middle and lower reaches of the North Branch.In the North Channel,the salinity decreases by approximately 0.5.In the North Passage,the salinity increases by 0.5-1.0.In the South Passage,the salinity increases by approximately 0.5 in the upper reaches and decreases by 0.2-0.5 on the north side of the middle and lower reaches.During neap tide,the cumulative effects of the four reclamation projects and the individual projects are similar to those during spring tide,but there are some differences.The effects of an individual reclamation project on WDR and saltwater intrusion during spring and neap tides are simulated and analyzed in detail.The cumulative effect of the four reclamation projects favors freshwater usage in the Changjiang River estuary.展开更多
The changes that have taken place in Nigerian fisheries are reviewed. Artisanal fishery has continued to dominate the fisheries,contributing over 85% of total fish production. The inland water and coastal seas are ful...The changes that have taken place in Nigerian fisheries are reviewed. Artisanal fishery has continued to dominate the fisheries,contributing over 85% of total fish production. The inland water and coastal seas are fully exploited and the increase in fishery production is not likely. Aquaculture potentials remain untapped as much as deep-sea fisheries. The combined potential of the fisheries resources-freshwater,marine and aquaculture can meet over 90% of the nation's demand for fish. Opportunities for invest-ments,therefore,exist in the various subsectors,especially in the areas of storage,processing and preservation for the capture fishery and fish seed multiplication for aquaculture.展开更多
This study assesses the seasonal regulation of river discharge by hydropower dam-induced cascade reservoirs in the Lancang River and its effect on downstream freshwater and estuarine saltwater intrusion.There are eigh...This study assesses the seasonal regulation of river discharge by hydropower dam-induced cascade reservoirs in the Lancang River and its effect on downstream freshwater and estuarine saltwater intrusion.There are eight main reservoirs in the Lancang River,with a total regulation capacity of 25.67 billion m3,which regulates river discharge by conserving water in the flood season and releasing water in the dry season.River discharge during the dry season from 1960 to 2009 accounted for 21%of the annual discharge before the cascade reservoirs were constructed and increased to 33%from 2010 to 2015 after the cascade reservoirs were constructed at the Jinghong hydrological station,which is the lowermost station in the Lancang River.During the 2016 extreme drought in the lower Mekong River basin,the river discharge increased by 550,367,1283,969,and 524 m3/s in January,February,March,April,and May,respectively,regulated by the cascade reservoirs at the Jinghong hydrological station.Considering runoff,tides,wind,and continental shelf currents,a high-resolution three-dimensional numerical model was used to simulate the effect of regulation of river discharge by the cascade reservoirs in the Lancang River on the saltwater intrusion in the Mekong River Delta(MRD).The simulation results show that the seasonal regulation of river discharge by the cascade reservoirs in the Lancang River weakens estuarine saltwater intrusion during the dry season,especially in the sand bar areas,which is much more significant in the extreme dry season of 2016.The seasonal regulation of river discharge by the reservoirs in the Lancang River makes the seasonal distribution of downstream river discharge more uniform,favoring down-stream freshwater utilization and alleviating flood disasters and saltwater intrusion in the MRD.展开更多
The massive Qingcaosha Reservoir(QCSR)is located in the Changjiang Estuary along the northwest coast of Changxing Island.The reservoir significantly narrowed the upper reaches of the North Channel and deepened the cha...The massive Qingcaosha Reservoir(QCSR)is located in the Changjiang Estuary along the northwest coast of Changxing Island.The reservoir significantly narrowed the upper reaches of the North Channel and deepened the channel near the reservoir.These topographical changes inevitably influenced hydrodynamic processes and saltwater intrusion in the estuary.A well-validated model was employed to investigate the influence of the QCSR on saltwater intrusion in the Changjiang Estuary.The model results showed that the narrowed upper reaches of the North Channel decreased the water diversion ratio and thus increased salinity in the North Channel.During the moderate tide after neap tide,the salinity decreased at the water intake of the QCSR because saltwater intrusion was obstructed at flood slack at the surface,while the salinity increase during the moderate tide after spring tide was mainly due to the intensified saltwater intrusion during spring tide.The deepening of the channel near the QCSR resulted in an increased water diversion ratio,and the salinity in the Eastern Chongming Shoal decreased by more than 0.5 psu during spring tide;however,the saltwater intrusion was enhanced due to the strengthened baroclinic force,which is proportional to the water depth.During neap tide,the salinity in the entire North Channel decreased because of a 1.4%increase in the water diversion ratio of the North Channel and the relatively weak tide.展开更多
文摘China has many lakes, marshlands and rivers. Due to their uneven geographical distribution and varied degrees of salinity, their exploitable freshwater resources are limited. In the wake of the highspeed growth of national economy in recent years, human infringement upon their natural settings has been increasingly intense, leading to the degeneration of China's lacustrine ecosystems and the degradation of their surrounding environments. Lakes are shrinking and becoming more saline. In arid and semi-arid inland areas, some of them have even disappeared. In addition, lake water pollution and eutrophication in densely populated areas are getting worse, resulting in serious water shortages in some places. Silt deposition in lake basins, water surface shrinkage caused by hectic and irrational reclamation for farmland, the prevalence of flooding and water-logging calamities and ecosystem depletion caused by predatory exploitation of fishery resources, all of these have become restrictive factors in regional sustainable development. The author of this article suggests measures for the protection and sustainable exploitation of limnetic settings in China.
基金Supported by the Science and Technology Commission of Shanghai Municipality(No.21JC1402500)。
文摘Estuarine projects can change local topography and influence water transport and saltwater intrusion.The Changjiang(Yangtze)River estuary is a multichannel estuary,and four major reclamation projects have been implemented in the Changjiang River estuary in recent years:the Xincun Shoal reclamation project(RP-XCS),the Qingcao Shoal reclamation project(RP-QCS),the Eastern Hengsha Shoal reclamation project(RP-EHS),and the Nanhui Shoal reclamation project(RP-NHS).The effects of the four reclamation projects and each project on the saltwater intrusion and water resources in the Changjiang River estuary were simulated in a 3D numerical model.Results show that for a multichannel estuary,local reclamation projects change the local topography and water diversion ratio(WDR)between channels and influence water and salt transport and freshwater utilization in the estuary.During spring tide,under the cumulative effect of the four reclamation projects,the salinity decreases by approximately 0.5in the upper reaches of the North Branch and increases by 0.5-1.0 in the middle and lower reaches of the North Branch.In the North Channel,the salinity decreases by approximately 0.5.In the North Passage,the salinity increases by 0.5-1.0.In the South Passage,the salinity increases by approximately 0.5 in the upper reaches and decreases by 0.2-0.5 on the north side of the middle and lower reaches.During neap tide,the cumulative effects of the four reclamation projects and the individual projects are similar to those during spring tide,but there are some differences.The effects of an individual reclamation project on WDR and saltwater intrusion during spring and neap tides are simulated and analyzed in detail.The cumulative effect of the four reclamation projects favors freshwater usage in the Changjiang River estuary.
文摘The changes that have taken place in Nigerian fisheries are reviewed. Artisanal fishery has continued to dominate the fisheries,contributing over 85% of total fish production. The inland water and coastal seas are fully exploited and the increase in fishery production is not likely. Aquaculture potentials remain untapped as much as deep-sea fisheries. The combined potential of the fisheries resources-freshwater,marine and aquaculture can meet over 90% of the nation's demand for fish. Opportunities for invest-ments,therefore,exist in the various subsectors,especially in the areas of storage,processing and preservation for the capture fishery and fish seed multiplication for aquaculture.
基金supported by the International Joint Laboratory of Estuarine and Coastal Research,Shanghai(21230750600).
文摘This study assesses the seasonal regulation of river discharge by hydropower dam-induced cascade reservoirs in the Lancang River and its effect on downstream freshwater and estuarine saltwater intrusion.There are eight main reservoirs in the Lancang River,with a total regulation capacity of 25.67 billion m3,which regulates river discharge by conserving water in the flood season and releasing water in the dry season.River discharge during the dry season from 1960 to 2009 accounted for 21%of the annual discharge before the cascade reservoirs were constructed and increased to 33%from 2010 to 2015 after the cascade reservoirs were constructed at the Jinghong hydrological station,which is the lowermost station in the Lancang River.During the 2016 extreme drought in the lower Mekong River basin,the river discharge increased by 550,367,1283,969,and 524 m3/s in January,February,March,April,and May,respectively,regulated by the cascade reservoirs at the Jinghong hydrological station.Considering runoff,tides,wind,and continental shelf currents,a high-resolution three-dimensional numerical model was used to simulate the effect of regulation of river discharge by the cascade reservoirs in the Lancang River on the saltwater intrusion in the Mekong River Delta(MRD).The simulation results show that the seasonal regulation of river discharge by the cascade reservoirs in the Lancang River weakens estuarine saltwater intrusion during the dry season,especially in the sand bar areas,which is much more significant in the extreme dry season of 2016.The seasonal regulation of river discharge by the reservoirs in the Lancang River makes the seasonal distribution of downstream river discharge more uniform,favoring down-stream freshwater utilization and alleviating flood disasters and saltwater intrusion in the MRD.
基金supported by the National Natural Science Foundation of China(41676083).
文摘The massive Qingcaosha Reservoir(QCSR)is located in the Changjiang Estuary along the northwest coast of Changxing Island.The reservoir significantly narrowed the upper reaches of the North Channel and deepened the channel near the reservoir.These topographical changes inevitably influenced hydrodynamic processes and saltwater intrusion in the estuary.A well-validated model was employed to investigate the influence of the QCSR on saltwater intrusion in the Changjiang Estuary.The model results showed that the narrowed upper reaches of the North Channel decreased the water diversion ratio and thus increased salinity in the North Channel.During the moderate tide after neap tide,the salinity decreased at the water intake of the QCSR because saltwater intrusion was obstructed at flood slack at the surface,while the salinity increase during the moderate tide after spring tide was mainly due to the intensified saltwater intrusion during spring tide.The deepening of the channel near the QCSR resulted in an increased water diversion ratio,and the salinity in the Eastern Chongming Shoal decreased by more than 0.5 psu during spring tide;however,the saltwater intrusion was enhanced due to the strengthened baroclinic force,which is proportional to the water depth.During neap tide,the salinity in the entire North Channel decreased because of a 1.4%increase in the water diversion ratio of the North Channel and the relatively weak tide.
