Hydrological processes in the mouth area of the Hong Ha (Red River)

The main features of hydrological processes taking place in the mouth area of the Hong Ha River in Vietnam are considered. The geographic and hydrological conditions in the Hong Ha River basin and in its receiving water body—the Gulf of Tonkin, South China Sea—are briefly characterized. The main features of the mouth area of the Hong Ha River as a specific geographic object are identified. The hydrological regime of the delta and the nearshore zone of the Hong Ha River are described in detail. Water balance of the delta, runoff water levels and delta inundation, water and sediment runoff distributions over delta branches, and the effect of tides, typhoons, and storm surges on delta regime are considered. Present-day problems of the use and protection of natural resources at the Hong Ha River mouth are briefly discussed.     

Hydrological and morphological processes in Senegal River mouth area

The main features of the structure and water regime of the mouth area of the Senegal River and their changes caused by river regulation in its upper reaches and within its delta area are considered. Data on water and sediment runoff of the Senegal River and their variations along the river are specified. River runoff was found to dramatically decrease in recent decades because of a drought. Zoning of river mouth area was carried out, and morphological processes in its estuary, in particular, the formation of a new outlet of the river into the ocean with the formation of a lagoon, are described.     

Hydrological and morphological processes at the Zhujiang River mouth area, China

Hydrological and morphological processes in the Zhujiang River (Pearl River) mouth area of China are discussed. The hydrological regime of the Xijiang River, which is the largest river of South China and the main source of water inflow into the Zhujiang mouth area, is described. The basic features of the hydrological regime of the delta and the near-shore zone of the Zhujiang River mouth are characterized, much attention being given to the role of tides and mixing of river and sea water in the hydrological regime. Special emphasis is placed on morphodynamic processes at the mouth area and the history of the Zhujiang Delta evolution.     

Sediment regime and morphological processes in the Hong Ha (Red River) mouth area

Main features of sediment regime in the mouth area of the Hong Ha River (Red River), Vietnam, are discussed. As shown, the hydraulic engineering construction on the Da tributary resulted in a nearly two-fold decrease of river sediment yield. Sediment budget components at the river mouth were analyzed to establish that more than 90% of the sediment yield was detained in the delta branches and in the nearshore zone of the river mouth. Morphological processes in the Hong Ha River mouth area were characterized in detail including delta evolution during Holocene and the dynamics of its channel network, coastline, and mouth bars. Special attention was given to modern processes of delta progradation at the mouths of main branches and to wave erosion of other parts of the delta coastline. The causes for the intensification of this kind of erosion and change of the delta type in the late XX century are discussed.     

Hydrological and morphological processes in the mouth area of the Columbia River (United States) and their changes under the impact of large-scale hydroengineering works

The main hydrological and morphological features of the Columbia River mouth area, including its tidal estuary, are discussed. Close attention is given to the characteristics of large-scale hydraulic projects in the river basin as well as to dredging and channel training operations in the river mouth area and to the assessment of the impact of these operations on hydrological and morphological processes. Variations in the regime of river flow after its regulation, processes of dynamic interaction and mixing of river and sea water in the estuary are characterized. Changes of the mouth bar and sea coasts near the Columbia River mouth as a result of construction of stream-training jetties are discussed.     

Hydrological-morphological processes in the mouth area of the Orinoco (Venezuela)

The peculiarities of the hydrological regime of the Orinoco River and the coastal zone of the Atlantic Ocean that affect the hydrological-morphological processes in the mouth area of the Orinoco River are considered. The major features of the delta water regime, including its inundation, runoff distribution over the delta branches, water and sediment balance, and the processes of river and sea water mixing are described. Special attention is paid to the morphological processes at the Orinoco mouth (delta evolution and modern processes at its coastline).     

Specific features of hydrological and morphological processes in the mouth area of the Mekong River

The geographical and hydrological features of the Mekong River basin and the nearshore zone of the South China Sea, which influence the hydrological regime of the Mekong River mouth, are discussed. Detailed characteristics are provided for the drainage system of the Mekong River mouth area, water flow distribution among the delta branches, processes of the delta submergence during floods, as well as propagation of tidal, surge-induced level fluctuations and seawater intrusion into the river. Regularities of the Holocene evolution of the Mekong River mouth area and recent processes of delta formation are also discussed.     

Hydrological and morphological features of the Upper Angara mouth area

The hydrological and morphological processes in the mouth area of the Upper Angara (which ranks second in terms of water abundance among Baikal Lake tributaries) are considered. The major external factors that determine those processes have been revealed. The main features of the delta??s water regime, including the effect of anthropogenic level rise in the lake, are described. Specific attention is paid to morphological processes in the delta and on the barrier bar, separating a large mouth lagoon from the lake.     

Hydrological processes at an Arctic river mouth: Case study of the Colville River, Alaska, USA

Data on the Colville River mouth (Alaska, USA) are used to discuss the regularities in hydrological processes taking place in river mouth areas, functioning under extreme arctic conditions. Seasons and periods are recognized in the annual cycle of the Colville river mouth hydrologic regime. A thick ice cover commonly forms in winter in the river, its delta distributaries, and the offshore zone. Water salinity in under-ice water in the distributaries and near-delta river reach appreciably increases in late winter. The spring flood is very short; in this period, snowmelt water propagates toward the ocean first over ice and next under it. A wedge of freshened waters forms in the nearshore zone above fast ice. River runoff abruptly drops in the summer-autumn low-water period. The morphological processes in the distributaries and some ecological conditions in the delta are also discussed.     

River and sea water interaction and delta formation in tidal mouth area of the Fraser River (Canada)

The history of studies and development of water resources of the Fraser River (Canada) and its mouth area is presented. The history of the Fraser River delta development and the hydrologomorphological processes that occur at this delta are discussed. Close attention is given to the analysis of processes of dynamic interaction and mixing of river and sea water under the joint impact of river flow and tidal fluctuations.     

Delta formation processes at the Mississippi River mouth

Specific processes of delta formation at the Mississippi River mouth are discussed. In the last 7000–8000 years, a series of large deltaic lobes was formed in succession at the Mississippi River mouth under the condition of high river sediment runoff and stabilization of the ocean level after its sudden postglacial rise. In the mid-XX century, the formation of a new deltaic lobe began at the Atchafalaya Branch mouth. Over the last centuries, the processes of delta formation at the Mississippi River mouth slowed down as a result of the river sediment runoff decrease after flow regulation of the Missouri and Arkansas tributaries; in some parts of the deltaic plain, these processes gave way to degradation of marshes and seashore erosion under the impact of intense land subsidence. The current processes of delta formation are under the great influence of local economic activities.     

Variations in Neman River annual runoff near Grodno Town

The results of studying the stability of sample estimates of statistical parameters for different segments of the initial time series of Neman River annual runoff values at Grodno Town in 1808–2000 are presented. Segments of the series with different extent of anthropogenic impact on runoff and types of atmospheric circulation are considered. Statistically significant changes were found to exist in the dynamics of Neman River annual runoff due to both natural-climatic and anthropogenic variations in the hydrological cycle.     

Anthropogenic transformation of biocenosis structural organization in Lena River mouth area

The structure of hydrobiocenosis communities in Lena River mouth area is studied. The qualitative and quantitative development characteristics of bacterio-, phyto-, zooplankton, and zoobenthos communities of aquatic organisms in this part of the river are examined. The state and structure of hydrobiocenosis suggest that the mouth area of the river functions under moderate pollution of the aqueous medium.     

Hydrological processes in the Amur Liman

Data collected in 2005–2009 are analyzed to study the main features of hydrological processes in the main part of the Amur estuary—the Amur Liman. Data on the morphological structure of the liman and the surge and tidal phenomena are analyzed. The variability of salinity field in different phases of river hydrological cycle is studied. Wind currents are shown to have an appreciable effect on the water exchange and river runoff distribution between the seas of Japan and Okhotsk in the ice-free season. In summer, the Amur runoff enters the Sea of Okhotsk. The main features of the structure of liman water in summer are identified. The northern part of the estuary is freshened by river runoff and partially mixed; it has a two-layer structure. A salt wedge forms at the northern exit from the liman into the Sea of Okhotsk, and strong water stratification is observed there.     

Water and sediment dynamics in the estuary and mouth area of the Seine River

The principal features of the hydrological regime of the Seine River mouth area are discussed. Attention is focused on studying the dynamics of water and sediments in the estuary of the Seine River and in its tidal mouth area under the combined effect of seasonal variations in river runoff and tides. The history of development and improvement of the estuary is described.     

Hydrological simulation of the Betwa River basin (India) using the SWAT model

A seasonal water budget analysis was carried out to quantify various components of the hydrological cycle using the Soil and Water Assessment Tool (SWAT) model for the Betwa River basin (43?500 km²) in central India. The model results were satisfactory in calibration and validation. The seasonal water budget analysis showed that about 90% of annual rainfall and 97% of annual runoff occurred in the monsoon season. A seasonal linear trend analysis was carried out to detect trends in the water balance components of the basin for the period 1973–2001. In the monsoon season, an increasing trend in rainfall and a decreasing trend in ET were observed; this resulted in an increasing trend in groundwater storage and surface runoff. The winter season followed almost the same pattern. A decreasing trend was observed in summer season rainfall. The study evokes the need for conservation structures in the study area to reduce monsoon runoff and conserve it for basin requirements in water-scarce seasons.

EDITOR Z.W. Kundzewicz

ASSOCIATE EDITOR F. Hattermann     

The characteristics of Quaternary activity of faults in the sea area near the Yangtze River mouth

Introduction As far as the frequency and magnitude are concerned, the earthquakes in the sea area to the east of Shanghai are far more strong than in land area with the largest one in the sea area near the Yangtze River mouth being MS=436, while in land, only MS=434 occurred on Sept. 1, 1624. As a moderately strong earthquake active area, the sea area near the Yangtze River mouth, may cause a potential risk to Shanghai. In 1971 and 1996, earthquakes with MS=5~6 occurred in this area. Geo…     

In situ record of sedimentary processes near the Rhône River mouth during winter events (Gulf of Lions,Mediterranean Sea)

The environment is impacted by natural and anthropogenic disturbances that occur at different spatial and temporal scales, and that lead to major changes and even disequilibria when exceeding the resiliency capacities of the ecosystem. With an annual mean flow of 1700 m³ s⁻¹, the Rhône River is the largest of the western Mediterranean basin. Its annual solid discharges vary between 2 and 20 Mt, with flood events responsible for more than 70% of these amounts.     

Hydrological and morphological processes in the Chao Phraya Mouth Area (Thailand) and their anthropogenic changes

The hydrological and morphological features of the Chao Phraya Mouth Area (Thailand) are considered. The attention is focused on the assessment of the effect exerted on the hydrological and morphological processes in the delta and the nearshore of the Chao Phraya River by a considerable anthropogenic drop in water and sediment runoff of the river; land subsidence near Bangkok caused by groundwater withdrawal; sea level rise; and wave intensification.     

Hydrological effects of water reservoirs on hydrological processes in the East River (China) basin: complexity evaluations based on the multi‐scale entropy analysis

Using the multi‐scale entropy analysis (MSE), we study the effects of water reservoirs on the river flow records based on long streamflow series covering January 1, 1954 and December 31, 2009 at four representative hydrological stations, i.e. the Longchuan, the Heyuan, the Lingxia and the Boluo stations. Hydrological effects of two major water reservoirs, the Xinfengjiang and the Fengshuba water reservoirs, are evaluated. The results indicate that: (1) before the construction of the water reservoirs, the complexity of the streamflow series comes to be decreasing from the upper to the lower East River and which should be attributed to the topographical properties and buffering effects of the river channel; (2) construction of water reservoirs greatly increases the complexity degree of the hydrological processes, and this influence is subjected to a damping process with the increase of distance between the water reservoirs and the hydrological stations; (3) power generation is the major function of the water reservoirs in the East River basin. The results of this study should be of theoretical and scientific merits in terms of conservation of the ecological environment and also water resources management under the influences of climate changes and intensifying human activities. Copyright © 2011 John Wiley & Sons, Ltd.