Tuesday, June 4, 2019

Influence on a River Rates of Discharge

Influence on a River Rates of DischargeIntroductionThe analysis of river go down regimes has evolved into a fundamental aspect of the geographical discipline. The contemporary geographer is certain of how a complex system of factors can influence a rivers rate of political campaign.Factors Influencing Flow RegimesThe six constituents of the hydrological cycle effect river break away regime. These are precipitation, infiltration, evaporation, transpiration, muster run-off and ground peeing flow.1 Veissman and Lewis eat noted the complexity of this cycle by stating paths taken by precipitated droplets of water are many and varied before the ocean is reached.2Precipitation takes vary in accordance with a variety of factors such as latitude, altitude, vegetation cover and micro-climatic particularities. However, precipitation is relatively uncomplicated to measure and then grants the most data.3 Ingle Smith and Stopp have highschoollighted that a rivers fall away is related to precipitation but complex.4 Indeed, there is always a time lag from the commencement of heavy periods of rainfall to a marked increase in river venting.5 The duration of time lag will depend upon the infiltration capacity of the soil in the rivers catchment area, as well as local topography and the presence of vegetation. Rivers obtain the majority of their water supply via the serve well of through flow.6 Through flow occurs when water held within the soil gradually travels to the river channel and explains why, even during dry periods, few rivers or streams cease to flow.7Vegetation plays a vital role in the lineament of river regimes. Surrounding plants and trees intercept precipitation and influence the amount of water which will ultimately pass to the water way.9 Rain water may land on foliage or dead organic matter and evaporate, or be absorbed by roots in the soil. These processes constitute the phenomenon known as evapotranspiration.10 Forests have a balancing effect on the hydrological cycle and restrict a superfluous quantity of water entering the river channel during periods of heavy rainfall.11 In colder climes, such as the Tiaga region, the shade from trees can prevent rapid snow melt causing flash floods.12 Deforestation has had a marked influence on the constitution of river regime characteristics.Comparison of Discharge ValuesThe correlation of the mean monthly exempt values of specific river regimes, in different locations, imparts much fascinating information. The cast off value of a river is measured in cubic metres per southond (m/sec).13The River Suir of the Republic of Ireland and the River Thames of Great Britain both exhibit very similar flow regimes of a uni-modal nature. The deuce rivers are situated in the north western European temperate zone and flow levels full point in January and ebb in July in tandem with the wet and dry seasons. On an annual basis the Suir has a mean monthly flow rate of 54.250 m/sec and the Th ames has a rate of 61.583 m/sec. The greatest deviation from mean rate occurs in January. During this month the Thames exhibits a discharge rate of 110m /sec whilst the Suirs rate is 92m /sec. The month of July provides the lowest discharge rate for both water ways 2.98% of constitutional annual discharge passes through the Thames, whilst it is 4.45% for the Suir.The Mediterranean zone offers a distinct form of river regime flow pattern. The Vinalopo River, which is situated in South East Spain near the town of Alicante, illustrates this actuality. Unlike the rivers of northern temperate regions, the Vinalopos range of discharge is more uttermost(prenominal), ranging from an average level of only 25m /sec in September to a substantial 410m /sec in January. This represents a range of 385m /sec. Indeed, the greatest deviations from the monthly mean value of 197.417m /sec take place in the winter, during January (410 m /sec) and February (380 m /sec), and in late summer, in lofty (3 0 m /sec) and September (25 m /sec).The mighty Yenisey River of Russia runs from the town of Kyzl in Southern Siberia and traverses theWest Siberian lowlands before entering the Kara Sea 388km away to the north.14 Mean monthly discharge is 17,916.667 m /sec, and gratuity discharge of 76,000 m /sec occurs in June, which constitutes 35.35% of total annual discharge in one month.. From November to April average discharge is only 4,750 m /sec and this six month period provides only 13.25% of total annual flow. Discharge rate increases abruptly in spring, peaks in June, and ebbs dramatically from July (28,000 m /sec) to October (15,000 m /sec). Thus, the Yenisey displays an entirely different regime to that of the Thames, the Suir and the Vinalopo. Base flow occurs during April and peak flow during June, and represents an astonishing range of 72,000m /sec throughout the year.South East Asia is home to the Brahamaputra River which flows from high in the Himalayan Mountains before meeting the Ganges River in the delta of southern Bangladesh.15 Like the Yenisey River, the Brahmaputra also crosses an array of climatic regions. A peak discharge rate of 43,120 m /sec occurs in August and constitutes 18.64% of total annual discharge. This represents the largest deviation from a mean monthly discharge of 19,277.50 m /sec. Base flow is recorded at a rate of 4,190 m /sec in February and represents a flow range of 38,930 m /sec. The Bramhaputra is comparable to the Yennisey as flow trend ebbs in winter and increases in spring and summer. However, flow peaks later in the year and the period of November to April constitutes 17.58 % of total annual discharge, which is slightly higher than that of the Yenisey. The range of discharge rate of this water way is also not as radical as that of the Yenisey River and is more dissipated throughout the months of may to October.The Congo (Zaire) River is the fifth largest river in the world and is situated in central Africa.16 The river flows through zones of tropical rainforest and savannah. The flow regime of the river is bi-modal callable to its situation in the tropics. Discharge peaks at 73,600 m /sec in December which constitutes 15.73% of total annual discharge. The secondary May peak of 62,100 represents 13.27% of yearly discharge. July witnesses a base flow level of 21,600 m /sec. Thus, the range of flow discharge is 52,000m/sec. Discharge follows an entirely different pattern to the said(prenominal) water ways. The volume increases and decreases twice on an annual basis. It rises from March to May and from July to December, respectively, and ebbs during the interim periods.Climatic and Regional InfluencesEach of the six river regimes exhibit these particular annual flow patterns due to the specific climatic and environmental factors which prevail within their catchment areas.The Thames and Suir regimes are situated in the temperate forest biome which experiences warm moist summers and easy winters.17 Precipitation occurs throughout the year and peaks during the winter.18 This is why both rivers experience the highest levels of discharge in January. Evapotranspiration peaks during the summer, but the heavy peaty soils continue to provide supplies of stored water to the rivers via the process of through flow.19The Alicante Mountains north and west of the town of Alicante rise to a height of almost 1600 metres and influence the flow regime of the Vinalopo River. Precipitation levels increase with altitude and, during the surrender and winter rains, the river discharge rate rises as water enters the main channel via mountain tributaries. Evapotranspiration rates far outbalance rainfall in the hot months of July and August when temperatures around the town of Elche can reach as high as 26C. Thus, discharge is severely reduced to only 2.33% of total annual discharge in August and September. Indeed, during this period of base flow the river benefits little from through flow as moistur e in the arid Mediterranean soil is apace evaporated upwards. The local demands of the population and vegetation also decreases the water table in the lower lying regions of the Vinalopo catchment. For example, the large incidence of palm trees surrounding the town of Elche by nature reduces the water budget in the region during the dry Mediterranean summer.The flow regime of the Yenisey river is influenced by the continental climate of the Asiatic land mass, which experiences great extremes of temperature.20 As temperatures gradually rise in the spring time, after the bitterly cold winter, snow melt in the mountains, and ablation of glaciers, causes a surge in discharge. The water from the melting precipitation and ice cannot be absorbed by the permafrost, which underlies the soil, and thus runs off directly to the river and its tributaries.21 Permafrost will also melt as temperatures rise providing an excess source of water via through flow.The discharge rate of the Brahmaputra River also increases in March and April due to Himalayan snow melt entering the river regime.22 The monsoon rains commence in April and continue until October. During this period up to 200cm of precipitation can fall and the Brahmaputra is swollen by June or July.23 Such a high influx of water explains why discharge increases rapidly. Non-equatorial tropical river systems experience higher rates of precipitation during the summer months and a considerable reduction in winter.24 Indeed, only 9.54% of total annual discharge flows through the Brahmaputra from December to March.The flow regime of the Congo River is unique amongst the six river regimes as it is of a bi-modal nature, ebbing and flowing twice annually. Precipitation levels are bi-modal25 and peak at the time of the equinoxes in March and April.26 This is due to the tropical equatorial location of the river, and discharge rate exhibits a marked increase after these months. Indeed, rainfall is continuous throughout the year and the annual level in Kasangani, Democratic Republic of Congo, is approximately 170cm. This factor highlights why the monthly discharge rate neer drops below 4.7% of the total annual volume. Temperature remains practically constant at 25C along the route of the Congo throughout the year due to the absence of seasonality in this biome.27ConclusionThe discharge levels of the Suir, Thames and Vinalopo rivers all correspond with increased levels of precipitation in the winter and reduced precipitation in the summer. The range of discharge in the Thames and Suir is much less than that of the Vinalopo. This is due to the fact that they are situated in a temperate climate and do not experience the extremes of high temperature, altitude and rainfall which exist in the Mediterranean environment. Increased autumn and winter precipitation rates on the Alicante mountains, and the dry hot summers, are accountable for a flow discharge rate which ranges from 410m /sec in January to only 25m /s ec in August.Mountain ranges also influence the discharge rates of the Brahmaputra and Yennisey Rivers profoundly. lead by the nose melt and glacial ablation at high altitudes cause a surge in discharge during the spring months in both rivers. However, discharge reduces to 6,000 m /sec on the Yennisey by November and this is due to the onset of the severely cold continental winter. Precipitation in the Siberian mountains is now frozen, and overland and through flow to the river channel is severely reduced. The monsoon climate of south east Asia ensures that the discharge of the Brahmaputra remains high for a longer period of time. In November average discharge is ease 11,735 m /sec almost double that of the Yennisey. Thus, total annual flow is dissipated over a longer time period than the more extreme freeze/thaw trend of the Yennisey regime.The Congo has a very different annual discharge trend to the other rivers due to its situation in equatorial Africa. The bi-modal rain season ensures that discharge rises and falls twice on an annual basis. The Congo has the highest total annual discharge of all the rivers. It is almost double that of the Brahmaputra and this is testimonial to the incessant precipitation of the equatorial tropics.BibliographyCHARLESWORTH, J. K. Historical Geology of Ireland, Oliver and Boyd, 1963Pages 439, 439DEWDNEY, J. C. A Geography of the Soviet Union, Pergamon Press, Third Edition, 1979Pages 5, 7, 13, 18, 20, 29, 31FACAROS, D. PAULS, M. Spain, Cadogan Books Ltd, Second Edition, 1989Pages 18, 160FORBARTH, P. The River Congo, Seeker and Warburg, 1978Pages 4, 5GANDERTON, P. Mastering Geography, MacMillan, 2000Pages 311, 313, 315, 317GOUDIE, A. THOMAS, D. S. G. The lexicon of Physical Geography, Blackwell, Third Edition, 2000Pages 209, 405HOLDEN, J. An Introduction to Physical Geography and the Environment, Pearson Education Ltd, 2005Pages 37, 39, 178, 179, 183, 185, 186, 189, 193, 194, 196, 301, 309, 312, 328, 470, 471, 476, 531INGLE SMITH, D. STOPP, P. The River Basin, An Introduction to the Study of Hydrology, Cambridge University Press, 1978Pages 15, 19VEISSMAN, W. LEWIS, G. L. Introduction to Hydrology, Pearson Education Inc, Fifth Edition, 2003Pages 2, 3, 9, 10, 27NICHOLSON, R. Nicholsons head for the hills to the Thames, From Source to Sea, Robert Nicholson Publications Ltd, Second Edition, 1974Pages 4, 5, 6WEIGHTMAN, B. A. Dragons and Tigers, A Geography of South, East and South East Asia, John Wiley and Sons, 2006Pages 191, 193, 194, 195WHITE, R. Africa Geographical Studies, Heinemann, 1984Pages 44, 45, 46, 167, 169, 170, 171, 286, 396 topic Geographic Atlas of the World, National Geographic Society, Sixth Edition, 1995Pages 74, 83, 941Footnotes1 W Viessman, G L Lewis, Introduction to Hydrology, Pearson, 2003) 22 W Viessman, G L Lewis) 33 D Ingle Smith, P Stopp, The River Basin, An entry to the Study of Hydrology, Cambridge, 1978) 154 D Ingle Smith, P Stopp) 155 D Ingle Smith, P Stopp) 156 J Holden, An Introduction to Physical Geography and the Environment, Pearson, 2005) 3127 D Ingle Smith, P Stopp) 159 D Ingle Smith, P Stopp) 910 J Holden) 3911 D S G Thomas, A Goudie, The Dictionary of Physical Geography, Blackwell, 2000) 20912 D S G Thomas, A Goudie) 20913 W Viessman, G L Lewis) 914 National Geographic Atlas of the World, National Geographic Society, 1995) 7415 National Geographic Atlas of the World) 8316 National Geographic Atlas of the World) 9417 P Ganderton, Mastering Geography, MacMillan, 2000) 31418 J Holden) 32819 J Holden) 32820 J C Dewdney, A Geography of the Soviet Union, Pergamon, 1979) 721 P Ganderton) 31122 B A Weightman, Dragons and Tigers, A Geography of South, East and South East Asia, Wiley, 2006) 19523 B A Weightman) 19524 J Holden) 32825 J Holden) 32826 R White, Africa Geographical Studies, Heinemann, 1984) 16927 R White) 167

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