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Phosphate levels in major basins Phosphate levels in major basins
A comparison of the major watersheds between the two decades showed that Northern Europe and North America had lower phosphate concentrations, while the Ganges and Brahmaputra watersheds in South Central Asia had higher concentrations. Nutrient control programmes in municipal and agricultural activities may be key factors in the observed reductions in phosphate concentrations.
17 May 2005 - by Philippe Rekacewicz, UNEP/GRID-Arendal
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Phosphate levels in major basins Phosphate levels in major basins
A comparison of the major watersheds between the two decades showed that Northern Europe and North America had lower phosphate concentrations, while the Ganges and Brahmaputra watersheds in South Central Asia had higher concentrations. Nutrient control programmes in municipal and agricultural activities may be key factors in the observed reductions in phosphate concentrations.
17 May 2005 - by Philippe Rekacewicz, UNEP/GRID-Arendal
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World's water cycle: schematic and residence time World's water cycle: schematic and residence time
The water cycle consists of precipitation, evaporation, evapotranspiration and runoff. This graphic explains the global water cycle, showing how nearly 577 000 km3 of water circulates through the cycle each year. A table of estimated residence times of the world's water shows the estimated times that water resources exist as biospheric water; atmospheric water; river channels; swamps; lakes and reservoirs; soil moisture; ice caps and glaciers; oc...
17 May 2005 - by Philippe Rekacewicz, UNEP/GRID-Arendal
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World's water cycle: schematic and residence time World's water cycle: schematic and residence time
The water cycle consists of precipitation, evaporation, evapotranspiration and runoff. This graphic explains the global water cycle, showing how nearly 577 000 km3 of water circulates through the cycle each year. A table of estimated residence times of the world's water shows the estimated times that water resources exist as biospheric water; atmospheric water; river channels; swamps; lakes and reservoirs; soil moisture; ice caps and glaciers; oc...
17 May 2005 - by Philippe Rekacewicz, UNEP/GRID-Arendal
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Major river basins of Africa Major river basins of Africa
This map shows the locations of 13 major river basins in Africa: the Senegal, Volta, Niger, Lake Chad, Nile, Lake Turkana, Juba Shibeli, Ogooue, Congo, Zambezi, Okavango, Limpopo and Orange river basins.
17 May 2005 - by Philippe Rekacewicz, Delphine Digout, UNEP/GRID-Arendal
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Major river basins of Africa Major river basins of Africa
This map shows the locations of 13 major river basins in Africa: the Senegal, Volta, Niger, Lake Chad, Nile, Lake Turkana, Juba Shibeli, Ogooue, Congo, Zambezi, Okavango, Limpopo and Orange river basins.
17 May 2005 - by Philippe Rekacewicz, Delphine Digout, UNEP/GRID-Arendal
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Alkalinity in major rivers Alkalinity in major rivers
This graphic shows the average bicarbonate concentrations, in milligrams per litre, at major river mouths for the time periods 1976 to 1990 and 1991 to 2000. The graphic also shows the changes in average bicarbonate levels between these two time periods. Bicarbonate is an indication of the alkalinity in the rivers which reflects the geology (rock, minerals, sand) and increases the buffering capacity, but can also increase the risk of eutrophicati...
17 May 2005 - by Philippe Rekacewicz, UNEP/GRID-Arendal
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Alkalinity in major rivers Alkalinity in major rivers
This graphic shows the average bicarbonate concentrations, in milligrams per litre, at major river mouths for the time periods 1976 to 1990 and 1991 to 2000. The graphic also shows the changes in average bicarbonate levels between these two time periods. Bicarbonate is an indication of the alkalinity in the rivers which reflects the geology (rock, minerals, sand) and increases the buffering capacity, but can also increase the risk of eutrophicati...
17 May 2005 - by Philippe Rekacewicz, UNEP/GRID-Arendal
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From wetlands to dry lands: the destruction of the Mesopotamian marshlands From wetlands to dry lands: the destruction of the Mesopotamian marshlands
The Mesopotamian marshlands in the Tigris and Euphrates river basins were devastated by damming and river channelisation during the late 1980s. This graphic illustrates the decline in the area's marshlands by comparing the locations of its marshlands and lakes in 1973 and in 2000. The graphic shows the locations of permanent and seasonal marshes; permanent, shallow and seasonal lakes and mud flats or temporary marshes. The graphic for the year 20...
17 May 2005 - by Philippe Rekacewicz, UNEP/GRID-Arendal
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From wetlands to dry lands: the destruction of the Mesopotamian marshlands From wetlands to dry lands: the destruction of the Mesopotamian marshlands
The Mesopotamian marshlands in the Tigris and Euphrates river basins were devastated by damming and river channelisation during the late 1980s. This graphic illustrates the decline in the area's marshlands by comparing the locations of its marshlands and lakes in 1973 and in 2000. The graphic shows the locations of permanent and seasonal marshes; permanent, shallow and seasonal lakes and mud flats or temporary marshes. The graphic for the year 20...
17 May 2005 - by Philippe Rekacewicz, UNEP/GRID-Arendal
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Long-term variations in river flow, by continent Long-term variations in river flow, by continent
River runoff is cyclical in nature, with alternating cycles of wet and dry years. Significant deviations from average values differ in duration and magnitude. For example, 1940-44, 1965-68 and 1977-79 are clearly low periods in terms of total runoff from the world's rivers. During these periods, the runoff was estimated at 1 600-2 900 km3 below the average value. By contrast, 1926-27, 1949-52 and 1973-75 saw much greater levels of river runoff (S...
17 May 2005 - by Delphine Digout, UNEP/GRID-Arendal
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Long-term variations in river flow, by continent Long-term variations in river flow, by continent
River runoff is cyclical in nature, with alternating cycles of wet and dry years. Significant deviations from average values differ in duration and magnitude. For example, 1940-44, 1965-68 and 1977-79 are clearly low periods in terms of total runoff from the world's rivers. During these periods, the runoff was estimated at 1 600-2 900 km3 below the average value. By contrast, 1926-27, 1949-52 and 1973-75 saw much greater levels of river runoff (S...
17 May 2005 - by Delphine Digout, UNEP/GRID-Arendal
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River runoff by continent, 1921-1985 River runoff by continent, 1921-1985
River runoff represents the accumlated water, from preciptation and meltwater, that feeds into rivers that feeds into seas. The estimated annual figures in this graphic is what volume of water that ends up in the World Ocean. Factors influencing this volume is primarily the area that drains (e.g. area of continent), precipitation and evaporation. Tropical regions typically exhibit greater river runoff volumes. The Amazon carries 15% of all the wa...
17 May 2005 - by Philippe Rekacewicz, UNEP/GRID-Arendal
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River runoff by continent, 1921-1985 River runoff by continent, 1921-1985
River runoff represents the accumlated water, from preciptation and meltwater, that feeds into rivers that feeds into seas. The estimated annual figures in this graphic is what volume of water that ends up in the World Ocean. Factors influencing this volume is primarily the area that drains (e.g. area of continent), precipitation and evaporation. Tropical regions typically exhibit greater river runoff volumes. The Amazon carries 15% of all the wa...
17 May 2005 - by Philippe Rekacewicz, UNEP/GRID-Arendal
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River fragmentation and flow regulation River fragmentation and flow regulation
This graphic shows the number of new dams that were under construction in 1998. It also indicates the areas which are most affected by river channel fragmentation and flow regulation. River fragmentation is defined as the interruption of a river's natural flow by dams, inter-basin transfers or water withdrawal, and is an indicator of the degree to which rivers have been modified by human activity.
17 May 2005 - by Philippe Rekacewicz, UNEP/GRID-Arendal
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River fragmentation and flow regulation River fragmentation and flow regulation
This graphic shows the number of new dams that were under construction in 1998. It also indicates the areas which are most affected by river channel fragmentation and flow regulation. River fragmentation is defined as the interruption of a river's natural flow by dams, inter-basin transfers or water withdrawal, and is an indicator of the degree to which rivers have been modified by human activity.
17 May 2005 - by Philippe Rekacewicz, UNEP/GRID-Arendal
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Nitrate in major rivers Nitrate in major rivers
Considering the data for all the rivers at the continental level, there has been little change in nitrate (NO3-N) concentrations between the two decades under comparison. Changes in the median value were not statistically significant. European rivers showed the highest nitrate loads transported to the marine environment. Comparing data from the two decades, North American and European rivers have remained fairly stable, while major river basins i...
17 May 2005 - by Philippe Rekacewicz, UNEP/GRID-Arendal
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Calcium levels in major rivers Calcium levels in major rivers
This graphic shows the average calcium levels, in milligrams per litre, at major river mouths for the time periods 1976 to 1990 and 1991 to 2000. The graphic also shows the changes in average calcium levels between these two time periods.
17 May 2005 - by Philippe Rekacewicz, UNEP/GRID-Arendal
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Calcium levels in major rivers Calcium levels in major rivers
This graphic shows the average calcium levels, in milligrams per litre, at major river mouths for the time periods 1976 to 1990 and 1991 to 2000. The graphic also shows the changes in average calcium levels between these two time periods.
17 May 2005 - by Philippe Rekacewicz, UNEP/GRID-Arendal
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Major river basins of the world Major river basins of the world
Rivers form a hydrological mosaic, with an estimated 263 international river basins covering 45.3% of the land surface area of the earth, excluding Antarctica. This graphic shows the locations of 26 of the world's major river basins. A basin is defined as the land area (watershed) where all surface water drains to a certain river.
01 Oct 2005 - by Delphine Digout, UNEP/GRID-Arendal
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