Rivers are terrestrial flowing surface waters that drain well defined watersheds. A river typically has a geographic origin, termed its headwaters. In general, there are smaller rivers or streams that merge into the principal river of a given watershed; such influent streams are called tributaries of the principal river. Most rivers either discharge to a larger watercourse or flow into one of the seas of the world. In the less common circumstance, a river may terminate in an inland lake, with no outlet; this circumstance is called an endorheic basin. Rivers are home to a diversity of flora and fauna.
The Yangtze River, Asia's longest watercourse at about 6300 kilometers, has a basin that holds approximately one third of the population of China. The headwaters of the...
Zambezian flooded grasslandsLast Updated on 2015-04-08 23:59:46
WWF Terrestrial Ecoregions Collection
Located within the miombo and mopane woodlands of the Central African Plateau, Zambezian flooded grasslands are an anomaly of productivity and abundance in a landscape characterized by nutrient deficient soil and associated vegetation. Unlike the surrounding woodlands that generally support animals only in rather low densities, the wetlands and floodplains of this ecoregion provide habitats to sizable faunal populations, since food and water are abundant throughout most of the year. Large populations of waterbirds gather during the rainy season, and numerous herd animals and carnivores frequent the landscape. However, in a climate of rapid population growth and increasing need for land and natural resources, this fragile ecoregion may face increasing threat. Several conservation measures are... More »
Daugava RiverLast Updated on 2015-01-12 07:37:16The Daugava River drains portions of the countries of Latvia, Belarus and Russia, prior to discharging to the Gulf of Riga. Also known as the West Dvina River, this watercourse is the fourth largest river discharging to the Baltic Sea catchment.
This 1005 kilometer long river has suffered environmental damage from agricultural runoff and from hydroelectric dam construction, with major impacts dealt in the Soviet era of collective farming. In ancient history the Daugava estuary was a locus of prehistoric settlement, and later marked one of the eastern limits of the voyages of the Vikings.
The lower Daugava valley (nearest the Gulf of Riga) was formed in relatively recent times, as glacial meltwater formed incision on the relatively level terrain near the Baltic Sea coast; these events occurred in the early Holocene, approximately 11,000 years before present. The relatively soft upper... More »
Mississippi RiverLast Updated on 2014-11-29 22:15:22The Mississippi River drains the largest river basin in North America, and is one of the major rivers of the world.
The Mississippi River watershed is the fourth largest in the world, extending from the Allegheny Mountains in the east to the Rocky Mountains in the west. The watershed includes all or parts of 31 states and two Canadian provences. The watershed measures approximately 1.2 million square miles (3.1 million square kilometers), covering about 40% of the lower 48 states. The Mississippi drains most of the United States between the Appalachian Mountains in the east and the Rocky Mountains in the West.
The mainstream of the Mississippi River has headwaters rising at Lake Itasca, Minnesota and flows approximately 2340 miles (3765 km). Though the longest part of the river includes the the Missouri River which flows approximately 2540 miles (4088 km) before joining the... More »
Ecoregions of Oklahoma (EPA)Last Updated on 2014-06-28 15:53:00
Ecoregions denote areas of general similarity in ecosystems and in the type, quality, and quantity of environmental resources. They are designed to serve as a spatial framework for the research, assessment, management, and monitoring of ecosystems and ecosystem components. By recognizing the spatial differences in the capacities and potentials of ecosystems, ecoregions stratify the environment by its probable response to disturbance (Bryce, Omernik, and Larsen, 1999).
Ecoregions are general purpose regions that are critical for structuring and implementing ecosystem management strategies across federal agencies, state agencies, and nongovernment organizations that are responsible for different types of resources in the same geographical areas (Omernik and others, 2000). A Roman numeral hierarchical scheme... More »
Nile Delta flooded savannaLast Updated on 2014-05-16 14:56:41
WWF Terrestrial Ecoregions Collection
Located on the northeastern corner of Africa, Egypt is part of the Palearctic realm linked to the north by the Middle East and the Mediterranean Sea, but also connected to sub-Saharan Africa by the Nile River. The Nile Delta is a vital stopover place for millions of birds making their annual migration between the Palearctic and Afrotropical realms, despite the fact that agriculture and dams have inextricably altered the floodplain delta ecosystem since 1960.
The Nile Delta Flooded Savanna ecoregion extends along the River Nile from the Aswan High Dam, 1,100 kilometers (km) downstream to the mouth of the Nile as it enters the Mediterranean Sea. The delta is about 175 km long and 260 km wide. Since the construction of the Aswan High Dam, the riverine floodplains and delta are no longer subject to annual... More »
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