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...
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 »
Nenjiang River grasslandLast Updated on 2014-05-16 14:56:08
WWF Terrestrial Ecoregions Collection
Nenjiang River grassland is an expansive low lying grassland drained by the Nenjiang and Songhua Rivers of China. The Nenjiang River originates among low hills that define China’s northeastern border with the Russian Far East. After winding through a series of valleys, the Nenjiang River flows down onto the Songhua-Nenjiang plain where flooded grasslands have historically provided important summer breeding habitat for a variety of migratory birds including six of the world’s fifteen crane species. The Red-crowned Crane, White-naped Crane, Siberian Crane and Demoiselle crane breed in this ecoregion, while the Common Crane and Hooded Crane stage here prior to migrating to their breeding habitat. Overfishing and agricultural development threaten the bird populations of this species-rich... More »
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