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The River Basin  
 Introduction
Geography
Climate and Weather
Hydrology
Water Quality
Ecology and Biodiversity
 Ecology
Aquatic Ecology
 Building Blocks
 Aquatic Habitats
 In the Basin
 Life in Aquatic Ecosystems
 Food Chains and Webs
 Biomass and Production
 Classification of Organisms
 Microorganisms
 Plants
 Invertebrates
 Vertebrates
 Fish Species
 Factors Affecting Ecosystems
 Wetlands
 Biodiversity
 Millennium Ecosystem Assessment
 References


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Ecology and Biodiversity:

Aquatic Ecology

   

Aquatic ecosystems include all forms of life within a waterbody including fish and aquatic invertebrates, along with related communities such as riparian vegetation.

To maintain a healthy aquatic environment, the overall health of the system should outweigh the demands of any one user. When humans impound river water, the downstream flow regime changes – and adequate base flow downstream is essential to ecosystem integrity. The amount and timing of water releases is often a complicated planning decision that must balance conflicting demands.

Streamflow is required to sustain aquatic habitats (including channel morphology and substrate) and to support spawning and the movement of aquatic organisms within the water column. These ecologically-required flows are commonly known as Environmental Flow Requirements (EFR). Environmental flows may describe both long-term average flows, and flow variability. Maintenance of environmental flows in a river has several advantages: it supports the riverine ecology, recharges riverine aquifers, and maintains river channel morphology.

The Khubelu River in Lesotho.
Source:Lesotho Water Commission 2002
( click to enlarge )

 

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Explore the sub-basins of the Orange-Senqu River


Tour video scenes along the Orange-Senqu River related to the River Basin


Investigate land cover and terrestrial ecoregions in the basin


Examine how the hydrologic cycle moves water through and around the earth


Explore the interactions of living organisms in aquatic environments


 
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