2. • They contain only about 0.0001% of the total amount of water in the world at any
given time, rivers are vital carriers of water and nutrients to areas all around the
earth.
3. • They are critical components of the hydrological cycle, acting as drainage
channels for surface water – the world's rivers drain nearly 75% of the earth's land
surface.
• They provide habitat, nourishment and means of transport to countless organisms.
• They provide travel means for exploration, commerce and recreation.
• They leave valuable deposits of sediments, such as sand and gravel.
• Their power provides much of the electrical energy we use in our everyday lives.
5. THERE ARE 3 MAIN SOURCES
FOR THIS WATER:
1) PRECIPITATION – RAIN OR
SNOW
2) GROUND WATER –
PRECIPITATION THAT HAS
BEEN STRORED DOWN FOR
A LONG TIME
3) MELTING GLACIERS
6. EXISTENCE OF RIVER DEPENDS ON:
• THE AVAILABILITY OF SURFACE WATER
• A CHANNEL IN THE GROUND
• AN INCLINED SURFACE
8. LOCTIC SYSTEMS
Rivers and streams are characterized by
flowing waters and are called lotic
systems (as opposed to lentic systems,
such as lakes)
• Lotic environments have been described as having four dimensions:
• a longitudinal dimension with a pronounced zonation of chemical, physical and biological
factors (comparable to the vertical stratification in lakes)
• a lateral dimension involving exchanges of organic matter, nutrients and biota between the
stream channel and the adjacent floodplain
• a vertical dimension consisting of a hydraulic connection linking the river channel
with groundwater.
• and a fourth dimension of time which pertains to the velocity of the water flow.
10. The shape, size and content of a river
are constantly changing, forming a close
and mutual interdependence between
the river and the land it traverses.
14. IT DIVIDES RIVERS INTO THREE PRIMARY ZONES:
• (a) The crenon is the uppermost zone at the source of the river. It is further divided into the
eucrenon (spring or boil zone) and the hypocrenon (brook or headstream zone). These
areas are characterized by low temperatures, reduced oxygen content and slow moving
water.
• (b) The rhithron is the upstream portion of the river that follows the crenon. It is
characterized by relatively cool temperatures, high oxygen levels, and fast, turbulent flow.
• (c) The potamon is the remaining downstream stretch of river. It is characterized by warmer
temperatures, lower oxygen levels, slow flow and sandier bottoms.
16. LIGHT
• REDUCED CLARITY OF RIVERS RESULTS FROM 2 MAIN
FACTORS:
1) RIVERS ARE IN INTIMATE CONTACT WITH THE SURROUNDING
LANDSCAPE, AND INORGANIC AND ORGANIC MATERIALS
CONTINUOUSLY WASH, FALL, OR BLOW INTO RIVERS.
2) RIVER TURBULENCE ERODES BOTTOM SEDIMENTS AND KEEPS THEM
IN SUSPENSION, PARTICULARLY DURING FLOODS.
17. THE EXTENT OF SHADING DECREASES PROGRESSIVELY
DOWNSTREAM AS STREAM WIDTH INCREASES.
FOREST STREAM DESERT STREAM
22. CURRENTS IN QUIET POOLS MAY FLOW AT ONLY A FEW MILLIMETERS PER
SECOND, WHILE WATER IN THE RAPIDS OF SWIFT RIVERS IN A FLOOD STAGE MAY FLOW
AT 6m PER SECOND.
THE AMOUNT OF WATER CARRIED BY RIVERS, WHICH IS CALLED RIVER
DISCHARGED, DIFFERS A LOT FROM ONE CLIMATIC REGIME TO ANOTHER.
RIVER FLOWS ARE OFTEN UNPREDICTABLE AND ―FLASHY‖ IN ARID AND SEMIARID
REGIONS, WHERE EXTENDED DROUGHTS MAY BE FOLLOWED BY TORRENTIAL
RAINS..
23. MANY TROPICAL RIVERS, WHICH FLOW VERY LITTLE
DURING THE DRY SEASON, BECOME TORRENTS
DURING THE WET SEASON.
24. SOME OF THE MOST CONSTANT FLOWS ARE FOUND IN FORESTED TEMPERATE
REGIONS, WHERE PRECIPITATION IS OFTEN FAIRLY EVENLY DISTRIBUTED
THROUGHOUT THE YEAR.
25. HISTORICAL PATTERNS OF FLODDING HAVE PATICULARLY IMPORTANT INFLUENCES ON
RIVER ECOSYSTEM PROCESSES, ESPECIALLY ON THE EXCHANGE OF NUTRIENTS AND
ENERGY BETWEEN THE RIVER CHANNEL AND THE FLOODPLAIN AND ASSOCIATED
WETLANDS.
27. SALINITY
• THE AMOUNT OF SALT DISSOLVED IN RIVER WATER REFLECTS THE HISTORY OF
LEACHING THAT HAS GONE ON ITS BASIN.
• MANY TROPICAL SOILS HAVE BEEN LEACHED OF MUCH OF THEIR SOLUBLE
MATERIALS AND IT IS IN THE TROPICS THAT THE SALINITY OF RIVER WATER IS
OFTEN VERY LOW.
• DESERT RIVERS GENERALLY HAVE THE HIGHEST SALINITIES.
28. OXYGEN
• OXYGEN CONTENT OF RIVER WATER IS INVERSELY CORRELATED WITH
TEMPERATURE.
• OXYGEN SUPPLIES ARE GENERALLY RICHEST IN COLD, THOROUGHLY MIXED
HEADWATER STREAMS AND LOWER IN THE WARM DOWNSTREAM SECTIONS OF
RIVERS.
• HOWEVER, BECAUSE THE WATERS IN STREAMS AND RIVERS ARE CONTINUOUSLY
MIXED, OXYGEN IS GENERALLY NOT LIMITING TO THE DISTRIBUTION OF RIVER
ORGANISMS.
30. The temperature is cooler at the source than it is at the mouth. The water is also
clearer, has higher oxygen levels, and freshwater fish such as trout and heterotrophs can
be found there. Towards the middle part of the stream/river, the width increases, as does
species diversity — numerous aquatic green plants and algae can be found. Toward the
mouth of the river/stream, the water becomes murky from all the sediments that it has
picked up upstream, decreasing the amount of light that can penetrate through the water.
Since there is less light, there is less diversity of flora, and because of the lower oxygen
levels, fish that require less oxygen, such as catfish and carp, can be found.
32. A river begins at a source and flows following
elevation gradients (i.e., by the force of gravity)
down to its endpoint, called the mouth (which
may be another river, a lake, or an ocean).
The source is the highest point in the
watercourse and may be a spring, a lake
or marshy area, or glacial melt waters in
high mountain regions.
The river continuum is a concept based on the
characteristic changes in a river as it progresses
from the source to the mouth. It identifies a
downstream gradient of physical and chemical
factors moving from the headwaters to
the lowland rivers, correlating this gradient with
changes in the biological communities.
34. FAST WATER:
REQUIRE HIGH, NEAR-SATURATION CONCENTRATIONS OF OXYGEN AND MOVING
WATER TO KEEP THEIR ABSORBING AND RESPIRATORYSURFACES IN CONTINUOUS
CONTACT WITH OXYGENATED WATER.
- STREAMLINED FORM, OFFERS LESS RESISTANCE TO WATER CURRENT.
Brook trout
dace
35. - LARVAL FORMS OF MANY SPECIES OF INSECTS CLING TO THE UNDERSURFACES OF
STONES, WHERE THE CURRENT IS WEAK.
- FLATTENED BODIES AND BROAD, FLAT LIMBS THAT ALLOW THE CURRENT TO FLOW
OVER THEM.
36. - SOME ATTACH THEMSELVES TO THE SUBSTRATE AND OBTAIN FOOD BY STRAINING
PARTICLES CARRIED TO THEM BY THE CURRENT.
- STICKY UNDERSURFACES HELP SNAILS AND PLANARIANS CLING TIGHTLY AND
MOVE ABOUT ON STONES AND RUBBLE IN THE CURRENT.
37. - WATER MOSS AND HEAVILY BRANCHED FILAMENTOUS ALGAE CLING TO ROCKS
BY STRONG HOLDFASTS.
- OTHER ALGAE GROW IN CUSHIONLIKE COLONIES OR CLOSELY APPRESSED
SHEETS THAT ARE COVERED WITH A SLIPPERY, GELETINOUS COATING AND
FOLLOW THE CONTOURS OF STONE AND ROCKS.
38. FOR SLOW-FLOWING STREAMS:
shiners
Small mouth bass
darters
- THEY TRADE STRONG LATERAL MUSCLES NEEDED IN FAST CURRENT FOR
COMPRESSED BODIES THAT ENABLES THEM TO MOVE THROUGH BEDS OF
AQUATIC VEGETATION.
39. - PULMONATE SNAILS AND BURROWING MAYFLIES REPLACE RUBBLE-DWELLING
INSECT LARVAE.
- CATFISH FEED ON LIFE IN THE SILTY BOTTOM, AND BACK SWIMMERS AND WATER
STRIDERS INHABIT SLUGGISH STRETCHES AND STILL BACKWATERS.
40. 4 MAJOR GROUPS OF INVERTEBRATES:
1) SHREDDERS – MAKE UP ONE LARGE GROUP OF INSECT LARVAE.
- FEED ON CPOM
- BREAK DOWN CPOM, FEEDING ON THE MATERIAL NOT
SO MUCH FOR THE ENERGY IT CONTAINS BUT FOR THE
BACTERIA AND FUNGI GROWING ON IT.
41. 2) FILTERING AND GATHERING COLLECTORS
- FEED ON FPOM.
3) GRAZERS – FEED ON ALGAL COATING OF STONES AND RUBBLES.
4) GOUGERS – ASSOCIATED WITH WOODY DEBRIS. THESE ARE THE INVERTEBRATES
THAT BURROW INTO WATER-LOGGED LIMBS AND TRUNKS OF FALLEN TREES.
FEEDING ON DETRITAL FEEDERS AND GRAZERS ARE:
