CHARACTERISTIC FEATURES, STRUCTURE AND FUNCTION STRUCTURE AND FUNCTION
3.16.2.Lakes 3.16.2.Lakes A
A lalake ke is is a a bobody dy of of wawateter r cocompmpleletetely ly susurrorrounundeded d by by lalandnd..
Lak
Lakes can eites can either be salher be salty or fresh waty or fresh waterter. . MosMost lakes are int lakes are in pl
placeaces s whewhere glacre glaciers useiers used to d to exiexist. st. WheWhen a n a glaglaciecier movesr moves forward, it carves away a deep valley and when the ice melts it forward, it carves away a deep valley and when the ice melts it forms a lake in
forms a lake in the valley. the valley. Other lakes aOther lakes are formed in craters ore formed in craters or r when a river changes its course.
when a river changes its course.
Lakes are short-lived surface features because the water can Lakes are short-lived surface features because the water can sink int
sink into the grouo the ground or evapond or evaporate into trate into the sky. he sky. In order for aIn order for a like to remain, it must be constantly fed by a river or rainfall.
like to remain, it must be constantly fed by a river or rainfall.
3.16.3.Rivers and Streams 3.16.3.Rivers and Streams
Ri
Rivevers rs arare e vevery ry imimpoportrtanant t to to EaEarth rth bebecacaususe e ththey ey are are mamajojor r ffoorcrcees s tthhaat t sshhaapps s tthhe e llaannddssccaappee. . AAllssoo, , hheey y pprroovviiddee tra
transpnsportortatiation on and and watwater er for for dridrinkinking ng waswashinhing g and and farmfarminging..
Rivers can flow on land or underground in deserts and seas.
Rivers can flow on land or underground in deserts and seas.
Rivers may come from mountain springs, melting glaciers or Rivers may come from mountain springs, melting glaciers or lakes.
lakes.
A river’s contribution to the cycle is that it collects water from A river’s contribution to the cycle is that it collects water from the ground and returns it to the ocean. The water w drink is the ground and returns it to the ocean. The water w drink is bout 3 billion years old because it has been recycled over and bout 3 billion years old because it has been recycled over and
over since the first rainfall.
over since the first rainfall.
A delta is wh
A delta is where a river meetere a river meets the sea. s the sea. UsuaUsually the rivelly the river flowsr flows more slowly at the delta than at its start because it deposits more slowly at the delta than at its start because it deposits sediment.
sediment. Sediment can be Sediment can be anything from anything from mud, sand anmud, sand and everyd every roc
rock fragmek fragmentsnts. . A speciA special envial environronmenment t is creatis created when theed when the fresh water from the river mixes with the salty ocean water.
fresh water from the river mixes with the salty ocean water.
This environment is called estuary.
This environment is called estuary.
The longest river is the Nile River in Africa, and the Amazon The longest river is the Nile River in Africa, and the Amazon Rive
River in South Americr in South America carries the mosa carries the most water. t water. The muddThe muddiestiest river is the Yellow River in
river is the Yellow River in China.China.
3.16.4Estuaries 3.16.4Estuaries
An estuary is an unique environment where fresh water and salt An estuary is an unique environment where fresh water and salt water come
water come together. together. Estuaries are found Estuaries are found on the coon the coast where aast where a river or bay or other sources of fresh water has access to the river or bay or other sources of fresh water has access to the open sea. A good example of an estuary is a salt marsh that can open sea. A good example of an estuary is a salt marsh that can
be foun
be found close to the cd close to the coast. oast. AnotAnother exampher example is when a river le is when a river feeds directly
feeds directly into the ocinto the ocean. ean. The largest esThe largest estuary in the tuary in the UnitedUnited States is the Chesapeake bay estuary on the east coast of the States is the Chesapeake bay estuary on the east coast of the U.S.
U.S.
Estuaries are affected
Estuaries are affected by the tidesby the tides. . So, there can bSo, there can be changes of e changes of sa
salilininityty, , tetempmperaeratuture re anand d ototheher r phphysysicical al prpropoperertities es in in anan estuarial system which means the organisms there must be very estuarial system which means the organisms there must be very toler
tolerant to changeant to change. . Even with thaEven with that considet considerationration, estuarie, estuaries ares are among the most
among the most fertile places in fertile places in the world. the world. All kinds All kinds of plantsof plants and anim
and animals live theals live there. re. When looWhen looking at estking at estuarieuaries, scients, scientistsists quickly realized that these areas were extremely nutrient-rich quickly realized that these areas were extremely nutrient-rich because of sediment deposit of rivers, creeks or streams feeding because of sediment deposit of rivers, creeks or streams feeding
int
into the o the salsalt t watwater envier environronmenment. t. UnfUnfortortunaunateltely, estuy, estuariarieses have
haven’t alwayn’t always been seen as vas been seen as valuablluable. e. In the pasIn the past, they wert, they weree seen as worthless and were used as dumps, or places for new seen as worthless and were used as dumps, or places for new land de
land develovelopment (by fipment (by fillinlling in the marsg in the marshy area). hy area). HoweHowever,ver, now the systems are being set up to establish, manage and now the systems are being set up to establish, manage and maintain estuary reserves, and to provide for their long-term maintain estuary reserves, and to provide for their long-term stewardship.
stewardship.
3.16.5Pond Ecosystem 3.16.5Pond Ecosystem
The definition of a pond is any body of water over 1m square The definition of a pond is any body of water over 1m square that is inundated, “wet” for more than8 months
that is inundated, “wet” for more than8 months of the year.of the year.
That definition tells us quite a lot about a ponds ecosystem.
That definition tells us quite a lot about a ponds ecosystem.
The first is obvious, it doesn’t have to be large to be useful, in The first is obvious, it doesn’t have to be large to be useful, in fact even a bird bath will be visited by the water boatman if he fact even a bird bath will be visited by the water boatman if he is in need of a place to rest and eat.
is in need of a place to rest and eat.
If a pond does dry out
If a pond does dry out it isn’t a disaster, both plants and animalsit isn’t a disaster, both plants and animals have adapted to this
have adapted to this eventuality.eventuality.
The pond is the most valuable as far as wildlife is concerned, if The pond is the most valuable as far as wildlife is concerned, if the pond is reasonably shallow (no more than 90 cm) and very the pond is reasonably shallow (no more than 90 cm) and very well planted it will support a vast array
well planted it will support a vast array of animals and plants.of animals and plants.
Some potential inhabitants and visitors are
Some potential inhabitants and visitors are frogs, Newts, Toads,frogs, Newts, Toads, Fox
Foxes, es, HedHedgehgehogsogs, , BadBadgergers s bibirdsrds, , BatBats, s, GraGrass ss snasnakeskes, , SloSloww worms, Water Voles, Birds of all sizes, Great diving beetles, worms, Water Voles, Birds of all sizes, Great diving beetles, Water boatman, Dragon fly Larvae and adults, Damsel flys, Water boatman, Dragon fly Larvae and adults, Damsel flys, Daph
Daphnia, nia, CyclCyclops, ops, SpidSpiders, ers, Water scorpion Water scorpion (not dangerous(not dangerous),), zoo plankton, Wirlygig beetle, Pond skaters, Lace wings. The zoo plankton, Wirlygig beetle, Pond skaters, Lace wings. The potential list of insects and other small
potential list of insects and other small things is huge.things is huge.